Cardiac Conduction

Question 1

what are the 2 atrioventricular valves?

Answer 1

mitral valve and tricuspid valve

Question 2

what does the mitral valve divide? another name for it is?

Answer 2

the left atrium and left ventricle
left atrioventricular valve

Question 3

what does the tricuspid valve divide? another name for it is?

Answer 3

the right atrium and right ventricle
right atrioventricular valve

Question 4

what are the 2 outflow valves?

Answer 4

aortic valve and pulmonary valve

Question 5

what does the aortic valve separate? another name for it is?

Answer 5

the left ventricle from the aorta
left semilunar valve

Question 6

what does the pulmonary valve separate? another name for it is?

Answer 6

right ventricle from the pulmonary artery
right semilunar valve

Question 7

what is the purpose of the outflow valves?

Answer 7

separate the heart from the two main arteries

Question 8

explain the process of the contraction and relaxation of the heart

Answer 8

depolarizing current passes through gap junctions to the contractile cell. action potential travels and opens Ca channels in plasma membrane and sarcoplasmic reticulum. Ca induces Ca release from SR which binds to troponin, exposing myosin-binding sites. crossbridge cycle begins and muscle fiber contracts. Ca is actively transported back into the SR and extracellular fluid. tropomyosin blocks myosin-binding sites and muscle fiber relaxes

Question 9

describe leakage channels and give an example

Answer 9

gates randomly open and close, K+ channels

Question 10

describe ligand gated channels and give an example

Answer 10

open and close in response to specific chemical stimulus- nicotinic cholinergic receptor opens when acetylcholine binds to it

Question 11

describe mechanically gated channels

Answer 11

channels which open in response to mechanical receptors

Question 12

a. an action potential in the heart is initiated by?

Answer 12

the SA node

Question 13

b. action potentials are conducted from the SA node to the?

Answer 13

arterial muscle

Question 14

c. action potentials spread through the atria to the?

Answer 14

AV node

Question 15

d. action potentials travel rapidly through the conduction system to the ___ of the heart

Answer 15

apex

Question 16

e. action potentials spread upward through the?

Answer 16

ventricular muscle

Question 17

f. what is the last step of an action potential?

Answer 17

the entire heart returns to the resting state until another action potential is generated in the SA node

Question 18

what is phase 0 of a ventricular and atrial action potential?

Answer 18

depolarization: voltage gated Na channels open

Question 19

what is phase 1 of a ventricular and atrial action potential?

Answer 19

initial repolarization: Na channels close and cell begins to repolarize as K leaves

Question 20

what is phase 2 of a ventricular and atrial action potential?

Answer 20

plateau: voltage gated Ca channels open and enter cell, fast K channels close

Question 21

what is phase 3 of a ventricular and atrial action potential?

Answer 21

repolarization: Ca channels close and slow K channels open

Question 22

what is phase 4 of a ventricular and atrial action potential?

Answer 22

resting potential: Na leaves and K reenters cells via the Na-K-ATPase pump

Question 23

describe the process of a nodal action potential:

Answer 23

Phase 4: spontaneous depolarization with Na currents
then phase 0: depolarization phase with increased Ca conductance
then phase 3: repolarization with K channels opening, Ca channels decrease
then back to phase 4

Question 24

how fast is phase 0 of an action potential?
how fast is the inactivation of phase 0?

Answer 24

very fast, fast

Question 25

how fast is phase 1 of an action potential?
how fast is the inactivation of phase 1?

Answer 25

fast, fast

Question 26

how fast is phase 2 of an action potential?
how fast is the inactivation of phase 2?

Answer 26

slow, slow

Question 27

how fast is phase 3 of an action potential?
how fast is the inactivation of phase 3?

Answer 27

very slow, no inactivation

Question 28

how fast is phase 4 of an action potential? (ventricular/atrial)
how fast is the inactivation of phase 4?

Answer 28

fast, no inactivation

Question 29

how fast is phase 4 of an action potential? (nodal)
how fast is the inactivation of phase 4?

Answer 29

slow, no inactivation

Question 30

how are contractile cell APs started versus autorhythmic?

Answer 30

contractile: depolarization via gap junction
auto: Na entry reinforced by Ca entry

Question 31

rising phase of AP is caused by what ion for contractile cells versus autorhythmic?

Answer 31

con: Na entry
auto: Ca entry

Question 32

refractory period of contractile cells vs autorhythmic?

Answer 32

con: long, resetting Na channels delayed
auto: no refractory period

Question 33

what does the P wave represent?

Answer 33

SA depolarization, action potential begins in atria

Question 34

the QRS complex represents?

Answer 34

ventricular depolarization

Question 35

what does the P-R interval represent?

Answer 35

time taken from first atrial depolarization to the first ventricular depolarization

Question 36

what does the ST segment represent?

Answer 36

period during ventricular depolarization (plateau)

Question 37

what does the T wave represent?

Answer 37

ventricular repolarization

Question 38

describe what a delayed afterdepolarization is

Answer 38

spontaneous release of Ca from SR under Ca overload, or extra cytosolic Ca is removed, or production of Na influx causes depolarization

Question 39

describe what a early afterdepolarization is

Answer 39

interruption of phase 3 repolarization or reactivation of Ca channels when AP is prolonged

Question 40

describe wolff-parkinson-white syndrome

Answer 40

A syndrome in which an extra electrical pathway in the heart causes a rapid heartbeat.

Question 41

List the layers of the heart from most outer to inner

Answer 41

Pericardium -> Epicardium -> Myocardium -> Endocardium