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Physiology 1 > Factors Affecting Blood Flow > Flashcards

Factors Affecting Blood Flow Flashcards

1
Q

What does an increased haematocrit indicate?

A

dehydration

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2
Q

What does an decreased haematocrit indicate?

A

anemia

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3
Q

What is the Buffy coat?

A

thin pale layer contains platelets (thrombocytes) and WBCs (leucocytes)

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4
Q

What is blood flow dependant on?

A

metabolic demands of each organ system

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5
Q

What does skeletal muscle requirement during exercise?

A

more oxygen therefore greater blood flow

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6
Q

What does the GI system require after a meal?

A

more oxygen therefore greater blood flow

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7
Q

Where in the body does blood flow align with cardiac output?

A

pulmonary system as all blood must pass through lungs for removal of CO2 and addition of oxygen

the lungs require a high blood flow rate to ensure that a large volume of blood is exposed to the alveoli for gas exchange. The cardiac output is the amount of blood pumped by the heart per minute and it must be equal to the blood flow to the lungs to ensure efficient gas exchange. This ensures that sufficient oxygen is delivered to the body tissues to meet metabolic demands and that excess carbon dioxide is removed from the body.

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8
Q

What are the two mechanisms that regulate blood flow?

A

local (intrinsic)
neural/hormonal (extrinsic)

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9
Q

What are specific needs of the tissue that blood flow provides?

A

delivery of oxygen and nutrients (glucose, amino acids, fatty acids)
removal of carbon dioxide and hydrogen ions
maintenance of ion concentrations
transport of hormones

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10
Q

Describe in what three ways can local (intrinsic) control occur?

A

Autoregulation
Maintenance of constant blood flow while arterial pressure changes
If coronary arterial pressure decreases, immediate compensatory vasodilatation of coronary arterioles to decrease coronary vasculature resistance, will attempt to maintain constant blood flow in this coronary artery.

Active Hyperemia
Blood flow to tissues is proportional to its metabolic activity
Increased blood flow when metabolic activity increases (exercising skeletal muscle increased O2 consumption / ATP demand)
Increased arteriolar dilation

Reactive Hyperemia
Increase in blood flow in response to a prior period of decreased blood flow.
E.g. following period of arterial occlusion, an O2 dept accumulates – longer the arterial occlusion, greater O2 debt, greater the increase in blood flow (above pre-occlusion levels) until the O2 dept reversed.

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11
Q

What layer of the vessel is responsible for vasoconstriction and vasodilation?

A

tunica media

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12
Q

What are the factors that determine resistance to blood flow?

A

vessel diameter
vessel length
viscosity of blood

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13
Q

How can blood become more viscous?

A

dehydration

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14
Q

What disease occurs when blood flow is reduced?

A

deep vein thrombosis

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15
Q

What is vessel resistance directly proportional to?

A

length of vessel
viscosity of blood

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16
Q

What is vessel resistance inversely proportional to?

A

diameter (radius)

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17
Q

What is the equation of flow?

A

flow(Q) = change in pressure/resistance

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18
Q

What is poiseulles equation?

A

flow is directly proportional to

(radius^4) X (change in pressure)
/
(viscosity of blood N) X (length of vessel L)

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19
Q

What does poiseulle’s equation tell us?

A

the flow (Q) of fluid is related to a number of factors: the viscosity (n) of the fluid, the pressure gradient across the tubing (P), and the length (L) and diameter(r) of the tubing.

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20
Q

What does poiseulles equation assume?

A

flow is through a straight tube
flow is non-fluctuating
flow is smooth

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21
Q

What aids venous return?

A

skeletal muscles compressing the veins

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22
Q

What is venous return aided by during exercise?

A

inter-thoracic pressure becoming more negative

23
Q

What can become a problem in coronary heart disease (angina) and heart failure?

A

if preload increases (heart will have to work harder)

24
Q

Where does blood supply to the heart derive from?

A

left and right corona arteries

25
Q

What does the left coronary artery branch into?

A

left circumflex artery,
left anterior interventricular artery
left marginal

26
Q

What does the right coronary artery branch into?

A

right posterior interventricular artery
right marginal artery

27
Q

Where do the coronary veins transport blood?

A

to the coronary sinus

28
Q

Where and what do thesbian veins drain?

A

drain deoxygenated blood from capillary network in ventricular wall directly into cardiac chambers

29
Q

What does exercise training increase?

A

number of arterioles and capillaries

30
Q

What increases in an athletic heart?

A

ventricular mass (hypertrophy)

31
Q

What cellular mechanisms differ?

A

exercise induced hypertrophy vs pathological cardiac hypertrophy

32
Q

During exercise what local vasodilators mediate blood flow?

A

lactate, adenosine, potassium ions (K+)

33
Q

Why is increased blood flow required during exercise in skeletal muscle?

A

higher oxygen and glucose levels required

34
Q

At rest, blood flow through skeletal circulation is regulated by what autonomic system?

A

sympathetic

35
Q

What do alpha 1 receptors cause?

A

vasoconstriction

36
Q

What does vasoconstriction cause in blood flow?

A

increased resistance, decreased blood flow

37
Q

What do beta 2 receptors cause?

A

vasodilation

38
Q

What does vasodilation cause in blood flow?

A

decreased resistance, increased blood flow

39
Q

What vessels dilate in skeletal circulation during exercise?

A

resistance vessels
(arterioles)

40
Q

How much does cerebral circulation account for vascular resistance?

A

50%

41
Q

What is the circle of willis made from?

A

basilar and internal carotid arteries that enter the cranial cavity

42
Q

When BP falls, what do cerebral resistance vessels do?

A

dilate to maintain perfusion

43
Q

When is severe hypotension and what can it cause?

A

below 60 arterial BP
mental confusion, syncope

44
Q

What are cerebral resistance vessels extremely sensitive to?

A

local hypoxia, arterial CO2

45
Q

What can hypercapnia cause blood vessels to do and what is that change mediated by?

A

vasodilation mediated by NO endothelial

hypercapnia causes vasodilation in the brain through cerebral autoregulation, which helps to ensure that the brain receives adequate blood flow and oxygen supply, and removes excess carbon dioxide from the brain tissue.

46
Q

What can hypocapnia cause?

A

vasoconstriction

In response to a decrease in arterial CO2 levels, the pH of the blood increases, leading to vasoconstriction of the cerebral blood vessels. This vasoconstriction reduces blood flow to the brain, which can decrease the delivery of oxygen and nutrients to the brain tissue

47
Q

What can reduce cerebral perfusion?

A

hyperventilation

48
Q

What does local hypoxia cause?

A

vasodilation

49
Q

Where does auto regulation happen?

A

heart, kidney, and brain

50
Q

What is the vessel resistance directly proportional to?

A

vessel length and blood viscosity

51
Q

Why do athletes have low BP?

A

after high exercise training, the sympathetic system drops decreasing noradrenaline and adrenaline however local vasodilators (NO and prostaglandin) are still maintained causing a decrease in systemic resistance and therefore BP

52
Q

What are two diseases that cause hypertrophy?

A

valve stenosis
hypertension

53
Q

Why do athletes have low heart rates?

A

Regular exercise leads to an increase in the size and strength of the heart muscle, which allows it to pump more blood with each beat. This increased stroke volume means that the heart doesn’t have to beat as frequently to meet the body’s oxygen demands, which leads to a lower resting heart rate.

Physiology 1 (25 decks)

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