heart contraction physiology

Question 1

What is the resting potential of the heart cells?

When ___ enters, it causes muscle cell
rapid depolarization.

Answer 1

-85mV
Na+

Question 2

After depolarization, the membrane potential is maintained, what is this phase known as?

Why does this happen? (hint: Ca2, Na+, and K+ channels)

Answer 2

Plateau phase

Voltage gated Ca2+ channels open for Ca2+ to enter cell
Na+ channels close
Some K+ channels open for K+ slowly exit

Question 3

What is the phase called when the cell returns to resting potential?

How does this happen?

Answer 3

Repolarization phase

All K+ channels open and K+ rapidly leaves the cell.

All Ca2+ channels close

Question 4

What is an EKG

Answer 4

an external measurement of electrical change in the heart

Question 5

What does the P wave represent

Answer 5

atrial depolarization

Question 6

What does the QRS wave represent

Answer 6

Ventrical depolarization

Question 7

What does the T wave represent

Answer 7

ventrical repolarization

Question 8

What indicates the heart rate on an EKG

Answer 8

distance from P wave to P wave

Question 9

What is a does first degree heart block look like on an EKG

What is the physiological result?

Answer 9

More time between P and QRS wave

The conduction in the heart is slowed

AKA “AV block”

Question 10

What does a second degree heart block look like on an EKG

What does this mean physiologically

Answer 10

more Ps than QRSs

some impulses are not conducted throughout the heart, “dropped beats”

AKA “2:1”

Question 11

What does a third degree block look like on an EKG?

What does this mean physiologically

Answer 11

P and QRS waves are not coordinated

no impulses from SA node to AV node. atria and ventricles pace independently, which causes incomplete filling of the heart

AKA “complete block”

Question 12

asynchronous contraction of muscle fibers so that chambers cannot pump

Answer 12

atrial and ventricular fibrilation

Question 13

strong brief shock resets conduction system led by SA node

Answer 13

defibrillation, give a stringer shock to act as the orginal signal that should have been given by the SA node

Question 14

Name the AV valves
What do they separate

Answer 14

Bicuspid: Left atrium/ventricle
Tricuspid: Right atrium/ventricle

Question 15

Name the semilunar valves
What do they separate

Answer 15

Aortic semilunar valve: left ventricle and aorta

Pulmonary semilunar: right ventricle and pulmonary trunk

Question 16

what process causes the first heart sound (lubb)?

Answer 16

AV valves closing

Question 17

what process causes the second heart sound (dubb)?

Answer 17

semilunar valves closing

Question 18

what is systole

Answer 18

contraction (think: squeze)

Question 19

what is diastole?

Answer 19

relaxation (think: destress or dilation)

Question 20

What is the first step of the cardiac cycle? (hint: first wave of EKG)

Answer 20

P wave

atrial depolarization which leads to atrial contraction (atrial systole).

Blood is “squeezed” out atria into ventricles

Question 21

What is the second step of the cardiac cycle? (hint: second wave of EKG)

Answer 21

QRS wave

ventricular depolarization which leads to ventricular contraction (ventricular systole).

ventricular pressure increases and the AV valves close (first heart
sound)

papillary muscles contract, pulling chordae tendineae to keep valves closed.

No blood has moved out yet.

Question 22

what is step 3 of the cardiac cycle? (hint: where does the blood go next? how does this happen?)

Answer 22

ventricular pressure > aortic pressure

semilunar valves open and blood ejected from the ventricle

Question 23

What is the fourth and final step of the cardiac cycle? (hint: final wave of EKG)

Answer 23

T wave

ventricular repolarization leads to ventricular muscle relaxation
(ventricular diastole).

aortic pressure > ventricular pressure, semilunar valves
shut (second heart sound and brief spike in aortic pressure = dicrotic notch)

no more blood exits ventricle (end systolic volume).

Question 24

End diastolic volume (blood in the ventricles before the heart contracts) – end systolic
volume (blood in the ventricle at the end of the systolic ejection phase =___

Answer 24

stroke volume

Question 25

Once atrial pressure > ventricular pressure, the ____ valves will open and blood will pass from atria to ventricles for new cycle

Answer 25

AV