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Cardiovascular > Physiology 6 + 7 > Flashcards

Physiology 6 + 7 Flashcards

1
Q

What are veins?

A

Capacitance vessels (contain most blood volume during rest ~60%)

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2
Q

What regulates HR? SV?

A
  • HR - autonomic NS

* SV - pre-load, myocardial contractility, after-load

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3
Q

What must be regulated to regulate MAP?

A

HR, SV and SVR

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4
Q

How is SVR regulated?

A

Vascular smith muscles

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5
Q

What is the main site of SVR?

A

Arterioles

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6
Q

What increases SVR and MAP? Decreases?

A
  • Vasoconstriction increases

* Vasodilation decreases

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7
Q

What are vascular smooth muscles controlled by?

A

Extrinsic and intrinsic mechanisms

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8
Q

What is the relationship between resistance to blood flow and blood viscosity? Blood vessel length? Radius of the blood vessel?

A
  • Resistance increases as blood viscosity increases
  • Resistance increases as blood vessel length increases
  • Resistance decreases as blood vessel radius increases
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9
Q

What is the equation for resistance to blood flow?

A

R = n x L/r^4

n = blood viscosity 
L = length of blood vessel
r = radius of blood vessel
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10
Q

What is resistance to blood flow mainly controlled by?

A

Vascular smooth muscles through changes in radius of arterioles

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11
Q

What does extrinsic control of vascular smooth muscle involve?

A

Hormones and nerves

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12
Q

What are vascular smooth muscles innervated by?

A

Sympathetic nerve fibres

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13
Q

What neurotransmitter is involved in vascular smooth muscle contraction?

A

Noradrenaline acting on a (alpha) receptors

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14
Q

What is vasomotor tone?

A

Vessels partially constricted at rest

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15
Q

What is equation for resistance? Flow?

A 
Resistance = 1/r^4
Flow = r^4
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16
Q

What is vasomotor tone caused by?

A

Tonic discharge of sympathetic nerves resulting in continuous release of noradernaline

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17
Q

What will increase vasomotor tone?

A

Increased sympathetic discharge resulting in vasoconstriction

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18
Q

What will decrease vasomotor tone?

A

Decreased sympathetic discharge resulting in vasodilation

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19
Q

Is there parasympathetic innervation of smooth muscle?

A

No, except for penis and clitoris

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20
Q

What hormone is involved in extrinsic control of vascular smooth muscle?

A

Adrenaline from adrenal medulla

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21
Q

What are the effects of adrenaline? (2)

A
  • Adrenaline acting on alpha receptors causes vasoconstriction
  • Adrenaline acting on B2 receptors causes vasodilation
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22
Q

Where are alpha receptors found? B2 receptors?

A
  • Alpha - skin, gut and kidney arterioles

* B2 - cardiac and skeletal muscle arterioles

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23
Q

What is the benefit of the effects of adrenaline being largely organ-specific?

A

Helps with strategic redistribution of blood e.g. during exercise

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24
Q

What are other hormones that affect vascular smooth muscle? (2)

A
  • Angiotensin II causes vasoconstriction

* Antidiuretic hormone causes vasoconstriction

25
Q

What does intrinsic control of vascular smooth muscle include?

A

Chemical and physical factors

26
Q

What is the role of intrinsic control of vascular smooth muscle?

A

Match blood flow of different tissues to their metabolic needs

27
Q

What do intrinsic control mechanisms of vascular smooth muscles have the ability to do?

A

Ove-ride extrinsic control mechanisms

28
Q

What are examples of intrinsic chemical control of vascular smooth muscle? (2)

A
  • Local metabolites

* Local humoral agents

29
Q

How do local metabolites cause VASODILATION and metabolic hyperaemia? (6)

A
  • Decreased local PO2
  • Increased local PCO2
  • Increased local [H+] (decreased pH)
  • Increased extra-cellular [K+]
  • Increased osmolality of ECF
  • Adenosine release from ATP
30
Q

What are local humeral agents released in response to?

A

Tissue injury or inflammation

31
Q

What are examples of local humeral agents that cause vasodilation of arterioles?

A
  • Histamine
  • Bradykinin
  • Nitric oxide (NO) - continuously released by endothelial cells of arteries and arterioles
32
Q

What is nitric oxide produced by?

