Flashcards in this deck (87)

• What are two primary functions of the spinal cord and its attached spinal nerves?

  • Pathway for sensory and motor impulses
  • Responsible for reflexes (quickest reactions to a stimulus)
  functions spinalcord
• What is the typical length of an adult spinal cord?

  • Between 42 and 45 centimeters (16 to 18 inches)
  measurement spinalcord
• How is the spinal cord shaped in cross section and what longitudinal surface depressions are present?

  • Roughly cylindrical, slightly flattened posteriorly and anteriorly
  • Posterior (dorsal) median sulcus
  • Anterior (ventral) median fissure
  structure anatomy
• Name the five regional divisions of the spinal cord.

  • Cervical
  • Thoracic
  • Lumbar
  • Sacral
  • Coccygeal
  regions spinalcord
• What is true about the cervical region of the spinal cord?

  • It is continuous with the medulla oblongata and contains neurons whose axons form the cervical spinal nerves
  cervical anatomy
• What is notable about the coccygeal region of the spinal cord?

  • It is the most inferior tip of the spinal cord and gives rise to one pair of coccygeal spinal nerves
  coccygeal anatomy
• Why does the diameter of the spinal cord change along its length?

  • Because the amount of gray matter and white matter and the function of the cord vary in different regions
  structure variation
• Where is the cervical enlargement of the spinal cord located and what does it innervate?

  • Located in the inferior cervical part of the spinal cord
  • Innervates the upper limbs
  spinalcord enlargement
• Where does the lumbosacral enlargement extend and what does it innervate?

  • Extends through the lumbar and sacral parts of the spinal cord
  • Innervates the lower limbs
  spinalcord enlargement
• Between which vertebral levels does the spinal cord typically end?

  • The spinal cord ends between L1 and L2
  spinalcord anatomy
• What is the conus medullaris?

  • The tapering inferior end of the spinal cord and the official end of the spinal cord proper, usually at the level of the first lumbar vertebra
  spinalcord conusmedullaris
• What is the cauda equina and why do the nerve roots elongate after age 4?

  • Cauda equina: nerve roots that project inferiorly from the spinal cord
  • Roots elongate because the vertebral column continues to elongate after age 4 while the spinal cord does not
  caudaequina development
• What is the filum terminale and its function?

  • A thin strand of pia mater within the cauda equina that helps anchor the conus medullaris to the coccyx
  filumterminale spinalcord
• How many pairs of spinal nerves are associated with the spinal cord and how are they distributed by region?

  • 31 pairs total:
  • 8 cervical (C1-C8)
  • 12 thoracic (T1-T12)
  • 5 lumbar (L1-L5)
  • 5 sacral (S1-S5)
  • 1 coccygeal (Co)
  spinalnerves numbers
• List the spinal meninges and spaces from outermost to innermost.

  • Vertebra
  • Epidural space
  • Dura mater
  • Subdural space
  • Arachnoid
  • Subarachnoid space
  • Pia mater
  meninges layers
• Do spaces between the spinal meninges have clinical significance?

  • Yes, some of the spaces between the meninges have clinical significance
  meninges clinical
• Where is the epidural space located and what does it contain?

  • Lies between the dura mater and periosteum covering the inner walls of the vertebra
  • Contains areolar connective tissue, blood vessels, and adipose connective tissue
  meninges epidural
• What is an epidural block used for?

  • Injection of anesthetic into the epidural space used to control pain
  clinical epidural
• Name key features of the dura mater in the spinal cord.

  • Most external meningeal layer
  • Fuses with connective layers surrounding spinal nerves
  • Separated from arachnoid by a narrow, potential subdural space
  meninges dura
• What is the arachnoid mater's location and role?

  • Lies deep to the dura mater and the subdural space
  • Is the middle meningeal layer
  meninges arachnoid
• What characterizes the subarachnoid space and a related clinical procedure?

