cardiac physiology

Question 1

atrial extrasystoles

Answer 1

arises from the atrial muscle.
the abnormal impulse resets the SA node and therefore it is sollwed by a normal period of diastole

Question 2

ventricular and nodal extrasystoles

Answer 2

arise from the ventricular muslce and AV node and bundle respectivel
this extrasystole does not reset the SA node and is therefore follwed by the normal impulse produced by the SA node which cannot be transmitted ot the ventricle due to them being in ARP. therefore they are followed by a compensatory pause due to a longer diastole.

Question 3

atrial flutter

Answer 3

the atria beat a high rate therefore their pumping action is diminished.
due to the long refractory period of the AV node, not all these impulses travel to the ventricle(heart block)

Question 4

atrial fibrillation

Answer 4

atria beat at an extreemly high rate and the individyual atrial fibres beat differently and the pumping action of the atria is completely lost. there will be irregular ventricular beating as well as the treshold is not alwasy reached.

Question 5

ventricular flutter

Answer 5

ventricles beat at a high rate, cardiac output is diminshed and may lead yo faintoing

Question 6

ventricular fibrillation

Answer 6

ventricles beat at a very high rate, myocardial fibres beat asynchronously , ventricular pumping action is completely lost usually leads to death

Question 7

conditions that give rise to circus movement

Answer 7

• decrease in the velocity of the impulse (blockage in purkinje fibres, ischaemia of the muscle, high blood potassium )
• length of the pathway (longer) (dilated heart)
• shortening of the refractory period (adrenaline or electric AC shock)

Question 8

3 factors that control stroke volume

Answer 8

preload - degreee of mycoardial distension
contractility (independant of preload)
afterload (force to push blood out - resistance to arteries

Question 9

factors affecting the preload

Answer 9

venous returna dn filling time

Question 10

factors affecting contractility

Answer 10

autonomic innervation and hormones

Question 11

factors affecting the afterload

Answer 11

vasodilation vasoconstriction

Question 12

factors affecting venous return

Answer 12

gravity, blood volume, sympathetic vasoconctrcion tone, respiratory pump, mean systemic filling pressure, skeletal pump, cardiac suction

Question 13

main 2 factors controlling heart rate

Answer 13

autonomic inervation and hormones

Question 14

factors affecting blood pressure

Answer 14

cardiac output
resistance
blood volume

Question 15

3 things used for the rapid regulation of blood pressure

Answer 15

• baroreceptors: stretch receptors, when stimulated they inhibity the vasoconstrictor centre and excite the vagal centre. vasodilation leads to decrease in HR and blood pressure
• chemoreceptors: 2 carotid bodies and several aortic. fall in bp leads to decrease on O2 and pH and ncrease in CO2. thsi stimulates chemorecpetors and vasoconstriction centre.
• atrial and pulmonary receptors: detetc changes in blood volume

Question 16

long term regulation of blood pressure

Answer 16

renal body fluid system
high bp results in increae in renal output of water and salts resulting in a decrease of ECF volume and tehrefore blood volume.

Question 17

how does laminar flow become turbluent flow

Answer 17

-increase in flood
- goes over obstruction
- makes a sharp turn
- passes over rough surface

Question 18

heart sounds

Answer 18

1- sudden closure of AV valves -systolic
2- sudden closure of aortic and pulmonary vialves- diastolic
3- vibrations in ventricular wall due to rapid filling
4 - auricular contraction and rush of blood into ventricle

between the first and second there is systol and from the second to the first there is diastole

Question 19

3 types of murmurs

Answer 19

systolic, diastolic and continuous

Question 20

systolic murmurs

Answer 20

occur during ventricular systole between 1st and 2nd heart sound

Organic murmurs
- narrowing or stenosis fo aortic or pulmoanry valves
- widening or regurgitation of the mitral or tricuspid valve
- congenital interventricular spetal defect

Functional murmurs: fever, anaemia exercise etc

Question 21

diastolic murmurs

Answer 21

occur during diastole after the second heart sound
Organic murmurs
- narrowing or stenosis of the mitral or tricuspid valve
- widening or regurgitation of the aortic or pulmonary valve

Question 22

continuous murmurs

Answer 22

occur during systolic and diastolic periods (machinery murmur)
eg due to duct between aorta and pulmonary artery at birth