Physiology 6 - Integration of CV Mechanisms Flashcards

1
Q

What are the major resistance vessels in the circulation?

A

The arterioles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What vessels contain most of the blood volume during rest?

A

The veins (the capacitance vessels)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the main regulator of the HR?

A

Autonomic nervous system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

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

A

Pre-loadAfter-loadMyocardial contractility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where is the main site of TPR?

A

Arterioles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How is the resistance to blood flow mainly controlled?

A

By vascular smooth muscle that changes the radius of arterioles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

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

A

Hormones and nerves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

SympatheticAlpha 1 (noradrenaline)There is no significant parasympathetic innervation of arterial smooth muscle except in the penis and clitoris

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

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

A

Increased vasomotor tone = increase vasoconstriction and vice versa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

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

A

AdrenalineAngiotensin 2Vasopressin (ADH)All cause vasoconstriction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What effect dies adrenaline have on vascular smooth muscle?

A

Adrenal is released from the adrenal medullaAdrenal 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)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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 pO2Increased local pCO2Increased local [H+] (decreased pH)Increased extra-cellular [K+]increased osmolarity of ECFadenosine 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

HistamineBradykinNO

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 NOSChemical 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

SerotoninThromboxane A2leukotrienesEndothelin

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 stresstemperatureMyogenic response to stretch

25
What effect does temperature have on vascular smooth muscle?
Cold = vasoconstrictionWarmth = vasodilation
26
What is the myogenic response to stretch?
If MAP rises, resistance vessels automatically constrict to limit flowIf MAP falls resistance vessels automatically dilate dilate to increase flow (especially important in tissues lie the brain and kidneys)
27
When is the maximal force generated in myocytes?
At optimal fibre length
28
What 5 factors increase venous return? (5)
Increased venomotor tone Increased skeletal muscle pumpIncreased respiratory pumpIncreased stroke volume = increased arterial pressureIncreased blood volume
29
What branch of the autonomic nervous system supplies your blood vessels?
Sympathetic
30
What does increased venomotor tone cause?
Due to increased sympathetic stimulation - increased venous constructionBlood driven to the right atrium increases (venous return), SV and MAP also increase
31
What does increased muscle activity cause in terms of venous return?
Increased venous return to the heart due to skeletal muscle pump
32
What effect does exercise have on the CVS?
Sympathetic nerve activity increasesHR and SV increase = increased COSympathetic vasomotor nerves reduce flow to kidneys and gut = vasoconstrictionIn skeletal and cardiac muscle, metabolic hyperaemia overcomes vasomotor tone = vasodilationIncrease 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