BERNSTEIN PHSC 2303 Electro-Physiology of the Heart (Cardiac Physiology)

two main types of action potential are generated in the heart via what four places

SA node, AV node, Purkinje fibers, and myocytes

velocity of action potential at SA node

0.05 m/s

intrinsic rate of action potential at SA node

80/min

velocity of action potential between SA node and AV node (Atria)

1 m/s

intrinsic rate of action potential between SA node and AV node (atria)

80/min

velocity of action potential at AV node

0.05 m/s

intrinsic rate of action potential at AV node

40-60/min

velocity of action potential at purkinje fibers

1.5-4 m/s

intrinsic rate of action potential at purkinje fibers

15-40/min

Action potential in a sino-atrial node is divided into how many phases

three

what are the three phases in sino-atrial node action potential

phase 0, 3, 4

action potential in a sino-atrial node:

depolarization

phase 0

action potential in a sino-atrial node:

during depolarization, what enters and lasts about 2 ms

sodium

action potential in a sino-atrial node:

repolarization

phase 3

action potential in a sino-atrial node:

during repolarization, what channel is open

potassium

action potential in a sino-atrial node:

ion distribution restored

phase 4

action potential in a sino-atrial node:

phase 4 includes what pump

Na+/K+

action potential in a cardiac muscle (purkinje fibers and myocytes) include how many phases

five

what are the five phases of action potential in a cardiac muscle

phase 0, 1, 2, 3, 4

action potential in a cardiac muscle (purkinje fibers and myocytes):

depolarization

phase 0

action potential in a cardiac muscle (purkinje fibers and myocytes):

during depolarization, sodium enters for about how long

2 ms

action potential in a cardiac muscle (purkinje fibers and myocytes):

early repolarization

phase 1

action potential in a cardiac muscle (purkinje fibers and myocytes):

during early repolarization, what channels start to inactivate

sodium

action potential in a cardiac muscle (purkinje fibers and myocytes):

plateau

phase 2

action potential in a cardiac muscle (purkinje fibers and myocytes):

during phase 2, what ion enters for about 200 ms

calcium

action potential in a cardiac muscle (purkinje fibers and myocytes):

how long does the plateau stage normally last

200 ms

action potential in a cardiac muscle (purkinje fibers and myocytes):

repolarization

phase 3

action potential in a cardiac muscle (purkinje fibers and myocytes):

during repolarization, what channel opens

potassium

action potential in a cardiac muscle (purkinje fibers and myocytes):

ion distribution restored

phase 4

action potential in a cardiac muscle (purkinje fibers and myocytes):

what pump is involved in phase 4

Na+/K+ pump

natural pacemaker of the heart and spontaneously creates action potential

SA node

specialized tissue is found close to the superior vena cava with what dimensions

3 mm x 15 mm x 1

phylogenic (genetic/historical) remnant of venous sinus of lower vertebrates are found at the SA node (true or false)

true

SA nodes are special by pacemaker cells also called what

p-cells

fibers found in the SA node are about ______ micrometers in diameter

3-5

pacemaker is also called an __________ pacemaker

ectopic

phase 4 is characterized by gradual diastolic _______________ (pacemaker potential)

depolarization

diastolic (relax) depolarization is caused by how many ionic currents

three

what are the three ionic currents that cause diastolic depolarization

potassium, sodium, and calcium

three ionic currents that cause diastolic depolarization:

sodium current flows ____________, calcium current flows ___________, potassium current flows ____________

inward, inward, outward

potential of SA node is slow to develop but fast to return (true or false)

false (slow to develop and slow to return)

activation threshold for action potential in SA node is what

-40 mv

conduction velocity in the SA node

0.05 m/s

intrinsic rate in the SA node

80/min

__________ bundles of atrial fibers conduct impulses from SA node to AV node

three

conduction velocity in atria

1 m/s

signal delay in atrias

0.03 s

what is the critical element in the conducting system

A-V node

the AV node performs the function of a _________

filter

the AV node is located in ________ of right atria close to tricuspid valve

septum

A-V node is divided into how many regions

three

what are the three regions in the AV node

atrionodal, nodal, and nodal-His

space behind A-V node is supplied by what

autonomic nerves

the electrophysiology of the A-V node closely resembles what

sinus node

AV node is capable of what

self-excitation

A-V node is characterized by __________ conduction through the A-V bundle

one-way

delay of the impulse in A-V bundle

0.13 s

total delay of the impulse in AV node

0.16 s

what is the cause of delay in AV node

thin fibers and few gap junctions

conduction velocity in AV node

0.05 m/s

intrinsic rate in AV node

40-60/min

what resembles embryonic muscle cells, have large fibers, and high permeability of gap junctions

purkinje fibers

the delay of the impulse in Purkinje fibers is about what

0.03 s

conduction velocity of action potential for purkinje fibers is what

1.5-4 m/s

high velocity allows almost immediate activation of ventricular system (true or false)

true

intrinsic rate of purkinje fibers

15-40/min

electrical current flows from _________ area to __________ area of the heart

depolarized, polarized

inside of ventricles is ______________ and outside is ____________

electronegative, electropositive

during depolarization, current flows from __________ to __________ (from the base toward the axis)

negative, positive

electrical currents are generated by what

cardiac muscle

electrocardiogram is externally measured and during depolarization and depolarization (true or false)

true

ECG is a simple recording (true or false)

false (it is complex)

for an ECG, comparison in voltage are detected from ____ mv to ____ mv

0.1, 4

algebraic sum of all myocardial action potentials

electrocardiogram

different points of measurements called ________ are used to detect waves

leads

ECG waves and ventricular contractions:

atrial depolarization (SA and atrias) before atrial contraction

P-wave

ECG waves and ventricular contractions:

ventricle depolarization at the beginning of ventricular systole

QRS complex

ECG waves and ventricular contractions:

ventricular depolarization after T wave - both ventricles are relaxed

T-wave

no atrial depolarization because the mass of the ventricle is greater than the atria so it coveres the electrical activity of the atrial. can fix this by poisoning the ventricle (true or false)

true

ECG and time intervals:

between the beginning of atria contraction and ventricle contraction

P-Q interval

how long is the P-Q interval

0.16 s

ECG and time intervals:

time from the beginning of P wave to QRS complex

P-R interval

how long is the P-R interval

0.2 s

ECG and time intervals:

time from S wave to T wave

S-T segment

how long is the S-T segment

0.1 s

ECG and time intervals:

time from QRS complex to end of T contraction of ventricles

Q-T interval

how long is the Q-T interval

0.35 s

Cardiac Cycle and ECG relationship:

atrial contraction is from ________ wave to ______ wave

P, Q

Cardiac Cycle and ECG relationship:

isometric ventricular contractions starts with what wave

R

Cardiac Cycle and ECG relationship:

ventricular ejection is from _______ to _______ wave

S, T

Cardiac Cycle and ECG relationship:

isovolumic ventricular relaxation begins at the end of what wave

T

passive ventricular filling is after the _____ wave to the ____ wave

T, P

electrical activity of the heart can be recorded by places __________ on the surface of the body

electrodes

a combination of two wires/electrodes to form a complete circuit

lead

two electrodes on a limb located on different sides of the heart

bipolar

typically how many leads to register ECG

three

standard bipolar limb leads:

(-) right arm to (+) left arm

Lead I

standard bipolar limb leads:

(-) right arm to (+) left leg

lead II

standard bipolar limb leads:

(-) left arm to (+) left leg

lead III

anterior surface of the chest/over the heart and there are _____ separate points on a chest

six