Cardiac centre

Question 1

Cardiac centre

Answer 1

events associated with one heartbeat

Question 2

cycle

Answer 2

In a normal cycle the atria contract while ventricles relax followed by atrial relaxation and ventricular contraction

Question 3

Systole

Answer 3

contraction

Question 4

Diastole

Answer 4

relaxation

Question 5

Relaxation period

Answer 5

end of heartbeat chambers in diastole

Question 6

isocolumetric relaxation

Answer 6

mitral and tricuspid valves closed no change in blood volume in ventricles

Question 7

ventricular filling

Answer 7

ventricle diastyole
intraventicular pressure drops below atrial pressure
AV valve opens
passive ventricle filling

rapid ventricular filling
diastasis- only small colume enters
atrial systole pumps 20-25mls of blood

Question 8

End-diastole volume

Answer 8

each ventricle contain 130mls
atrial systole 20-30% of EDV
Aortic and Pulmonary valves remain shut

Question 9

Ventricular Stystole

Answer 9

near end of atrial systole ventricles depolarise and ventricular contraction begins
A-V valves are pushed closed by blood
after 0.05 seconds all valves are shut
isovolumetric contraction occurs
ventricular ejection occurs when pressure in ventricle opens Ao and pulmonary valve

Question 10

t wave

Answer 10

ventricular polarasation

Question 11

Cardiac Output

Answer 11

CO = SV x HR
ml per min

the total amount of blood ejected from the left ventricle in one minute

Question 12

Cardiac reserve

Answer 12

Cardiac reserve refers to the difference between the rate at which the heart pumps blood and its maximum capacity for pumping blood at any given time

cardiac reserve is 4-5x than at rest

Question 13

Age related changes

Answer 13

decreased maximal CO
changes in nodal and conducting cells
decreased elasticity of fibrous skeleton

Question 14

Stroke volume factor

Answer 14

preload
contractility
afterload

Question 15

Preload

Answer 15

greater preload on cardiac muscles fibers prior to contraction increases their force of contraction

if HR > 160 bpm SV falls due to reduced filling time
low heart rate have longer filling times raising preload giving larger stroke volumes

Question 16

Starlings law of the heart

Answer 16

The more the heart is filled in diastole, the greater the stretch and the greater the force of systole

Question 17

Contractility

Answer 17

the strength of contraction at a given preload

Question 18

positive inotropic substances

Answer 18

calcium

adrenaine

Question 19

negative inotrophic substances

Answer 19

beat blockers

calcium channel blockers

Question 20

Afterload

Answer 20

the pressure in the aorta and pulmonary artery that needs to be exceeded
increased after load result in reduced SV
more blood remainsin ventricle at end of systole

Question 21

preload

Answer 21

volume of blood im ventricles at end of diastole

increased
-hypervolemia
regurgataion of cardiac valves
heart failure

Question 22

Afterloas

Answer 22

resistance left ventricle must overcome to circulate blood

• increase
• hypertension
• vasoconstriction

higher after load = higher cardiac workload

Question 23

regulation of HR

Answer 23

autonomic control

sympathetic and parasympathetic

Question 24

sympathetic

Answer 24

sympathetic nerve increases the HR and strength of contraction

Question 25

parasympathetic

Answer 25

parasympathetic nerve slows HR

Question 26

Input to cardiovascular centre

Answer 26

cerebral cortex limbic system hypothalamus proprio-receptors chemo-receptor baro-receptors

Question 27

output to heart (sympatheitc)

Answer 27

cardiac accelerator nerve increased rate of spontaneous depolarization of SA node and AV node increasing HR Increased contractility of atria and ventricles increasing stroke volume

Question 28

output to heart (parasympatheitc)

Answer 28

Vagus nerves (cranial nerve X) decreased rate of spontaneous depolarization in SA node and AV node decreasing HR

Question 29

Chemical regulaiton hormones

Answer 29

adrenal medulla produces adrenaline and noradrenalince thyroid hormones increases HR and contractility

