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Which brain structures are listed as core components of the CNS overview map?
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What connection does the hypothalamus have according to the systems map?
Hypothalamus controls ANS
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Name three sensory receptor types mentioned in the PNS & Sensory section.
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How are sensory receptor adaptation types categorized in the overview?
Adaptation is categorized as tonic vs. phasic
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Which pain fiber types are listed in the PNS & Sensory section?
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What exception to typical autonomic structure is noted in the ANS section?
Adrenal medulla exception
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Which autonomic receptors are named in the ANS overview?
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How does the ANS control pupil size according to the Vision section?
Parasympathetic constricts pupil; sympathetic dilates pupil
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Which ear-related system shares cranial nerve VIII with the cochlea?
Vestibular system (CN VIII shared with cochlea)
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Which vestibular organs detect linear vs. rotational acceleration?
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How does olfaction relate to other brain systems in the chemosensation section?
Olfaction projects heavily to limbic system
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What are key components of GI motility listed in the systems map?
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What does the systems map say about enteric nervous system function?
Enteric NS can function independently
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Which GI secretory cells or components are specifically named in the GI Secretion & Absorption section?
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What feedback loop involving hormones is mentioned in the GI Secretion & Absorption section?
Gastrin → somatostatin feedback loop
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What structural feature is described as critical for intestinal absorption?
Surface area (villi/microvilli) critical for absorption
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What is 'gray matter' in the CNS?
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What is 'white matter' in the CNS?
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What are 'basal nuclei' and how do they relate to 'basal ganglia'?
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What structures make up the diencephalon as listed?
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What are 'association areas' in the cerebral cortex?
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Which structures comprise the brain stem and their primary role?
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What is the primary role of the thalamus?
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What is the cerebellum's main function?
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What is the primary function of the occipital lobe?
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What is the primary function of the temporal lobe?
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What is the primary function of the parietal lobe?
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What is the primary function of the frontal lobe?
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What is the sensory homunculus principle?
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What is the motor homunculus principle?
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What is meant by lateralization of sensory/motor signals?
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How do the cerebral hemispheres communicate?
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Where is Broca's area located and what is its primary function?
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What deficit results from damage to Broca's area?
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Where is Wernicke's area located and what is its primary function?
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What deficit results from damage to Wernicke's area?
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What does neuroplasticity allow after early-life language-area damage?
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What is the primary role of the basal nuclei and its key neurotransmitter?
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What clinical dysfunction results from basal nuclei problems?
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What are the primary roles of the hypothalamus?
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What functions are associated with the limbic system and which neurotransmitters are involved?
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What clinical issues are linked to limbic system dysfunction and targeted by SSRIs/SNRIs/MAOIs?
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How is neurotransmitter action terminated at the synapse?
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How do SSRIs and MAO inhibitors alter synaptic neurotransmitter levels?
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Why do many current drugs have broad side effect profiles regarding neurotransmitter systems?
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What historical procedure illustrates the prefrontal cortex's role in personality and planning?
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What does the term afferent neuron mean?
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What does the term efferent neuron mean?
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What are interneurons?
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Define a neuron's receptive field.
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What is lateral inhibition in sensory systems?
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What is a nociceptor?
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How do sensory receptors encode stimulus magnitude?
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How do receptors transduce stimuli into electrical signals?
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Contrast tonic and phasic receptor adaptation.
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Name the main peripheral mechanoreceptor types and one key feature each.
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What determines acuity in touch perception?
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What is the function of lateral inhibition in sensory perception?
Suppresses signals from surrounding areas to accentuate the precise stimulus location.
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How do somatic afferents differ from visceral afferents in conscious perception?
Somatic afferents are generally accessible to conscious perception; visceral afferents are subconscious.
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Why can visceral pain be poorly localized and referred to somatic sites?
Because visceral and somatic afferents converge in the spinal cord, producing poorly localized and referred pain.
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Give an example of referred visceral pain mentioned in the notes.
Heart attack pain felt in the left arm.
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Compare the speed and typical sensation of A-delta fibers versus C fibers.
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What are the myelination and typical triggers for A-delta and C fibers?
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Which chemical mediator from tissue injury is given as an example that stimulates chemical nociceptors?
Bradykinin.
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Which neurotransmitters are involved in CNS processing of pain according to the notes?
Substance P and glutamate.
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Name the endogenous peptides that suppress pain transmission in the spinal cord.
Enkephalins and endorphins.
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How do enkephalins and endorphins affect pain and when does their production increase?
They diminish but do not eliminate pain; production increases during stress, exercise, and acupuncture.
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What is a preganglionic fiber in the autonomic nervous system?
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What is a postganglionic fiber in the autonomic nervous system?
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Define a ganglion in the peripheral nervous system.
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What receptor type mediates transmission at all autonomic ganglia?
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Which receptor type mediates parasympathetic effects at target organs?
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What receptors mediate sympathetic target organ responses?
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What does 'dual innervation' mean?
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What is tonic regulation in autonomic control?
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State the key distinction between 'automatic' and 'autonomic'.
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What is the high-yield rule about the number of neurons in autonomic efferent pathways?
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List the main structural and neurotransmitter differences between sympathetic and parasympathetic pathways.
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Are sympathetic and parasympathetic actions always stimulatory or inhibitory?
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What is 'dual innervation' in autonomic control?
Both sympathetic and parasympathetic divisions innervate an organ and produce opposing effects; the outcome is a balance between them.
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Give an example of dual innervation in the bronchioles.
Sympathetic stimulation dilates bronchioles; parasympathetic stimulation constricts bronchioles.
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How does dual innervation affect GI motility?
Parasympathetic activity increases GI motility while sympathetic activity decreases it.
