Cardiovascular anatomy & physiology

Question 1

Identify the statements that BEST describe ventricular myocytes. (select 3)
a. hyperkalemia increases threshold potential
b. they contain more mitochondria than skeletal myocytes
c. T-tubules spread the wave of depolarization throughout the myocardium
d. resting membrane potential is -90 mV
e. sodium conductance is greater than potassium conductance at rest
f. hypokalemia decreases resting membrane potential

Answer 1

b. they contain more mitochondria than skeletal myocytes
d. resting membrane potential is -90 mV
f. hypokalemia decreases resting membrane potential

Question 2

________________ initiate and propagate action potentials that trigger a coordinated myocardial contraction.

Answer 2

Myocardial cells

Question 3

_______________ is the ability to generate an action potential spontaenously.

Answer 3

Automaticity

Question 4

______________ is the ability to respond to an electrical stimulus by depolarizing and firing an action potential.

Answer 4

Excitability

Question 5

Cardiac myocytes contain

Answer 5

contractile elements (actin & myosin myofilaments)

Question 6

_______________- is the difference in electrical potential between the inside and outside of the cell.

Answer 6

The resting membrane potential (RMP)

Question 7

__________________ is the voltage change that must occur to initiate depolarization.

Answer 7

Threshold potential

Question 8

______________ is the movement of a cell’s membrane potential to a more positive value.

Answer 8

Depolarization

Question 9

______________ is the return of a cell’s membrane potential towards a more negative value after depolarization

Answer 9

Repolarization

Question 10

_______________ is the movement of a cell’s membrane potential to a more negative value beyond the baseline RMP

Answer 10

Hyperpolarization

Question 11

When serum K+ decreases, RMP becomes more

Answer 11

negative. making the myocytes more resistant to depolarization

Question 12

In excitable tissue, the primary job of the sodium-potassium ATPase is to

Answer 12

restore the ionic balance towards resting membrane potential

Question 13

When serum K+ increases, RMP becomes more

Answer 13

positive, making the myocytes depolarize more easily

Question 14

Severe hyperkalemia can

Answer 14

block depolarization

Question 15

What facilitates the spread of a cardiac action potential throughout the myocardium?

Answer 15

gap junctions

Question 16

__________ describes the situation when there is no net movement of an ion across a cell membrane.

Answer 16

Equilibrium potential

Question 17

_________ is the ability to transmit electrical current

Answer 17

Conductance

Question 18

____________ describes the force of myocardial contraction during systole.

Answer 18

Inotropy

Question 19

_____________ describes the heart rate

Answer 19

Chronotropy

Question 20

________________describes conduction velocity through the heart

Answer 20

Dromotropy

Question 21

_________ describes the rate of myocardial relaxation during diastole.

Answer 21

Lusitropy

Question 22

The primary determinant of threshold potential is

Answer 22

Serum Ca2+

Question 23

What are the two purposes that the Na-K+ ATPase pump serves?

Answer 23

it removes the Na+ that enters the cell during depolarization
it returns K+ that has left the cell during repolarization

Question 24

The primary determinant of resting membrane potential is

Answer 24

serum K+

Question 25

How does hypercalcemia affect the cell?

Answer 25

the threshold potential becomes more positive the cells become more resistant to depolarization

Question 26

Resting membrane potential is established by what 3 mechanisms?

Answer 26

1. chemical force 2. electrostatic counterforce 3. sodium/potassium ATPase

Question 27

Which phase of the ventricular action potential is associated with the GREATEST calcium conductance? a. 1 b. 2 c. 3 d. 4

Answer 27

b. 2

Question 28

Unlike neurons, the cardiac myocyte's action potential has a _____________

Answer 28

plateau phase where depolarization is prolonged

Question 29

The plateau phase gives the cardiac myocytes time

Answer 29

to contract

Question 30

The myocyte action potential consists of

Answer 30

5 phases: phase 0, 1, 2, 3, and 4

Question 31

Describe phase 0.

Answer 31

depolarization: Na+ in

Question 32

Describe phase 1.

Answer 32

initial repolarization: Cl- in and K+ out

Question 33

Describe phase 2.

Answer 33

Plateau: Ca2+ in and K+ out

Question 34

Describe phase 3.

Answer 34

Repolarization: K+ out

Question 35

Describe phase 4.

Answer 35

maintenance of transmembrane potential: K+ out and Na/K-ATPase function

Question 36

These parts of the heart do not have a plateau phase

Answer 36

the SA & AV node

Question 37

Which current is responsible for spontaneous phase four depolarization in the SA node? a. I-Na b. I-K c. I-Ca d. I-f

Answer 37

d. I-f

Question 38

Describe the cardiac conduction system.

Answer 38

SA node--> internodal tracts--> AV node--> bundle of His--> left & right bundle branches--> Purkinje fibers

Question 39

The heart rate is determined by the

Answer 39

intrinsic firing rate of the SA node & autonomic tone

Question 40

_____________ depress the automaticity of the SA node which explains why these drugs can cause a junctional rhythm.

Answer 40

Volatile anesthetics

Question 41

________________ of the SA node impairs its function as the dominant pacemenaker

Answer 41

Disease or hypoxia

Question 42

If disease or hypoxia of the SA node occurs, the cells with __________________________ will assume the pacemaker responsibility.

Answer 42

the next highest rate of spontaneous phase 4 depolarization

Question 43

The SA & AV node action potential consists of

Answer 43

3 phases

Question 44

The 3 phases of the SA & AV node AP include

Answer 44

Phase 4= spontaneous depolarization : Na+ in (I-f) and then Ca2+ in (t-type) Phase 0= depolarization: Ca2+ in (L-type) Phase 3= repolarization: K+

Question 45

Physiologically, we can increase the heart rate by

Answer 45

increasing the rate of phase 4 spontaneous depolarization and or/bringing RMP and TP closer together

Question 46

At rest, ______ tone exceeds __________ tone in the heart

Answer 46

PNS; SNS

Question 47

The PNS tone for the heart is the

Answer 47

vagus nerve- innervates the SA node (right) and left vagus innervates the AV node

Question 48

The SNS tone for the heart is the

Answer 48

cardiac accelerator fibers (T1-T4)