the peripheral circulation

Question 1

capillary properties

Answer 1

thin walled - small diffusion barrier

small diameter - big surface area:volume ratio

Question 2

continous capillaries

Answer 2

no clefts or pores e.g. brain

clefts only e.g. muscle

Question 3

fenestrated capillaries

Answer 3

clefts and pores e.g. intestine

Question 4

discontinuous capillaries

Answer 4

clefts and massive pores e.g. liver

Question 5

diffusion

Answer 5

self-regulating, non-saturable

non-polar surfaces across membrane, polar substances through clefts/channels

Question 6

types of exchange at capillaries

Answer 6

diffusion
carrier-mediated transport
bulk flow

Question 7

hydrostatic pressure

Answer 7

pushed water out - leaves behind solutes and so conc increases

Question 8

osmotic (oncotic pressure)

Answer 8

pulls liquid in

Question 9

starling’s forces

Answer 9

balance between hydrostatic and oncotic pressure

Question 10

oedema

Answer 10

acculumation of excess fluid

Question 11

causes of oedema

Answer 11

lymphatic obstruction
raised CVP
hypoproteinemia
inc capillary permeability

Question 12

MAP =

Answer 12

CO x TPR

Question 13

extrinsic control of ateriolar resistance

Answer 13

neural

hormonal

Question 14

sympathetic effect on arteriolar resistance

Answer 14

noradrenaline acts on a-1 receptors to cause arteriolar constriction
increases TPR

Question 15

hormonal effect on TPR - adrenaline

Answer 15

released from adrenal medulla, acts on a-1 receptors
inc TPR

in some tissues acts on B-2 receptors to cause dilation and dec TPR

Question 16

hormonal effect on TPR - angiotensin

Answer 16

produced in response to low blood volume

causes arteriolar constriction and so inc TPR

Question 17

hormonal effect on TPR - vasopressin

Answer 17

antidiuretic hormone

arteriolar constrictoin and so inc TPR

Question 18

hormonal effect on TPR - ANP

Answer 18

arteriolar dilation and so dec TPR

Question 19

local (intrinsic) controls of TPR

Answer 19

active hyperaemia
pressure flow autoregulation
reactive hyperaemia
injury response

Question 20

effect on TPR - active hyperaemia

Answer 20

inc metabolic activity caused inc concentration of metabolites
release of EDRF/NO which causes ateriolar dilation - inc flow to wash out metabolites

Question 21

effect on TPR - pressure flow autoregulation

Answer 21

decreased MAP causes decreased flow, metabolites accumulate - release of EDRF/NO
arterioles dilate and flow restored to normal

Question 22

effect on TPR - reactive hyperaemia

Answer 22

occlusion of blood supply caused subsequent increase in blood flow
extreme version of pressure autoregulation

Question 23

effect on TPR - injury response

Answer 23

substance P released and acts on mast cell

mast cell releases histamine - arteriolar dilation : inc blood flow and permeability