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Human Physiology and Pharmacology > Week 17: (C) Pressure gradients, blood flow & peripheral resistance > Flashcards

Week 17: (C) Pressure gradients, blood flow & peripheral resistance Flashcards

1
Q

What are all blood vessels lined with?

A

a layer of endothelial cells

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2
Q

What are the 3 layers of a blood vessel?

A 
endothelial cells (intimal layer)
Smooth muscle cells (medial layer)
Connective tissue (adventitial layer)
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3
Q

What is the emption of the capillaries?

A

just a thin layer of endothelial cells

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4
Q

What provides elastin and collagen?

A

tunica media

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5
Q

What pathway innervates the smooth muscle of arterioles?

A

sympathetic, allow regulation of blood flow

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6
Q

What changes the venous reservoir?

A

contraction and relaxation of smooth muscle veins. altered vol of blood back to the heart known as venous return

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7
Q

What are arterioles, venues and capillaries collectively known as?

A

microcirculation

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8
Q

What is the lumen diameter of the capillaries?

A

~3 micrometers

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9
Q

What pressures does F go to and from?

A

always from region of higher pressure to a region of lower

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10
Q

What do you call the pressure exerted by a fluid called?

A

hydrostatic pressure

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11
Q

What are the units of flow?

A

volume per unit time (l/min or ml/min)

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12
Q

What are units of the pressure difference (deltaP)?

A

mmHg

this drives the flow

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13
Q

What do we need to calculate flow rate?

A

the pressure difference between 2 points (delta P) & the resistance (R)

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14
Q

What does resistance measure?

A

how difficult it is for blood to flow between two points at any given pressure difference.
i.e a measure of the friction impeding flow

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15
Q

What does blood flow through a vessel depend upon?

A

pressure gradient and vascular resistance

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16
Q

What is the blood flow equation?

A

change in pressure/ resistance

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17
Q

What is a pressure gradient?

A

difference in pressure between beginning and end of vessel

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18
Q

What causes friction in resistance?

A

the friction between moving blood and stationary vessel wall

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19
Q

If resistance increases, what must be altered to maintain flow rate?

A

pressure must increase

20
Q

What is parabolic distribution?

A

blood in contact with the epithelial wall, move slower due to increased friction (resistance). Blood flowing the centre has less resistance, flows quicker

21
Q

What 3 factors does resistance to blood flow depend upon?

A

1) viscosity of blood (n eta)
2) vessel length (L)
3) vessel radius (r)

22
Q

Why is L unimportant?

A

the length is constant

23
Q

What is the major determinant of resistance to flow along a vessel?

A

radius (r)

slight change in radius = notable change in flow

24
Q

What is the effects of a 2-fold change in radius on flow?

A

produce a 16-fold change in flow

Flow

25
Q

How to calculate mean arterial pressure?

A

= diastolic pressure + 1/3 pulse pressure

26
Q

What does arterial blood pressure fluctuate in relation to?

A

ventricular systole and diastole

27
Q

How to calculate pulse pressure?

A

systolic arterial pressure - diastolic arterial pressure.

28
Q

Why does arterial pressure not drop to zero during diastole?

A

as arterioles have a higher resistance to blood than

29
Q

How much blood enters arteries and flows to arterioles?

A

more blood enters arteries than leaves to arterioles

30
Q

what happens to arteries when heart is reeling and filling?

A

passively recoil, like a balloon
exerting pressure on the blood in the arteries during diastole, pushes blood into vessels downstream. ensuring continued blood flow to organs as heart is relaxing

31
Q

Where so the arteries store excess pressure energy during systole?

A

in their stretched walls

32
Q

What does the pressure drop to on arterioles?

A

~37 mmHg

33
Q

What vessel has the slowest velocity? and why?

A

capillaries, to allow adequate time for the exchange of nutrients and waste products between the blood and cells of tissues

34
Q

What vessel has the highest cross sectional area?

A

capillaries

35
Q

What happens to the pressure in the arterioles?

A

They have high resistance so results in decreased pressure

36
Q

What the the change in mean pressure in the arterioles from~93 to ~37mmHg result in?

A

pressure drop

pressure gradient helps drive blood from the heart to the tissue capillary beds.

37
Q

What is the thick layer in arteriolar walls?

A

smooth muscle

38
Q

What type of nerves innervate the smooth muscle of arteriolar walls?

A

sympathetic

39
Q

What is the smooth muscle also sensitive to?

A

many local chemical changes and certain circulatory hormones

40
Q

What happens when contraction of the smooth muscle or arteriole occurs?

A

contraction= decreased radius,

increased resistance= decreased blood local flow= vasoconstriction

41
Q

What happens when relaxation of the arteriole occurs?

A

relaxation= increased radius,

decreased resistance= increased local blood flow= vasodilation

42
Q

What is vascular tone?

A

when the arteriolar smooth muscle displays a state of partial constriction

43
Q

What 2 factors are responsible for vascular tone?

A

1) myogenic activity

2) sympathetic activity

44
Q

What is myogenic activity?

A

relates to the contraction initiated by smooth muscle itself, independent any external occurrence or nerve stimulation

45
Q

What is sympathetic activity (smooth muscle)?

A

increase sympathetic activity, increase contraction, vasoconstriction…decrease blood flow through vessel

46
Q

Why is vascular tone important?

A

makes it possible to decrease or increase contractile activity

47
Q

What is Poiseulle’s law?

A

any change in contractility of arteriolar smooth muscle will substantially change resistance to flow in these vessels

Human Physiology and Pharmacology (31 decks)

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