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Flashcards in CONTROL OF CIRCULATION Deck (23)
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1

what is resistance like in arteries?

low resistance - media contains elastic and smooth muscles which cushions systole

2

what is resistance like in arterioles?

high
total arteriolar resistance = total peripheral resistance

3

which circulating humoral factors are vasoconstrictors?

epinephrine - acts on alpha receptors
angiotensin II
vasopressin

4

which circulating humoral factors are vaosdilators?

epinephrine - acts on beta receptors
atrial natriuretic peptide

5

which local humoral factors are vasoconstrictors?

endothelin-1 produced by endothelium
internal blood pressure - autoregulation

6

which local humoral factors are vasodilators?

hypoxia
prostacyclin
adenosine
NO- from endothelium
CO2
K+
H+
tissue breakdown products

7

how is NO produced?

ACh and insulin stimulate calcium release which leads to L arginine being converted to NO aided by NO synthase
NO results in target vessels dilating

8

how is endothelin - 1 produced?

angiotensin II, vasopressin, cytokines, thrombin, oxidative reactive species, shearing forces all stimulate production of endothelin-1
big endothelin 1 (ET1) converted to endothelin 1 by endothelin converting enzyme
endothelin 1 acts on G coupled proteins which stimulate IP3 calcium release - results in smooth muscle contraction

9

what systems control blood volume?

RAAS system
ADH
adrenal and kidneys

10

how is circulation controlled?

autoregulation (smooth muscles)
local mediators
humoral mediators
baroreceptors (pressure sensing)
central (neural control loops)

11

what are peripheral chemoreceptors sensitive to?

very sensitive to pO2
will also detect pCO2 and pH decrease

12

what happens when chemoreceptors detect a decrease in pO2?

increased sympathetic and decreased parasympathetic output
this increases heart rate
this increases cardiac output
increases breathing rate as well

13

what do central chemoreceptors detect?

most sensitive to PCO2 and pH
less sensitive to pO2

14

what does increased firing of central chemoreceptors result in?

increased sympathetic output
this causes arterial vasoconstriction in skeletal muscle, renal and splanchnic system
this increases TPR

15

where are baroreceptors found?

primarily in carotid sinus and aortic arch

secondary in vein, myocardium and pulmonary vessels

16

what are the afferent nerves from baroreceptors?

glossopharyngeal nerve to medulla

17

what are the efferent nerves from baroreceptors?

sympathetic and vagus

18

what happens when baroreceptors detect and increased blood pressure?

baroreceptors send impulses via glossopharyngeal nerve to medulla where there is increased firing
this results in parasympathetic stimulation of vagus nerve and a decrease in sympathetic stimulation
this results in decreased CO and TPR

19

what is the role of arterial baroreceptors?

- they are involved in short term regulation of BP
- new baseline is formed if arterial pressure has deviated for more than a few days - can lead to hypertension

20

what is the role of cardiopulmonary baroreceptors?

found in atria, ventricles and pulmonary artery
- when baroreceptors are stimulated, it decreases vasoconstrictors and decreases BP
- the decreased release of angiotensin, aldosterone and vasopressin leads to fluid loss

21

what is the effect of high PaCO2 being detected by central chemoreceptors?

vasoconstriction
this leads to high peripheral resistance and high blood pressure

22

what is the effect of low PaCO2 being detected by central chemoreceptors?

low medullary activity
this decreases blood pressure

23

what are the key central effectors of blood pressure control?

blood vessels (vasoconstriction/dilation)
heart (rate/contractility)
kidney (fluid balance)