Central and humoral control of blood pressure (montemayor LECT)

Question 1

what 9s the short term BP regulation mechanism

Answer 1

Neural

Effectors: Cardiac (SA node, myocardium)
Vascular smooth muscle
Adrenal medulla

Question 2

what is the long term BP regulation mechanism

Answer 2

Endocrine/Paracrine
Effectors:
Vascular smooth muscle
Kidneys (regulation of blood volume)

Question 3

what happens with massive sympathetic discharge on cerebral and cardiac?
what about skin, renal and splanchnic

Answer 3

Minimal effect: cerebral and cardiac resistance vessels

Significant constriction: skin, renal, and splanchnic vessels

Question 4

what is the difference in TPR control of resting versus exercising skeletal muscle?

Answer 4

Resting skeletal muscle: neural control dominates (vasoconstrictor tone)

Exercising skeletal muscle:
intrinsic regulation dominates (vasodilation)
Local metabolic effect in active tissue overrides general sympathetic output during exercise

Question 5

what does B1 agonist do to funny current

Answer 5

If (diastolic Na+ current)
Increases steepness of phase 4 slow depolarization

increases rate of slow depolarization

Question 6

what does B1 agonist do to ca current

Answer 6

Increases steepness of phase 4 slow depolarization
Threshold more negative (reached sooner)

shorter diastolic duration and threshold reached more rapidly so increased HR

Question 7

how does sympathetic input increase contractility

Answer 7

↑ Ca2+ influx via L-type DHDP channels: ↑ [Ca2+]i and ↑ Ca2+-dependent Ca2+ release from the SR

2. ↑ sensitivity of RYR to [Ca2+]i
3. ↑ SERCA activity (remove phospholamban inhibition), ↑ Ca2+ stores
4. ↑ ECF Ca2+ influx, ↑ SR Ca2+ stores over time

Increase

Ca2+ –> ↑ contractile force –> ↑ SV –> ↑ CO

Question 8

how can there be parasympathetic influence on TPR

Answer 8

postganglionic parasympathetic ACh release acts on muscarinic receptors on endothelium of vasculature. this releases NO which causes vasodilation

so this is all indirectly

Question 9

what are the 3 currents that parasympathetic innervation influences and what does it do to these currents

Answer 9

Increased K+ conductance:
More negative maximum diastolic potential (KAch channel)

Decreased funny current:
Decreases slow depolarization rate (steepness of phase 4)

Decreased ICa:
Decreases slow depolarization rate (steepness of phase 4)
Threshold more positive (takes longer to reach)

Question 10

what is the main integration center in the brain

Answer 10

medulla oblongata

key for regulating homeostasis of MAP

mediates sympathetic and parasympathetic effects

Question 11

what is the bainbridge reflex

Answer 11

an increase in venous return causes increased right atrial pressure

these will cause an increase in HR to move blood through more quickly

this opposes the high pressure baroreceptor reflex

Question 12

accumulation of too much CO2 is usually associated with

Answer 12

decreased MAP

Question 13

what do chemoreceptors do in response to too much CO2 (decreased ph)

Answer 13

stimulates vasoconstriction leading to increased TPR

and the opposite happens for decreased CO2 (decrease vasoconstriction)

Question 14

what happens with exercise and CO2 (peripheral)

Answer 14

there is usually normal CO2 levels b/c of hyperventilating during exercise

If PaCO2 incrases then there is going to be generalized vasoconstriction

intrinsic control of exercsiing muscle maintains vasodilation

Question 15

what happens in cerebral ischemia

Answer 15

Local ↑ Pco2, ↑ [H+] leads to peripheral vasoconstriction

Prolonged severe ischemia leads to extreme depression of cerebral function –> MAP falls

Question 16

what is the chemoreceptor response normally

Answer 16

↓ PO2
↑ Pco2
↓ pH,↑ [H+]
Stimulates increased ventilation
Afferents from pulmonary stretch receptors inhibit the cardioinhibitory center → ↑ HR
Increased ventilation: ↓ Pco2 (↓ [H+]) in the brain, inhibiting the cardioinhibitory center → ↑ HR

Net Physiologic Effect: ↑ Sympathetic N.S.
↑ HR
↑ TPR (↑ vasoconstriction)
↑ MAP

Question 17

what is a vasoactive substance

Answer 17

endocrine or paracrine factor that impacts vasodilation or vasoconstriction

Question 18

what are the major vasoconstrictors?

Answer 18

epinephrine
serotonin
ANG II
AVP (ADH) 
Endothelin

Question 19

what are the major vasodilators

Answer 19

Epinephrine 
histamine
ANP
Bradykinins
NO

Question 20

what causes Macula densa cells (of the renal juxtaglomuler apparatus) to secrete renin?

Answer 20

Detection of decrease Na in the distal tubule
which represents a decrease in MAP and decrease in GFR leading to increased Na reabsorption

SNS also stimulates renin release

Question 21

what happens when renin is secreted?

Answer 21

*Converts angiotensinogen –> ANG I

ACE then converts ANG I to ANG II

Question 22

what are the six effects of ANG II

Answer 22

Vasoconstriction
Stimulates adrenal gland aldosterone production
Stimulates ADH/AVP
Stimulates thirst
Stimulates renal Na+ reabsorption
Stimulates SNS activity

Question 23

what does aldosterone do and what is it secreted from?

Answer 23

Secretion by adrenal cortex triggered by ANG II

Promotes renal Na+ reabsorption

H2O follows by osmosis

↑ Effective Circulating Volume

↑ MAP