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What is 'tonic regulation' in autonomic control?
Only one autonomic division innervates the target and regulation occurs by varying a constant background activity.
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Provide an example of tonic regulation involving vascular smooth muscle.
Vascular smooth muscle is innervated only by sympathetic fibers: baseline sympathetic tone causes vasoconstriction; ↑ activity causes more constriction; ↓ activity causes vasodilation.
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How is resting heart rate regulated by autonomic tone?
Parasympathetic tone is dominant at rest; high vagal tone keeps heart rate low and increases in heart rate occur mainly by parasympathetic withdrawal.
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Name one exception where ATP functions in autonomic neurotransmission.
ATP can act as a sympathetic neurotransmitter by binding receptors (not for energy transfer).
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What is an exception to the usual parasympathetic neurotransmitter?
Some parasympathetic fibers release nitric oxide instead of acetylcholine.
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What are autoreceptors in autonomic neurons?
Norepinephrine and acetylcholine can bind to the releasing neuron to modulate their own activity via autoreceptors.
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How does the adrenal medulla differ from the typical postganglionic sympathetic pathway?
Preganglionic sympathetic fibers release acetylcholine onto chromaffin cells, which secrete epinephrine into the blood, effectively replacing the postganglionic neuron.
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Why can nicotine produce both GI stimulation and mild bronchodilation?
Nicotine activates nicotinic receptors at both sympathetic and parasympathetic ganglia, producing simultaneous parasympathetic and sympathetic effects.
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What is a photoreceptor in the retina?
A light-sensitive cell in the retina (rod or cone) that transduces light into an electrical signal.
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What is the fovea?
The central retinal pit containing only cones and representing the highest acuity point.
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What is the macula?
The area around the fovea with high cone density and some rods.
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Define accommodation of the eye.
The process of changing lens shape to focus on near versus far objects.
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What is meant by transduction in vision?
Converting one energy form to another, specifically light into an electrical signal.
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What role does cyclic GMP (cGMP) play in photoreceptors in the dark?
cGMP is a second messenger that keeps Na⁺ channels open in photoreceptors in the dark.
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Describe the main light path through the eye and which structure does most refraction.
Light passes through cornea → pupil → lens → focuses on retina (image inverted). The cornea is responsible for most light refraction; the lens fine-tunes focus.
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What are the actions and autonomic controls of the circular (sphincter) iris muscle?
It constricts the pupil (miosis) and is controlled by the parasympathetic system; tropicamide (a cholinergic antagonist) blocks it leading to dilation.
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What are the actions and autonomic controls of the radial (dilator) iris muscle?
It dilates the pupil (mydriasis) and is controlled by the sympathetic system; phenylephrine (an α-adrenergic agonist) activates it causing dilation.
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What is the clinical rationale for combining tropicamide and phenylephrine in dilation drops?
Tropicamide relaxes the circular muscle by blocking parasympathetic input, while phenylephrine contracts the radial muscle by mimicking sympathetic input, together producing pupil dilation.
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What does the pupillary light reflex assess?
It assesses brainstem and occipital cortex function.
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How do ciliary muscle states affect lens shape for near versus distance vision?
Contracted ciliary muscles produce a round lens for near vision; relaxed ciliary muscles produce a flat lens for distance vision.
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Compare rods and cones in light sensitivity and color.
Rods are extremely sensitive and function in dim light, providing grayscale only; cones require higher intensity light and provide color vision with red, green, and blue subtypes.
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Where are rods predominantly located in the retina?
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Where are cones concentrated in the retina?
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What is the typical wiring ratio of many rods to bipolar cells and its consequence?
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What is the typical wiring relationship of cones to bipolar cells and its consequence?
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Explain rod bleaching and dark adaptation time
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Why can dim stars vanish when looked at directly?
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In darkness, what is the cGMP level and photoreceptor membrane state?
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In light, what happens to cGMP, Na+ channels, and photoreceptor state?
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What is the key enzyme cascade in phototransduction after retinal activation?
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Describe the main visual signal pathway to cortex
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How do lateral and medial visual fields project across hemispheres?
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What is the basis of depth perception described in the notes?
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What visual condition causes central vision loss due to macula damage?
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What causes a cataract and how is it treated?
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What does LASIK do to correct vision?
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What are the three middle ear bones and their primary function?
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What structure seals the cochlea and receives vibrations from the stapes?
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How do hair cells transduce mechanical bending into neurotransmitter release?
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What happens when hair cell stereocilia bend in the opposite direction?
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What is tonic activity in hair cells?
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How does tonic activity help auditory encoding?
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Describe the transmission pathway of sound from air to hair cells.
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How is pitch encoded along the basilar membrane?
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According to the text, what determines perceived pitch?
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How is loudness encoded in the auditory system?
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What is the clinical significance of fluid in the middle ear?
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What is the function of the Eustachian tube related to hearing?
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What is conduction deafness?
Hearing loss caused by a mechanical defect before the hair cells (e.g., eardrum, ossicles, fluid).
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What are common causes of conduction deafness?
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What treatments improve conduction deafness prognosis?
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What is neural (sensorineural) deafness?
Hearing loss due to damage at or beyond the hair cells, affecting the neural pathway.
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How does repair potential compare for sensorineural versus conduction deafness?
Sensorineural deafness is more difficult to repair than conduction deafness.
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Which frequencies does age-related hearing loss (presbycusis) primarily affect?
High frequencies.
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Which part of hearing is preferentially damaged by loud noise?
High-frequency regions are preferentially damaged by loud noise.
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What is the vestibular system?
Inner ear structures detecting head position and movement; shares CN VIII with cochlea
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What do the utricle and saccule detect?
