Chapter 19- Heart Part 2

Autorhythmic cells

- repeatedly and rhythmically generate action potentials

Pace maker

sets rhythm of the heart

Order of cardiac conduction

1. Sinoatrial (SA) Node

2. Atrioventricular (AV) node

3. Atrioventricular bundle ( bundle of his)

4. Right and left bundle branches

5. pukinje fibers

Membrane potential

difference in electrical potential on either side of the membrane

Resting membrane potential

differences in an unstimulated cell

• negative charges in cystol, positive charges in ECM = polarized

Depolarization

decreases in difference between outside and inside cell

Repolarization

returning membrane to resting membrane potential after a disturbance

Action potential

rapid polarization and repolarization

ECG

pattern of electrical activity of the heart

P wave

depolarization of atria

QRS wave

depolarization of ventricles

T wave

repolarization of ventricles

Relaxation period

• all 4 chambers in diastole (relaxation)

• atrial pressure > ventricular pressure < arterial pressure

Atrial systole

• atria contract

• atrial pressure > ventricular pressure < arterial pressure

Ventricular systol

• ventricles contracts

• 2 parts

1st part of ventricular systole

• atrial pressure < ventricular pressure < arterial pressure

• all valves closed

2nd part of ventricular systole

• atrial pressure < ventricular pressure > arterial pressure

• semilunar valves open, blood is ejected

Heart sounds

4 sounds caused by turbulence of blood

1st sounds

av vlaves closing (lub)

2nd sound

semilunar valves closing (dub)

3rd sound

ventricular filing in relaxation (not heard)

4th sound

atrial systole (not heard)