Cardiovascular physiology

Pacemaker Potential, Cardiac Potential, EKG, Parasympathetic/Sympathetic Control, Hormonal, Physical Factors

Pacemaker Potential Phase 1

Sodium influx, Potassium Efflux

Pacemaker Potential Phase 2

Potassium Channels Close

Pacemaker Potential Phase 3

Threshold

Pacemaker Potential Phase 4

Calcium Influx (depolarization)

Pacemaker Potential Phase 5

AP Generated

Pacemaker Potential Phase 6

Potassium Channels Open

Pacemaker Potential Phase 7

Potassium efflux (repolarization), Calcium Channel Closes

Cardiac Potential Phase 4

Nothing happens

Cardiac Potential Phase 0

Sodium influx (depolarization)

Cardiac Potential Phase 1

Potassium efflux, Chloride influx (-2)

Cardiac Potential Phase 2 (plateau)

Calcium Channels Open, Calcium influx (+2), heart stays contracted

Cardiac Potential Phase 3

Potassium efflux (repolarization), all other channels close

P Wave

Atrial depolarization

PR interval

Ventricles BEGIN to depolarize

QRS complex

Ventricular depolarization, Atrial repolarization

QT interval

Ventricles complete contraction, heart relaxes

T Wave

Ventricular repolarization

Parasympathetic Control

ACh hyperpolarizes membrane and reduces HR

Sympathetic Control

NE increase rate of depolarization and increases HR

Hormonal Control

Epinephrine and Norepinephrine increase HR and force of contraction in response to stimulus

Physical factors: Age

Age increases, CO decreases

Physical factors: Gender

1. Females have higher CO than males

2. Males can transport more oxygen than females (increased testosterone)

Physical Factors: Exercise

Increased HR during exercise, reduced resting HR

Physical Factors: Body Temperature

HR lowered when cold, lack of O2