Head tilt (position) and linear acceleration/deceleration
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How do the utricle and saccule transduce linear acceleration or tilt?
Gravity/inertia shifts otolith mass, bending embedded hair cells in the cupula
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What do the semicircular canals detect?
Rotational movement in three-dimensional axes (x, y, z)
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What is the transduction mechanism for the semicircular canals?
Head rotation moves bone before fluid; lagging endolymph bends hair cells causing signal
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What is the cupula in vestibular organs?
A gelatinous mass containing embedded hair cells in vestibular organs
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What is nystagmus?
Involuntary, abnormal eye movements caused by disrupted vestibular input
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Which cranial nerve carries vestibular signals?
The vestibular branch of CN VIII (vestibulocochlear nerve)
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What clinical test assesses utricle and saccule function?
Head tilt test
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How does sensory integration produce dizziness after conflicting inputs?
The brain coordinates vestibular, visual, and proprioceptive inputs; conflict (e.g., spinning then stopping) causes nystagmus and dizziness
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What common causes of vestibular disorders are mentioned?
Infections or fluid imbalance causing conflicting sensory information and dizziness
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What is a chemoreceptor?
A receptor activated by specific chemicals binding to it.
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Which receptor type mediates sweet, bitter, and umami tastes?
G protein-coupled receptors (GPCRs) using intracellular signaling cascades.
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How is salty taste transduced at the receptor level?
Direct Na+ entry through ion channels; Na+ is most effective, K+ less so.
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How is sour taste detected by receptors?
Direct stimulation of ion channels by H+ (protons) caused by acidity.
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What characterizes bitter taste receptors and their significance?
Many GPCR receptor types; evolutionarily linked to avoiding toxic alkaloids.
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What does the umami taste receptor respond to?
GPCRs that respond to amino acids, especially glutamate (MSG).
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Are taste receptors localized to specific tongue regions?
No; taste receptors are scattered across the tongue and the 'tongue map' is oversimplified.
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Describe the main olfactory pathway from epithelium to brain.
Chemoreceptive cilia in olfactory epithelium → olfactory bulb via mitral cells and glomeruli.
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How many distinct odors can humans detect and how does receptor count compare to dogs?
Humans detect 100,000+ distinct odors from ~hundreds of receptor types; dogs have over 10,000 receptor types.
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Why is smell strongly linked to memory and emotion?
A large portion of olfactory input projects to the limbic system, linking smell with memory and emotion.
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What is the vomeronasal organ and what does it detect?
A specialized organ in sinuses that detects pheromones affecting physiology and behavior subconsciously.
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Does the vomeronasal organ produce conscious smell perception?
No; it does not produce conscious smell perception but affects mood and attraction subconsciously.
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What can cause olfactory hallucinations and why are they clinically useful?
Mental illness or lesions causing inappropriate neuronal stimulation; they have diagnostic utility.
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What commonly causes taste or smell loss such as after COVID infection?
Interference with neural transmission rather than direct receptor cell death.
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How does receptor density for taste change across individuals and age?
Receptor density changes with age and varies between individuals, which may explain childhood taste aversions.
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What is the primary function of the gastrointestinal (GI) system?
Transfer nutrients, water, and electrolytes from food into the body's internal environment.
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What are the four major processes of the GI system?
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Define peristalsis in the GI tract.
Sequential contraction of circular muscle behind a bolus plus longitudinal shortening ahead, propelling contents forward.
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What is segmentation and where is it the main motility during meals?
Alternating contractions that mix contents without net propulsion; main small intestine motility during meals.
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What are slow waves in GI smooth muscle and what generates them?
Regular depolarization/repolarization cycles in smooth muscle, generated by interstitial cells of Cajal (ICC).
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When do smooth muscle contractions occur relative to slow waves?
Contraction occurs only when slow waves reach threshold; additional depolarization increases the number of action potentials.
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How is a 'sphincter' defined in the GI context?
A ring of circular smooth muscle regulating passage between GI regions (more accurate term than 'valve').
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What is the migrating motor complex (MMC)?
Strong interdigestive peristaltic sweeps that occur between meals.
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What composes the enteric nervous system and its capability?
Intrinsic nerve plexuses (myenteric and submucosal) that can function independently of the CNS.
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What three systems make up the Regulatory Triad controlling GI function?
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What types of receptor feedback inform GI regulation?
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List the GI wall layers from outside to inside.
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What is the mesentery and one of its functions?
Connective tissue sheets with blood vessels that attach GI structures to the peritoneal wall, preventing bowel telescoping and knotting.
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What are the main roles of the mouth in digestion?
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How does swallowing transition from voluntary to involuntary control?
Swallowing is voluntary in the mouth/pharynx then becomes involuntary at the pharynx; the epiglottis closes the airway and the UES & LES regulate entry/exit.
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Which neural center controls involuntary phases of swallowing?
The brain stem controls involuntary aspects of swallowing.
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Describe the main mixing functions of the stomach.
Stomach mixes food via peristaltic waves + churning, exhibits receptive relaxation before food arrives, and the pyloric sphincter meters chyme into the duodenum.
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What phases regulate stomach activity and their primary triggers?
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What effects occur during the gastric phase of stomach regulation?
During the gastric phase there is ↑ acid, ↑ pepsinogen, ↑ motility, and gastrin release from G cells.
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How does the intestinal phase affect gastric emptying?
The intestinal phase slows gastric emptying and decreases acid while releasing CCK & secretin.
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What are the two main motor patterns of the small intestine and when do they occur?
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What are the primary motor patterns of the large intestine and their functions?
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Outline the neural control and sequence leading to defecation.
Rectal distension activates sensory afferents → internal anal sphincter relaxes (involuntary) → urge to defecate; the external anal sphincter remains under voluntary control.
