Lecture 2: the Spinal and Autonomic Nerves (part 1 of 2)

Question 1

define encephalopathy

Answer 1

a disease in the brain

Question 2

define myelopathy

Answer 2

a disease in the spinal cord

Question 3

define peripheral neuropathy

Answer 3

a disease in the peripheral nerves

Question 4

the presence of what 4 conditions differentiates peripheral neuropathy from CNS encephalopathy and myelopathy?

Answer 4

1. hyporeflexia, hypotonia (less muscle tone)
2. “denervation” atrophy
3. unilateral motor and/or sensory deficits
4. normal function cranial and caudal to nerve lesion site

Question 5

are cenral lesions usually unilateral or bilateral?

Answer 5

bilateral

Question 6

what are the 4 main branches of spinal nerves?

Answer 6

1. dorsal branch
2. ventral branch
3. communicating branch
4. meningeal branch

Question 7

what are the 4 anatomical parts to the typical spinal nerve?

Answer 7

1. roots
2. main trunk
3. the four primary branches
4. peripheral branches of these primary branches

Question 8

where are roots of spinal nerves located?

Answer 8

within the vertebral canal

Question 9

roots of spinal nerves are functionally associated with what?

Answer 9

functionally associated with the spinal cord even though they belong to the peripheral nervous system.

Question 10

are dorsal roots and spinal (dorsal root) ganglia afferent or efferent in function?

Answer 10

afferent ie sensory

Question 11

Are ventral roots afferent or efferent in function?

Answer 11

efferent ie motor

Question 12

describe an identifying characteristic of the main trunk of typical spinal nerves and their location in most cases

Answer 12

it is typically very short and located in the intervertebral foramen

Question 13

what is the spinal nerve formula for the horse?

Answer 13

C8 T18 L6 S5 Cd7

Question 14

where does the first cervical nerve emerge from?

Answer 14

it emerges from the lateral vertebral foramen located in the atlas

Question 15

where does the second cervical nerve emerge from?

Answer 15

it exits from the lateral vertebral foramen of the second cervical vertebrae (axis)

Question 16

where does the eight cervical nerve run through?

Answer 16

the intervertebral foramen between the seventh cervical and first thoracic vertebrae

Question 17

how many cervical nerves and cervical vertebrae are there in the horse?

Answer 17

8 cervical nerves but only 7 cervical vertebrae

Question 18

what does the dorsal primary branch supply?

Answer 18

dorsal axial (epaxial) muscles and skin over the dorsal and dorsolateral body areas

Question 19

what does the ventral primary branch supply?

Answer 19

supplies ventral axial (hypaxial) muscles, muscles of ventral and ventrolateral regions like the thoracic and pelvic limbs and skin over these regions

Question 20

what do ventral branches of the lower cervical and thoraci region (C6 - T1 or T2) form?

Answer 20

the brachial plexus

Question 21

what do ventral branches of L4 - S4 form? what does it supply?

Answer 21

the lumbosacral plexus which supplies the pelvic limb and the perineal region

Question 22

what does the meningeal branch supply?

Answer 22

it supplies the coverings of the spinal cord (meninges), blood vessels in the vertebral canal, and the intervertebral discs. these are implicated in back pain

Question 23

what is an identifiable physical characteristic of the meningeal branch?

Answer 23

its is very small - difficult to see grossly

Question 24

where does the communicating branch (ramus communicans) run?

Answer 24

it runs from the main trunk of a spinal nerve to the sympathetic trunk and chain ganglia

Question 25

what is the communicating branch associated with functionally?

Answer 25

visceral function

Question 26

what is a somatic structure?

Answer 26

it is associated with the body wall (skin, subcuntaneous tissue, skeletal muscle, joints, tendons, etc)

Question 27

what is a visceral structure?

Answer 27

associated with internal organs, smooth muscle, cardiac muscle and glands.

Question 28

what is a cutaneous nerve?

Answer 28

peripheral nerves that go to the skin only

Question 29

what are cutaneous nerves sometimes called? it can be misleading…

Answer 29

they are sometimes called sensory but this is a misleading name because they innervate the smooth muscle around blood vessels; thus contain visceral efferent nerve fibers

Question 30

what are muscle nerves?

Answer 30

they are peripheral nerves that go to muscle only

Question 31

what are muscle nerves also commonly called? why is it misleading?

Answer 31

muscle nerves are also commonly called motor nerves.

this is misleading because many nerve fibers in muscle are muscle afferents (sensory) from muscle proprioceptors

Question 32

what are most large nerves? cutaneous or muscle nerves?

Answer 32

most are actually mixed nerves because they go to both skin and muscle.

Question 33

is the femoral nerve a cutaneous nerve, muscle nerve or mixed nerve?

Answer 33

mixed because it branches peripherally into both cutaneous and muscle nerves

Question 34

what are the functional components of cutaneous nerves (there are 3)

Answer 34

somatic afferents
visceral afferents
visceral efferents

Question 35

where do the somatic afferents for cutaneous nerves come from?

Answer 35

from receptors in skin and subcutaneous tissue

Question 36

where do the visceral afferents for cutaneous nerves come from?

Answer 36

from receptors in blood vessels

Question 37

where do the visceral efferents for cutanoues nerves come from? what do these fibers supply?

Answer 37

postganglionic sympathetic fibers which have their cell bodies in chain ganglia. these fibers supply the smooth muscle of blood vessels to erector pilae muscles associated with hairs and sweat glands.

there are NO somatic Efferents because there is no striated muscle

Question 38

define cutaneous area

Answer 38

the area of skin supplied by a given cutaneous nerve

Question 39

what are the two zones within a cutaneous area?

Answer 39

overlap zones and autonomous zones

Question 40

define overlap zone

Answer 40

an area supplied by more than one cutaneous nerve

Question 41

define autonomous zone

Answer 41

an area supplied by only one cutaneous nerve

Question 42

which region would experience anesthesia resulting from severe damage to one peripheral nerve and is thus the area of most diagnostic value in determining level of nerve damage in a patient?

Answer 42

the autonomous zone

Question 43

what are the 4 functional components of muscle nerves?

Answer 43

1. somatic afferents (sensory)
2. visceral afferents (sensory)
3. visceral efferents (motor)
4. somatic efferents (motor)

Question 44

the presence of which type of fiber distinguishes muscle nerves from cutaneous nerves?

Answer 44

somatic efferents

Question 45

where can muscle nerves originate from?

Answer 45

1. dorsal or ventral primary branches

2. mixed nerves