Blood Circulation

HEARTA hollow muscular, cone-shape, pumping organAbout the size of a CLOSED FISTWeighs about 300g, located w/in the mediastinum

(2nd rib -> BASE)

(6th rib ->APEX)

FUNCTIONWorks hand in hand -> RESPIRATORY SYSTEM -> GAS EXCHANGE and DISTRIBUTIONResponsible -> EJECTING and PUMPINGSYSTEMIC and PULMONARY circulation

HANAP VID PUMPING ACTION

STRUCTURE OF THE HEART

LAYERSEndocardium (innermost) -> endothelial tissue

lining the inner chambers and heart valves

Myocardium (middle) -> striated muscle fibers forming interlaced bundles -> CONTRACTION

Pericardium (outermost) -> squamous epithelial cells overlies connective tissue

*PARIETAL PERICARDIUM*PERICARDIAL SPACE

CHAMBERS OF THE HEART RECEIVING AND COLLECTING CHAMBERS -> RA AND LA DISCHARGING AND PUMPING CHAMBERS -> RV AND LV

VALVES OF THE HEART

TRIcuspid -> 3 LEAFLETS◦ Right side of the heart◦ Separates RA from the RVBIcuspid -> 2 LEAFLETS◦ Left side of the heart◦ Separates LA from the LVPULMONIC -> RV to PAAORTIC-> LV to A

BLOOD CIRCULATION

PULMONARY and SYSTEMIC CIRCULATION

SINOATRIAL NODE-pacemaker-initiates each heartbeat-generates electrical impulses at 60 to 100 times per minute

ATRIOVENTRICULAR NODE- Recieves electrical impulses form SA node- If SA NODE fails, AV NODE can intiates 40 to 60 beats per minute

BUNDLE OF HIS- Continuation of AV NODE- - braches into the right bundle branch, which extends down the right side of

interventricular septum, and the left bundle branch, which extends into the left ventricle

PURKINJE FIBERS

- diffuse network of conducting strands located beneath the ventricular endocardium

- spread the wave of depolarization through ventricles

CONDUCTIVITY SA node -> impulses -> A contracts -> AV

NODE -> delay impulses -> AV BUNDLES activated -> diffuses impulses -> PURKINJE FIBERS -> V contraction

The pump needs electricity to work. The human heart has a similar need for a power source and

also uses electricity.

ELECTROPHYSIOLOGIC AUTOMATICITY

-> spontaneous & repetitively beats

-> ability to generate electrical impluse

CONDUCTIVITY

->ability to pass impulse to the next cell

CONTRACTILITY

EXCITABILITY

-> ability to depolarize in response to a stimulus

REFRACTORINESS-> heart’s inability to respond to a new stimulus

CARDIAC CYCLE