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Cardiovascular > Integrating of Cardiovascular Mechanisms > Flashcards

Integrating of Cardiovascular Mechanisms Flashcards

Week 1

1
Q

What is the heart?

A

It is a muscle that pumps blood around the body to oxygenate tissues and remove carbon dioxide.

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2
Q

What are the arteries?

A

They are the passageways of blood form the heart to the tissues. Pressure must be maintained but not to high.

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3
Q

What are the arterioles?

A

These are the major resistance vessels that regulate flow.

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4
Q

What are the capillaries?

A

They are the site of gas, nutrient and water exchange between blood and tissues.

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5
Q

What are the veins?

A

They are the capacitance vessels, as the hold the most of the blood volume. They then return blood to the heart. Venous return must be high enough so that the heart has enough blood to pump around the body.

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6
Q

What part of the nervous system regulates heart rate?

A

The autonomic nervous system. this includes the sympathetic and parasympathetic divisions.

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7
Q

What factors affect the stroke volume?

A

Cardiac pre-load, myocardial contractility and cardiac after-load.

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8
Q

What is the equation for cardiac output?

A

CO = Heart Rate x Stroke Volume

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9
Q

What is the equation for Mean Arterial Pressure?

A

MAP = Cardiac Output x Systemic Vascular Resistance.

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10
Q

What equation can be used to estimate MAP?

A 
MAP = DBP + 1/3(Pulse Pressure)
MAP = (SBP + 2(DBP))/3
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11
Q

What is Systemic Vascular Resistance?

A

Resistance of the whole vasculature to blood flow.

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12
Q

What regulates Systemic Vascular Resistance?

A

Vascular smooth muscles. The main site of SVR is the arterioles.

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13
Q

How does vascular smooth muscle control SVR?

A

Contraction of vascular smooth muscles causes vasoconstriction and therefore increases SVR and MAP..
Relaxation of vascular smooth muscle causes vasodilation and decreases SVR and MAP.

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14
Q

What are the two types of controls of vascular smooth muscle?

A

They are controlled by both extrinsic and intrinsic controls.

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15
Q

How does blood viscosity relate to resistance?

A

The relationship is proportional. As viscosity increases, resistance increases.

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16
Q

How does the length of blood vessels relate to resistance?

A

The relationship is proportional. As the length of the blood vessels increases, the resistance also increases.

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17
Q

How does the radius of the blood vessel relate to the resistance?

A

The relationship is inversely proportional. As the radius of the blood vessel increases, the resistance decrasees.

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18
Q

What is the main factor that controls the resistance to blood flow?

A

The radius of arterioles. They are therefore the main area of Bloop Pressure control.

19
Q

Is intrinsic or extrinsic control more likely to influence the overall resistance?

A

Extrinsic control.

20
Q

What is involved in extrinsic control of vascular smooth muscle?

A

Hormones and nerves.

21
Q

What type of nerves are involved in supplying vascular smooth muscle and how do they act?

A

The vascular smooth muscle is supplied by sympathetic nerves. The neurotransmitter noradrenaline acts upon alpha receptors.

22
Q

What is vasomotor tone?

A

When we are at rest the arterioles are partially constricted by the tonic discharge of sympathetic nerves.resulting in continuous release of noradrenaline.

23
Q

How is vasoconstriction brought about?

A

There is increased sympathetic discharge. This increases the vasomotor tone and results in vasoconstriction.

24
Q

How is vasodilation brought about?

A

There is decreased sympathetic discharge. This decreases the vasomotor tone and results in vasodilation.

25
Q

Describe the parasympathetic influence on arterial smooth muscles.

A

There is no significant parasympathetic innervation of arterial smooth muscles

26
Q

How does the hormone, adrenaline, control vascular smooth muscle?

A

The effect of adrenaline is organ specific and depends on the type of receptors that are present on the organ.
Adrenaline acts on alpha receptors causing vasoconstriction.
Adrenaline acts on alpha receptors causing vasodilation.

27
Q

Where is the hormone, adrenaline, released from?

A

It is released from the adrenal medulla.

28
Q

How does adrenaline affect the arterioles in the skin, gut and kidneys?

A

These organs have predominately α receptors. This means that adrenaline release causes vasoconstriction in these arterioles. This is useful because it restricts blood flow to these areas and redirects it to vital organs when required.

29
Q

How does adrenaline affect the arterioles in the cardiac and skeletal muscle arterioles?

A

These organs have predominantly β2 receptors. This means that adrenaline release causes vasodilation in these arterioles. This is useful because it increases blood flow to these areas when required.

30
Q

How does angiotensin II control vascular smooth muscles?

A

Angiotensin II causes vasoconstriction. Think about the Renin Angiotensin Aldosterone System.

31
Q

How does antidiuretic hormone (vasopressin) affect vascular smooth muscle?

A

Antidiuretic hormone causes vasoconstriction.

32
Q

Why are hormones useful for the control of vascular smooth muscle?

A

They are useful for intermediate control of blood pressure.

33
Q

Why are INTRINSIC controls required to regulate blood flow?

A

They match the blood flow of different tissues to their metabolic needs. They can also override the EXTRINSIC control mechanisms.

34
Q

What are the local physical factors that cause relaxation of arteriolar smooth muscles?

A 
Decreased local PO2
Increased local PCO2
Increased local [H+]
Increased extracellular [K+]
Increased osmolality of extra cellular fluid
Adenosine release from ATP
35
Q

When would local (chemical factors) humoral agents be released to influence arteriolar smooth muscle?

A

They can be released in response to tissue injury or imflammation.

36
Q

What are some examples of humoral agents causing RELAXATION of arteriolar smooth muscle causing VASOCONSTRICTION?

A

Hustamine
Bradykinin
Nitric Oxide

37
Q

Where is Nitric Oxide produced?

A

It is continuously produced by the vascular endothelium from the amino acid L-arginine through the enzymatic action of Nitric Oxide Synthase

38
Q

Describe the action of Nitric Oxide.

A

It is a potent VASODILATOR with a short life of a few seconds

39
Q

What is FLOW DEPENDENT NITRIC OXIDE FORMATION?

A
  1. There is stress on the vascular endothelium due to increased blood flow.
  2. This causes a release of calcium in vascular endothelial cells.
  3. There is subsequent activation of Nitric Oxide Synthase.
40
Q

What is RECEPTOR STIMULATED NITRIC OXIDE FORMATION?

A

Chemical stimuli can induce NO formation. There are many different vasoactive substances that act through the stimulation of NO formation.

41
Q

How does Nitric Oxide caused vasodilation?

A
  1. NO diffuses from the vascular endothelium into the adjacent smooth muscle cells.
  2. This activates the formation of cGMP.
  3. The cGMP serves as a second messenger for signalling smooth muscle relaxation
42
Q

What are some examples of humoral agents causing CONTRACTION of arteriolar smooth muscle causing VASODILATION?

A

Serotonin
Thromboxane A2 (from platelets)
Leukotrienes (from WBC)
Endothelin

43
Q

What are some of the physical local controls of vascular smooth muscle?

A

Temperature
Myogenic response to stress
Sheer stress

44
Q

What is the myogenic response to strech?

A

If MAP rises resistance vessels automatically constrict to limit flow.
If MAP falls, vessels automatically dilate to increase flow.

Cardiovascular (3 decks)

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