The heart as a pump

Question 1

where is the heart located?

Answer 1

within a fluid filled membrane sac called the pericardium

Question 2

what is the inner lining of the pericardium

Answer 2

epicardium

Question 3

what is the walls of the heart that are composed of muscle cells called?

Answer 3

myocardium (composed of myocytes)

Question 4

what is the in surface of walls that is in contact with blood?

Answer 4

the endocardium

Question 5

what prevents back flow from the ventricles back to the atrium?

Answer 5

atrio-ventricular valves

Question 6

what is the right and left AV valve called?

Answer 6

Right - tricuspid
Left - mitral

Question 7

what prevents backflow from the pulmonary trunk into the right ventricle?

Answer 7

pulmonary valve

Question 8

what prevents the backflow from the aorta into left ventricle?

Answer 8

aortic valve

Question 9

what are the two phases following a single heart beat?

Answer 9

contractile (systole)
relaxation filling phase (diastole)

Question 10

what is cardiac ejection fraction?

Answer 10

the amount of blood ejected per min
stroke volume (left ventricle contraction)

Question 11

how can you calculate stroke volume?

Answer 11

end diastolic volume - end systolic volume divided by EDV

Question 12

what does ejection fraction depend on?

Answer 12

volume, heart chamber dimensions, ventricular heart rate, valve function, preload and afterload

Question 13

what is preload?

Answer 13

the pressure of the blood on the ventricles at the end of diastole

Question 14

what is afterload?

Answer 14

the pressure in the wall of the left ventricle during ejection

Question 15

where does the depolarisation stimulus for the normal heartbeat originate?

Answer 15

sinoatrial node (SA)
- collection of pacemaker cells
- fire spontaneously
- exhibit automaticity

Question 16

where do nerve cells terminate in the heart?

Answer 16

the SA node

Question 17

what is the control of heart rhythm?

Answer 17

1. pacemaker generates wave of signals to contract (SA node)
2. signals delayed at AV node
3. Signals pass to heart apex
4. signal spread through ventricles

Question 18

What are the different stages of a ECG wave?

Answer 18

first bump = atrial events (P wave)
QRS - ventricular events
T waves - repolarisation

Question 19

what is the normal sinus rhythm?

Answer 19

60-100bpm

Question 20

what is the frequency of the heartbeat and hr regulated by?

Answer 20

input from the autonomic nervous system

Question 21

what is the intrinsic rate of the SA node in the absence of any input?

Answer 21

90-100 bpm

Question 22

How can cardiac myocytes be described?

Answer 22

electrically excitable

Question 23

what is the resting intracellular voltage of myocardial cells?

Answer 23

-90mV

Question 24

how does an action potential occur?

Answer 24

when Na enters the cell and sets up a depolarisation current

Question 25

what does stimulation of a single muscle fibre cause?

Answer 25

electrical activity to spread across the myocardium

Question 26

what is inotropy?

Answer 26

Force

Question 27

what is chronotropy?

Answer 27

Rate

Question 28

What happens to ventricular filling rate as HR increases?

Answer 28

It is reduced

Question 29

what does the Frank Starling law state?

Answer 29

the stroke volume of the left ventricle will increase as the left ventricular volume increases due to the myocyte stretch causing a more forceful systolic contraction.

Question 30

how to calculate stroke volume?

Answer 30

Cardiac output/HR

Question 31

what factors effect stroke volume?

Answer 31

Contractibility
Preload
Afterload