Circulation

Question 1

what is diastolic pressure

Answer 1

pressure supplied by elastic recoil in artery walls

Question 2

describe the intima of arteries

Answer 2

inner surface lining of endothelial cells and a small amount of collagen

Question 3

describe the adventitia of arteries

Answer 3

mainly collagenous connective tissue

Question 4

what type and how many lamina are there in arteries

Answer 4

2; elastic

internal and external

Question 5

what is the resistance within arteries

Answer 5

low

Question 6

where is the principle site of resistance to vascular flow

Answer 6

arterioles

Question 7

what determines the radius of arteries

Answer 7

vascular smooth muscle

Question 8

what is poorly defined on smaller arterioles

Answer 8

elastic lamina

Question 9

what is the major role of arterioles

Answer 9

determining arterial pressure and flow to tissue and organs

Question 10

what cells are present in capillaries

Answer 10

endothelial cells and pericytes

Question 11

what controls blood flow to tissues in capillaries

Answer 11

precapillary sphincters

Question 12

what is the rate of flow in capillaries and what is the purpose of this

Answer 12

slow to allow time for nutrient/ wast exchanger

Question 13

what determines distribution of ECF

Answer 13

plasma or interstitial flow

Question 14

what determines rate of flow in capillaries

Answer 14

arteriole resistance and no of open precapillary sphincters

Question 15

what influences velocity in capillaries

Answer 15

cross sectional area - not dependent on proximity to heart

Question 16

what allows movement of fluid across capillary membrane

Answer 16

fenestrated and very thin

Question 17

what is the resistance in veins

Answer 17

low

Question 18

what is the percentage of blood volume in capillaries

Answer 18

up to 70%; capacitance vessels

Question 19

what is the purpose of valves

Answer 19

aid venous return against gravity by preventing backflow

Question 20

what aids return of blood in veins

Answer 20

skeletal muscle and respiratory pump

Question 21

how does respiratory pump aid venous return

Answer 21

in inspiration, diaphragm descends, pushes on abdominal cavity and increases intra-abdominal pressure which is transmitted to abdominal veins, whilst thorax pressure decreases so intrathoracic vein pressure decreases creating a pressure difference

Question 22

what is the property of fluid in lymphatics

Answer 22

eosinophilic, no RBC/ large proteins

Question 23

how is lymphatic fluid returned to CVS

Answer 23

thoracic duct into left subclavian vein

Question 24

what 3 features help maintain unidirectional flow of lymoh fluid

Answer 24

smooth muscle in lymphatic vessels
skeletal muscle pump
respiratory pump

Question 25

what is the main goal of central circulation control

Answer 25

maintain MAP; average blood pressure in arteries during cardiac cycle

Question 26

what is basically the same as TPR

Answer 26

arteriolar resistance

Question 27

what determines the radius of arterioles

Answer 27

vascular smooth muscle

Question 28

what does stimulation of baroreceptors do

Answer 28

leads to inhibition of vasoconstrictor centre in medulla so decrease BP

Question 29

what is the afferent of baroreceptors

Answer 29

CN 9

Question 30

what is the efferent of baroreceptors

Answer 30

sympathetic and CN 10

Question 31

what is the firing rate of baroreceptors

Answer 31

proportional to MAP and PP

Question 32

what happens if BP increases

Answer 32

baroreceptors increase firing rate so increase PNS and decrease SNS so decrease CO/ TPR so decrease BP

Question 33

where are central baroreceptors found

Answer 33

atria, ventricle, pulmonary artery

Question 34

are central baroreceptors involved in long or short term regulation

Answer 34

long term

Question 35

how are baroreceptors involved with RAAS

Answer 35

stimulation of baroreceptors leads to inhibition of RAS; decrease release of angiotensin, aldosterone and ADH leading to fluid loss so BP decreases

Question 36

where are central chemoreceptors

Answer 36

Chemosensitive regions in medulla

Question 37

what happens if PaCO2 increases (chemoreceptors)