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What commonly causes constipation according to the notes?
Constipation often results from excessive water removal in the colon (dehydration).
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What is a parietal cell and what does it secrete?
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What is a chief cell and what does it secrete?
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Write the chemical sequence used by parietal cells to generate acid.
\(CO_2 + H_2O \rightarrow \text{carbonic acid (via carbonic anhydrase)} \rightarrow H^+ + HCO_3^-\); H^+ is pumped by H+/K+-ATPase into the lumen
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What is the 'alkaline tide' after meals?
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How does chloride contribute to gastric acid formation?
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How does the gastric mucus layer protect the epithelium?
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How do NSAIDs increase risk of acid-induced ulceration?
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How does H. pylori increase gastric acid secretion?
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What is a micelle and what is its role in digestion?
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What are brush border enzymes and their function?
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What is a chylomicron and its role after fat absorption?
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Which stimuli activate parietal cells according to the table?
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Which stimuli activate chief cells according to the table?
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What do G cells secrete and what stimulates them?
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What do D cells secrete and what stimulates them?
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What is the primary function of goblet cells in the GI tract?
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What cells produce gastrin and what stimuli increase its release?
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What are the main effects of gastrin on gastric cells?
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Which hormone is released by I cells and what triggers its release?
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List the main actions of CCK on the digestive system.
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Which hormone do S cells release and what stimulates it?
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What are the primary effects of secretin on the pancreas and stomach?
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What triggers somatostatin release and what does it inhibit?
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What do pancreatic acinar and duct cells produce?
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Which hormones drive pancreatic bicarbonate and enzyme release?
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What are the main functions of bile and the gallbladder?
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How are glucose and galactose absorbed across the apical membrane?
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How is fructose absorbed by enterocytes?
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How are single amino acids transported into enterocytes?
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How are dipeptides and tripeptides absorbed and processed intracellularly?
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In what form are fats absorbed and how are they transported after re-esterification?
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How is intestinal surface area maximized and how often is the lining replaced?
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Where do brush border enzymes perform final digestion of disaccharides and peptides?
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How does loss of intestinal surface area (eg, flattened villi) affect nutrient absorption?
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What is the mechanism by which lactase deficiency causes diarrhea?
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What is the primary effect of orlistat on digestion and vitamins?
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How do GLP-1 agonists affect appetite, gastric emptying, and fat absorption?
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What does the hepatic portal vein deliver to the liver first?
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What feature of hepatic sinusoidal capillaries enables exchange with hepatocytes?
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How is bilirubin handled by the liver?
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What is the liver's role in cholesterol balance compared with dietary intake?
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How does the sympathetic nervous system affect heart rate?
Increases heart rate (but primarily controlled by parasympathetic withdrawal).
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How does the parasympathetic nervous system affect heart rate at rest?
Decreases heart rate (dominant at rest due to vagal tone).
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Which autonomic division primarily increases cardiac contractility?
The sympathetic division primarily increases contractility.
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What effect do sympathetic and parasympathetic systems have on bronchioles?
Sympathetic: dilation. Parasympathetic: constriction.
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Compare sympathetic and parasympathetic effects on GI motility.
Sympathetic: decreases GI motility. Parasympathetic: increases GI motility.
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How do sympathetic and parasympathetic systems affect pupil size and which muscles are involved?
Sympathetic: dilation (radial muscle). Parasympathetic: constriction (circular muscle).
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What is the sympathetic effect on most blood vessels?
Sympathetic constriction (tonic — only sympathetic control of vessels).
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Describe the difference in salivation between sympathetic and parasympathetic activation.
Sympathetic: thick, viscous saliva. Parasympathetic: watery, copious saliva.
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How do autonomic divisions control the bladder during filling and voiding?
Sympathetic: relaxation for filling. Parasympathetic: contraction for voiding.
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What stimuli activate free nerve endings and what is a key fact about them?
Detect pain, temperature, crude touch; adaptation varies; they are the most widespread receptor.
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What do Merkel's disks detect and how do they adapt?
Detect light sustained touch; adapt slowly (tonic) for continuous pressure monitoring.
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What stimuli do Meissner's corpuscles detect and what is their adaptation type?
Detect light touch and texture; adapt rapidly (phasic) and are abundant in fingertips.
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What do Pacinian receptors detect and how do they adapt?
Detect vibration and deep pressure; adapt rapidly (phasic) and detect changes only.
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What stimuli do Ruffini endings detect and how do they adapt?
Detect deep pressure and stretch; adapt slowly (tonic) for sustained deformation.
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What triggers gastrin release and what is its primary action?
Triggered by peptides and stomach distension; increases acid and pepsinogen secretion.
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What triggers CCK release and what are its main actions?
Triggered by fat and protein; increases pancreatic enzymes, causes gallbladder contraction, and decreases gastric emptying.
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What triggers secretin release and what is its primary action?
Triggered by acid in the duodenum; increases pancreatic HCO₃⁻ and decreases acid.
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What is the primary effect of somatostatin released from D cells in low pH?
Inhibits gastrin, gastric acid, and digestive enzyme secretion (acts as a systemic brake).
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In dim light, which photoreceptor type is most sensitive?
Rods are highly sensitive in dim light.
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Which photoreceptor type mediates color vision and which colors are indicated?
Cones mediate color vision: red, green, and blue.
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Compare acuity and wiring between rods and cones.
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Where are rods and cones primarily located on the retina?
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Which deep brain structure acts as a sensory relay and active filter?
Thalamus functions as a sensory relay and active filter.
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What role and key neurotransmitter are associated with the basal nuclei?
Basal nuclei inhibit unwanted movements and use dopamine as a key neurotransmitter.
