Control of systemic arterial blood pressure

Question 1

list the 3 major principles guiding circulatory function

Answer 1

1. tissue blood flow the meets each tissue’s needs
2. cardiac output that moves into circulation all the blood returned to the heart
3. maintain constant, normal mean arterial blood pressure

Question 2

calculate mean arterial pressure (MAP) when given systolic and diastolic blood pressure

Answer 2

MAP = DBP + 1/3(SBP-DBP)
MAP = CO X SVR
MAP = (HR X SV) X SVR

Question 3

name the 2 branches of the autonomic nervous system

Answer 3

motor and sensory; sympathetic and parasympathetic

Question 4

describe the neurotransmitters, receptors, and effects of receptor stimulation associated with each ANS branch

Answer 4

Sympathetic (adrenergic) receptors are activated by:
norepinephrine: neurotransmitter released from sympathetic nerves
epinephrine (adrenaline): hormone released into bloodstream by adrenal glands in response to sympathetic stim

alpha-1 adrenergic receptors: in most vascular beds, cause vasoconstriction
beta-1 adrenergic receptors: increased heart rate and contractility
beta-2 adrenergic receptors: in some vascular beds, cause vasodilation

Parasympathetic (muscarinic) receptors:
activated by acetylcholine (a neurotransmitter released from parasympathetic nerve terminals); stimulation leads to decreased heart rate, and a minor decrease in contractility

Question 5

understand the global cardiovascular effects of increased sympathetic nervous system tone

Answer 5

effect of increased sympathetic tone: increase in MAP, increase CO by increased HR and contractility via increase in beta-1, increase in net vasoconstriction (SVR) by increasing alpha-1 more than beta-2

effect of decreased parasympathetic tone: increase in MAP, increased HR and decreased parasympathetic muscarinic receptors, minimal effect on SVR

effect of decreased sympathetic tone: resultant decrease in MAP; decreased HR and contractility (CO) by decrease in beta-1, decreased SVR by causing net vasodilation by decreasing alpha-1

effect on increased parasympathetic tone: resultant decrease in MAP by decreasing HR and increasing muscarinic receptors (CO), minimal effect on SVR

Question 6

diagram and label the neural pathways associated with the baroreceptor reflex and explain the effects of baroreceptor stimulation on mean arterial pressure

Answer 6

1. increase in MAP causes increased stretch of arterial baroreceptors (located in the carotid sinuses and walls of the aortic arch)
2. increased stretch of arterial baroreceptors causes increase firing rate of signals carried from carotid baroreceptors by CN IX (glossopharyngeal) and aortic baroreceptors by CNX (vagus)
3. these increased signals reach the vasomotor center of the brain, which responds by decreasing sympathetic outflow and increasing parasympathetic outflow
4. the decreased sympathetic outflow causes generalized systemic vasodilation, decreased heart rate, and decreased contractility to lower MAP
5. the increased parasympathetic outflow decreases heart rate and contractility to decrease MAP

Question 7

what is the baroreceptor reflex essential for?

Answer 7

essential for acute, short term BP adjustments after abrupt changes in
1. blood volume
2. cardiac output
3. systemic vascular resistance
4. changes in body position