Autonomic Nervous System

Question 1

What is Congential Megacolon / Hirschsprung Disease?

Answer 1

Failure of these enteric neuronal precursor cells to migrate into the wall of the developing lower gut
- Aganglionic segment of the gut (colon) is paralyzed in constriction –> distention of ganglionic segment

Question 2

What does interruption of descending reticulospinal and hypothalamospinal fibers that regulate sympathetic preganglionic neurons INITIALLY cause? (this is above T6 level)

Answer 2

• Lowered blood pressure
• Orthostatic hypotension
• Bradycardia

Reduction in sympathetic activity

Question 3

What is autonomic dysreflexia? (hyperreflexia - an emergency)

Answer 3

Hyperactivity of sympathetic reflexes that develops a while after interruption of descending fibers.

• Hypertension
• Urinary retention
• Piloerection
• Profuse sweating
• Reduction of blood flow to peripheral tissues

Question 4

What is the baroreceptor reflex?

Answer 4

Buffers blood pressure against a sudden change in posture (in general, sense changes in blood pressure and accommodates accordingly)

Question 5

Absence of the baroreceptor reflex results in:

Answer 5

Orthostatic hypotension - severe drop in blood pressure when the patient assumes an upright position

Question 6

What is causalgia? (complex region pain syndrome type II)

Answer 6

Partial peripheral nerve injury that causes:

• Spontaneous burning pain
• Hypersensitivity in skin (even to noise)
• Hyperacusia
• Strong emotions
• Sweating
• Mottling of skin
• Edema in extremity

Question 7

What is the etiology of causalgia?

Answer 7

Sympathetic postganglionic neurons are injured –> abnormal connection to nociceptive DRG –> nociceptive neurons could develop abnormal responsiveness

Question 8

How to treat causalgia?

Answer 8

Sympathectomy or blocking sympathetic function

Question 9

What is congenital insensitivity to pain with anhidrosis caused by?

Answer 9

Deprivation of NGF (neurotrophin nerve growth factor) or its receptor (trkA). Also called “hereditary sensory neuropathy type II”.

Question 10

How do UTIs affect the bladder?

Answer 10

Irritation of afferent innervation of lining and activation of micturition reflex leads to strong urge to void the bladder (even with low urine volume)

Question 11

What is multiple system atrophy?

Answer 11

Loss of preganglionic input to the brainstem and spinal cord; common in demyelinating diseases and diabetes

First symptoms are typically bladder involvement (progression is relentless)

Question 12

What is neurogenic bladder?

Answer 12

Detrusor areflexia leads to lack of voiding and causes UTIs

Question 13

List a few vasomotor disorders:

Answer 13

• Hyperhidrosis (facial)
• Raynaud’s
• Acrocyanosis

Question 14

What is the quantitative sudomotor axon reflex test (QSART)?

Answer 14

Test used to assess small nerve fibers linked to sweat glands (post-ganglionic)

Question 15

What autonomic deficit does Parkinson’s lead to?

Answer 15

bladder and GI motility

Question 16

What autonomic deficit does epilepsy lead to?

Answer 16

arrhythmia, GI

Question 17

What autonomic deficit does MS lead to?

Answer 17

bladder, bowel, sexual function

Question 18

What autonomic deficit does spinal cord injury lead to?

Answer 18

upper and lower function

Question 19

What autonomic deficit does diabetes lead to?

Answer 19

peripheral neuropathies

Question 20

What is familial dysautonomia?

Answer 20

Genetic disorder that disturbs cells in the autonomic nervous system, which controls involuntary actions such as digestion, breathing, production of tears, and the regulation of blood pressure and body temperature

Question 21

How does the thermoregulatory sweat test work?

Answer 21

• Apply indicator powder (Alizarin red, corn starch, sodium bicarbonate)
• Turns purple when wet
• Localization of sweating abnormality becomes apparent

Post- and pre-ganglionic

Question 22

Describe the pathway for disrupted micturition reflex where…

there is a lesion to the lumbosacral spinal cord

Answer 22

Lesion to lumbosacral spinal cord –> abolish normal reflex due to loss of autonomic input –> no sympathetic tone –> incontinence

Question 23

Describe the pathway for disrupted micturition reflex where…

there is no pontine (L, M) control

Answer 23

No pontine control –> no voluntary control

Question 24

Describe the pathway for disrupted micturition reflex where…

denervation upregulates alpha-receptors and sympathetic sprouting

Answer 24

Denervation –> increased sympathetic tone –> voiding becomes difficult –> cystitis or catheterization

Question 25

Describe the pathway for disrupted micturition reflex where…

there is a lesion between lumbar cord and pons

Answer 25

Lesion between lumbar cord and pons –> areflexic bladder and NO voluntary control –> incomplete bladder emptying –> cystitis and UTI