Physiology Exam 2

Question 1

Two types of junctions in the intercalated discs

Answer 1

Desmosomes- do the holding together (MECHANICAL)

Gap Junctions- allow communication b/w the cells so they can work in syncytium (ELECTRICAL)

Question 2

The only point of Electrical Contact b/w the Atria and Ventricles

Answer 2

AV Node

Question 3

Rate of conduction through AV node

Answer 3

SLOW. Allows adequate time for ventricles to fill between beats

Question 4

Rate of conduction through Purkinje Fibers

Answer 4

FAST. allows for efficient contraction & ejection of blood flow

Question 5

What are the 3 reasons that a latent/intrinsic pacemaker can assume the pacemaker role instead of the SA node?

Answer 5

• If SA node firing rate decreases or stops (vagal stimulation, SA node destroyed, removed, or suppressed by drugs)
• Latent/intrinsic rate is faster than SA node
• if SA node action potential conduction to rest of the heart is locked d/t disease in conducting pathways

Question 6

Pacemaker (Nodal) cells

Answer 6

SA and AV node. Slow action potentials.

Major Fx: pacemaker activity (with SA node being the primary pacemaker)

Question 7

Conductile Cells

Answer 7

Bundle of His & Purkinje Fibers
Fast Action Potentials.
Major Fx: rapid spread of electrical signal

Question 8

Contractile Cells

Answer 8

Ventricular and Atrial Cells
Major fx: contraction (pumping)
Fast Action Potentials

Question 9

Why can we not have summation or tetanus in cardiac cells?

Answer 9

The long refractory period occurs in conjugation with the Prolonged Plateau Phase

Question 10

Why is it important that we have a long refractory period and NO tetanus or summation?

Answer 10

This ensures that we have both contraction and relaxation and in order which is essential for pumping blood

Question 11

Contraction happens during:

Answer 11

Refractory period

We need the long refractory period to make sure we can do contraction!

Question 12

Where does calcium come from for cardiac muscles?

Answer 12

Both from the SR and outside of the cell through calcium channels

Question 13

How are intracellular Ca2+ levels decreased in cardiac cells?

Answer 13

Same as smooth muscle!

• SERCA
• Sarcolemmal Na+/Ca2+ Exchanger
• Sarcolemmal Ca2+ ATPase

Question 14

Force of cardiac muscle contraction depends on:

Answer 14

Initial fiber length!

Question 15

Chronotropy

Answer 15

Heart Rate
SA Node
“Impulse Generation”

Question 16

Dromotropy

Answer 16

AV-Conduction
AV Node
“Impulse Contraction”
How fast is the impulse conducted?

Question 17

Ionotropy

Answer 17

Contractility
Electro-Mechanical coupling
How strong (force) is the muscle contraction?

Question 18

Types of Cardiac Drugs

Answer 18

• Sodium potassium pump blocker (lead to increased contraction)
• Calcium channel blocker (lead to decreased contraction)
• B-receptor agonist (lead to increased contraction)

Question 19

Beta receptor agonist drug

Answer 19

(+) positive Ionotropy result
via cAMP pathway
given for CHF and Heart Attack (MI)

Question 20

Na-K pump blocker drug

Answer 20

leads to increased Ca, and increased contraction!

+ ionotropy

Question 21

Ca channel blocker drug

Answer 21

• ionotropy bc not as much calcium available

Question 22

T wave inversion can be a sign of

Answer 22

LVH

or Coronary Ischemia

Question 23

“Peaked” (tall & narrow) T waves can indicate

Answer 23

Hyperkalemia

repolarization wave is detected stronger

Question 24

Flat T waves may indicate

Answer 24

HypOkalemia

or Coronary Ischemia (again)

Question 25

S-T segment corresponds to :

Answer 25

plateau phase of Fast ventricular action potential (when ca L type influx) Ventricles are contracting!

Question 26

P-R interval

Answer 26

Represents time for Atria to depolarize and get through the AV node ONE LARGE BOX 0.12-0.2 seconds Longer: Conduction delay, AV block

Question 27

Another way to think about S-T segment

Answer 27

Ventricular contraction and emptying

Question 28

Q-T interval

Answer 28

All of ventricle activity Depol-Repol Ventricles are contracting, relaxing, and filling.

Question 29

We need to know this timing for exam | P-R interval! time it takes atria to depolarize and get signal to ventricles

Answer 29

0. 12-0.20 seconds is normal | longer: conduction delay or AV block

Question 30

1st degree AV block

Answer 30

prolonged PR interval due to delayed conduction thru AV node or Bundle of HIS one P wave for every QRS

Question 31

2nd degree AV block

Answer 31

partial dissociation b/w atria & ventricles not every P wave is followed by QRS may have 2 P waves, then 1 QRS. maybe 3 P waves, then QRS

Question 32

3rd degree AV block

Answer 32

Complete Heart Block no correlation b/w P wave and QRS- meaning atria and ventricles are acting totally independent of each other No conduction b/w AV node

Question 33

S2 2nd sound | "Dub"

Answer 33

closing of Semilunar valves (to body and lungs) to CLOSE

Question 34

End systolic volume

Answer 34

All valves closed | Ventricular blood volume is at lowest after ejection completed

Question 35

Difference between End diastolic volume and End systolic voluem

Answer 35

tells us how much blood was actually pumped out into the body Stroke volume = ~70 mL

Question 36

S3 = normally not heard

Answer 36

Rapid ventricular filling may indicate tensing of chordae tendinae and AV valve ring -normal in chidren -pathologic in adults, cause dby ventricular dilation

Question 37

Longest phase of the cardiac cycle

Answer 37

Reduced Ventricular Filling At the very end of the ventricles filling process- eventually the pressure in ventricles increases bc they are filling so much and rate of filling decreases

Question 38

How does increased HR affect Reduced Cardiac filling?

Answer 38

decreases the time available for the ventricles to finish filling decreases filling OR reduces preload and thus Stroke Volume decreases

Question 39

"Lub" sound

Answer 39

pressure increase in ventricles causes AV valves to close`

Question 40

S1

Answer 40

Isovolumic contraction "Lub" AV valves closing

Question 41

S2

Answer 41

Isovolumic relaxation "Dub" two components (the aortic valve closing and the pulmonary valve closing)

Question 42

S3

Answer 42

Ventricles filling rapidly normal in children, not audibly normal in adults

Question 43

S4

Answer 43

Atrial systole | where ventricular compliance is decreased- Ventricular Hypertrophy

Question 44

S4

Answer 44

Ventricular Hypertrophy