de for Exam 4

Spinal Cord

1. Define epidural space.

Epidural space - cushion of fat and connective tissue that helps protect spinal cord

Location-  area between the dura mater (a membrane) and the vertebral wall, containing fat and small blood vessels

2. What are the 3 meninges? Define them.

·      Dura mater, Most superficial. Thick strong layer composed of dense irregular CT

·      Arachnoid mater, Thin covering composed of collagen and elastic fibers. Avascular

·      Pia mater, innermost layer that adheres to surface of spinal cord and brain. Thin squamous to cuboidal cells with collagen and elastic fibers

Vascular-provides oxygen and nutrients to spinal cord

3. What is the subarachnoid space?

Filled with cerebral fluid- below arachnoid layer between arachnoid and pia mater

4. Which part of the brain stem does the spinal cord extend from?  And how far down the vertebrae does the spinal cord extend?

Extends from medulla oblongata of brain to the superior border of the second lumbar vertebra

5. Are the spinal cord and vertebral column the same length?

Spinal cord is shorter than the vertebral column

6. What are the 2 spinal cord enlargements?  Where do these nerves go?

Spinal cord contains 2 enlargements

Cervical enlargement

•       Extends from C4 to T1

•       Nerves to and from upper limbs arise from cervical enlargement

Lumbar enlargement

•       extends from L2-S3

•       Nerves to and from lower limbs arise  from lumbar enlargement

7. What is the conus medullaris?

Spinal cord terminates as tapered, conical structure, ends between L1 and L2

8. What is the filum terminale?

   1. extension of pia mater

                                               i.     fuses with arachnoid mater and dura mater

                                             ii.     anchors spinal cord to coccyx

9. How many pairs of cervical nerves?  Thoracic nerves?  Lumbar?  Sacral?  Coccygeal?

Cervical nerves- 8 pairs

Thoracic nerves 12 pairs        

Lumbar 5 pairs

Sacral 5 pairs

Coccygeal 1 pair

10. What are roots?  Rootlets?

roots-2 bundles of axons that connect each spinal nerve to a segment of the cord by even smaller bundles called  rootlets

11. Internal anatomy of spinal cord.  (white matter, gray matter, anterior median fissure, posterior median sulcus, posterior gray horns, anterior gray horns, lateral gray horns, gray commissure, central canal, anterior and posterior and lateral white columns, anterior white commissure)

12. Posterior dorsal gray horn receives information from what type of neuron (sensory or motor)? What organs?

sensory

13. Spinal nerves leaving anterior ventral gray horn leave through what type of neuron (sensory or motor)?

motor

14. What information is regulated in lateral gray horns?

Autonomic motor neurons. Regulate cardiac and smooth muscles and glands

15. How is white matter in spinal cord arranged?  (e.g., rows, diagonally, columns?)

    1. Contains spinal tracts that carry information up and down spinal cord

    2. Some tracts are sensory (ascending tracts)

    3. Some tracts are motor (descending tracts)

16. What are sensory tracts vs. motor tracts?

Sensory tracts– consist of axons that conduct nerve impulses toward the brain

Motor tracts – tracts consisting of axons that carry nerve impulses from brain

17. Where is gray matter of the spinal cord found in the largest amount? (e.g., which segment of the spinal cord?)

    1. Amount of gray matter is largest in cervical and lumbar segments of spinal cord

18. Where is white matter found in the largest amount in the spinal cord?

Cervical segment

19. What does the endoneurium, perineurium, and epineurium cover?

Endoneurium- wraps axons withing nerve

Perineurium wraps fascicles

Epineurium- covers entire nerve

20. How many pairs of spinal nerves are there?

31 pairs

21. Distribution of spinal nerves.  Where does each of the following plexuses supply nerves to? (Cervical plexus, brachial plexus, lumbar plexus, sacral plexus)

}  Cervical plexus-nerves that supply skin and muscles of head, neck, and upper part of shoulder (formed by roots of C1-C5)

}  Brachial plexus-nerves that supply upper limbs and neck and shoulder muscles

Roots of spinal nerves C5-T1

}  Lumbar plexus-nerves that supply abdominal wall, external genitals, and lower limbs (roots of spinal nerves L1-L4)

}  Sacral plexus-nerves that supply buttocks and lower limbs

}  Coccygeal plexus-nerves that supply skin of coccygeal region

22. What does the phrenic nerve innervate?  Where does the sciatic nerve innervate?

Phrenic nerve (c3-c5)- innervates diaphragm

Sciatic nerve innervates  L4-S3; as descends through thigh, it sends branches to hamstring muscles and adductors

23. How many spine segments of the spinal cord are there? (Hint: dermatomes)

31 segments

24. What is a reflex?  What is a spinal reflex vs. a cranial reflex?  Where does integration take place for each?

Reflex-fast, predictable sequence of involuntary actions which occurs in response to certain changes in environment

Spinal reflex-integration takes place in spinal cord gray matter (patellar reflex)

Cranial reflex-integration occurs in brain stem (reading)

25. Know the reflex arc. See figure.

Reflex arc -pathway followed by nerve impulses that produce a reflex

26. What is a tendon reflex?  What is its function?

Tendon reflex -  Controls muscle tension by causing muscle relaxation before muscle force becomes so great that tendons might tear.

•       Instead of resulting in a contraction, it results in relaxation of a muscle

•       It is inhibitory reflex

27. What is a flexor reflex?  What is function?  When would it occur?

Polysynaptic reflex arc

27. Polysynaptic reflex arc-more than 1 CNS

28.  synapse and more than 2 different neurons are involved

withdrawal reflex”

28. Which reflexes are polysynaptic vs. monosynaptic?

Monosynaptic reflex-  stretch reflex (patellar reflex),

Polysynaptic reflex – flexor reflex (withdrawal reflex)

Stretch reflex- Causes contraction of skeletal muscle (effector) in response to stretching of muscle