A

Continuously produced by vascular endothelium from amino acid L-arginine through enzymatic action of nitric oxide synthase (NOS)

33
Q

What is nitric oxide?

A

Potent vasodilator with a short half life of a few seconds

34
Q

What is NO important in? (2)

A

Regulation of blood flow and maintenance of vascular health

35
Q

What results in activation of NOS? (2)

A
  • Stress on vascular endothelium as a result of increased flow
  • Causes release of calcium in vascular endothelial cells which activates NOS
36
Q

What is activation of NOS by increased flow called?

A

Flow dependent NO formation

37
Q

What is receptor simulated NO formation?

A

Chemical stimuli inducing NO formation

38
Q

How does NO cause vasodilation?

A
  • Diffuses from vascular endothelium into smooth muscle cells
  • Activates formation of cGMP which is a second messenger for signalling smooth muscle relaxation
39
Q

What are examples of local humeral agents that cause vasoconstriction of arterioles? (4)

A
  • Serotonin
  • Thromboxane A2
  • Leukotrienes
  • Endothelin
40
Q

What is endothelin?

A

Potent vasoconstrictor released from endothelial cells

41
Q

What can endothelial damage/dysfunction be caused by? (4)

A
  • High blood pressure
  • High cholesterol
  • Diabetes
  • Smoking
42
Q

What are features of endothelial-produced vasodilators?

A
  • Anti-thrombotic
  • Anti-inflammatory
  • Anti-oxidants
43
Q

What are features of endothelial-produced vasoconstrictors? (3)

A
  • Pro-thrombotic
  • Pro-inflammatory
  • Pro-oxidants
44
Q

What are examples of intrinsic physical control of vascular smooth muscle?

A
  • Temperature
  • Myogenic response to stretch
  • Sheer stress
45
Q

How does temperature control vascular smooth muscle? (2)

A
  • Cold - causes vasoconstriction

* Warmth - causes vasodilation

46
Q

How does myogenic response to stretch control vascular smooth muscle?

A
  • If MAP rises, resistance vessels constrict to reduce blood flow
  • If MAP falls, resistance vessels dilate to increase flow
47
Q

What tissues is myogenic response to stretch important in? (2)

A

Brain and kidneys

48
Q

How does sheer stress control vascular smooth muscle?

A

Dilatation of arterioles causes sheer stress in the arteries upstream to make them dilate

49
Q

What is the effect of vasodilation caused by sheer stress?

A

Increases blood flow to metabolically active tissues

50
Q

What factors increase venous return? (5)

A
  • Increased venomotor tone
  • Increased skeletal muscle pump
  • Increased respiratory pump
  • Increased stroke volume
  • increased blood volume
51
Q

What are venous smooth muscles supplied with?

A

Sympathetic nerve fibres

52
Q

What does increased VENOmotor tone result in?

A
  • Increased venous return
  • Increased SV
  • Increased MAP
53
Q

What does increased VASOmotor tone result in? (2)

A
  • Increased SVR

* Increased MAP

54
Q

How does skeletal muscle pump increase venous return?

A
  • Large veins in limbs lie between skeletal muscles

* Contraction of muscles aids venous return

55
Q

What is heart rate influenced by?

A
  • Parasympathetic stimulation
  • Sympathetic stimulation
  • Hormone adrenaline
56
Q

What are acute CVS responses to exercise? (7)

A
  • Sympathetic nerve activity increases
  • HR and SV increase which increases CO
  • Sympathetic vasomotor nerves reduce flow to kidneys and gut - vasoconstriction
  • In skeletal and cardiac muscle, metabolic hyperaemia overcomes vasomotor drive - vasodilation
  • Blood flow to skeletal and cardiac muscles increase
  • Increase in CO increases systolic blood pressure
  • Metabolic hyperaemia decreases SVR and decreases DBP (pulse pressure increases)
57
Q

What are the acute CVS responses to exercise known as?

A

Post-exercise hypotensive response

58
Q

What are chronic CVS responses to regular exercise? (6)

A
  • Reduction in sympathetic tone and noradrenaline levels
  • Increased parasympathetic tone to the heart
  • Cardiac remodelling
  • Reduction in plasma renin levels
  • Improved endothelial function: increased vasodilators, decreased vasoconstrictors
  • Arterial stiffening

Cardiovascular (28 decks)

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