Control of CV

Question 1

function

Answer 1

transport nutrients, transfer heat, buffer pH, transport hormone, respond to infection and urine filtration

Question 2

cardiac cycle

Answer 2

consists of systole and diastole of atria then ventricles

Question 3

direction of blood flow

Answer 3

high to low pressure

Question 4

starlings law

Answer 4

CO = SV x HR

Question 5

initiate impulse

Answer 5

an action potential is created in the SA node which spread to atria then ventricles.

Question 6

AV node

Answer 6

slows conduction and acts as secondary pacemaker

Question 7

EC coupling

Answer 7

purkinje fibresn interdigitate with myocytes to spread impulse across ventricles

Question 8

ECG

Answer 8

detects phasic change in potential difference between two electrodes and is recorded on paper, computer or oscilloscope

Question 9

sequence of cardiac cycle

Answer 9

atrial and ventricular diastole: AV open and SL closed
atrial systole and ventricular diastole: AV open and SL closed
atrial diastole and ventricular diastole: AV closed and SL open

Question 10

automaticity

Answer 10

that it fires spontaneously controlled by autonomic nervous system

Question 11

SA Node

Answer 11

fastest intrinsic rate so determine heart rate

Question 12

Lub

Answer 12

closure of the AV (ventricular systole)

Question 13

Dup

Answer 13

SL and AV valves closing (atrial systole)

Question 14

ESV (end systolic volume)

Answer 14

ventricles not completely emptied during systole: allows to increase stroke volume under certain circumstances (exercise) 50mL

Question 15

SV (stroke volume)

Answer 15

blood ejected per beat which is 70mL (values change during exercise)

Question 16

conduction

Answer 16

very rapid and co-ordinated which results in rise and fall of BP

Question 17

arrhythmias

Answer 17

irregular heart beat

Question 18

Order on ECG

Answer 18

atrial depolarisation
ventricular depolarisation
ventricular repolarisation

Question 19

delay through AV node (PR interval) then

Answer 19

Plateau phase of AP (ST interval)

Question 20

SA node action potential

Answer 20

Phase 0 - slow depolarisation due to inward calcium
No phase 1/2 - no Na+ current
Phase 3 - repolarisation due to inward Ca2+ current counterbalanced by outward K+
Phase 4 - pacemaker potential - slow spontaneous depolarisation due to activated cAMP channels and transient Ca2+ channels

Question 21

nodal tissue

Answer 21

there is a lack Na+ channels

Question 22

K+ permeability increases

Answer 22

longer time to reach threshold resulting in fewer BPM and reduced HR

Question 23

ACh

Answer 23

released from vagus nerve - parasympathetic

Question 24

Ca2+ permeability increases

Answer 24

shorter time to reach action potential - higher BPM and increased HR

Question 25

noradrenaline

Answer 25

sympathetic innervation

Question 26

purkinje action potential

Answer 26

Phase 0: rapid depolarisation due to inward Na+
Phase 1: partial repolarisation occurs as Na+ current is inactivated
Phase 2: plateau results from inward Ca2+ current counterbalanced by outward K+ currents
Phase 3: repolarisation due Ca2+ current inactivating and delayed rectifier K+ channel activate
Phase 4: resting state of the cell membrane potential (no pacemaker potential)

Question 27

calcium enter cardiac muscle cells

Answer 27

trigger contraction - allows for greater contraction for a small movement of calcium (amplify)

Question 28

adrenoceptors

Answer 28

alpha and beta subtypes

Question 29

adrenoceptors in heart

Answer 29

beta1 in nodal tissue, conducting system and myocardium - binds noradrenaline and circulating adrenaline

Question 30

effects of noradrenaline

Answer 30

-positive inotropy
-positive chronotropy
-positive lusitropy
-positive dromotropy

Question 31

vagus nerve

Answer 31

terminated in nodal tissue
- right vagus supplys SA node
- left vagus supplys AV node

Question 32

Release of ACh from nerve terminals (vagus nerve)

Answer 32

activates muscarinic (M2) receptors which reduces HR due to increase K+ permeability