Visceral Nervous System

Question 1

What is another term for the motor portion of the visceral nervous system?

Answer 1

Autonomic NS

Question 2

What spinal levels is the sympathic nervous system at?

Answer 2

T1-L2

Question 3

What spinal levels is the parasympathetic nervous system at?

Answer 3

Brainstem + cranial nerves

S2-S4

Question 4

How does the distribution of sympathetic vs. parasympathetic innervation differ in the body?

Answer 4

Sympathetic goes everywhere
Parasympathetic doesn’t go to the periphery!

In other words - the core has both sympathetic and parasympathetic innervation, but the extremities only have sympathetic innervation

Question 5

Where are preganglionic sympathetic neurons found?

Answer 5

In the lateral horns of the SC from T1-L2

Question 6

Describe the location of sympathetic Ganglia with relation to distance from SC and distance from target organ

Answer 6

Sympathetic ganglia are far from their target organ and close the spinal cord (sympathetic chain)

Question 7

As a rule, where are MOST pre-ganglionic and postganglionic neurons found (for both sympathetic and parasympathetic?)

Answer 7

Preganglionic neurons are found inside the CNS, postganglionic are found outside the CNS with cell body in a ganglion

Question 8

Which sympathetic ganglia do not lie within the sympathetic chain?

Answer 8

Prevertebral, or pre-aortic ganglia (they are close to the aorta) - the neurons travel through the sympathetic chain without synapsing to get to the prevertebral ganglia and synapse

Question 9

What regions do the pre-aortic ganglia go to? What about the sympathetic chain ganglia?

Answer 9

Pre-aortic = abdominal and pelvic viscera

Sympathetic chain = thorax and limbs

Question 10

In the sympathetic NS, pre-ganglionic neurons release ___________ and post-ganglionic neurons release ___________ .

Answer 10

acetylcholine, adrenaline or noradrenaline

Question 11

Describe the location of parasympathetic Ganglia with relation to distance from SC and distance from target organ

Answer 11

Parasympathetic ganglia are found far from the spinal cord and close to their target organ

Question 12

Which sympathetic organ is considered a misplaced sympathetic ganglion?

Answer 12

The adrenal medulla - it is directly innervated by a preganglionic sympathetic neuron

Question 13

Give some examples of when the sympathetic and parasympathetic nervous systems are not working anatagonistically (which they usually do)?

Answer 13

Sexual function - they work together

Blood vessels - only receive sympathetic stimulation

Salivary gland secretion - only parasymp. stim.

Question 14

Why is it called the parasympathetic NS?

Answer 14

Because “para” = around - the parasympathetics are situated around the sympathetics

Question 15

Where do pre-ganglionic parasympathetic fibers come from?

Answer 15

Specific brainstem nuclei, or lateral horn of the spinal cord at level S2-S4

Question 16

What neurotransmitters are used in the parasympathetic NS?

Answer 16

Preganglionic = Ach
Postganglionic = Ach

Question 17

What is the overall role of the parasympathetic nervous system?

Answer 17

Enhance energy storage

Question 18

What is the main function of the autonomic nervous system?

Answer 18

To maintain homeostasis

Question 19

How does the autonomic nervous system maintain homeostasis?

Answer 19

It integrates with the endocrine system (hypothalamus integrates)

Question 20

Give some examples of symp. and parasymp. working antagonistically

Answer 20

Symp = increase HR, promote bowel filling
Parasymp = decrease HR, promote bowel emptying

Question 21

How do the sympathetic and parasympathetic NS work together for sexual function?

Answer 21

Parasymp - promote erection

Symp - ejaculation

Question 22

how does the parasympathetic nervous system decrease HR?

Answer 22

Signal is sent to dorsal motor nucleus and nucleus ambiguus of vagus nerve -> vagus nerve to heart

Question 23

How does the parasympathetic NS decrease blood pressure?

Answer 23

By decreasing heart rate and force of contraction -> this decreases cardiac output -> decreased BP

Question 24

What spinal levels promote increased HR in the sympathetic NS?

Answer 24

T1-T4

Question 25

How do the carotid sinus reflexe work?

Answer 25

Visceral sensory neurons (baroreceptors) in carotid sinus and aortic arch sense changes in BP -> info is sent to CN IX and X -> reaches brainstem nuclei -> CN IX and X send motor response to either increase or decrease HR -> @ same time, the opposite system will be inhibited -> results in either increased or decreased BP

Question 26

What causes Horner's Syndrome?

Answer 26

Lack of sympathetic outflow to the head Damage to T1 up to the ganglia in the head (because T1 controls sympathetic outflow to the head)

Question 27

What are the sx. or Horner's syndrome?