Answer 37

pH decreases so vasoconstriction occurs so increase TPR so increase BP

Question 38

what happens if PaCO2 decreases

Answer 38

decreae medullary tonic activity so decrease BP

Question 39

which has more effect on medulla, PaO2 or PaCO2

Answer 39

PaCO2

Question 40

what does PaO2 have a main affect on

Answer 40

peripheral chemoreceptors

Question 41

what does a moderate decrease in PaO2 do

Answer 41

vasoconstriction

Question 42

what does a severe decrease in PaO2 do

Answer 42

general depression

Question 43

what are the 2 medullary cardiovascular centres

Answer 43

pressor and depressor regions

Question 44

is the pressor region sympathetic or parasympathetic

Answer 44

sympathetic

Question 45

is the depressor region sympathetic or parasympathetic

Answer 45

parasympathetic

Question 46

does the pressor region increase or decrease BP

Answer 46

increase

Question 47

how does the pressor region increase BP

Answer 47

increases vasoconstriction, increasing CO (increases HR and SV), increases contractility

Question 48

what is the route of the pressor region

Answer 48

pressor region goes to sympathetic route to medulla to spinal cord to synapses at T1-L2 to heart

Question 49

what is the route of depressor region

Answer 49

depressor region to medulla to vagus nerve to heart

Question 50

how does the depressor region decrease BP

Answer 50

inhibits pressor region

Question 51

how is BP maintained on standing

Answer 51

standing decreases venous return so CO decreases so BP decreases so baroreceptors stimulated to increase BP

Question 52

What happens in intrinsic autoregulation

Answer 52

when arterioles ether vasoconstrict or dilate in response to changes in resistance seemingly automatically with the aim of maintaining constant blood flow

Question 53

what is myogenic regulation

Answer 53

when blood flow is increased and stretched vascular smooth muscle

Question 54

what happens in myogenic regulation

Answer 54

muscle autonomically constricts until diameter is normalised or slightly reduced - when smooth muscle isn't stretched due to low BP the muscle relaxes and dilates in response

Question 55

what is hyperemia

Answer 55

increase in blood flow

Question 56

what is active hyperemia

Answer 56

increase in blood flow when metabolic activity is increased

Question 57

what is reactive hyperemia

Answer 57

when an organ/ tissue has had its own blood supply completely occluded

Question 58

what do arterioles respond to

Answer 58

BP and also other vasoconstricting/ dilating factors

Question 59

how do arterioles respond to BP

Answer 59

muscle of arterioles contracts so decreasing radius so increasing resistance to flow so decreasing blood flow

Question 60

what are local humoral factor vasoconstrictors

Answer 60

endothelin-1, increased internal BP

Question 61

what is endothelin-1 released by and what does it do

Answer 61

endothelial cells, vasoconstriction

Question 62

what is the effect of increased internal blood pressure - vasoconstriction or dilation

Answer 62

constriction; myogenic contraction occurs - a form of autoregulation

Question 63

what are local humoral factor vasodilators

Answer 63

hypoxia, bradykinin, NO, increase K, CO2, H, tissue breakdown product (lactic acid), prostaglandin I2)

Question 64

what does hypoxia do

Answer 64

increases local blood flow

Question 65

what are circulating vasoconstrictors

Answer 65

adrenaline (dependent on receptor presence), angiotensin II, vasopressin

Question 66

what are circulating vasodilators

Answer 66

adrenaline (dependent on receptor presence), atrial natriuretic pepride

Question 67

where is the carotid sinus

Answer 67

where left and right common carotid divide into internal and external

Question 68

what are arterial baroreceptors

Answer 68

stretch receptors that respond to pressure

Question 69

where are arterial baroreceptors found

Answer 69

aortic arch and carotid sinus

Question 70

what do arterial baroreceptors do

Answer 70

decrease sympathetic and increase parasympathetic

Question 71

what does the medulla respond to

Answer 71

changes in pH as CO2 can't cross the BBB