Bio 209 Ch. 13

  1. Describe the function of the spinal cord
    • (1) Pathway for sensory info – axons of sensory neurons enter spinal cord and travel through spinal cord to brain
    • (2) Pathway for motor info – axons of motor neurons travel from brain through the spinal cord; when axons of motor neurons exit spinal cord, they travel to effectors
  2. Vertebral Column
    rigid structure that protects the spinal cord; spinal cord located within vertebral canal (vertebral canal formed by vertebral foramina; vertebral foramen is the opening in the middle of vertebra)
  3. Meninges (dura mater, arachnoid mater, and pia mater)
    Dura Mater: outer, tough layer of meninges

    Arachnoid: middle layer of meninges

    Pia Mater: inner layer of meninges (denticulate ligaments: lateral extensions of pia mater – help hold spinal cord in place)
  4. Cerebral spinal fluid in subarachnoid space as structure that protects spinal cord
    acts as a shock absorber
  5. Adipose tissue in epidural space as structure that protects spinal cord
    located between wall of vertebral column and dura mater; contains adipose and connective tissue that cushion the spinal cord
  6. Epidural
    injection of anesthetic into the epidural space
  7. Meningitis
    inflammation of the meninges caused by an infection
  8. Spinal Tap
    insertion of a needle into the subarachnoid space to collect CSF for a diagnostic
  9. Where the spinal cord begins and ends
    • Begins: base of the Medulla Oblongata where the spinal cord passes thru the Foramen Magnum à Extends to the superior border of the second lumbar vertebra
    • - In infants, the spinal cord extends to the third/fourth lumbar vertebra. Difference due to growth, until it ends at the age of 4-5 years
  10. Cervical Enlargement
    located within cervical region of vertebral column; enlarged due to sensory & motor neuron axons that serve the upper limbs enter and leave the spinal cord from here; these axons form the nerves that serve the upper limbs
  11. Lumbar Enlargement
    located within lower thoracic region of vertebral column; enlarged due to sensory & motor neurons that serve the lower limbs and enter and leave the spinal cord from here; these axons form the nerves that serve the lower limbs
  12. Conus Medullaris
    tapering end of spinal cord that is inferior to lumbar enlargement; located at level of intervertebral disc between L1 & L2
  13. Filum Terminale
    pia mater that extends from conus medullaris; anchors spinal cord to coccyx
  14. Cauda Equina
    spinal cord ends between L1 & L2; lumbar sacral and coccygeal spinal nerves exit vertebral column inferio to the conus medullaris; bundles of axons that form the lumbar, sacral and coccygeal spinal nerves exit spinal cord and hang inferiorly to conus medullaris (looks like a “horse’s tail” hence cauda = tail equine = horse)
  15. Spinal Nerves
    bundles of sensory and motor axons; 31 pairs (each pair is named for the spinal segment from which it arises)
  16. Posterior (Dorsal) Root
    contain only axons of sensory neurons
  17. Anterior (Dorsal) Root
    contain only axons of motor neurons
  18. Dorsal Root Ganglion
    swelling in posterior root that contains sensory neuron cell bodies
  19. Compare the function of the posterior root and the anterior root.
    Posterior Root: carries nerve impulses to the spinal cord FROM sensory receptors

    Anterior Root: carries nerve impulses from the spinal cord TO the effectors
  20. Anterior Median Fissure
    wide groove on anterior (ventral) surface of spinal cord
  21. Posterior Median Sulcus
    narrow groove on posterior (dorsal) surface of spinal cord
  22. Gray Commissure
    crossbar of letter “H”
  23. Central Canal
    space in middle of spinal cord that is filled with CSF
  24. Anterior White Commissure
    anterior TO gray commisure; connects white matter of right and left sides of spinal cord
  25. Anterior Gray Horns
    contain clusters of somatic motor neuron cell bodies (nuclei)
  26. Lateral Gray Horns
    contain clusters of autonomic motor nuclei and are only found in the thoracic and upper lumbar segments of spinal cord
  27. Compare the function of the anterior gray horn, the lateral gray horn, and the posterior gray horn.
    Anterior: initiates nerve impulses that control skeletal muscle

    Lateral: initiates nerve impulses that control cardiac & smooth muscles, and glands

  28. Identify the spinal cord structure destroyed by the polio virus
    The Anterior Horn of the Spinal Cord is affected by the Polio Virus
  29. State the cause of shingles, the location of the dormant virus, and why blisters are located in a specific area
    Cause: Chicken Pox Virus

    Located: Posterior Dorsal Root Ganglion

    Blisters located along sensory nerve belonging to the infected dorsal root ganglion
  30. Compare the function of ascending tracts and motor tracts
    • Sensory (Ascending) Tracts: TO the brain
    • Motor (Descending) Tracts: FROM the brain
  31. Describe how spinal cord transection affects sensory and motor function
    (1) Sensory and Motor Tracts are severed

