Lecture 2: Autonomic nerves (part 2 of 2)

Question 0

postganglionic fiber

Answer 0

an unmyelinated nerve fiber of ANS with cell body in autonomic gangion in PNS

Question 1

preganglionic fiber

Answer 1

an unmyelinated fiber of ANS with its cell body in the CNS and its axon and termination in a peripheral autonomic gangion

Question 2

3 types of ganglia

Answer 2

paravertebral (vertebral, chain), prevertebral (collateral, intermediate), and terminal ganglia

Question 3

where are paravertebral ganglia located? Are they sympathetic, parasym, or both?

Answer 3

alongside vertebral column within the sympathetic trunk. Sympathetic only

Question 4

Where are prevertebral ganglia located and what is their classification?

Answer 4

between the sympathetic trunk and the effector organ. Both sym. and parasym.

Question 5

Where are terminal ganglia located and what is their classification?

Answer 5

intrinsic neural plexuses of the gastrointestinal, respiratory, and urogenital tracts. Bothe sym. and parasym. (mostly parasym.)

Question 6

Where are parasympathetic preganglionic cell bodies located?

Answer 6

in the brain stem and sacral regions of the spinal cord (the craniosacral region of the ANS)

Question 7

Where are sympathetic preganglionic cell bodies located?

Answer 7

thoracic and upper lumbar spinal cord. (The thoracolumbar division of the ANS)

Question 8

Where are parasympathetic postganglionic cell bodies located?

Answer 8

terminal and prevertebral ganglia

Question 9

Where are the sympathetic postganglionic cell bodies located?

Answer 9

paravertebral (chain) and prevertebral ganglia

Question 10

What groups of structures are innervated by parasympathetic postganglionic fibers?

Answer 10

cardiac muscle, glands and smooth m. of eye, digestive, respiratory and urogenital systems

Question 11

What groups of structures are NOT innervated by the parasym. postganglionic fibers?

Answer 11

sweat glands, smooth mm of skin, blood vessels of head, body wall and extremities

Question 12

What structures are innervated by sympathetic postganglionic fibers?

Answer 12

cardiac muscle, all glands, all smooth m. of the body

Question 14

explain the sympathetic nerve supply to the head and C1 and C2 regions

Answer 14

• preganglionic fibers pass through the cervicothoracic ganglion and travel cranially in the vagosympathetic trunk in the neck to eventually synapse with their postganglionic fibers in the cranial cervical ganglion.
• postganglion fibers going to the C1 and C2 body region travel to the main trunk of C1 and C2 via the communicating branch.
• postganglinoic fibers destined for the head travel along a plexus surrounding the inernal carotid artery and are distributed distally along branches of most cranial nerves and smaller blood vessels.

Question 15

what is the significance of the arrangement of

the sympathetic supply to the head and C1-C2 region?

Answer 15

serious damage to the vagosympathetic trunk in the cervical region will eliminate the preganglionic supply to the cranial cervical ganglion and the entire sympathetic supply to the head will be essentially removed. this condition is called Horner’s syndrome. It’s often a condition that results from avulsion of the roots of the spinal nerves contributing to the brachial plexus.

Question 16

what are the 5 classical signs of Horner’s syndrome?

Answer 16

1. constriction of the pupil on the inured side (parasympathetics take over)
2. nicitating membrane protrudes over the eye (prolapse) - paralysis of smooth muscle retracting it
3. partial ptosis (drooping) of upper eye lid
4. enophthalmia - recession of the eyeball within the orbit
5. will show excessive sweating in the affected area (C1 and C2 and rest of the head on the affected side)

Question 17

what is unusual about the symptom of excessive sweating in horses with horner’s syndrome?

Answer 17

in all species, the sympathetics supply the sweat glands.

humans and many animals that have horner’s experience anihidrosis - lack of sweating - on the affected side. this is because the neurotransmitter at the end of the postganglionic fiber is acetylcholine (muscarinic).

in horses however, the neurotransmitter is norepinephrine - an adrenergic sympathetic junction. so instead of experiencing anihidrosis, horses show EXCESSIVE sweating in the affected area.

Question 18

why do horses experience excessive sweating with horner’s?

Answer 18

because denervated structures are supersensitive to small doses of the neurotransmitter and respond to the circulating epinephrine released from the adrenal gland during stress.

the excessive sweating response is caused by denervation supersensitivity - a phenomenon caused by a proliferation of adrenergic receptors on sweat glands.

