Peripheral circulation

Question 1

processes involved in transport between capillaries and tissues

Answer 1

diffusion, carrier mediated transport, bulk flow (when 3L of fluid is lost per day)

Question 2

blood brain barrier

Answer 2

highly selective semipermeable border of endothelial cells that prevents solutes in the circulating blood from non-selectively crossing into the extracellular fluid of the central nervous system where neurons reside

Question 3

starlings forces

Answer 3

the movement of fluids between the vasculature and interstitial spaces. Fluid movement is determined by the balance of hydrostatic and osmotic pressure gradients

Question 4

lymphatic system in relation to oedema

Answer 4

3 L left in capillaries per day drains into lymphatic system and gets put back into low pressure part of the system (vena cava). sometimes there is lymphatic obstruction due to filiarsis or surgery which can cause oedema

Question 5

oedema

Answer 5

accumulation of excess fluid

Question 6

continuous capillaries

Answer 6

no clefts or pores eg brain (hence the blood brain barrier)

Question 7

fenestrated capillaries

Answer 7

clefts and pores eg intestine and kidney, specialised for fluid exchange

Question 8

discontinuous

Answer 8

clefts and massive pores eg liver for proteins

Question 9

poiseuilles law takes into account

Answer 9

varying the radius of the resistance vessels is used to control flow and redirect blood

Question 10

active hyperaemia

Answer 10

increase in metabolic activity increases con of metabolites which triggers release of paracrine signal which causes arteriolar dilation which increases flow to wash out metabolites

Question 11

pressure autoregulation

Answer 11

decrease in mean arterial pressure causes decrease in flow so metabolites accumulate which triggers release of paracrine signal which causes arterioles to dilate and flow is restored to normal

Question 12

reactive hyperaemia

Answer 12

triggered by occlusion of blood supply and this causes a subsequent increase in blood flow which causes an extreme version of pressure auto regulation

Question 13

neural factors affecting arteriolar tone

Answer 13

sympathetic nerves by releasing noradrenaline which bind to alpha 1 receptors and cause constriction, parasympathetic which has no effect on vessels apart from genitalia and salivary glands

Question 14

hormonal factors affecting arteriolar tone

Answer 14

adrenaline which is released and binds to alpha 1 receptors and causes arteriolar constriction but can also act on beta 2 receptors and make arteries dilate significant in exercise

Question 15

dominant factors controlling blood flow in cardiac vascular beds

Answer 15

blood supply interrupted by systole but still has to cope with increased demand during exercise which it does by expressing many beta.2 receptors and has excellent hyperaemia which swamp any sympathetic arteriolar constriction

Question 16

dominant factors controlling blood flow in cerebral vascular beds

Answer 16

excellent pressure auto regulation because needs to be kept stable at all times

Question 17

dominant factors controlling blood flow in pulmonary vascular beds

Answer 17

decrease in PO2 causes arteriolar constriction so the opposite response to most tissues. ensures blood is directed to the best ventilated parts of the lung

Question 18

dominant factors controlling blood flow in renal vascular beds

Answer 18

filtration which depends on pressure. changes in MAP would have big effects on blood volume shows excellent pressure auto regulation

Question 19

importabt equation for systemic circulation

Answer 19

mean arterial pressure = Cardiac Output x Total Peripheral Resistance

Question 20

arteriolar radius affects

Answer 20

flow through individual vascular bed and arterial pressure. cannot affect one without the other

Question 21

how is blood flow to vascular beds and arterial pressure kept in the right range

Answer 21

controlling the smooth muscle around arterioles. by local mechanisms and central mechanisms