  • A real space filled with cerebral spinal fluid (CSF)
  • Spinal tap withdraws CSF for diagnostic purposes
  meninges clinical
• What are the main features of the pia mater?

  • Innermost meningeal layer that adheres directly to the spinal cord
  • Delicate, composed of elastic and collagen fibers and supports blood vessels
  • Has denticulate ligaments that suspend and anchor the cord laterally to the dura mater
  meninges pia
• What are the main components of spinal cord gray matter?

  • Contains dendrites and cell bodies of neurons
  • Contains unmyelinated axons and glial cells
  spinalcord graymatter
• What composes the white matter of the spinal cord?

  • Contains myelinated axons
  spinalcord whitematter
• How is white matter organized on each side of the spinal cord?

  • Posterior funiculus between posterior gray horns and posterior median sulcus
  • Lateral funiculus on each lateral side
  • Anterior funiculus between anterior gray horns and anterior median fissure
  • Anterior funiculi interconnected by the white commissure
  • Funiculus = white column; composed of tracts
  spinalcord whitematter funiculus
• What is the shape and central location of gray matter in the spinal cord?

  The gray matter is centrally located in the spinal cord and its sectioned shape resembles a letter H or a butterfly.
  spinal structure
• What do the anterior horns of spinal cord gray matter contain and innervate?

  They house the cell bodies of somatic motor neurons which innervate skeletal muscle.
  anterior motor
• Where are lateral horns found and what do they contain?

  Lateral horns are found in the T1-L2 parts of the spinal cord and contain cell bodies of autonomic motor neurons that innervate cardiac muscle, smooth muscle, and glands.
  lateral autonomic
• What do the posterior horns of the spinal cord gray matter contain?

  They contain axons of sensory neurons and cell bodies of interneurons.
  posterior sensory
• What is the gray commissure and what does it contain?

  The gray commissure contains unmyelinated axons, serves as a communication route between right and left sides, and houses a narrow central canal that contains cerebrospinal fluid (CSF).
  commissure csf
• What functional groups of neuron cell bodies are found in spinal gray matter and where?

  • Sensory nuclei: posterior horns (interneuron cell bodies of somatic and visceral sensory nuclei)
  • Motor nuclei: anterior horns (somatic motor nuclei)
  • Autonomic motor nuclei: lateral horns
  nuclei functional
• How many pairs of spinal nerves are there and what do they connect?

  There are 31 pairs of spinal nerves that connect the central nervous system to muscles, glands, and receptors.
  spinal nerves
• How is each spinal nerve formed and why are spinal nerves called mixed nerves?

  Each spinal nerve is formed by the union of an anterior root and a posterior root within the intervertebral foramen; spinal nerves contain both motor axons and sensory axons, so they are mixed nerves.
  formation mixed
• How are spinal nerves numbered in the cervical region regarding exit relative to vertebrae?

  In the cervical region, the first seven pairs (C1-C7) exit above the vertebra of the same number, and the eighth pair (C8) exits above the first thoracic vertebra.
  numbering cervical
• Where do the remaining pairs of spinal nerves exit relative to the vertebra of the same number?

  They exit below the vertebra of the same number.
  spinal anatomy
• Why do the lumbar and sacral nerve roots travel inferiorly before exiting?

  Because the spinal cord is shorter than the vertebral canal, their roots travel inferiorly to reach their intervertebral foramen.
  spinal roots
• What are the main branches a typical spinal nerve splits into after leaving the intervertebral foramen?

  It splits into rami, primarily the posterior ramus and the anterior ramus.
  spinal rami
• What does the posterior ramus innervate?

  The posterior ramus innervates the deep muscles of the back and the skin of the back.
  posterior innervation
• What does the anterior ramus innervate and what does it do next?

  The anterior ramus innervates the anterior and lateral trunk and the limbs, and it splits into multiple other branches.
  anterior innervation
• What are rami communicantes?

  Rami communicantes are additional rami that extend between the spinal nerve and a sympathetic trunk ganglion.
  rami sympathetic
• Define a dermatome.