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What are the main functions of the hypothalamus?
Autonomic and endocrine master control of temperature, hunger, and thirst.
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Contrast A-delta fibers and C fibers in pain transmission.
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Which brain structures are listed as core components of the CNS overview map?
What connection does the hypothalamus have according to the systems map?
Hypothalamus controls ANS
Name three sensory receptor types mentioned in the PNS & Sensory section.
How are sensory receptor adaptation types categorized in the overview?
Adaptation is categorized as tonic vs. phasic
Which pain fiber types are listed in the PNS & Sensory section?
What exception to typical autonomic structure is noted in the ANS section?
Adrenal medulla exception
Which autonomic receptors are named in the ANS overview?
How does the ANS control pupil size according to the Vision section?
Parasympathetic constricts pupil; sympathetic dilates pupil
Which ear-related system shares cranial nerve VIII with the cochlea?
Vestibular system (CN VIII shared with cochlea)
Which vestibular organs detect linear vs. rotational acceleration?
How does olfaction relate to other brain systems in the chemosensation section?
Olfaction projects heavily to limbic system
What are key components of GI motility listed in the systems map?
What does the systems map say about enteric nervous system function?
Enteric NS can function independently
Which GI secretory cells or components are specifically named in the GI Secretion & Absorption section?
What feedback loop involving hormones is mentioned in the GI Secretion & Absorption section?
Gastrin → somatostatin feedback loop
What structural feature is described as critical for intestinal absorption?
Surface area (villi/microvilli) critical for absorption
What is 'gray matter' in the CNS?
What is 'white matter' in the CNS?
What are 'basal nuclei' and how do they relate to 'basal ganglia'?
What structures make up the diencephalon as listed?
What are 'association areas' in the cerebral cortex?
Which structures comprise the brain stem and their primary role?
What is the primary role of the thalamus?
What is the cerebellum's main function?
What is the primary function of the occipital lobe?
What is the primary function of the temporal lobe?
What is the primary function of the parietal lobe?
What is the primary function of the frontal lobe?
What is the sensory homunculus principle?
What is the motor homunculus principle?
What is meant by lateralization of sensory/motor signals?
How do the cerebral hemispheres communicate?
Where is Broca's area located and what is its primary function?
What deficit results from damage to Broca's area?
Where is Wernicke's area located and what is its primary function?
What deficit results from damage to Wernicke's area?
What does neuroplasticity allow after early-life language-area damage?
What is the primary role of the basal nuclei and its key neurotransmitter?
What clinical dysfunction results from basal nuclei problems?
What are the primary roles of the hypothalamus?
What functions are associated with the limbic system and which neurotransmitters are involved?
What clinical issues are linked to limbic system dysfunction and targeted by SSRIs/SNRIs/MAOIs?
How is neurotransmitter action terminated at the synapse?
How do SSRIs and MAO inhibitors alter synaptic neurotransmitter levels?
Why do many current drugs have broad side effect profiles regarding neurotransmitter systems?
What historical procedure illustrates the prefrontal cortex's role in personality and planning?
What does the term afferent neuron mean?
What does the term efferent neuron mean?
What are interneurons?
Define a neuron's receptive field.
What is lateral inhibition in sensory systems?
What is a nociceptor?
How do sensory receptors encode stimulus magnitude?
How do receptors transduce stimuli into electrical signals?
Contrast tonic and phasic receptor adaptation.
Name the main peripheral mechanoreceptor types and one key feature each.
What determines acuity in touch perception?
What is the function of lateral inhibition in sensory perception?
Suppresses signals from surrounding areas to accentuate the precise stimulus location.
How do somatic afferents differ from visceral afferents in conscious perception?
Somatic afferents are generally accessible to conscious perception; visceral afferents are subconscious.
Why can visceral pain be poorly localized and referred to somatic sites?
Because visceral and somatic afferents converge in the spinal cord, producing poorly localized and referred pain.
Give an example of referred visceral pain mentioned in the notes.
Heart attack pain felt in the left arm.
Compare the speed and typical sensation of A-delta fibers versus C fibers.
What are the myelination and typical triggers for A-delta and C fibers?
Which chemical mediator from tissue injury is given as an example that stimulates chemical nociceptors?
Bradykinin.
Which neurotransmitters are involved in CNS processing of pain according to the notes?
Substance P and glutamate.
Name the endogenous peptides that suppress pain transmission in the spinal cord.
Enkephalins and endorphins.
How do enkephalins and endorphins affect pain and when does their production increase?
They diminish but do not eliminate pain; production increases during stress, exercise, and acupuncture.
What is a preganglionic fiber in the autonomic nervous system?
What is a postganglionic fiber in the autonomic nervous system?
Define a ganglion in the peripheral nervous system.
What receptor type mediates transmission at all autonomic ganglia?
Which receptor type mediates parasympathetic effects at target organs?
What receptors mediate sympathetic target organ responses?
What does 'dual innervation' mean?
What is tonic regulation in autonomic control?
State the key distinction between 'automatic' and 'autonomic'.
What is the high-yield rule about the number of neurons in autonomic efferent pathways?
List the main structural and neurotransmitter differences between sympathetic and parasympathetic pathways.
Are sympathetic and parasympathetic actions always stimulatory or inhibitory?
What is 'dual innervation' in autonomic control?
Both sympathetic and parasympathetic divisions innervate an organ and produce opposing effects; the outcome is a balance between them.
Give an example of dual innervation in the bronchioles.
Sympathetic stimulation dilates bronchioles; parasympathetic stimulation constricts bronchioles.
How does dual innervation affect GI motility?
Parasympathetic activity increases GI motility while sympathetic activity decreases it.
