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System 2: Cardiovascular AM > Physiology: The Peripheral Circulation > Flashcards

Physiology: The Peripheral Circulation Flashcards

1
Q

What is the function of capillaries?

A

For exchange

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2
Q

What are the features of capillaries?

A

Thin walled - 1 cell thick

Small Diameter - bug surface area: volume ratio

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3
Q

What are the different types of capillaries?

A

Continuous
Fenestrated
Discontinuous

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4
Q

What are the features of continuous capillaries?

A

No clefts or pores

Clefts only in muscles

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5
Q

Where are continuous capillaries found in the body?

A

Brain and Muscle

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6
Q

What are features of fenestrated capillaries?

A

Clefts and pores

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7
Q

Where are fenestrated capillaries found in the body?

A

Intestine

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8
Q

What are the features of discontinuous capillaries?

A

Massive clefts and pores

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9
Q

Where are discontinuous capillaries found in the body?

A

Liver

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10
Q

What factors effect diffusion from the capillaries to the cells?

A

Self regulating
Non-saturable
Non-polar substances across the membrane
Polar substances through clefts/ channels

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11
Q

Where is carrier mediated transport observed in capillaries?

A

The brain with glucose transporters

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12
Q

What effect does starlings forces have on gas exchange entering and leaving the capillaries?

A

Hydrostatic Pressure is strong nearer the arterioles and decreases towards the venules - nutrients leaving the capillaries
Osmotic Pressure increases going towards the venules - nutrients entering the capillaries

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13
Q

How much blood is lost and regained through the capillaries?

A

~ 20L is lost and ~17L is regained

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14
Q

What are the functions of the lymphatic system?

A

Excess fluid is drained and filtered

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15
Q

What is an oedema?

A

Accumulation of excess fluid in interstitial area

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16
Q

Name causes of oedema

A

Lymphatic Obstruction
Raised Central Venous Pressure due to Ventricular failure
Hypoproteinaemia
Increased capillary permeability

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17
Q

How is peripheral blood flow controlled?

A

Controlled by resistance of arterioles which is controlled by the radius of the vessel

18
Q

What is the formula of Mean Arterial Pressure?

A

MAP= CO x TPR

19
Q

What effect does intrinsic mechanisms have on control of the peripheral circulation?

A

Concerned with meeting the selfish needs of the tissue

20
Q

What are the effects of extrinsic mechanisms on the control of the peripheral circulation?

A

Concerned with controlling the TPR and therefore controlling MAP

21
Q

What extrinsic control neurally?

A

Sympathetic - release noradrenaline which bind to alpha 1 receptors causing constriction of arterioles and therefore increase TPR
Parasympathetic - no effect

22
Q

What effect does adrenaline have on the peripheral circulation?

A

Act on alpha 1 receptors and cause arteriolar constriction

However in some tissues the hormone binds to Beta 2 receptors and cause arteriolar dilation and decreases TPR

23
Q

What are the extrinsic controls of peripheral circulation?

A

Hormonal

Neural

24
Q

What are some of the hormones that effect on the peripheral circulation?

A

Adrenaline
Angiotensin II
Vasopressin
Atrial Natriuretic Factor

25
Q

What types of tissue have arteriolar dilation when adrenaline is secreted into the blood?

A

Skeletal muscle and cardiac muscle

26
Q

When is angiotensin II secreted into the blood?

A

When there is low blood volume

27
Q

What effect does angiotensin II have on TPR?

A

Causes arteriolar constriction which increases TPR

28
Q

When is Vasopressin (antidiuretic hormone) secreted into the blood?

A

When there is low blood volume

29
Q

What effect does vasopressin have on TPR?

A

Causes arteriolar constriction causing TPR

30
Q

When is Atrial Natriuretic Factor secreted into the blood?

A

When there is a high blood volume

31
Q

What effect does atrial natriuretic factor have on TPR?

A

Causes arteriolar dilation which causes a decrease in TPR

32
Q

What are the local controls of local tissue flow in peripheral circulation?

A

Active (metabolic) hyperaemia
Pressure (flow) autoregulation
Reactive Hyperaemia
Injury Response

33
Q

What events occur when there is increased metabolic activity in the local tissue?

A

The increases conc of metabolites triggers the release of endothelial dependant relaxing factor (EDRF) causing arteriolar dilation
This allows the wash out of the metabolites

34
Q

What events occur in local tissue when there is a decrease in arterial pressure? (Pressure auto-regulation)

A

The decrease in flow causes an accumulation of metabolites in the cerain tissue allowing EDRF to be released.
This causes arterioles to dilate allowing blood flow to be normalised
Can allow maintenance of blood supply even with changes of MAP

35
Q

What does an occlusion of blood supply cause to local arterioles in a tissue? (Reactive Hyperaemia)

A

There is an increase in blood flow due to arteriolar dilation

36
Q

What are the events the occur in arterioles when there is an injury to the local tissue?

A

Mast cells produce histamine which cause arteriolar dilation (increasing flow) and an increase in permeability

37
Q

When is there blood flow highest in the aorta?

A

During systole

38
Q

When is the blood flow highest in the coronary arteries?

A

During diastole

39
Q

What is special about the coronary circulation?

A

Blood supply interrupted by systole
Able to cope with increased demand during exercise
Active Hyperaemia
Expresses B2 receptors
Swamps sympathetic arteriolar constriction

40
Q

What is special about the cerebral circulation?

A

Need to be kept stable

Shows excellent pressure auto regulation

41
Q

What is special about the pulmonary circulation?

A

Decrease in O2 causes arteriolar constriction which is opposite other tissue
Allows blood to be directed to highly ventilated parts of the lung

42
Q

What is special about the renal circulation?

A

Main function is filtration
Dependant on pressure
Changes in MAP have big effect on blood volume
Excellent pressure auto-regulation

System 2: Cardiovascular AM (9 decks)

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