  A dermatome is a specific segment of skin supplied by a single spinal nerve.
  dermatome sensory
• Which spinal nerve does not innervate a dermatome?

  C1 does not innervate a segment of skin.
  dermatome c1
• How can dermatome anesthesia be clinically important?

  Anesthesia in one or more dermatome segments could indicate potential spinal nerve damage.
  clinical dermatome
• Give an example of referred visceral pain involving a dermatome.

  Appendicitis can refer pain to the T10 dermatome area in the umbilicus region because the appendix is innervated by axons from T10.
  referred dermatome
• What is a nerve plexus?

  A nerve plexus is a network of interweaving anterior rami of spinal nerves that forms a complex interwoven network of fibers of adjacent spinal nerves.
  plexus network
• What happens to nerves arising from a plexus?

  Nerves arising at a plexus are mixed nerves that split into multiple named nerves to innervate body structures.
  plexus nerves
• What are the principal nerve plexuses named in the notes?

  • Cervical plexuses
  • Brachial plexuses
  • Lumbar plexuses
  • Sacral plexuses
  plexuses list
• What spinal nerve roots form the intercostal nerves?

  • Anterior rami of spinal nerves T1–T11
  intercostal spinal
• Where do intercostal nerves travel anatomically?

  • In the intercostal space sandwiched between two adjacent ribs
  intercostal anatomy
• Do intercostal nerves form plexuses?

  • No; they do not form nerve plexuses except T1
  intercostal plexus
• What is the subcostal nerve and where does it arise?

  • T12 called the subcostal nerve — arises below the ribs
  intercostal subcostal
• Which spinal nerves form the cervical plexus and what does it innervate?

  • C1–C4; innervates neck, thoracic cavity, and diaphragm
  cervical plexus
• Which nerve from the cervical plexus supplies the diaphragm?

  • Phrenic nerve
  phrenic diaphragm
• Which spinal nerves form the brachial plexus and what regions do they innervate?

  • C5–T1; innervates shoulder/pectoral girdle and upper limbs
  brachial plexus
• Which nerves branch from the brachial plexus to supply lateral and medial forearm muscles?

  • Radial nerve supplies lateral forearm muscles; ulnar nerve supplies medial forearm muscles
  brachial nerves
• Which spinal nerves form the lumbar plexus and what does it innervate?

  • L1–L5; innervates pelvic girdle and lower limbs
  lumbar plexus
• Which nerve branches from the lumbar plexus to supply anterior thigh muscles?

  • Femoral nerve
  lumbar femoral
• Which spinal nerves form the sacral plexus and what does it innervate?

  • L4–S4; innervates pelvic girdle and lower limbs
  sacral plexus
• Which nerve branches from the sacral plexus to supply posterior thigh and leg muscles?

  • Sciatic nerve
  sacral sciatic
• What is a reflex?

  • A rapid, automatic, involuntary reaction of muscles or glands to a stimulus
  reflex definition
• What key property of reflexes ensures a rapid response?

  • Few neurons involved and minimal synaptic delay
  reflex properties
• When does awareness of the stimulus occur relative to the reflex action?

  • After the reflex action has been completed
  reflex timing
• List the core characteristics of a reflex.

  • Requires a specific stimulus (sensory input)
  • Involuntary/automatic
  • Rapid
  • Stereotyped
  reflex characteristics
• What is the basic meaning of a neural reflex regarding motor response?

  • One neural reflex produces one motor response
  reflexes
• What is a reflex arc?

  • A reflex arc is the neural wiring of a single reflex
  • It begins at a receptor in the PNS, communicates with the CNS, and ends at a peripheral effector
  reflex_arc
• What defines an ipsilateral reflex arc?

  • Both the receptor and effector organs are on the same side of the spinal cord
  • Example: left arm muscles pull left hand away from a hot object
  ipsilateral
• What defines a contralateral reflex arc?