What is 'tonic regulation' in autonomic control?
Only one autonomic division innervates the target and regulation occurs by varying a constant background activity.
Provide an example of tonic regulation involving vascular smooth muscle.
Vascular smooth muscle is innervated only by sympathetic fibers: baseline sympathetic tone causes vasoconstriction; ↑ activity causes more constriction; ↓ activity causes vasodilation.
How is resting heart rate regulated by autonomic tone?
Parasympathetic tone is dominant at rest; high vagal tone keeps heart rate low and increases in heart rate occur mainly by parasympathetic withdrawal.
Name one exception where ATP functions in autonomic neurotransmission.
ATP can act as a sympathetic neurotransmitter by binding receptors (not for energy transfer).
What is an exception to the usual parasympathetic neurotransmitter?
Some parasympathetic fibers release nitric oxide instead of acetylcholine.
What are autoreceptors in autonomic neurons?
Norepinephrine and acetylcholine can bind to the releasing neuron to modulate their own activity via autoreceptors.
How does the adrenal medulla differ from the typical postganglionic sympathetic pathway?
Preganglionic sympathetic fibers release acetylcholine onto chromaffin cells, which secrete epinephrine into the blood, effectively replacing the postganglionic neuron.
Why can nicotine produce both GI stimulation and mild bronchodilation?
Nicotine activates nicotinic receptors at both sympathetic and parasympathetic ganglia, producing simultaneous parasympathetic and sympathetic effects.
What is a photoreceptor in the retina?
A light-sensitive cell in the retina (rod or cone) that transduces light into an electrical signal.
What is the fovea?
The central retinal pit containing only cones and representing the highest acuity point.
What is the macula?
The area around the fovea with high cone density and some rods.
Define accommodation of the eye.
The process of changing lens shape to focus on near versus far objects.
What is meant by transduction in vision?
Converting one energy form to another, specifically light into an electrical signal.
What role does cyclic GMP (cGMP) play in photoreceptors in the dark?
cGMP is a second messenger that keeps Na⁺ channels open in photoreceptors in the dark.
Describe the main light path through the eye and which structure does most refraction.
Light passes through cornea → pupil → lens → focuses on retina (image inverted). The cornea is responsible for most light refraction; the lens fine-tunes focus.
What are the actions and autonomic controls of the circular (sphincter) iris muscle?
It constricts the pupil (miosis) and is controlled by the parasympathetic system; tropicamide (a cholinergic antagonist) blocks it leading to dilation.
What are the actions and autonomic controls of the radial (dilator) iris muscle?
It dilates the pupil (mydriasis) and is controlled by the sympathetic system; phenylephrine (an α-adrenergic agonist) activates it causing dilation.
What is the clinical rationale for combining tropicamide and phenylephrine in dilation drops?
Tropicamide relaxes the circular muscle by blocking parasympathetic input, while phenylephrine contracts the radial muscle by mimicking sympathetic input, together producing pupil dilation.
What does the pupillary light reflex assess?
It assesses brainstem and occipital cortex function.
How do ciliary muscle states affect lens shape for near versus distance vision?
Contracted ciliary muscles produce a round lens for near vision; relaxed ciliary muscles produce a flat lens for distance vision.
Compare rods and cones in light sensitivity and color.
Rods are extremely sensitive and function in dim light, providing grayscale only; cones require higher intensity light and provide color vision with red, green, and blue subtypes.
Where are rods predominantly located in the retina?
Where are cones concentrated in the retina?
What is the typical wiring ratio of many rods to bipolar cells and its consequence?
What is the typical wiring relationship of cones to bipolar cells and its consequence?
Explain rod bleaching and dark adaptation time
Why can dim stars vanish when looked at directly?
In darkness, what is the cGMP level and photoreceptor membrane state?
In light, what happens to cGMP, Na+ channels, and photoreceptor state?
What is the key enzyme cascade in phototransduction after retinal activation?
Describe the main visual signal pathway to cortex
How do lateral and medial visual fields project across hemispheres?
What is the basis of depth perception described in the notes?
What visual condition causes central vision loss due to macula damage?
What causes a cataract and how is it treated?
What does LASIK do to correct vision?
What are the three middle ear bones and their primary function?
What structure seals the cochlea and receives vibrations from the stapes?
How do hair cells transduce mechanical bending into neurotransmitter release?
What happens when hair cell stereocilia bend in the opposite direction?
What is tonic activity in hair cells?
How does tonic activity help auditory encoding?
Describe the transmission pathway of sound from air to hair cells.
How is pitch encoded along the basilar membrane?
According to the text, what determines perceived pitch?
How is loudness encoded in the auditory system?
What is the clinical significance of fluid in the middle ear?
What is the function of the Eustachian tube related to hearing?
What is conduction deafness?
Hearing loss caused by a mechanical defect before the hair cells (e.g., eardrum, ossicles, fluid).
What are common causes of conduction deafness?
What treatments improve conduction deafness prognosis?
What is neural (sensorineural) deafness?
Hearing loss due to damage at or beyond the hair cells, affecting the neural pathway.
How does repair potential compare for sensorineural versus conduction deafness?
Sensorineural deafness is more difficult to repair than conduction deafness.
Which frequencies does age-related hearing loss (presbycusis) primarily affect?
High frequencies.
Which part of hearing is preferentially damaged by loud noise?
High-frequency regions are preferentially damaged by loud noise.
What is the vestibular system?
Inner ear structures detecting head position and movement; shares CN VIII with cochlea
What do the utricle and saccule detect?
Head tilt (position) and linear acceleration/deceleration
How do the utricle and saccule transduce linear acceleration or tilt?