    (2) Loss of Sensory Input and Motor Output of spinal nerves that emerge inferior to the transaction à loss of sensation and loss of motor function (paralysis)
  32. Describe how spinal nerves are formed
    Anterior and Posterior Roots at each Spinal Cord Segment combine to form spinal nerve (all spinal nerves mixed nerves contain sensory & motor info)
  33. 31 Pairs of Spinal Nerves
    • - 8 Cervical
    • - 12 Thoracic
    • - 5 pairs of Lumbar
    • - 5 pairs of Sacral
    • - 1 pair of Coccygeal
  34. Endonerium
    connective tissue that surrounds each axon within a nerve; can be found surrounding both myelinated & unmyelinated axons
  35. Fascicle
    bundles of axons with their endoneurium
  36. Perneurium
    connective tissue that surrounds fascicles
  37. Epineurium
    outermost connective tissue covering of nerve
  38. Rami
    branch of spinal nerves after passing thru intervertebral foramen
  39. Plexus
    network of axons; axons from anterior rami of spinal nerves (except thoracic nerves T1-T12) form plexuses on right and left side of body
  40. Name the important nerves that arise from the cervical, brachial, lumbar and cervical plexuses and state what each of these nerves innervates.
    Cervical: C1-C5; innervates skin and muscles of head, neck, shoulder; Phrenic Nerve is most important (supplies diaphragm)

    Brachial: C5-C8 & T1; innervates muscles and skin of upper limbs; Major nerves it innervates = Axillary (deltoid and teres minor), Musculocutaneous (muscle on anterior arm), Median (muscles on anterior forearm and hand, Radial (muscles on posterior arm and forearm), Ulnar (muscles on medial forearm and hand)

    Lumbar: L1-L4; innervates skind and muscles of abdomen, pelvis, partial lower limbs; Major nerves it innervates = Femoral (flexor muscles of thigh and extensor muscles of legs), Obturator (adductor muscles)

    • Sacral: L4-L5 & S1-S4; innervates skin and muscles of butt, perineum, lower limbs; Major nerves it innervates = Pudendal (muscles of perineum), Sciatic (two nerves tibial
    • and common fibular bound together by connective tissue), Tibial (supplies muscles of posterior and lateral leg), Common Fibular (supplies muscles of
    • anterior leg and foot)
  41. Define transection
    In the case of a spinal cord, when it is completely severed, cutting all sensory & motor tracts resulting loss of motor & sensory functions below transection
  42. Know what muscle functions are retained at the following levels of spinal cord transection at C3, C4-C5, T1-T3, T10-L2
    • At C3: no function from neck down, ventilator required for breathing
    • At C4-C5: diaphragm functional
    • At T1-T3: complete arm function
    • At T10-L1: most thigh muscles, walk with LONG braces
    • At L1-L2: most leg muscles, walk with SHORT braces
  43. Define dermatome and describe how dermatomes help clinicians locate damaged regions of the spinal cord
    • Dermatome: area of skin that is served by one spinal nerve or the trigeminal (V) nerve (cranial nerve)
    • - Stimulating a dermatome can help determine if a spinal cord is damaged
  44. Define Reflex
    fast, predictable, automatic responses to stimuli
  45. Define spinal reflexes, cranial reflexes, somatic reflexes, and autonomic reflexes
    Spinal : involves spinal nerves and spinal cord

    Cranial : involves cranial nerves and brain

    Somatic : involve skeletal muscles, consciously perceived

    Autonomic : involved smooth muscle, cardiac muscle, glands ; not consciously perceived
  46. Name and describe the components of a reflex arc
    • Sensory Receptor: responds to stimulus
    • - Induces Graded Potential
    • (Generator Potential) in dendrite of sensory neuron
    • - If Graded Potential depolarizes axon to threshold an action potential is generated
    • Sensory Neuron Axon: carries nerve impulse to CNS
    • - Intensity of stimulus coded by frequency of nerve impulse
    • Integration Center:
    • - Monosynaptic Reflex – integrating center is single synapse between sensory and motor neuron
    • - Polysynaptic Reflex – integrating center consists of one or more interneurons; interneuron synapses onto the motor neuron
    • Motor Neuron: interneurons initiate nerve impulses in motor neuron
    • - Axon of motor neuron leaves CNS
    • Effector: innervated by motor neuron
    • - Somatic Reflex: effector skeletal muscle
    • - Autonomic Reflex: effector is cardiac muscle, smooth muscle, gland
  47. Define monosynaptic reflex arc and polysynaptic reflex arc
    • - Monosynaptic Reflex – integrating center is single synapse between sensory and motor neuron
    • - Polysynaptic Reflex – integrating center consists of one or more interneurons; interneuron synapses onto the motor neuron
  48. Describe the purpose of the stretch reflex, the tendon reflex, and the flexor and crossed extensor reflexes
    Stretch Reflex: controls muscle length by causing contraction of stretched muscle; important for maintaining posture

    Tendon Reflex: controls muscle tension and causes muscle relaxation before muscle force becomes great enough to tear tendons

    Flexor Reflex: response to painful stimulus and causes movement of limb away from stimulus

    Crossed Extensor Reflex: controls balance; flexor reflex causes one leg to move away from a painful stimulus while crossed extensor reflex causes opposite leg to extend and maintain balance
  49. Describe the clinical importance of reflex testing
    • (1) Reflexes are predictable responses to stimuli
    • (2) Reflex testing indicates health of nervous system
    • (3) Abnormalities in reflex may indicate problem in reflex pathway (arc)
  50. Briefly describe the following reflex tests: patellar reflex, Achilles reflex, Babinski sign, abdominal reflex
    Patellar: stretch reflex; tapping of leg at knee joint causes contraction of quad muscle and entension of knee

    Achilles: stretch reflex; tapping Achilles tendon causes contraction of the gastrocnemius and soleus muscles and plantar flexion

    Banbinski Sign: gentle stroking of outer margin of sole of foot normally causes plantar flexion (curling toes) or a negative sign after 1.5 years; Positive sign occurs when great toe dorsiflexes (normal before 1.5 years)
Card Set
Bio 209 Ch. 13
Spinal Cord and Spinal Nerves