Ch 14 - spinal cord

Question 1

what does the dorsal horn contain?

Answer 1

interneurons + central terminations of sensory afferent fibers

Question 2

what does the ventral horn contain?

Answer 2

interneurons + somatic motor neurons that innervate skeletal muscle.

Question 3

what does the intermediate zone and central gray contain?

Answer 3

interneurons and visceral motoneurons associated with autonomic funciton

Question 4

what two things do you have to keep in mind with regards to the spinal cord and the vertebral column?

Answer 4

1. there is a mismatch between the location of the spinal cord segment and the vertebral segment of the same number because the spinal cord and vertebral column grow at different rates after birth
2. the spinal cord ends quite cranial to the sacrum.

Question 5

how many spinal cord segments are in the adult dog

Answer 5

8 cervical, 13 thoracic, 7 lumbar, 3 sacral, 5 caudal

Question 6

what is unique about the cervical roots?

Answer 6

they exit above the same numbered vertebra

Question 7

which cervical nerve does not have a corresponding vertebra?

Answer 7

CN 8 - it exits between vertebrae C7 and T1.

Question 8

where does the spinal cord terminate? and where does this occur in the dog?

Answer 8

the conus medullaris; L6 or L7

Question 9

what is the name for the nerves that extend collectively in the caudal direction?

Answer 9

the cauda equina

Question 10

what does the central canal contain and describe its structure

Answer 10

it contains CSF and is lined with a single layer of ependymal cells.

Question 11

where do the filum terminate? what does it penetrate? what does it connect?

Answer 11

it terminates in an extension of the pia mater which penetrates the dura and connects the conus medullaris with the periosteum of the caudal vertebrae.

Question 12

where does the brachial or cervical enlargement occur?

Answer 12

extends from spinal segments C7 to T2 and is the site of exit of the spinal nerves of the brachial plexus which innervate the forelimbs

Question 13

where does the lumbar enlargement extend?

Answer 13

from spinal segments L4 to S1 and is the exit point of nerves of the lumbosacral plexus which supply the hindlimbs

Question 14

define divergence

Answer 14

each single sensory primary afferent fiber ENTERING the spinal cord (via the dorsal root) bifurcates many times to send collateral axons to several spinal and supraspinal destinations.

Question 15

define convergence

Answer 15

multiple motor axons LEAVE the spinal cord from more than one ventral root/spinal nerve to innervate the same skeletal muscle

Question 16

one presynaptic neuron may have connections with multiple postsynaptic neurons OR
may have multiple connections with one postynaptic neuron. is this convergence or divergence?

Answer 16

divergence

Question 17

one postsynaptic neuron may receive connections from many presynaptic neurons. is this convergence or divergence?

Answer 17

convergence

Question 18

describe the withdrawal reflex

Answer 18

an animal withdraws by flexing its limb, may show a crossed-extensor reflex (if standing) and does not show signs of pain perception - they may be stoic.
this typically occurs when animal encounters something it simply does not like.

Question 19

describe the pain response

Answer 19

an animal withrdawals its limb, turns its head toward the painful stimulus, may attempt to bite, tries to move away, whines or barks and will have a disrupted respiratory pattern.