Gravity/inertia shifts otolith mass, bending embedded hair cells in the cupula
What do the semicircular canals detect?
Rotational movement in three-dimensional axes (x, y, z)
What is the transduction mechanism for the semicircular canals?
Head rotation moves bone before fluid; lagging endolymph bends hair cells causing signal
What is the cupula in vestibular organs?
A gelatinous mass containing embedded hair cells in vestibular organs
What is nystagmus?
Involuntary, abnormal eye movements caused by disrupted vestibular input
Which cranial nerve carries vestibular signals?
The vestibular branch of CN VIII (vestibulocochlear nerve)
What clinical test assesses utricle and saccule function?
Head tilt test
How does sensory integration produce dizziness after conflicting inputs?
The brain coordinates vestibular, visual, and proprioceptive inputs; conflict (e.g., spinning then stopping) causes nystagmus and dizziness
What common causes of vestibular disorders are mentioned?
Infections or fluid imbalance causing conflicting sensory information and dizziness
What is a chemoreceptor?
A receptor activated by specific chemicals binding to it.
Which receptor type mediates sweet, bitter, and umami tastes?
G protein-coupled receptors (GPCRs) using intracellular signaling cascades.
How is salty taste transduced at the receptor level?
Direct Na+ entry through ion channels; Na+ is most effective, K+ less so.
How is sour taste detected by receptors?
Direct stimulation of ion channels by H+ (protons) caused by acidity.
What characterizes bitter taste receptors and their significance?
Many GPCR receptor types; evolutionarily linked to avoiding toxic alkaloids.
What does the umami taste receptor respond to?
GPCRs that respond to amino acids, especially glutamate (MSG).
Are taste receptors localized to specific tongue regions?
No; taste receptors are scattered across the tongue and the 'tongue map' is oversimplified.
Describe the main olfactory pathway from epithelium to brain.
Chemoreceptive cilia in olfactory epithelium → olfactory bulb via mitral cells and glomeruli.
How many distinct odors can humans detect and how does receptor count compare to dogs?
Humans detect 100,000+ distinct odors from ~hundreds of receptor types; dogs have over 10,000 receptor types.
Why is smell strongly linked to memory and emotion?
A large portion of olfactory input projects to the limbic system, linking smell with memory and emotion.
What is the vomeronasal organ and what does it detect?
A specialized organ in sinuses that detects pheromones affecting physiology and behavior subconsciously.
Does the vomeronasal organ produce conscious smell perception?
No; it does not produce conscious smell perception but affects mood and attraction subconsciously.
What can cause olfactory hallucinations and why are they clinically useful?
Mental illness or lesions causing inappropriate neuronal stimulation; they have diagnostic utility.
What commonly causes taste or smell loss such as after COVID infection?
Interference with neural transmission rather than direct receptor cell death.
How does receptor density for taste change across individuals and age?
Receptor density changes with age and varies between individuals, which may explain childhood taste aversions.
What is the primary function of the gastrointestinal (GI) system?
Transfer nutrients, water, and electrolytes from food into the body's internal environment.
What are the four major processes of the GI system?
Define peristalsis in the GI tract.
Sequential contraction of circular muscle behind a bolus plus longitudinal shortening ahead, propelling contents forward.
What is segmentation and where is it the main motility during meals?
Alternating contractions that mix contents without net propulsion; main small intestine motility during meals.
What are slow waves in GI smooth muscle and what generates them?
Regular depolarization/repolarization cycles in smooth muscle, generated by interstitial cells of Cajal (ICC).
When do smooth muscle contractions occur relative to slow waves?
Contraction occurs only when slow waves reach threshold; additional depolarization increases the number of action potentials.
How is a 'sphincter' defined in the GI context?
A ring of circular smooth muscle regulating passage between GI regions (more accurate term than 'valve').
What is the migrating motor complex (MMC)?
Strong interdigestive peristaltic sweeps that occur between meals.
What composes the enteric nervous system and its capability?
Intrinsic nerve plexuses (myenteric and submucosal) that can function independently of the CNS.
What three systems make up the Regulatory Triad controlling GI function?
What types of receptor feedback inform GI regulation?
List the GI wall layers from outside to inside.
What is the mesentery and one of its functions?
Connective tissue sheets with blood vessels that attach GI structures to the peritoneal wall, preventing bowel telescoping and knotting.
What are the main roles of the mouth in digestion?
How does swallowing transition from voluntary to involuntary control?
Swallowing is voluntary in the mouth/pharynx then becomes involuntary at the pharynx; the epiglottis closes the airway and the UES & LES regulate entry/exit.
Which neural center controls involuntary phases of swallowing?
The brain stem controls involuntary aspects of swallowing.
Describe the main mixing functions of the stomach.
Stomach mixes food via peristaltic waves + churning, exhibits receptive relaxation before food arrives, and the pyloric sphincter meters chyme into the duodenum.
What phases regulate stomach activity and their primary triggers?
What effects occur during the gastric phase of stomach regulation?
During the gastric phase there is ↑ acid, ↑ pepsinogen, ↑ motility, and gastrin release from G cells.
How does the intestinal phase affect gastric emptying?
The intestinal phase slows gastric emptying and decreases acid while releasing CCK & secretin.
What are the two main motor patterns of the small intestine and when do they occur?
What are the primary motor patterns of the large intestine and their functions?
Outline the neural control and sequence leading to defecation.
Rectal distension activates sensory afferents → internal anal sphincter relaxes (involuntary) → urge to defecate; the external anal sphincter remains under voluntary control.
What commonly causes constipation according to the notes?
Constipation often results from excessive water removal in the colon (dehydration).
What is a parietal cell and what does it secrete?
What is a chief cell and what does it secrete?
