Lecture 2- Spinal And Autonomic Nerves

Question 1

Encephalopathy

Answer 1

Brain disease

Question 2

Myelopathy

Answer 2

Disease of the spinal cord

Question 3

Peripheral neuropathy

Answer 3

Disease of the peripheral nerves

Question 4

What symptoms would indicate you are dealing with a peripheral neuropathy instead of diseases in the CNS?

Answer 4

Hyporeflexia, hypotonia, denervation atrophy, unilateral sensory/motor deficits, normal function cranial and caudal to lesion site

Question 5

Anatomical parts of a spinal nerve

Answer 5

Roots, trunk, four primary branches, peripheral branches

Question 6

Roots

Answer 6

Located in vertebral canal;
Belong to PNS, but are associated with spinal cord;
Dorsal roots= sensory;
Ventral roots= motor

Question 7

Main trunk

Answer 7

Located in intervertebral foramen;

Very short

Question 8

Spinal nerve formula

Answer 8

Number of vertebrae + 1 in cervical region

ex: horse vertebrae= C7 T18 L6 S5 Cd7
Horse spinal nerve= C8 T18 L6 S5 Cd7

Question 9

Four primary branches of spinal nerves

Answer 9

Dorsal= supplies epaxial muscles and dorsal skin

Ventral= largest; supplies hypaxial muscles and skin, thoracic and pelvic lims; form brachial and lumbosacral plexus

Meningeal =supplies meninges and intervertebral discs; very small

Communicating= runs to sympathetic trunk; visceral function (ANS)

Question 10

Peripheral branches of spinal nerves

Answer 10

Have different functional components

Can be cutaneous, muscle, or mixed

Question 11

Cutaneous nerves

Answer 11

Somatic afferents
Visceral afferents
Visceral efferents
NO somatic efferents

Question 12

Cutaneous area

Answer 12

Area of skin supplied by a given cutaneous nerve

Made up of autonomous zone and overlap zone

Different from a dermatome

Question 13

Dermatome

Answer 13

Area supplied by a spinal nerve

Question 14

Muscle nerves

Answer 14

A type of peripheral spinal nerve branch

Has all four functional components

Question 15

Autonomic nervous system

Answer 15

General visceral efferent

Has both symp and parasymp innervation

Two neuron system- pre and post ganglionic

Question 16

Postganglionic fiber

Answer 16

Usually unmyelinated; terminates in one of three regions:

1. Paravertebral- sympathetic only (in the trunk)
2. Prevertebral- between symp trunk and effector organ (symp and parasymp)
3. Terminal ganglia- intrinsic plexuses of gastrointestinal, respiratory, and urogenital tracts; mostly parasymp

Question 17

Location of parasymp preganglionics

Answer 17

Craniosacral region

Question 18

Symp preganglionic location

Answer 18

Thoracolumbar division

Question 19

Location of parasymp postganglionic

Answer 19

Mostly terminal ganglia

Question 20

Location of sympathetic postganglionics

Answer 20

Mostly chain ganglia

Question 21

Distribution of symp postganglionic fibers

Answer 21

To cardiac muscle, all glands, all smooth muscle of body

Question 22

Distribution of parasymp postganglionic fibers

Answer 22

Cardiac muscle, glands and smooth muscle of the eye, digestive, respiratory, and urogenital systems.

NO sweat glands, skin,

Question 23

Sympathetic route to head

Answer 23

Pregangs are located in T1-T5

Leave spinal via ventral roots of T1-T5 and join main trunk

Fibers leave main trunk and join sympathetic trunk by way of communicating branch

Fibers run cranially along symp trunk, pass through cervicothoracic ganglion, synapse in cranial cervical ganglion

Post gangs leave cranial cervical ganglion and 1. Head back to C1 and C2 through symp trunk OR 2. Go towards head via internal carotid plexus

Question 24

Damage to vagosympathetic trunk

Answer 24

Results in Horner’s syndrome- lack of symp innervation in one side of head

symptoms:
Constriction of pupil
Protruding nictitating membrane
Partial ptosis (drooping of eyelid)
Enophthalmia- recession of eyeball within orbit
Lack of sweating EXCEPT in horses where there is an excess of sweating. This is because horses use norepinephrine rather than acetylcholine.

Question 25

Symp route to abdominal/ pelvic viscera

Answer 25

Pregangs are in T8-L3
Enter symp trunk, and run caudally
Synapse on a number of prevertebral ganglia
Either leave the trunk via thoracic splanchnic nerves and perforate the diaphragm and enter the abdominal cavity OR leave symp trunk in lumbar region via lumbar splanchnic nerves

Those fibers destined for pelvic and urogenita synapse on the caudal mesenteric ganglion and leave via hypogastric nerve and pass through the pelvic plexus

Question 26

Symp route to hindlimb

Answer 26

Pregangs are in L1-L3
Enter symp trunk at L4-S1 and synapse on chain ganglia
Post gangs run back to spinal nerve via communicating branch for distribution into body wall

Question 27

Parasymp route to abdominal viscera

Answer 27

Pregangs travel out of brainstem via vagus nerve
Descend caudally via vagosympathetic trunk
Pass through thorax via dorsal and ventral vagal trunks
Reach abdominal plexuses and pass through
Synapse in terminal ganglion in effector organ

Question 28

Parasymp route to pelvic viscera

Answer 28

Pregangs in S3-S4 travel through pelvic nerve
Descends into pelvic cavity and forms pelvic plexus
Most synapse here, but others pass through and synapse on a terminal ganglion