Blood Pressure Regulation

Question 1

what are the three major determinants of BP

Answer 1

1. blood volume
2. vascular resistance
3. compliance

Question 2

what is blood pressure and how does it change throughout the circulatory system

Answer 2

force exerted by the blood per unit area of the vessel wall

arteries: high pressure system
venous: low pressure system

Question 3

what affects preload

Answer 3

vein compliance
blood volume

Question 4

what is intrinsic regulation of blood flow

Answer 4

mechanisms used by the critical organs (heart, brain, kidney, spinal cord, working skeletal muscle) to maintain perfusion based on metabolic need

uses local mediators to maintain stable perfusion pressure to organs despite changes in systemic pressure

Question 5

what are the short term BP regulatory mechanisms

Answer 5

1. ANS regulation
2. baroreceptor reflex
3. chemoreceptor reflex
4. arterial and pulmonary reflexes

Question 6

what are the long term BP regulatory mechanisms

Answer 6

1. RAAS system
2. natriuretic peptides

Question 7

how does ANS regulation of blood pressure work

Answer 7

vasomotor center (in medulla) sends signals to the heart and blood vessels via the spinal cord (SNS) or vagus nerve (PNS)

Question 8

does SNS or PNS predominate BP signaling to heart and vasculature

Answer 8

sympathetic

parasympathetic predominates heart rate control

Question 9

vasomotor tone

Answer 9

the continuous partial contraction of the vasculature that is maintained by the vasomotor center continuously transmitting signals

maintains baseline level of constriction (tone)

Question 10

sympathetic nervous system receptor types and effects

Answer 10

a1/a2: arterioles and veins –> vasoconstriction
- arteriole vasoconstriction = decrease blood flow and increase SVR
- venous vasoconstriction = increase venous return/preload

B1: cardiomyocytes and conduction cells –> increase chrono/dromo/ino/lusitropy to increase CO

B2: coronary and skeletal arterioles –> vasodilation –> increase blood flow to coronary arteries and skeletal muscle

Question 11

parasympathetic nervous system receptor types and effects

Answer 11

M2: SA and AV node, atria –> decrease chrono/dromotropy –> decrease CO and oppose SNS

Question 12

baroreceptor reflex

Answer 12

negative feedback loop that relies almost exclusively on neural reflexes that control ANS

inc. BP causes stretch –> BR detect stretch –> increase firing to vasomotor center –> inc PNS and dec SNS –> vasodilation and decreased CO

Question 14

where are baroreceptors located

Answer 14

carotid sinus
aortic arch

Question 15

what afferent nerves do the baroreceptors in the carotid sinus use

Answer 15

hering’s nerve –> CN IX (glossopharyngeal)

Question 16

what afferent nerves do the baroreceptors in the aortic arch use

Answer 16

aortic nerve –> CN X (vagus nerve)

Question 17

what is the overall function of the baroreceptor reflex

Answer 17

to buffer acute changes in systemic BP associated with daily events

maintains a stable MAP despite acute changes

Question 18

what two conditions decrease responsiveness of the body to baroreceptor signaling

Answer 18

1. heart failure
2. systemic hypertension

Question 19

vago-vagal syncope

Answer 19

exaggerated baroreceptor reflex response in which a sudden change in posture/excitement can cause a drastic increase in PNS/decrease in SNS signaling

leads to rapid vasodilation and decreased HR –> sudden drop in BP –> syncope (fainting)

Question 20

chemoreceptor reflex

Answer 20

responds to acute drops in pO2 and rises in pCO2 (when blood pressure drops below systolic 80 mmHg)

chemoreceptors signal to VM center –> increase in SNS signaling –> increase HR and vasoconstriction

Question 21

components of the RAAS system that result in long term BP regulation

Answer 21

1. ANG II
2. aldosterone
3. ADH

Question 21

mechanism of RAAS system

Answer 21

JG apparatus sense decreases in BP or NaCl delivery –> JG cells release renin –> renin converts angiotensinogen to ANG I –> ACE converts ANG I to ANG II –> vasoconstriction + Na/H2O reabsorption + aldosterone + ADH secretion

Question 21

what stimulates renin release

Answer 21

SNS stimulation
renal (and systemic) hypotension
decreased NaCl delivery to JG apparatus

Question 23

what produces aldosterone and what are its effects

Answer 23

adrenal cortex

increase Na/H2O reabsorption
increase K excretion

overall increase in blood volume

Question 24

what produces ADH and what are its effects

Answer 24

(vasopressin) posterior pituitary

increased water reabsorption
vasoconstriction

Question 25

what are the effects of ANG II

Answer 25

vasoconstriction
aldosterone release
ADH release
direct stimulation of Na/H2O reabsorption
stimulates thirst
stimulates SNS

Question 26

natriuretic peptides

Answer 26

hormones secreted by cardiomyocytes in response to wall stress of stretch

intrinsic mechanism in response to VOLUME overload

Question 27

effect of natriuretic peptides

Answer 27

counteract diuretic hormones by causing vasodilation and Na/H2O excretion, and inhibiting renin release

BUT - body favors RAAS, so chromic RAAS and SNS stimulation overpowers natriuretic peptides

Question 28

what can be used as a biomarker of heart disease

Answer 28

pro-BNP; synthesized by the ventricles

high levels indicates overproduction in response to a constitutive activation of RAAS during heart disease