ANS Disorders

Question 1

clinical assessments of autonomic function: easy to? but difficult to? purpose?

Answer 1

easy to perform, difficult to interpret. to decide if dysfunction is visceral sensory, central reflex, or efferent autonomic

Question 2

orthostatic test/tilt-table: how to test

Answer 2

90 degree head up passive tilt, blood goes to leg veins

Question 3

orthostatic test/tilt-table: what happens in normal subject?

Answer 3

increased heart rate, little change in blood pressure, but heart rate increase not always seen in trained athletes

Question 4

orthostatic test/tilt-table: normal subjects - reason for response?

Answer 4

baroreceptor reflex: vagally mediated increase in HR, followed by sympathetically mediated further HR increase. vasoconstriction in splanchnic, renal, skeletal muscle vascular beds

Question 5

orthostatic test/tilt-table: with mild autonomic impairment?

Answer 5

dramatic tachycardia, but no fall in blood pressure. so baroreceptors functional, increased HR accounts for mild peripheral denervation

Question 6

orthostatic test/tilt-table: moderate autonomic neuropathy?

Answer 6

tachycardia, orthostatic hypotension may occur. the worse the neuropathy, the worse the hypotension

Question 7

orthostatic test/tilt-table: severe autonomic neuropathy?

Answer 7

BP can fall to less than 100 mmHg with no change in heart rate

Question 8

valsalva maneuver: what? result?

Answer 8

exhale against a closed glottis = increased intrathoracic pressure

Question 9

valsalva maneuver: see what two things in pressure?

Answer 9

initial increase in aortic pressure (mechanical). followed by cardiac output + BP fall, because of decreased venous input

Question 10

valsalva: what happens to heart rate?

Answer 10

initial decrease in HR, but later reflex tachycardia (+ peripheral vasoconstriction)

Question 11

valsalva: after exhaling what happens?

Answer 11

BP overshoots normal values b/c of persisting vasoconstriction. parasymp effects then cause reflex bradycardia.

Question 12

cold pressor test?

Answer 12

hands in ice water = vasoconstriction, increase in BP, reflex bradycardia

Question 13

mental arithmetic test: what? doesn’t depend on?

Answer 13

stress of doing math in noisy surroundings = increase in pulse rate + BP. response doesn’t depend on activation of afferent limb of a symp reflex arc.

Question 14

skin temp: sympathetic vs. parasymp temp?

Answer 14

sympathetic = cool. parasymp = warm.

Question 15

skin conductance

Answer 15

lie detector: increased sweating = increased skin conductance. but questionable reliability

Question 16

QSART: stands for? what?

Answer 16

quantitative sudomotor axon reflex test. apply ACh to skin, normally causes increased sweating because it evokes an axon reflex from symp cholinergic axons

Question 17

paroxysmal autonomic syncope: what?

Answer 17

fainting: transient decreased perfusion of reticular activating system of brainstem

Question 18

3 causes of paroxysmal autonomic syncope

Answer 18

orthostatic hypothension. acute decrease in cardiac output (from baroreceptor sensitization, or activation of cardiac mechaonoreceptors after prolonged tachycardia). acute increase in cerebrovascular reistance.

Question 19

orthostatic hypotension: drugs?

Answer 19

blockade of sympathetic tone to blood vessels

Question 20

orthostatic hypothension: neurally mediated?

Answer 20

neurally mediate syncope, aka vasovagal attack: sudden change in ANS activity = acute hemodynamic reaction = reverse the normal pattern of outflow that maintains BP

Question 21

orthostatic hypotension: what do the paras/symp do?

Answer 21

increase parasymp outflow = bradycardia. decreased symp = vasodilation

Question 22

orthostatic hypotension: triggered by? (4) pathway of signals?

Answer 22

pain, fear, anxiety, embarassment: descending signals from cortical, limbic or hypothalamic structures to autonomic centers in medulla

Question 23

orthostatic hypotension: peripheral mechs? (2)

Answer 23

compression of carotid barorecetpors. rapid emptying of distended bladder.

Question 24

acute rise in cerebrovascular resistance: causes?

Answer 24

increased intracranial pressure, panic attacks (hyperventilation = decreased CO2 in blood = cerebral vasoconstriction = decreased perfusion of RAS).