Integrating of Cardiovascular Mechanisms

Question 1

What is the heart?

Answer 1

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

Question 2

What are the arteries?

Answer 2

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

Question 3

What are the arterioles?

Answer 3

These are the major resistance vessels that regulate flow.

Question 4

What are the capillaries?

Answer 4

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

Question 5

What are the veins?

Answer 5

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.

Question 6

What part of the nervous system regulates heart rate?

Answer 6

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

Question 7

What factors affect the stroke volume?

Answer 7

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

Question 8

What is the equation for cardiac output?

Answer 8

CO = Heart Rate x Stroke Volume

Question 9

What is the equation for Mean Arterial Pressure?

Answer 9

MAP = Cardiac Output x Systemic Vascular Resistance.

Question 10

What equation can be used to estimate MAP?

Answer 10

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

Question 11

What is Systemic Vascular Resistance?

Answer 11

Resistance of the whole vasculature to blood flow.

Question 12

What regulates Systemic Vascular Resistance?

Answer 12

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

Question 13

How does vascular smooth muscle control SVR?

Answer 13

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.

Question 14

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

Answer 14

They are controlled by both extrinsic and intrinsic controls.

Question 15

How does blood viscosity relate to resistance?

Answer 15

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

Question 16

How does the length of blood vessels relate to resistance?

Answer 16

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

Question 17

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

Answer 17

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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

Extrinsic control.

Question 20

What is involved in extrinsic control of vascular smooth muscle?

Answer 20

Hormones and nerves.

Question 21

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

Answer 21

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

Question 22

What is vasomotor tone?

Answer 22

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

Question 23

How is vasoconstriction brought about?

Answer 23

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

Question 24

How is vasodilation brought about?

Answer 24

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

Question 25

Describe the parasympathetic influence on arterial smooth muscles.

Answer 25

There is no significant parasympathetic innervation of arterial smooth muscles

Question 26

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

Answer 26

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.

Question 27

Where is the hormone, adrenaline, released from?

Answer 27

It is released from the adrenal medulla.

Question 28

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

Answer 28

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.

Question 29

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

Answer 29

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.

Question 30

How does angiotensin II control vascular smooth muscles?

Answer 30

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

Question 31

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

Answer 31

Antidiuretic hormone causes vasoconstriction.

Question 32

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

Answer 32

They are useful for intermediate control of blood pressure.

Question 33

Why are INTRINSIC controls required to regulate blood flow?

Answer 33

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

Question 34

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

Answer 34

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

Question 35

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

Answer 35

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

Question 36

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

Answer 36

Hustamine Bradykinin Nitric Oxide

Question 37

Where is Nitric Oxide produced?

Answer 37

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

Question 38

Describe the action of Nitric Oxide.

Answer 38

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

Question 39

What is FLOW DEPENDENT NITRIC OXIDE FORMATION?

Answer 39

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.

Question 40

What is RECEPTOR STIMULATED NITRIC OXIDE FORMATION?

Answer 40

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

Question 41

How does Nitric Oxide caused vasodilation?

Answer 41

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

Question 42

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

Answer 42

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

Question 43

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

Answer 43

Temperature Myogenic response to stress Sheer stress

Question 44

What is the myogenic response to strech?

Answer 44

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