Answer 27

Ptosis - droopy eyelid Anhydrosis - not sweating Miosis - constriction of pupil Vasodilation of skin arterioles

Question 28

Who is at highest risk of Autonomic Dysreflexia?

Answer 28

Those with cervical injuries, but can happen to anyone with SCI T6 or higher

Question 29

What is the trigger for autonomic dysreflexia? How does the body respond? What are the symptoms?

Answer 29

1) Trigger is a noxious stimulus BELOW the level of SCI 2) Stimulus activates symp. NS and BP increases (below the level of injury) -> there is no cortical inhibition so BP really increases -> results in sweating, extremely high BP, erythema (redness), and headache

Question 30

What are some things that can cause Autonomic Dysreflexia?

Answer 30

UTI, urinary retention, blocked catheter, kidney stones, fecal impaction or fissures in bowel, pressure ulcers in skin

Question 31

What parts of the nervous system are involved in the urinary system? what are their roles?

Answer 31

Parasympathetic = visceral sensory neurons send bladder fullness signal -> goes to spinal cord and then to both parasympathetic preganglionic neuron and somatic motor neuron -> message goes to the Pontine Mictruition Center, but also can complete reflex arc without -> contraction of detrusser muscle when bladder is completely full (only activated when completely full) Sympathetic = in those with prostates, it keeps the internal urethral sphincter closed to prevent backflow during ejaculation - this is inhibited when there is a full bladder Somatic - conscious control over the timing of bladder emptying - somatic NS innervates the external urethral sphincter

Question 32

When the bladder is ready to empty the parasympathetic NS receives ___________ signals and the symp NS receives _________ signals

Answer 32

excitatory, inhibitory

Question 33

What is the role of the PMC in bladder emptying?

Answer 33

Coordinate inhibition of symp, excitation of parasymp, and inhibition of somatic motor during bladder emptying

Question 34

What can cause hyperreflexive (spastic) bladder? Explain the mechanisms. What are the symptoms of spastic bladder?

Answer 34

Damage above S2 Still have reflex emptying of bladder due to parasympathetic reflex arc - detruser muscle contracts when bladder is full No longer have cortical control over somatic neurons below level of damage (i.e. cannot control somatics at S2-S4) so unable to relax EUS (no inhibition, high tone) Results in incomplete emptying and backflow of urine which can cause chronic UTIs, can also result in overflow incontinence

Question 35

What can cause areflexive bladder? What are the mechanisms and symptoms?

Answer 35

SC damage at S2-S4 (including cauda equina) Reflex arc is damaged - unable to contract detruser muscle, it is flaccid. The somatic MNs innervating the EUS are damaged which results in flaccid EUS. Result is constant dribbling of urine.

Question 36

What parts of the NS are involved in bowel control? What are their roles?

Answer 36

Parasympathetic - vagus nerve innervates the upper and midgut, S2-S4 innervates the hindgut and internal anal sphincter - parasympathetic activation causes gut peristalsis and secretions, and relaxation of the internal anal sphincter Sympathetic - L1 and L2 (or T5 to L2, UNCLEAR?) - prevents peristalsis and tightens internal anal sphincter Somatic - conscious control over external anal sphincter and abdominal muscles

Question 37

Describe the symptoms and mechanisms of hyperreflexive bowel (AKA UMN bowel syndrome)

Answer 37

Damage above S2-S4 - Parasympathetics can still reflexively do peristalsis - Not cortical input to somatic motor system, so the external anal sphincter has high tone and cannot be inhibited - Results in some constipation - Often can have BM with digital stim.

Question 38

Describe the symptoms and mechanisms of areflexive bowel (AKA LMN bowel syndrome)

Answer 38

Damage to S2-S4 LMN results in inability to do peristalsis in hindgut. Also, somatic innervation to external anal sphincter is damaged, so cannot tighten it. Leads to high degree of constipation, and incontinence when fecal matter reaches EAS

Question 39

Describe the roles of the sympathetic and parasympathetic nervous systems in sexual function

Answer 39

Parasympathetic (S2-S4): - erection - sexual secretions Sympathetic (T10-L2): - decrease psychogenic arousal - inhibiting parasympathetics - vaginal and vas deferens contractions - ejaculation

Question 40

Describe the impacts of different levels of injury on sexual function

Answer 40

1) Above T10 - no psychogenic erection (can get reflex erection) 2) At L1-L2 - no ejaculation 3) Above L1 - reflex ejaculation is possible 4) At S2-S4 - no reflex erection, can get psychogenic erection

Question 41

How does referred pain work?

Answer 41

Visceral nervous system sends pain signal to dermatome from same spinal level that innervate the internal organ that is in pain

Question 42

What is the name of the condition that results form disruption to sympathetic outflow to the head?

Answer 42

Horner's Syndrome