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Study Notes - Cardiology > *physiology 6 (lecture 6) > Flashcards

*physiology 6 (lecture 6) Flashcards

1
Q

What are the major resistance vessels in the circulation?

A

The arterioles

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2
Q

What vessels contain most of the blood volume during rest?

A

The veins (the capacitance vessels)

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3
Q

What is the main regulator of the HR?

A

Autonomic nervous system

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4
Q

What are the main regulators of the stroke volume? (3)

A

Pre-load
After-load
Myocardial contractility

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5
Q

Where is the main site of TPR?

A

Arterioles

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6
Q

How is resistance to blood flow related to blood viscosity and length of blood vessel?

A

Directly proportional to blood viscosity and length of blood vessel

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7
Q

How is resistance to blood flow related to the radius of the blood vessel?

A

Inversely proportional to the radius of the blood vessel to the power of 4

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8
Q

Equation for what resistance to blood flow is related to?

A

blood viscosity X length of blood vessel divided by radius of blood vessel to the power of 4

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9
Q

How is the resistance to blood flow mainly controlled?

A

By vascular smooth muscle that changes the radius of arterioles

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10
Q

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

A

Hormones and nerves

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11
Q

What branch of the autonomic nervous system supplies the vascular smooth muscle?
What receptors on the smooth muscle does the released neurotransmitter act on?

A 
Sympathetic
Alpha 1 (noradrenaline)
There is no significant parasympathetic innervation of arterial smooth muscle except in the penis and clitoris
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12
Q

what is the state of the vascular smooth muscle at rest?

Why?

A

It is partially constricted due to the vasomotor tone - tonic discharge of sympathetic nerves resulting in continuous release of noradrenaline

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13
Q

What effect does increased sympathetic stimulation have on vascular smooth muscle?

A

Increased vasomotor tone = increase vasoconstriction and vice versa

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14
Q

What hormones are involved in the control of vascular smooth muscle? (3)

A

Adrenaline
Angiotensin 2
Vasopressin (ADH)
All cause vasoconstriction

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15
Q

What effect dies adrenaline have on vascular smooth muscle?

A

Adrenal is released from the adrenal medulla
Adrenal acting on B2 adrenoceptors causes vasodilation (cardiac and skeletal muscle arterioles)
Adrenaline acting on alpha 1 adrenoceptors causes vasoconstriction (predominant in skin, gut and kidney arterioles)

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16
Q

What is the purpose of intrinsic controls of vascular smooth muscle?

A

To match the blood flow of different tissues to their metabolic needs (they can over red the extrinsic control mechanisms)
They include local chemical and physical factors

17
Q

What local metabolites (chemicals) cause vasodilation? (6)

A 
Decreased local pO2
Increased local pCO2
Increased local [H+] (decreased pH)
Increased extra-cellular [K+]
increased osmolarity of ECF
adenosine release (from ATP)
18
Q

What are local humoral agents released in response to?

A

Tissue injury or inflammation

19
Q

What are examples of local humoral agents which cause relaxation of arteriolar smooth muscle resulting in vasodilation? (3)

A

Histamine
Bradykin
NO

20
Q

Where is NO released from?

What causes its release?

A

Continuously produced by the vascular endothelium from the amino acid L-arginine through enzymatic action of nitric oxide synthase (NOS)
Shear stress on vascular endothelium as a result of increased flow causes release of of calcium in vascular endothelial cells and the subsequent activation of NOS
Chemical stimuli can also induce NO formation

21
Q

How does NO causes vasodilation?

A

NO diffuses from the vascular endothelium into the adjacent smooth muscles where it activates the formation of cGMP that serves as a second messenger for signalling smooth muscle relaxation

22
Q

Examples of humoral factors that cause vasocontraction? (4)

A

Serotonin
Thromboxane A2
leukotrienes
Endothelin

23
Q

In terms for thrombotic, inflammatory and oxidant effect, what are endothelial produced vasodilators?

A

Anti-thrombotic, anti-inflammatory, anti-oxidants (and vice versa for endothelial produced vasoconstrictors

24
Q

Apart from chemicals, what else can intrinsically control vascular smooth muscle?

A

Physical factors:
Sheer stress
temperature
Myogenic response to stretch

25
Q

What effect does temperature have on vascular smooth muscle?

A 
Cold = vasoconstriction
Warmth = vasodilation
26
Q

What is the myogenic response to stretch?

A

If MAP rises, resistance vessels automatically constrict to limit flow
If MAP falls resistance vessels automatically dilate dilate to increase flow
(especially important in tissues lie the brain and kidneys)

27
Q

When is the maximal force generated in myocytes?

A

At optimal fibre length

28
Q

What 5 factors increase venous return? (5)

A 
Increased venomotor tone 
Increased skeletal muscle pump
Increased respiratory pump
Increased stroke volume = increased arterial pressure
Increased blood volume
29
Q

What branch of the autonomic nervous system supplies your blood vessels?

A

Sympathetic

30
Q

What does increased venomotor tone cause?

A

Due to increased sympathetic stimulation - increased venous construction
Blood driven to the right atrium increases (venous return), SV and MAP also increase

31
Q

What does increased muscle activity cause in terms of venous return?

A

Increased venous return to the heart due to skeletal muscle pump

32
Q

What effect does exercise have on the CVS?

A

Sympathetic nerve activity increases
HR and SV increase = increased CO
Sympathetic vasomotor nerves reduce flow to kidneys and gut = vasoconstriction
In skeletal and cardiac muscle, metabolic hyperaemia overcomes vasomotor tone = vasodilation
Increase in CO increases systolic BP
The increase in CO increases systolic BP and the metabolic hyperaemia decreases TPR and decreases DBP (pulse pressure increases)
Post exercise hypotensive response

Study Notes - Cardiology (25 decks)

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