  • Sensory impulses cross the spinal cord to activate effector organs in the opposite limb
  • Example: step on sharp object with left foot and contract right leg muscles to maintain balance
  contralateral
• How do monosynaptic and polysynaptic reflexes differ?

  • Monosynaptic: sensory axons synapse directly on motor neurons
  • Polysynaptic: pathways with multiple synapses involving interneurons
  mono_vs_poly
• What are key features of monosynaptic reflexes?

  • Simplest reflexes with no interneurons
  • Example: patellar (knee-jerk) reflex; tapping patellar ligament stretches quadriceps muscle spindles and produces leg kick
  monosynaptic
• What are key features of polysynaptic reflexes and the withdrawal reflex?

  • Polysynaptic reflexes have interneurons and more synapses, causing a more prolonged delay
  • Withdrawal (flexor) reflex: painful stimulus -> sensory info to spinal cord -> interneurons stimulate motor neurons to contract flexor muscles
  polysynaptic flexor
• What is the primary outcome of the withdrawal (flexor) reflex?

  Quick contraction of flexor muscles causing withdrawal of a limb from an injurious stimulus, e.g., pulling a hand away from a hot stove.
  reflex withdrawal
• What mechanism ensures antagonistic extensor muscles do not oppose the withdrawal reflex?

  Reciprocal inhibition: interneurons in the spinal cord inhibit the stretch reflex of antagonistic (extensor) muscles so the flexor reflex can work.
  reciprocal inhibition
• What is the function of the crossed extensor reflex during a flexor reflex?

  It straightens the opposite limb to support body weight while the injured limb is withdrawn.
  crossed reflex
• What type of reflex is the stretch reflex and what does it regulate?

  Monosynaptic reflex that monitors and regulates skeletal muscle length.
  stretch monosynaptic
• What receptor monitors stretch in a muscle?

  The muscle spindle monitors stretching of a muscle.
  muscle spindle
• Provide an example of a stretch reflex and its action.

  The patellar (knee-jerk) reflex: tap on patellar tendon causes contraction of quadriceps femoris and extension of the knee joint.
  patellar example
• What is the role of the Golgi tendon reflex?

  Prevents skeletal muscles from tensing excessively by allowing the associated muscle to relax when Golgi tendon organs activate interneurons that inhibit motor neurons.
  golgi tendon
• Where are Golgi tendon organs located and when are they activated?

  Nerve endings located within tendons near a muscle-tendon junction; activated by increased tension in the tendon as the muscle contracts.
  location activation
• How are reflexes used clinically?

  Reflexes test specific muscle groups and spinal cord segments; abnormal responses may indicate nervous system or muscle damage; responses can be normal, hypoactive, or hyperactive.
  clinical testing
• From what embryonic structure does the central nervous system form?

  The central nervous system forms from the embryonic neural tube.
  development embryology
• From which embryonic cells do cranial and spinal nerves form?

  Cranial and spinal nerves form from neural crest cells that split off from the developing neural tube.
  development neural_crest
• What does the cranial (superior) part of the neural tube develop into?

  The cranial (superior) part of the neural tube expands and develops into the brain.
  development neuroanatomy
• What does the caudal (inferior) part of the neural tube form?

  The caudal (inferior) part of the neural tube forms the spinal cord.
  development neuroanatomy
• What is a common result of physical trauma to the spinal cord?

  Physical trauma to the spinal cord commonly results in paralysis.
  clinical spinal_cord
• Define paraplegia as related to spinal cord injury.

  Paraplegia is loss of motor control of the lower limbs following damage to the thoracic spinal cord.
  clinical paraplegia
• Define quadriplegia and its usual spinal level cause.

  Quadriplegia is lack of sensation and motor control of upper and lower limbs due to extensive damage at or superior to the 5th cervical vertebra.
  clinical quadriplegia
• What is hemiplegia and its usual cause?

  Hemiplegia is paralysis of the upper and lower limbs on one side of the body, usually due to a stroke (brain injury).
  clinical hemiplegia