Integration of Cardiovascular Mechanisms

Question 1

the capillaries are the site of exchange of gas, nutrients and water between….

Answer 1

the blood and the tissues

Question 2

what is the main factor affecting the regulation of heart rate?

Answer 2

Mainly autonomic nervous system but an have some hormonal control

Question 3

how is the TPR controlled?

Answer 3

it is regulated by vascular smooth muscles

Question 4

what is the main site of TPR?

Answer 4

the arterioles

Question 5

what does contraction of vascular smooth muscles cause?

Answer 5

vasoconstriction and increase TPR and MAP (i.e. pressure upstream)

relaxation causes the opposite

Question 6

resistance to blood flow is directly proportional to____ and ____

Answer 6

blood viscosity and length of blood vessel

Question 7

resistance to blood flow is inversely proportional to ____

Answer 7

the radius of the blood vessel to the power 4

Question 8

what is the Resistance to flow equation?

Answer 8

R ∝ η.L

r4

Question 9

what is the main way that resistance t flow is regulated?

Answer 9

by changes in the radius of arterioles

Question 10

the smaller the radius …..

Answer 10

the higher the resistance

Question 11

what are 2 examples of extrinsic control of vascular smooth muscle?

Answer 11

nerves and hormones

Question 12

what reflex regulates the innervation which is important to blood pressure regulation?

Answer 12

baroreceptor reflex

Question 13

The vascular smooth muscles are supplied by SYMPATHETIC nerve fibers. What is the neurotransmitter?

Answer 13

noradrenaline

Question 14

what is the receptor for vascular smooth muscle for noradrenaline

Answer 14

alpha receptors

Question 15

resistance is _____ proportional to the radius ^4

Answer 15

inversely

Question 16

flow is _____ proportional to the radius ^4

Answer 16

directly

Question 17

there is a constant constriction on the blood vessels even at rest. what is this called?

Answer 17

vasomotor tone

Question 18

what causes the vasomotor tone?

Answer 18

caused by tonic discharge of sympathetic nerves resulting in continuous release of noradrenaline

Question 19

what will increased sympathetic discharge do?

Answer 19

increase the vasomotor tone resulting in vasoconstriction

Question 20

what will decreased sympathetic tone do?

Answer 20

decrease the vasomotor tone

Question 21

what is the effect of parasympathetic innervation of arterial smooth muscles?

Answer 21

there is no significant innervation

Question 22

what hormone controls vascular smooth muscle

Answer 22

adrenaline

Question 23

what is the effect of adrenaline largely dependent on?

Answer 23

the organ it is acting on. It is organ specific

Question 24

what does adrenaline acting on alpha receptors do?

Answer 24

causes vasoconstriction

Question 25

what does adrenaline acting on beta receptors do?

Answer 25

causes vasodilation

Question 26

where are alpha receptors predominant?

Answer 26

in skin, gut, kidney arterioles

Question 27

where are beta receptors predominant?

Answer 27

in cardiac and skeletal muscle arterioles

Question 28

what does this organ specific effect of adrenaline mean during exercise?

Answer 28

that there is strategic redistribution of blood

Question 29

what are the other hormones that can affect vascular smooth muscles?

Answer 29

angiotensin II: causes vasoconstriction ADH : causes vasoconstriction these are important in the intermediate control of blood pressure

Question 30

what kind of factors are involved in the intrinsic control of vascular smooth muscle?

Answer 30

chemical and physical factors

Question 31

what do the intrinsic mechanisms do?

Answer 31

match the blood flow of different tissues to their metabolic needs. They can OVER_RIDE the extrinsic control mechanisms in specific tissues

Question 32

what are examples of factors which chemical factors causing local metabolic changes which influence the contraction of arteriolar smooth muscles causing relaxation and thus vasodilation?

Answer 32

Decreased local PO2 Increased local PCO2 Increased local [H+] (decreased pH) Increased extra-cellular [K+] Increased osmolality of ECF Adenosine release (from ATP)

Question 33

what does decreased local PO2 cause in pulmonary circulation and what does it cause in systemic circulation?

Answer 33

decreased local Po2 will cause vasoconstriction in the pulmonary circulation and vasodilatation in the systemic circulation

Question 34

what other local chemicals released within an organ influence the contraction of arteriolar and arterial smooth muscles?

Answer 34

local humoral agents

Question 35

when are local humoral agents released?

Answer 35

can be released in response to tissue injury or inflammation

Question 36

what are some examples of humoral agents which cause RELAXATION and thus VASODILATATION?

Answer 36

histamine bradykinin NO

Question 37

how often and where is NO released from?

Answer 37

this is released continuously by endothelial cells of arteries and arterioles

Question 38

how is NO produces?

Answer 38

NO is continuously produced by the vascular endothelium from the amino acid L-arginine through enzymatic action of Nitric Oxide Synthase (NOS)

Question 39

what does NO do?

Answer 39

NO is a potent vasodilator (with a short life of few seconds) which is important in the regulation of blood flow and maintenance of vascular health

Question 40

what are the two main stimuli which can up regulate the production of NO?

Answer 40

1. shear stress on the vascular endothelium as a result of increased flow (flow dependent NO formation) 2. chemical stimuli can also induce NO formation (receptor stimulated NO formation)

Question 41

what happens in flow dependent No formation as a result of increased flow?

Answer 41

this causes the release of calcium in vascular endothelial cells and the subsequent activation of NOS - the NOS makes NO

Question 42

what happens in receptor stimulated NO formation?

Answer 42

stimulators like bradykinin and things are vasoactive stimulators which can stimulate NO formation

Question 43

what does NO do once formed?

Answer 43

diffuses from the vascular endothelium into the adjacent smooth muscle cells where it activates the formation of cGMP that serves as a second messenger for signalling smooth muscle relaxation

Question 44

what are some examples of humoral agents which cause contraction and thus VASOCONSTRICTION?

Answer 44

serotonin thromboxane A2 leukotrienes endothelin

Question 45

what is endothelin?

Answer 45

this is a potent vasoconstrictor released from endothelial cells. Its production is stimulated by various agents which cause vasoconstriction

Question 46

what sometimes produce serotonin and thromboxane A 2

Answer 46

platelets

Question 47

what factors can cause endothelial damage/ dysfunction?

Answer 47

high BP, high cholesterol diabetes and smoking

Question 48

what are some of the functions of endothelial vasodilatores?

Answer 48

anti-thrombotic, anti-inflammatory, anti-oxidants

Question 49

what are some of the functions of endothelial vasoconstrictors?

Answer 49

pro-thrombotic, pro-inflammatory, pro-oxidants

Question 50

what are 3 examples of physical intrinsic factors that control smooth muscle

Answer 50

- temperature - myogenic response - sheer stress

Question 51

what is the myogenic response if MAP rises (in a specific organ) ?

Answer 51

resistance vessels automatically constrict to limit flow

Question 52

what is the myogenic response if MAP falls (in a specific organ) ?

Answer 52

resistance vessels automatically dilate to increase flow

Question 53

which organs if myogenic response important for?

Answer 53

brain and kidneys

Question 54

what effect does sheer stress have?

Answer 54

Dilatation of arterioles causes sheer stress in the arteries upstream to make them dilate. This increases blood flow to metabolically active tissues

Question 55

what is the main controller of BP in the cerebrum?

Answer 55

myogenic response - this helps to keep a relatively constant blood flow in relation to a changing BP

Question 56

Sympathetic nervous system plays the primarily role on the control of arteriolar radius and TPR (the brain is an exception, where vasoconstriction will increase the TPR )

Answer 56

yes