Write the chemical sequence used by parietal cells to generate acid.
\(CO_2 + H_2O \rightarrow \text{carbonic acid (via carbonic anhydrase)} \rightarrow H^+ + HCO_3^-\); H^+ is pumped by H+/K+-ATPase into the lumen
What is the 'alkaline tide' after meals?
How does chloride contribute to gastric acid formation?
How does the gastric mucus layer protect the epithelium?
How do NSAIDs increase risk of acid-induced ulceration?
How does H. pylori increase gastric acid secretion?
What is a micelle and what is its role in digestion?
What are brush border enzymes and their function?
What is a chylomicron and its role after fat absorption?
Which stimuli activate parietal cells according to the table?
Which stimuli activate chief cells according to the table?
What do G cells secrete and what stimulates them?
What do D cells secrete and what stimulates them?
What is the primary function of goblet cells in the GI tract?
What cells produce gastrin and what stimuli increase its release?
What are the main effects of gastrin on gastric cells?
Which hormone is released by I cells and what triggers its release?
List the main actions of CCK on the digestive system.
Which hormone do S cells release and what stimulates it?
What are the primary effects of secretin on the pancreas and stomach?
What triggers somatostatin release and what does it inhibit?
What do pancreatic acinar and duct cells produce?
Which hormones drive pancreatic bicarbonate and enzyme release?
What are the main functions of bile and the gallbladder?
How are glucose and galactose absorbed across the apical membrane?
How is fructose absorbed by enterocytes?
How are single amino acids transported into enterocytes?
How are dipeptides and tripeptides absorbed and processed intracellularly?
In what form are fats absorbed and how are they transported after re-esterification?
How is intestinal surface area maximized and how often is the lining replaced?
Where do brush border enzymes perform final digestion of disaccharides and peptides?
How does loss of intestinal surface area (eg, flattened villi) affect nutrient absorption?
What is the mechanism by which lactase deficiency causes diarrhea?
What is the primary effect of orlistat on digestion and vitamins?
How do GLP-1 agonists affect appetite, gastric emptying, and fat absorption?
What does the hepatic portal vein deliver to the liver first?
What feature of hepatic sinusoidal capillaries enables exchange with hepatocytes?
How is bilirubin handled by the liver?
What is the liver's role in cholesterol balance compared with dietary intake?
How does the sympathetic nervous system affect heart rate?
Increases heart rate (but primarily controlled by parasympathetic withdrawal).
How does the parasympathetic nervous system affect heart rate at rest?
Decreases heart rate (dominant at rest due to vagal tone).
Which autonomic division primarily increases cardiac contractility?
The sympathetic division primarily increases contractility.
What effect do sympathetic and parasympathetic systems have on bronchioles?
Sympathetic: dilation. Parasympathetic: constriction.
Compare sympathetic and parasympathetic effects on GI motility.
Sympathetic: decreases GI motility. Parasympathetic: increases GI motility.
How do sympathetic and parasympathetic systems affect pupil size and which muscles are involved?
Sympathetic: dilation (radial muscle). Parasympathetic: constriction (circular muscle).
What is the sympathetic effect on most blood vessels?
Sympathetic constriction (tonic — only sympathetic control of vessels).
Describe the difference in salivation between sympathetic and parasympathetic activation.
Sympathetic: thick, viscous saliva. Parasympathetic: watery, copious saliva.
How do autonomic divisions control the bladder during filling and voiding?
Sympathetic: relaxation for filling. Parasympathetic: contraction for voiding.
What stimuli activate free nerve endings and what is a key fact about them?
Detect pain, temperature, crude touch; adaptation varies; they are the most widespread receptor.
What do Merkel's disks detect and how do they adapt?
Detect light sustained touch; adapt slowly (tonic) for continuous pressure monitoring.
What stimuli do Meissner's corpuscles detect and what is their adaptation type?
Detect light touch and texture; adapt rapidly (phasic) and are abundant in fingertips.
What do Pacinian receptors detect and how do they adapt?
Detect vibration and deep pressure; adapt rapidly (phasic) and detect changes only.
What stimuli do Ruffini endings detect and how do they adapt?
Detect deep pressure and stretch; adapt slowly (tonic) for sustained deformation.
What triggers gastrin release and what is its primary action?
Triggered by peptides and stomach distension; increases acid and pepsinogen secretion.
What triggers CCK release and what are its main actions?
Triggered by fat and protein; increases pancreatic enzymes, causes gallbladder contraction, and decreases gastric emptying.
What triggers secretin release and what is its primary action?
Triggered by acid in the duodenum; increases pancreatic HCO₃⁻ and decreases acid.
What is the primary effect of somatostatin released from D cells in low pH?
Inhibits gastrin, gastric acid, and digestive enzyme secretion (acts as a systemic brake).
In dim light, which photoreceptor type is most sensitive?
Rods are highly sensitive in dim light.
Which photoreceptor type mediates color vision and which colors are indicated?
Cones mediate color vision: red, green, and blue.
Compare acuity and wiring between rods and cones.
Where are rods and cones primarily located on the retina?
Which deep brain structure acts as a sensory relay and active filter?
Thalamus functions as a sensory relay and active filter.
What role and key neurotransmitter are associated with the basal nuclei?
Basal nuclei inhibit unwanted movements and use dopamine as a key neurotransmitter.
What are the main functions of the hypothalamus?
Autonomic and endocrine master control of temperature, hunger, and thirst.
Contrast A-delta fibers and C fibers in pain transmission.
Mathematical/chemical summary: - \(\(\mathrm{CO_2 + H_2O \xrightarrow{CA} H_2CO_3 \leftrightarrow H^+ + HCO_3^-}\)\) (used later in parietal cells section).
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