Exam 3: Need to review

Question 1

pacemaker potential

Answer 1

exhibit slow spontaneous depolarization to threshold

Question 2

Ectopic pacemaker

Answer 2

• stimulated to produced APs by SA node before spontaneously depolarize to threshold
• If APs from SA node are prevented from reaching these, they will generate pacemaker potential

Question 3

Myocardial cells have RMP of

Answer 3

• 90 mV; depolarized to threshold by APs originating in SA node

Question 4

plateau phase of myocardial APs

Answer 4

• MP rapidly increases to +15 mV and stays there for 200-300 msec
• results from balance between slow Ca2+ influx and K+ efflux

Question 5

APs from SA node spread through

Answer 5

atrial myocardium via gap junction

- need special pathway to ventricles because of non-conductive fibrous tissue

Question 6

special pathway to ventricles

Answer 6

AV node at base of right atrium and bundle of HIS conduct APs to ventricles

Question 7

In septum of ventricles

Answer 7

• bundle of HIS divides into right and left bundle branches

- which give rise to Purkinje fibers in walls of ventricles: these stimulate contraction of ventricles

Question 8

Excitation- contraction coupling

- depolarization of myocardial cells

Answer 8

• opens V-gated Ca2+ channels in sarcolemma

- calcium-stimulated-calcium- release

Question 9

refractory period

Answer 9

• heart contract syncytium and cannot sustain force
• almost as long as AP
• no summation

Question 10

Cardiac cycle in 7 phases

Answer 10

Phase 1 - Atrial Contraction   
Phase 2 - Isovolumetric Contraction 
Phase 3 - Rapid Ejection 
Phase 4 - Reduced Ejection 
Phase 5 – Isovolumetric Relaxation 
Phase 6 - Rapid Filling
Phase 7 – Reduced Filling

Question 11

Phase 1 - atrial contraction

Answer 11

• av valves open; semilunar valve close

- atrial depolarization causes contraction of the atria

Question 12

Phase 1

as atria contracts

Answer 12

• pressure within atrial chambers increases –> more blood flow to AV valves –> rapid flow of blood into ventricles

Question 13

Phase 1

atrial contraction accounts for

Answer 13

• 10 % of left ventricular filling

Question 14

Phase 1
at high heart rates
- aka atrial kick

Answer 14

• atrial contraction may account for upto 40% of ventricular filling
• aka atrial kick

Question 15

phase 1

- after atrial contraction complete

Answer 15

• pressure falls –> ventricular volume are maximal –> end diastolic volume EDV

Question 16

Phase 2

Isovolumetric contraction

Answer 16

• all valves closed

- ventricular depolarization occurs and a rapid increase in intraventricular pressure

Question 17

Phase 2

AV valves to close as

Answer 17

intraventricular pressure exceeds atrial pressure

Question 18

Phase 2

closure of the AV valves results in

Answer 18

first heart sound (S1) lub

Question 19

Phase 2
isovolumetric contraction
re: volume

Answer 19

• ventricular volume does not change because all valves are closed
• Contraction, therefore, is said to be “isovolumic” or “isovolumetric.”

Question 20

Phase 3

Rapid ejection

Answer 20

• Aortic and Pulmonic Valves Open; AV Valves Remain Closed

- Rapid ejection of blood into the aorta and pulmonary arteries from the left and right ventricles

Question 21

Phase 3

Rapid ejection begins when

Answer 21

when the intraventricular pressures exceed the pressures within the aorta and pulmonary artery
causes the aortic and pulmonary valves to open

Question 22

Phase 3
Rapid ejection
- heart sound
-

Answer 22

No heart sounds are ordinarily noted during ejection because the opening of healthy valves is silent.

Question 23

Phase 3
Rapid ejection
- Blood continues to flow into

Answer 23

the atria and the atrial pressures begin to rise, and continue to rise until the AV valves open at the end of phase 5.

Question 24

Phase 4

Reduced Ejection

Answer 24

• Aortic and Pulmonic Valves Open; AV Valves Remain Closed

- after the beginning of ventricular contraction, ventricular repolarization occurs

Question 25

Phase 4
Reduced Ejection
Repolarization leads to

Answer 25

• a decline in ventricular tension and therefore the rate of ejection (ventricular emptying) falls.
• Ventricular outward flow still occurs

Question 26

Phase 4
Reduced Ejection
Left atrial and right atrial pressures

Answer 26

gradually rise due to continued venous return from the lungs and from the systemic circulation, respectively.

Question 27

Phase 5

Isovolumetric Relaxation

Answer 27

All Valves Closed

Question 28

Phase 5
Isovolumetric Relaxation

When the intraventricular pressures falls at the end of phase 4

Answer 28

aortic and pulmonary valves close causing second heart sound (S2) and the beginning of isovolumetric relaxation.

Question 29

Phase 5
Isovolumetric Relaxation

-After valve closure

Answer 29

• the aortic and pulmonary artery pressures rise slighty following by a slow decline in pressure.

Question 30

Phase 5
Isovolumetric Relaxation

• ventricular volumes

Answer 30

• remain constant because all valves are closed
• volume of blood that remains in a ventricle is called the end-systolic volume and is ~50 ml in the left ventricle.
• Left atrial pressure (LAP) continues to rise because of venous return from the lungs.

Question 31

Phase 6

Rapid filling

Answer 31

• A-V Valves Open
• intraventricular pressure will fall below atrial pressures
  
  • causing AV valves to open and ventricular filling begins
  • ventricular pressures slowly rise as they fill with blood from the atria.

Question 32

Phase 7

Reduced Filling

Answer 32

A-V Valves Open

Question 33

Phase 7
Reduced Filling

• As the ventricles continue to fill the

Answer 33

intraventricular pressures rise

reduces the pressure gradient across the AV valves so that the rate of filling falls.

Question 34

Phase 7
Reduced Filling
In normal, resting hearts

Answer 34

• the ventricle is about 90% filled by the end of this phase.
• Aortic pressure and pulmonary arterial pressures continue to fall