Cv Physiology

Front 1

1^ AV block

Back 1

Increased delay at AV node. No impulses are fully blocked.
Most common.
P wave ALWAYS precedes QRS

EKG Findings:
PR >.20
normal: Pwave, QRS
Regular rhythm

Front 2

2^ AV Block

Back 2

45, 210

Ventricles do not respond to all atrial stimuli.
P waves sometimes precede QRS.

EKG Findings:
progressive PR lengthing until QRS-T stops.
Normal P wave, QRS.
RR interval shortened.

Front 3

3^ AV Block

Back 3

45, 214
Complete heart block.
Atria & Ventricles depolarize independently.
AV conduction is blocked, so secondary pacemaker is found anywhere below the blockage.

EKG findings:
no assoc btwn p waves & QRS.
1st: 40-55 bpm, normal QRS, PP
2nd: 20-40 bpm, QRS wide & weird

Front 4

Paroxysmal Atrial Tachycardia (PAT)

Back 4

46, 158

Functioning antegrade impulse propagates retrograde through blocked AV path.

Type of reentrant tachy

EKG findings:
negative (retrograde) P wave

Front 5

Ventricular Impulse Origin

Back 5

46

Occurs if all supraventricular pacemaker sites are dysfunctional.

Ventricular impulses dominate rate & rhythm.

EKG findings:
wide QRS
no P-wave
bradycardia <40 bpm

Same EKG would show for: ectopic ventricular impulse

Front 6

Wandering Atrial Pacemaker

Back 6

46, 166

Site of atrial impulse generation changes from beat to beat.
Pacemaker site may alternate btwn SA and AV.

EKG findings:
P wave can be normal or inverted.

Front 7

Atrial Fibrillation

Back 7

46, 164

Chaotic atrial depolarizaitons cause tachy.

EKG:
no P-wave
irregular RR intervals

Front 8

Ventricular Fibrillation

Back 8

46, 190

Heart depolarizes in the midst of its repolarization.
An "R on T" ventricular premature impulse triggers life threatening tachy.

EKG:
no P wave, T wave, QRS

Front 9

Premature Atrial Complex (PAC)

Back 9

46, 154

Ectopic atrial impulses can reset (=repolarize) the SAN node earlier than usual. This causes an early P-wave.

If the SA node is NOT reset by ectopic impulses, a pause will occur in EKG because the AV is refractory.

If AV is not refractory at the next normal SA, an SA impulse is transmitted.

Front 10

Basic concept of myocyte depolarization

Back 10

47

Arrival of AP causes sarcoplasmic Ca to rise from .1 um to 2 um in about 10 msec.

This is enough to activate some, not all, of the available cross bridges.

Front 11

Things that increase cytosolic Ca

Back 11

47

sympathetic activation
adrenaline
positive inotropic drugs

Front 12

Ca supply in myocytes

Back 12

47

80% from SR, 20% from Ca current during Phase 2.

Front 13

Process of Ca release from SR

Back 13

47

SR membrane has calcium release channels that open at increased levels of local cytoplasmic Ca (=Calcium Induced Calcium Release CICR)

Front 14

Trigger Ca

Back 14

47

Trigger Ca raises Cai causing opening of Ca-release channels (CICR).

Ca diffuses rapidly to nearby sarcomeres, causing contraction.

Front 15

How is contraction terminated?

Back 15

47

elevated free Ca in the sarcoplasm increases the activity of the Ca pump and ion transporter activity. Over time, this reduces Cai by SR re-uptake and expulsion by sarcolemmal transporters.

Front 16

How does SR re-uptake work?

Back 16

47

Works via Ca-ATPase pump and controlled by phospholamban.

Front 17

Phospholamban

Back 17

47

Phospholamban inhibits Ca re-uptake.

Reducing phospholamban's inhibition of Ca re-uptake will allow more Ca to be re-uptaked and will enhance relaxtion.

Front 18

Effects of ectopic stimuli on SR Ca levels

Back 18

47

Because it takes time for the SR to take up Ca and get back to normal levels, an ectopic stimuli will result in a reduced contraction force.

Front 19

Preload Definition

Back 19

47

The amount of stretch on a single muscle fiber as it starts to contract.

Front 20

Preload in the heart

Back 20

47

Preload is the volume in the ventricle at the instant the ventricle starts to contract. This volume is called: End Diastolic Volume (EDV)

Front 21

End Diastolic Volume (EDV)

Back 21

47

The preload volume of a ventricle.

Front 22

Force and pressure developed by the contraction depends directly on the ____

Back 22

47

PRELOAD

Front 23

Frank-Starling Law

Back 23

47

The heart can increase its force of contraction when the muscles are stretched (by an increased venous return).

Basically, developed contractile force increases with length.

http://www.cvphysiology.com/Cardiac%20Function/CF003.htm

Front 24

Contractility depends on ?

Back 24

48

Stored Ca pool at start of systole.

Front 25

Stored Ca pool depends on:

Back 25

48

1. amount of Ica
2. relative Ca influx (systole)
3. relative Ca efflux (diastole)
4. [Ca]e

Front 26

Define afterload

Back 26

48

the load that contracting muscle works against and must move