cardiac system 2

Question 1

autorhythmicity of the heart

Answer 1

heart beats rhythmically as result of action potentials it generates by itself

Question 2

what are the two specialized types of cardiac muscle cells

Answer 2

contractile cells and autorhythmic cells

Question 3

contractile cells

Answer 3

99% of cardiac muscle cells
do mechanical work of pumping
normally do not initiate own action potentials

Question 4

autorhythmic cells

Answer 4

do not contract
specialized for initiating and conducting action potentials responsible for contraction of working cells

Question 5

action potential in contractile cardiac cells steps

Answer 5

1. resting potential- cell is polarized- -80mv
2. rapid depolarization until about 50mv
3. rapid repolarization- cell starts to reverse polarity because of a specific k+ current is activated whule fast sodium channels close
4. plateau- L type calcium channels open during the rapid depolarization and remain open, also calcium entry causes calcium release from internal stores
5. reporlarization- closing L type calcium channles and dominant outward K current

Question 6

ECG purpose

Answer 6

means of observing cardiac electrical events

Question 7

how are electrical currents from the heart measured

Answer 7

by using electrodes placed on the skin
- changes in electrical activity in the heart detectable in skin due to conductiev nature of body fluids
-ECG tracing shows the direction and magnitude of currents over time and sum of all electrical currents at any given time dominated by contractile cell activity due to their high number

Question 8

different parts of the ECG recrod can be correlated to

Answer 8

specific cardiac events

Question 9

P wave

Answer 9

atrail depolarzation

Question 10

PR segment

Answer 10

AV nodal delay

Question 11

QRS complex

Answer 11

ventricular depolarization (atria repolarizing simultaneously)

Question 12

ST segment

Answer 12

time during which ventricles are contracting and emptying

Question 13

T wave

Answer 13

ventricular repolarization

Question 14

TP interval

Answer 14

time during wich ventricles are relazing and filling

Question 15

alternating electrical stimulation of atria and ventricles

Answer 15

heart is a 2 stage pump
-atria pump first and prime the right and left ventricles
-right and left ventricles pump blood into the pulmonary and systemic circulation respectively
-this alternating pumping action establishes pressure gradients that drive blood flow between the 4 chambers of the heart
-pressure gradients between chambers can reverse and so the valves are present to ensure flow only continues in one direction

Question 16

cardiac cycle

Answer 16

alternating periods of systole and diastole

Question 17

systole

Answer 17

period of contraction and emptying

Question 18

diastole

Answer 18

period of relaxation and filling

Question 19

cardiac cycle steps

Answer 19

1. passive filling during ventricular and atrial diastole
2. atrial contraction
3. isovolumetric ventricular contraction
4. ventricular ejection
5. isovolumetric ventricular relaxation