Question 30

chemical regulation IONS

Answer 30

increased potassium and sodium decrease HR and contractility increased calcium increases HR and contractility

Question 31

Phases

Answer 31

``` Atrial contraction isovolumetric contraction rapid ejection reduced ejection isovolumetric relaxation rapid filling reduced filling ```

Question 32

atrial systole

Answer 32

P wave of the EGC electrical depolarization of the atria atria contract atrial pressure increases blood flows through AV valve Aortic + Pulmonary valves remain shut so no blood leaves ventricles Delay before qrs complex because allow ventricles to fill before contracting rapid blood flow into ventricles (1/3 of filling time), pumps 20-25 mls of blood, each ventricle contains about 130ml (EDV) pumps 20-30% of EDV.

Question 33

End diastole volume

Answer 33

after atrial contraction atrial pressure falls pressure gradient across AV valve AV valve closes ventricular volumes are maximal-EDV

Question 34

Preload

Answer 34

left ventricle end diastole volume | 120ml

Question 35

Isovolumetic contraction

Answer 35

QRS complex of the the ECG ventricular depolirisation excition-contraction coupling myocyte contraction rapid increase in intraventricular pressure AV valve closes when intraventricular pressure exceeds atrial pressure contraction of ventricles increases pressure with no change in volume as semilunar valves are closed

Question 36

Rapid ejection

Answer 36

interventricular pressie exceed the pressures within the aorta and pulmonary artery aortic valves and pumonic valve open blood ejected due to pressure gradient between ventricles and arteries

Question 37

Reduced ejection

Answer 37

T- wave of ecg ventricular repolarization ventricle emptying falls

Question 38

isovolumetric relaxation

Answer 38

all valves closed | intraventricular pressures fall aortic and pulmonic valve close

Question 39

rapid filling

Answer 39

ventricles relax intraventricular pressure falls below atrial pressure AV valves rapidly open passive ventricular filling intraventricular pressure continues to fall as ventricles relaxation occurs

Question 40

reduced filling

Answer 40

ventricle fill with blood increase intraventricular pressure decreased pressure gradient 90% of ventricle filling is passive

Question 41

Cardiac cycle

Answer 41

- all chambers in diastole at end of heartbeat,. The pressure in the ventricles falls and therefore Aortic and Pulmonary valves close - Isovolumetric relaxation - Mitral & tricuspid closed, no change in blood volume in ventricles. The ventricles continue to relax & pressure falls. - rapid ventricular filling (1/3 of filling time) AV (Mitral & tricuspid) valves open. Blood pours from atria into the ventricles passively. - Atrial Diastasis only small volume enters - Atrial systole resembles P wave (final 1/3 of time), pumps 20-25 mls of blood, each ventricle contains about 130ml (EDV) pumps 20-30% of EDV. Aortic + Pulmonary valves remain shut so no blood leaves ventricles Delay before qrs complex because allow ventricles to fill before contracting - - Ventricular contraction QRS wave - Ventricular systole - near end of atrial systole ventricles depolarise and ventricular contraction begins, A-V valves are pushed closed by blood All valves are now closed (0.05 secs) - Isovolumetric contraction occurs, contraction of ventricles increases pressure with s semilunar valves are closed therefore pressure in ventricles rises - Ventricular ejection interventricular pressure exceed the pressures within the aorta and pulmonary artery opening Aortic and Pulmonary valves , lasts 0.25 secs valves close, relaxation begins again - T wave resemble ventricular repolarisation, QRS complex cover atrial repolarisation

Question 42

3 factors that govern cardiac output

Answer 42

Preload- (end diastolic volume) i that is amount of blood returning to left ventricle i.e. venous return. Greater venous return greater CO. Starlings law of heart s the amount of strectch of the left ventricle at the end of diatole prior to contraction related to muscle sarcomere length. Afterload- pressure in the ascending aorta that has to overcome to open aortic valve and eject blood. Contracility- the force of contraction at a given preload