Physiology Notecards

Front 1

heart murmur

Back 1

sound of blood leaking through a narrow (stenosed) valve or a valve that fails to close properly; caused by a leaky valve

Front 2

special features of cardiac muscle

Back 2

myogenic - nerves not needed to stimulate contraction

generate own action potential for contraction

pacemaker cells have the highest rate of action potentials

stimulate the other cells at the pacemaker rate (intact heart)

Front 3

syncytium

Back 3

electrical coupling (gap junctions) and tight membranous connections (intercalated disks) in cardiac muscles allow for many cells to contract as a single unit

Front 4

what is ischemia?
give an example

Back 4

absence of blood flow (low O2 levels)
causes cell death and acute pain

Ex: myocardial infarction (heart attack)

Front 5

what happens to O2 starved cardiac cells?

Back 5

ATP deficiency would lead to inability to pump Ca++ out of muscle cells

lactic acid + HIGH Ca++ causes:
->gap junctions close
->no transfer of ions b/w cells
->no contraction

Front 6

how does Ca++ enter cardiac muscle cells?

Back 6

Ca++ enters cell from the plasma by an action potential that opens voltage gated Ca++ channels. This triggers Ca++ ions from the sarcoplasmic reticulum (SR) to enter the cardiac muscle

Front 7

how does Ca++ leave cardiac muscle cells?

Back 7

2 pumps are used:
(1)Na/Ca exchanger linked to Na/K ATPase
->moves Ca++ into extracellular fluid
(2)Ca ATPase
->moves Ca++ into SR

Front 8

what's the difference between skeletal and cardiac muscle contraction?

Back 8

skeletal - force of a single twitch is ALL or NONE

cardiac - contraction is graded
->HIGH concentration of Ca++
->INCREASE in cross bridges
->MORE forceful contraction

Front 9

what is cardiac glycosides as digitalis?

Back 9

substance that prevents removal of Ca++ back into the plasma

causes INCREASE Ca++ levels -> MORE forceful contraction of the heart

Front 10

effect of catecholamines on cardiac muscle

Back 10

binds to beta 1 receptors in cardiac muscle
->INCREASES force of contraction
->DECREASES duration of contraction

Front 11

effect of catecholamines on pacemaker cells

Back 11

bind to beta 1 receptors on pacemaker cells
->INCREASES the frequency of action potentials
->INCREASES the rate of contraction

Front 12

special features of action potential in ventricular cells

Back 12

1)rapid depolarization due to Na+ entry
2)influx of Ca++ causes a long plateau
3)long refractory period prevents muscle tetany

Front 13

special features of action potential in pacemaker cells

Back 13

1)resting membrane potential unstable
2)slow depolarization begins spontaneously after repolarization
->ion flow in I_f channels (funny-current channels)
3)Ca++ influx causes depolarization
4)K+ efflux causes repolarization

Front 14

electrical activity pathway for heart

Back 14

-SA node (Pacemaker) sends electrical signal
->travels to Left/Right Atria through internodal fibers (atria contract)
->AV node and AV bundle
->Left/Right Ventricles through bundle branches
->Perkinje Fibers
->ventricular muscles (causes ventricle to contract)

Front 15

important function of AV node

Back 15

1)prevents action potentials from moving directly from atria to top of the ventricles

2)delays conduction of action potentials from atria to ventricles
=>allows time for the atria to complete contraction before the ventricles contract

Front 16

If abnormal pacemaker function, then...?

Back 16

-next fastest cells set the pace of action potentials
-heart rate will be too slow
-mechanical pacemaker correct the problem.

Front 17

what is heart block?
list 2 types of heart block

Back 17

abnormal pacemaker function
->poor conduction from the atria to ventricles

complete hb
-atria generates HIGHER action
potentials then ventricles
-mechanical pacemaker corrects problem

partial hb
-slows conduction from atria to ventricles

Front 18

what is ECG?

Back 18

represents the electrical activity of the heart recorded from electrodes placed on the surface of the skin

measures net charge moving towards and away the recording electrodes

voltage measured b/w 2 electrodes (lead)

does NOT record action potentials

Front 19

what is einthoven's triangle?

Back 19

represents minimal # of leads to give an ECG

lead I - left/right arms
lead II - right arm/left leg
lead III - left leg/left arm

Front 20

what are the following:
p wave
qrs complex
t wave
pr interval
qt interval

Back 20

P wave - atrial depolarization (atrial contraction)
QRS complex - ventricular depolarization (ventricular contraction)
T wave - ventricular repolarization (ventricles recharging for next contraction)
PR interval - time of electrical conduction from atria to ventricles
QT interval - time required for depolarization and repolarization of the ventricles.

Front 21

factors changing the recording of an ECG

Back 21

1)dial on the ECG is placed on lead II
->taller peaks than lead I or III

2)reverse position of electrodes
->waves inverted (neg rather than positive)

3)patient sitting vs lying down

Front 22

determining heart rate on ECG

Back 22

count number of R waves over a few seconds then # of waves in 60 seconds

Ex) 4 R Waves over 3 seconds
4/3sec = HR/60sec
HR = 80 waves/sec = bpm

Front 23

abnormalities of heart from ECG

Back 23

3rd degree block
atrial fibrillation
ventricular fibrillation
prolonged PR interval
prolonged QT interval (QT Syndrome)

Front 24

what is 3rd degree block?

Back 24

more than 1 P Wave before QRS complex

causes complete heart block

more P Waves (atria) than R Waves (ventricles) = HIGHER action potential in atria then ventricles

Front 25

what does a prolonged PR interval cause?

Back 25

partial heart block
-slows conduction b/w atria and ventricles

Front 26

steps of the cardiac cycle

Back 26

1)diastole (ventricles fill w/ blood)
2)atrial systole (blood -> ventricles)
3)EDV (end ventricle relaxation)
4)isovolumetric ventricular contraction
-all valves closed
5)ventricular ejection (opens semilunar valve/blood ejected)
6)ESV
7)isovolumetric ventricular relaxation

Front 27

closure of which valve causes a particular heart sound

Back 27

S1(first) - closure of AV valves
S2(second) - closure of semilunar valves

Front 28

what are types of AV and semilunar valves?

Back 28

AV valve
-tricuspid (right)
-bicuspid (mitral) (left)
semilunar valves
-aortic
-pulmonary

Front 29

when in the cardiac cycle is the volume of blood in the left ventricle maximal and minimal?

Back 29

maximal - EDV (ventricle filled)
minimal - ESV (ventricles empty)

Front 30

what's stroke volume and cardiac output?

Back 30

SV
=volume pumped/beat (ml/min)
=EDV - ESV

CO = HR x SV
INCREASE HR, INCREASE CO
(beats/min X ml/min)

Front 31

what modulates Heart Rate?

Back 31

autonomic neurons
-tonic parasympathetic signals (DECREASE HR)
-sympathetic neurons from medulla oblangata (INCREASE HR)

Front 32

what conditions decrease cardiac output?

Back 32

tachycardia
-very FAST HR that decreases the filling time

ventricular fibrillation

Front 33

what affects stroke volume?

Back 33

1)contractility
-Ca++, Norepinephrine

2)stretch of fibers (prop to venus return)

-venous return (HIGH)
=>inspiration (blood -> heart)
=>exercise leg muscles (one-way valve)
=>constriction (blood -> heart)

-venous return (LOW)
=>gravity