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Flashcards in hormonal control of BP Deck (37):
1

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

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

2

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

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

3

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

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

4

when does the CNS ischemic response occur?

when there begins to be ischemia in the CNS

5

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

activated at BPs below 60 mmHg
receives greatest amount of stimulation of a BP at 15-20 mmHg

6

what is the cushing reaction?

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

7

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

when the CSF pressure equals that of the arterial blood pressure

8

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

NO!

9

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

thrist
transcapillary refill
renal conservation of salt and water

10

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

-high pressure baroreceptors
-low pressure baroreceptors
-peripheral chemoreceptors
-central chemoreceptors

11

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

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

12

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

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

13

describe the function of peripheral chemoreceptors

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

14

describe the function of central chemoreceptors

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

15

baroreceptors and chemoreceptors together result in what?

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

16

how long does renin circulate in the system?

30-60 minutes

17

where is renin synthesized?

kidney in response to decreased MAP

18

what is the function of renin?

if cleaves angiotensinogen to make angiotensin I

19

what enzyme converts angio I to angio II?

ACE

20

where is ACR located

in the endothelium of the lung vessels

21

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

is is a short acting arterial vasoconstrictor
raises MAP by increasing TPR and promotes venous return to the heart by venoconstriction

22

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

-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

23

what does unstressed volume refer to?

volume of blood that veins can hold. produces no pressure

24

what does stressed volume refer to?

the volume of blood that veins can hold
this produces pressure by stretching the elastic fibers in the walls of the vessels

25

increased salt intake does what to renin-angiotension activity?

decreases it

26

where is ADH synthesized?

hypothalamus in the supraopic nuclei. some in paraventricular nuclei

27

where is ADH stored and secreted from?

pituitary gland

28

what is the main function of ADH?

water balance

29

list some conditions that will increase the release of ADH

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

30

what is the effect of atrial nautretic peptide on ADH?

it inhibits it

31

where does the greatest resistance to flow occur?

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

32

what is the effect of ANP on smooth muscle?

dilates it

33

what is endothelin?

potent vasoconstrictor derived from the endothelium

34

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

shear stress, acetylcholine and bradykinin

35

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

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

36

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

atrial natiuretic peptide (ANP)

37

what are the effects of ANP?

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