cardiac physiology and conduction disorders

Question 1

three types of cardiac cells

Answer 1

pacemaker
conducting
contracting

Question 2

conducting cells

Answer 2

carry signals to the muscle wall

Question 3

contracting cells

Answer 3

do the contracting

Question 4

where are pacemaker cells found (5)

Answer 4

SA node –> superior part of the R atrium

AV node–> in the atrioventricular septum

bundle of his

left and right branches

purkinje fibers

Question 5

what specific subset of pacemakers cells set the rhythm of the heart

Answer 5

SA node in the superior part of the right atrium

Question 6

pacemaker cells in the AV node respond to

Answer 6

signals sent from the SA node and then fire impulses that are conducted in the ventricle

Question 7

what is the bundle of his

Answer 7

bundle of fibers that rub within the ventricular septum and when they get to the apex of the heart the fibers loop around and extend up the wall of the ventricles as the L and R bb

Question 8

describe the three types of channel states

Answer 8

open allows for the flow of ions

closed inhibits the flow of ions and

inactivated is where the flux is inhibited by a gate function of a part of the protein called the inactivation gate

Question 9

describe how the inactivation gate works

Answer 9

when the voltage gets to a certain point the flux of ions is so great that the inactivation gate closes which inhibits the flow of ions then the membrane has to reset that electrical charge back to normal so that the channel can reset to normal posture

close–>open–>inactivated–>closed

Question 10

what does the term threshold mean with respects to voltage gating

Answer 10

the membrane potential where predominance of a given channel is open

Question 11

three types of channels in cardiac cells

Answer 11

fast
slow
and
potassium

Question 12

how do pacemakers cells differ from regular muscle

Answer 12

closer to the threshold because of more positive resting potential

and have a innate permeability to sodium which pushes the cell charge up

this permeability is what give the cell it’s rhymic nature because it is always climbing toward threshold

Question 13

falling phase of pacemaker cells happens as a result of what

Answer 13

K channels opening

Question 14

phases of pacemaker cells

Answer 14

0 - upstroke d/t opening of voltage gated sodium/calcium channels

3- repolarization d/t inactivation of sodium/calcium channels and opening of potassium channels

4 - resting, d/t slow leak of sodium into cell

Question 15

how do contracting cells differ from pacemaker cells physiologically speaking

Answer 15

0 = fast Na+ channels (as opposed to slow acting) 
1 = K+

Potassium channels starting to open and membrane potential starting to reset but then calcium channels start to open

2 = Ca++

3 = K+

Question 16

60-100 bpm pace is seen where

Answer 16

a. SA node

Question 17

40-55 bpm seen at what pacemakers

Answer 17

AV node

Question 18

25-40 bpm seen in what pacemakers

Answer 18

Purkinje cells

Question 19

which area of pacemakers set the heart rate usually?

Answer 19

SA node unless there is an issue in which case you might see a much lower heart rate

Question 20

what is normal sinus rhthym

Answer 20

Normal basically means that the contraction or electrical spike is generated from the atrium. If it is not generated in the atrium, then it is not normal

1. If b/w 60-100bpm and there is a p wave for every QRS complex, then you can call it NSR

Question 21

45 yo man w/ chest pain. If he is shown to have a block at the SA node due to infarction, what would his HR be if all other areas are normal?

Answer 21

The AV node provides the next faster pace; that is probably going to give you the heart rate of 40-55 bpm

Question 22

P wave

Answer 22

= atrial contraction

depolarization of atria

Question 23

Q wave

Answer 23

= ventricular contraction

Question 24

Gap b/w p wave and QRS complex is represented by what in a EKG

Answer 24

delay in AV node

Question 25

Atrial repolarization results in what EKG marker

Answer 25

loss in QRS spike

Question 26

sinus bradycardia

Answer 26

coming from the sinus node seen as P waves but less than 60 bpm

Question 27

what is a respiratory sinus arrhythmia

Answer 27

Arrhythmia (first 2 spikes are farther apart, next 3 are closer together and last 2 are further apart í so pace is speeding up and slowing down which corresponds with respiration

Question 28

i. Atrial flutter

Answer 28

flutter waves which occur at a very rapid rate (>200 bpm) but ventricular rate remains regular b/c only so many atrial contractions get transmitted to the ventricle

Question 29

atrial flutter is characterized by what in EKG

Answer 29

flutter waves

Question 30

Atrial fibrillation

Answer 30

í disco-ordinated contraction; wave but not as crisp as you would see in flutter

Question 31

Atrial fibrillation seen as

Answer 31

Disorganized atrial activity

Question 32

PAT

Answer 32

rapid rate, P for every QRS but at the onset you see it accelerate dramatically Sudden onset, occurs in phases of very rapid rate triggered by the atria

Question 33

Premature atrial contractions

Answer 33

abnormally short interval between contractions before the atrium fires another P wave

Question 34

First-degree block

Answer 34

elongation of normal interval b/w P wave and R wave. Two parties are growing apart

Question 35

what are heart blocks

Answer 35

disorders at the AV node

Question 36

Second degree block

Answer 36

sometimes you have a P wave w/ no QRST complex One of the parties doesn't come home

Question 37

third degree block

Answer 37

total disconnect; no real relationship between atrial activity (p wave) and the ventricular activity

Question 38

PVC

Answer 38

ventricle spontaneously contracts (sometimes electrical abnormality and sometimes a volume problem)

Question 39

Ventricular tachycardia

Answer 39

rapid rate triggered by ventricle; the spike gets very wide

Question 40

Ventricular fibrillation

Answer 40

disorganized electrical activity

Question 41

polarization is when there are more ____ ions on the outside of the cell than are on the inside

Answer 41

positive ions on the outside=polarization

Question 42

what is the membrane potential

Answer 42

it is the difference between the positive charge we see outside the cell and the less positive charge we see in side the cell

Question 43

membrane potential decreasing in multiple cells is known as a

Answer 43

depolarization wave auto iirrhytmic pacemaker cells self generate ap and trigger each other

Question 44

describe the depolarization wave seen in pacemaker and myocytes

Answer 44

fast in pacemaker connects atria through bundle branches and will be see traveling slow in myoctes leads to the contraction of the atria

Question 45

depolarization wave will travel from the SA node to the AV node and conduction velocity will change here because

Answer 45

the AV node cells have very small diameters which increases resistance to electrical flow and they use slower opening Ca ion channels rather than the faster opening Na channels

Question 46

pacemaker cell phases

Answer 46

4 0 3 4