hormonal control of BP

Question 1

what are the 3 rapidly acting control mechanisms of MAP? and how fast do these act?

Answer 1

-baroreceptors
-chemoreceptors
-CNS ischemic response
seconds to minutes to act

Question 2

what are the intermediate control mechanisms of MAP? (3) and how fast do these acT?

Answer 2

-renin angiotension vasoconstritcor mechanism
-stress relaxation mechanism
-capillary fluid shift mechanism
minutes to hours

Question 3

what is the long term control of MAP? and how fast does this act?

Answer 3

-volume control by the kidneys (renin-angiotensisin-aldosterone system)
days or longer

Question 4

when does the CNS ischemic response occur?

Answer 4

when there begins to be ischemia in the CNS

Question 5

at what BP is CNS ischemic response stimulated, and when does it receive its maximum degree of stimulation?

Answer 5

activated at BPs below 60 mmHg

receives greatest amount of stimulation of a BP at 15-20 mmHg

Question 6

what is the cushing reaction?

Answer 6

type of CNS ischemic response that results from increased pressure of the CSF around the vrain in the cranial vault

Question 7

relating to the arterial blood pressure, when does the cushing reaction occur?

Answer 7

when the CSF pressure equals that of the arterial blood pressure

Question 8

do the baroreceptor reflexts compensate for the primary disturbance causing the decrease in MAP?

Answer 8

NO!

Question 9

what mechanisms compensate for the primary disturbance causing the decreased MAP?

Answer 9

thrist
transcapillary refill
renal conservation of salt and water

Question 10

what are the 4 major groups of receptors that compensate for the fall in MAP?

Answer 10

• high pressure baroreceptors
• low pressure baroreceptors
• peripheral chemoreceptors
• central chemoreceptors

Question 11

what is the low pressure baroreceptor’s response to decreased MAP?

Answer 11

decrease firing rate due to decreased circulating volume. Leads to increase SNS mediated vasoconstriction, especially in renal bed. They also stimulate ADH release

Question 12

what is the high pressure baroreceptor’s response to decreased MAP?

Answer 12

decrease their firing rate leading to increased HR, cardiac contractility and vasoconstriction

Question 13

describe the function of peripheral chemoreceptors

Answer 13

respond to local hypoxia by increasing firing rate of chemoreceptor afferents leading to increased firing of SNS vasoconstriction fibers and changes in ventilation

Question 14

describe the function of central chemoreceptors

Answer 14

respond to brain ischemia (fall in pH) leading to powerful SNS output (kidney can stop producing urine all together)

Question 15

baroreceptors and chemoreceptors together result in what?

Answer 15

increased TPR enough to keep MAP near normal with moderate blood loss (10-20%) but CO remains depressed

Question 16

how long does renin circulate in the system?

Answer 16

30-60 minutes

Question 17

where is renin synthesized?

Answer 17

kidney in response to decreased MAP

Question 18

what is the function of renin?

Answer 18

if cleaves angiotensinogen to make angiotensin I

Question 19

what enzyme converts angio I to angio II?

Answer 19

ACE

Question 20

where is ACR located

Answer 20

in the endothelium of the lung vessels

Question 21

what is the function of ang II in the short term?

Answer 21

is is a short acting arterial vasoconstrictor

raises MAP by increasing TPR and promotes venous return to the heart by venoconstriction

Question 22

what is the function of ang II in the long term?

Answer 22

• decreases renal excretetion of salt and water–slowly increases ECF volume and then artieral pressure
• also acts on adrenal glad to release aldosterone
• also promotes release of ADH/vasopression from posterior pituitary gland

Question 23

what does unstressed volume refer to?

Answer 23

volume of blood that veins can hold. produces no pressure

Question 24

what does stressed volume refer to?

Answer 24

the volume of blood that veins can hold

this produces pressure by stretching the elastic fibers in the walls of the vessels

Question 25

increased salt intake does what to renin-angiotension activity?

Answer 25

decreases it

Question 26

where is ADH synthesized?

Answer 26

hypothalamus in the supraopic nuclei. some in paraventricular nuclei

Question 27

where is ADH stored and secreted from?

Answer 27

pituitary gland

Question 28

what is the main function of ADH?

Answer 28

water balance

Question 29

list some conditions that will increase the release of ADH

Answer 29

• increased body osmolarity
• decreased blood volume
• decreased BP
• increased levels of ang II
• pain/stress
• nausea/vomiting (because it causes dehyration)

Question 30

what is the effect of atrial nautretic peptide on ADH?

Answer 30

it inhibits it

Question 31

where does the greatest resistance to flow occur?

Answer 31

in the arterioles and small arteries which are regulated by the SNS

Question 32

what is the effect of ANP on smooth muscle?

Answer 32

dilates it

Question 33

what is endothelin?

Answer 33

potent vasoconstrictor derived from the endothelium

Question 34

what types of substances will causes the endothelium to secrete N.O. and PG12

Answer 34

shear stress, acetylcholine and bradykinin

Question 35

what do the low pressure baroreceptors in the heart and pulmonary circulation do?

Answer 35

they respond to changes in blood volume and modulate sympathetic activity and vasopression (ADH) release

Question 36

if there is elevated blood volume in the atrium, what will it secrete?

Answer 36

atrial natiuretic peptide (ANP)

Question 37

what are the effects of ANP?

Answer 37

it has direct effects on the kidney (natriuresis and diuresis) and also inhibits aldosterone release by the adrenal medulla