CARDIOVASCULAR SYSTEM

Heart Physiology

CARDIAC CYCLE

Systole*Atria Contract, Ventricles Fill*Ventricles Contract, Blood Forced

into Aorta and Pulmonary TrunkDiastole

*Atria Relax & Fill*Ventricles Passively Receive Blood

from the Atria

BLOOD PRESSURE

BP = pressure blood exerts on inner blood vessel walls

BP keeps blood moving between heart contractions

BP rises & falls in response to heart contraction & relaxation

BLOOD PRESSURE

Systole- Contraction of ventricles causes arterial

pressure to rise- Systolic pressure (SBP) is the maximum

pressure during contraction

BLOOD PRESSURE CONTINUED

Diastole- Relaxation and refilling of ventricles while

semilunar valves are closed- Arterial pressure drops as blood flows

“downstream”- Diastolic pressure (DBP) is the minimum

pressure just before the next systole

Average BP = 120/80Arterial surge in

pressure = PulsePulse rate usually =

heart rateAverage adult pulse =

60-80 BPM

CONDUCTION SYSTEM OF THE HEART

Specialized Cardiac Muscle TissueCapable of Generating & Conducting

Action Potentials AutorhythmicStimulates Contraction of Myocardial

Tissue

CONDUCTION SYSTEM OF THE HEART continued

5 Components:- Sinoatrial Node (Pacemaker)

* Right Atrium* Spontaneously Depolarize* Activates Atrial Contraction* Origin of Heart Beat* Action Potential Spreads to:

CONDUCTION SYSTEM OF THE HEART continued

- Atrioventricular (AV) Node* Rt. atrium (interatrial septum) * Action potential spreads to:

- Atrioventricular Bundle (Bundle of His)* Only electrical pathway between atria &

ventricles (C.T.Block)* Interventricular septum* Carries action potential through

interventricular septum to:

CONDUCTION SYSTEM OF THE HEART continued

- Bundle Branches (Left & Right )

* Interventricular septum* Carries action potential toward

respective ventricles- Purkinje Fibers

* Myocardium of Ventricles* Conduct action potentials to ventricular

myocardium

ELECTROCARDIOGRAM (ECG/EKG)

Record of Electrical Changes in Heart MuscleElectrical Changes due to Depolarization &

Repolarization of Cardiac Muscle FibersMetal Electrodes Applied to Skin, Attached to

Physiograph, Pick-up Electrical ActivityNormal Cardiac Cycle Gives Rise to

Characteristic “Waves”

ELECTROCARIDOGRAM (ECG/EKG) continued

P Wave- SA Node Stimulates Atrial Depolarization

- Occurs Prior to Atrial Contraction

QRS Complex- Ventricular Depolarization

- More Tissue, More Electrical Activity, Larger Wave

- Occurs Prior to Ventricular Contraction

T Wave- Ventricular Repolarization

HEART SOUNDS

Caused by Closing of Heart ValvesAV Valves

- prevent blood from flowing backwards into atria

- “Lubb”Semilunar Valves

- prevent blood from flowing backwards into ventricles

- “Dupp”

HEART MURMURS

Abnormal soundOften indicates valve disorderCauses:

- Congenital defects- Scarring- Insufficiency/Backflow