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Cardiovascular: physiology > Integration of Cardiovascular Mechanisms > Flashcards

Integration of Cardiovascular Mechanisms Flashcards

1
Q

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

A

the blood and the tissues

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2
Q

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

A

Mainly autonomic nervous system but an have some hormonal control

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3
Q

how is the TPR controlled?

A

it is regulated by vascular smooth muscles

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4
Q

what is the main site of TPR?

A

the arterioles

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5
Q

what does contraction of vascular smooth muscles cause?

A

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

relaxation causes the opposite

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6
Q

resistance to blood flow is directly proportional to____ and ____

A

blood viscosity and length of blood vessel

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7
Q

resistance to blood flow is inversely proportional to ____

A

the radius of the blood vessel to the power 4

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8
Q

what is the Resistance to flow equation?

A

R ∝ η.L

r4

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9
Q

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

A

by changes in the radius of arterioles

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10
Q

the smaller the radius …..

A

the higher the resistance

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11
Q

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

A

nerves and hormones

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12
Q

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

A

baroreceptor reflex

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13
Q

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

A

noradrenaline

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14
Q

what is the receptor for vascular smooth muscle for noradrenaline

A

alpha receptors

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15
Q

resistance is _____ proportional to the radius ^4

A

inversely

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16
Q

flow is _____ proportional to the radius ^4

A

directly

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17
Q

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

A

vasomotor tone

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18
Q

what causes the vasomotor tone?

A

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

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19
Q

what will increased sympathetic discharge do?

A

increase the vasomotor tone resulting in vasoconstriction

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20
Q

what will decreased sympathetic tone do?

A

decrease the vasomotor tone

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21
Q

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

A

there is no significant innervation

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22
Q

what hormone controls vascular smooth muscle

A

adrenaline

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23
Q

what is the effect of adrenaline largely dependent on?

A

the organ it is acting on. It is organ specific

24
Q

what does adrenaline acting on alpha receptors do?

A

causes vasoconstriction

25
Q

what does adrenaline acting on beta receptors do?

A

causes vasodilation

26
Q

where are alpha receptors predominant?

A

in skin, gut, kidney arterioles

27
Q

where are beta receptors predominant?

A

in cardiac and skeletal muscle arterioles

28
Q

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

A

that there is strategic redistribution of blood

29
Q

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

A

angiotensin II: causes vasoconstriction

ADH : causes vasoconstriction

these are important in the intermediate control of blood pressure

30
Q

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

A

chemical and physical factors

31
Q

what do the intrinsic mechanisms do?

A

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

32
Q

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?

A

Decreased local PO2

Increased local PCO2

Increased local [H+] (decreased pH)

Increased extra-cellular [K+]

Increased osmolality of ECF

Adenosine release (from ATP)

33
Q

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

A

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

34
Q

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

A

local humoral agents

35
Q

when are local humoral agents released?

A

can be released in response to tissue injury or inflammation

36
Q

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

A

histamine

bradykinin

NO

37
Q

how often and where is NO released from?

A

this is released continuously by endothelial cells of arteries and arterioles

38
Q

how is NO produces?

A

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

39
Q

what does NO do?

A

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

40
Q

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

A
  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)
41
Q

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

A

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

42
Q

what happens in receptor stimulated NO formation?

A

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

43
Q

what does NO do once formed?

A

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

44
Q

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

A

serotonin

thromboxane A2

leukotrienes

endothelin

45
Q

what is endothelin?

A

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

46
Q

what sometimes produce serotonin and thromboxane A 2

A

platelets

47
Q

what factors can cause endothelial damage/ dysfunction?

A

high BP,
high cholesterol
diabetes and smoking

48
Q

what are some of the functions of endothelial vasodilatores?

A

anti-thrombotic, anti-inflammatory, anti-oxidants

49
Q

what are some of the functions of endothelial vasoconstrictors?

A

pro-thrombotic, pro-inflammatory, pro-oxidants

50
Q

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

A
  • temperature
  • myogenic response
  • sheer stress
51
Q

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

A

resistance vessels automatically constrict to limit flow

52
Q

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

A

resistance vessels automatically dilate to increase flow

53
Q

which organs if myogenic response important for?

A

brain and kidneys

54
Q

what effect does sheer stress have?

A

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

55
Q

what is the main controller of BP in the cerebrum?

A

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

56
Q

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 )

A

yes

Cardiovascular: physiology (11 decks)

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