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Cardiovascular > Physiology 6 + 7 > Flashcards

Physiology 6 + 7 Flashcards

(58 cards)

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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)

Study These Flashcards
A
  • Angiotensin II causes vasoconstriction

* Antidiuretic hormone causes vasoconstriction

25
What does intrinsic control of vascular smooth muscle include?
Chemical and physical factors
26
What is the role of intrinsic control of vascular smooth muscle?
Match blood flow of different tissues to their metabolic needs
27
What do intrinsic control mechanisms of vascular smooth muscles have the ability to do?
Ove-ride extrinsic control mechanisms
28
What are examples of intrinsic chemical control of vascular smooth muscle? (2)
* Local metabolites | * Local humoral agents
29
How do local metabolites cause VASODILATION and metabolic hyperaemia? (6)
* Decreased local PO2 * Increased local PCO2 * Increased local [H+] (decreased pH) * Increased extra-cellular [K+] * Increased osmolality of ECF * Adenosine release from ATP
30
What are local humeral agents released in response to?
Tissue injury or inflammation
31
What are examples of local humeral agents that cause vasodilation of arterioles?
* Histamine * Bradykinin * Nitric oxide (NO) - continuously released by endothelial cells of arteries and arterioles
32
What is nitric oxide produced by?
Continuously produced by vascular endothelium from amino acid L-arginine through enzymatic action of nitric oxide synthase (NOS)
33
What is nitric oxide?
Potent vasodilator with a short half life of a few seconds
34
What is NO important in? (2)
Regulation of blood flow and maintenance of vascular health
35
What results in activation of NOS? (2)
* Stress on vascular endothelium as a result of increased flow * Causes release of calcium in vascular endothelial cells which activates NOS
36
What is activation of NOS by increased flow called?
Flow dependent NO formation
37
What is receptor simulated NO formation?
Chemical stimuli inducing NO formation
38
How does NO cause vasodilation?
* Diffuses from vascular endothelium into smooth muscle cells * Activates formation of cGMP which is a second messenger for signalling smooth muscle relaxation
39
What are examples of local humeral agents that cause vasoconstriction of arterioles? (4)
* Serotonin * Thromboxane A2 * Leukotrienes * Endothelin
40
What is endothelin?
Potent vasoconstrictor released from endothelial cells
41
What can endothelial damage/dysfunction be caused by? (4)
* High blood pressure * High cholesterol * Diabetes * Smoking
42
What are features of endothelial-produced vasodilators?
* Anti-thrombotic * Anti-inflammatory * Anti-oxidants
43
What are features of endothelial-produced vasoconstrictors? (3)
* Pro-thrombotic * Pro-inflammatory * Pro-oxidants
44
What are examples of intrinsic physical control of vascular smooth muscle?
* Temperature * Myogenic response to stretch * Sheer stress
45
How does temperature control vascular smooth muscle? (2)
* Cold - causes vasoconstriction | * Warmth - causes vasodilation
46
How does myogenic response to stretch control vascular smooth muscle?
* If MAP rises, resistance vessels constrict to reduce blood flow * If MAP falls, resistance vessels dilate to increase flow
47
What tissues is myogenic response to stretch important in? (2)
Brain and kidneys
48
How does sheer stress control vascular smooth muscle?
Dilatation of arterioles causes sheer stress in the arteries upstream to make them dilate
49
What is the effect of vasodilation caused by sheer stress?
Increases blood flow to metabolically active tissues
50
What factors increase venous return? (5)
* Increased venomotor tone * Increased skeletal muscle pump * Increased respiratory pump * Increased stroke volume * increased blood volume
51
What are venous smooth muscles supplied with?
Sympathetic nerve fibres
52
What does increased VENOmotor tone result in?
* Increased venous return * Increased SV * Increased MAP
53
What does increased VASOmotor tone result in? (2)
* Increased SVR | * Increased MAP
54
How does skeletal muscle pump increase venous return?
* Large veins in limbs lie between skeletal muscles | * Contraction of muscles aids venous return
55
What is heart rate influenced by?
* Parasympathetic stimulation * Sympathetic stimulation * Hormone adrenaline
56
What are acute CVS responses to exercise? (7)
* 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
What are the acute CVS responses to exercise known as?
Post-exercise hypotensive response
58
What are chronic CVS responses to regular exercise? (6)
* 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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