Question 19

Which are longer: preganglionic sympathetic or parasympathetic fibers?

Answer 19

parasympathetic

Question 20

Which are longer: sympathetic or parasym. postganglionic fibers?

Answer 20

sympathetic

Question 21

Does parasympathetic system in general act locally or globally to effect change on body?

Answer 21

locally. It is of the “anabolic type”

Question 22

Does sympathetic system act locally or globally to effect change on the body?

Answer 22

globally. It is of the “catabolic type”

Question 23

Where is Ach released in sym. and parasym. systems?

Answer 23

Released from preganglionic fiber of sympathetic system, and both pre and postganglionic fibers of parasym. system

Question 24

Where is NE released?

Answer 24

From postganglionic sympathetic fibers

Question 25

Where are nicotinic receptors found?

Answer 25

1) preganglionic-postganglionic junctions of both sym. and parasym. systems 2) somatic neuromuscular junctions

Question 26

Where are muscarinic receptors located?

Answer 26

at the parasym. postganglionic-effector junction

Question 27

2 types of adrenergic receptors (receive NE) on the effector organs

Answer 27

1) alpha adrenergic | 2) beta adrenergic

Question 28

T or F: sympathetic system supplies all regions of the body wall from head to tail

Answer 28

True

Question 29

Normal pathway of the sympathetic fibers from spinal cord to effector organs in the NECK region.

Answer 29

cell bodies in T1-T5 spinal cord --> preganglionic fibers exit spinal cord and join main trunk of their respective spinal nerves --> leave main trunk and enter sympathetic trunk --> synapse with postganglionic fibers in the stellate ganglion --> post. fibers travel in vertebral n. to cervical spinal nerves --> effector organs of neck region

Question 30

Normal pathway of sympathetic fibers from spinal cord to effector organs in C1/C2.

Answer 30

cell bodies in T1-T5 spinal cord --> preganglionic fibers exit spinal cord and join main trunk of their respective spinal nerves --> leave main trunk and enter sympathetic trunk--> stellate ganglion --> vagosympathetic trunk --> synapse with post-ganglionic fibers in cranial cervical ganglion --> communicating branch --> main trunk of C1/C2

Question 31

Normal pathway of sympathetic fibers from spinal cord to the effector organs in the HEAD region.**

Answer 31

cell bodies in T1-T5 spinal cord --> preganglionic fibers exit spinal cord and join main trunk of their respective spinal nerves --> leave main trunk and enter sympathetic trunk--> stellate ganglion --> vagosympathetic trunk --> synapse with post-ganglionic fibers in cranial cervical ganglion --> plexus surrounding internal carotid a. --> cranial nerves 3-7,9,10 and smaller blood vessels

Question 32

enophthalmia

Answer 32

recession of the eyeball within the orbit. Caused by denervation of sympathetic input

Question 33

anihidrosis

Answer 33

lack of sweating

Question 34

denervation supersensitivity

Answer 34

condition in which denervated structures are supersensitive to small doses of neurotransmitter

Question 35

Pathway of sympathetic fibers from spinal cord to abdominal/pelvic cavities and genitalia

Answer 35

cell bodies in T8-L3 --> preganglionics in sympathetic trunk --> thoracic splanchnic (for abdominal cavity) or lumbar splanchnic nn. (for pelvic cavity and genitalia) --> synapse in prevertebral ganglia --> postganglionics travel to effector organs via arterial plexuses

Question 36

Normal pathway for sympathetic fibers from spinal cord to body wall in L4-Cd region (including the pelvic limb)

Answer 36

preganglionics in L1-L3 enter sympathetic trunk --> synapse on chain ganglia of L4-S1 --> postganglionics run in communicating branch to spinal nerve of that segment and are distributed to body wall

Question 37

Normal pathway of parasympathetic fibers from brain stem to visceral organs as far distally as transverse colon

Answer 37

preganglionics in brain stem --> vagus n. --> vagosympathetic trunk --> dorsal/ventral vagal trunks --> synapse in terminal ganglion in effector organ --> short postganglionics from terminal ganglion to effector.

Question 38

Normal pathway of parasympathetic fibers from spinal cord to visceral organs distal to the transverse colon

Answer 38

preganglionics in S3-S4 --> pelvic nerve --> pelvic plexus --> synapse on pelvic plexus or terminal ganglion --> postganglionics go from plexus/ganglion to effector organ