circulation 5

Question 1

blood vessel function

Answer 1

venous system: collect and store blood
arterial system: distribution and store blood
arterioles: flow and pressure control

Question 2

importance of arterioles and poiseuille’s law:

Answer 2

vascular resistance=vessel length/radius^4
-bp decreases from ventricle to arteries, then decreases very rapidly at arterioles so blood flow does not damage capillaries and can exchange properly with tissues

Question 3

arteriolar vascular smooth muscle (VSM) and blood flow at capillaries

Answer 3

• VSM controls vascular resistance through vasoconstriction/relaxation
• allow blood flow to be prioritized according to tissues that need it, ie. digestion vs exercise
• also because not all capillary beds can be fully perfused with each heartbeat, and cardiac output is finite, so there will always be vascular resistance at some points

Question 4

2 vascular control mechanisms

Answer 4

1. central control via ANS

2. local control (myogenic, paracrine, autocrine, or gasomitter)

Question 5

central control via ans

Answer 5

-nerual and hormonal, ie. sympathetic nerves, alpha adrenergic vasocontrictions, and beta-adrenergic vasorelaxations

Question 6

local control

Answer 6

myogenic: originate in the muscle, stretch of arterial wall=-ve feedback
paracrine: cell-cell stimulation, endothelin, histamine
autocrine: same-cell stimulation, ie metabolit like adp or H+
gasomitterL NO, CO, H2S

Question 7

local control of arteriolar vr

Answer 7

-controlled by metobolic need (ie hypoxia), which alters vascular tone:
decreased o2 and increased waste causes arteriolar smooth muscle to vasodilate, decreasing resistance, increasing blood flow, and increasing o2 delivery, co2 and waste removal
-this is a negative feedback loop

Question 8

vasoconstriction causing substances

Answer 8

stretch of arteriolar wall, endothelin, serotonin, vasopressin, norepinephrine

Question 9

vasodilation causing substances

Answer 9

hypoxia, increased co2, H+, K+, nitric hoxide, epinephrine, ACh

Question 10

regulating central arterial bp/mean arterial blood pressure (map)

Answer 10

MAP=Q*TPR

• controlled by ANS
• decreased sympathetic output=DECREASED NOREPIN RELEASE CAUSES vasodilation, decreased ventricle contraction, and slowing sa node rate
• vasodilation decreases peripheral resistance TPR, and decrease contractions and heart rate decreases output Q

Question 11

blood pressure sensing system to regulate high map

Answer 11

-sensors: arterial baroreceptors/stretch receptors increase discharge to medulla in proportion to bp
-control centre, medulla: processes input and adjusts arteriolar tone
-effector system: symp/parasym innervation of heart and vessels (symp=less adrenal release)
MAP(or BP)=QTPR (cardiac outputtotal peripheral resistance)

Question 12

human bp vs fish

Answer 12

human bp much higher than fish because terrestrial

Question 13

guiding principles

Answer 13

1. hearts generate bp
2. pressure gradients needed for blood flow
3. valves regulate direction
4. bp lost primarily at arterioles and control distribution to capillary beds
5. all caps cannot be fully perfused, priorities go to the tissues most needing
6. central/mean arterial bp is regulated