location of the heart

3 layers of the heart

-endocardium-- smooth, thin, simple squamus layer

-myocardium--thick, cardiac mm layer

--epicardium-- serous membrane (part of pericardium)

cardiac muscle

-slightly striated like skeletal mm

*branched mm fibers transfer action potential to several other fibers

*intercalated discs--pieces of cell membrane attaching the cells together

-allows for fast transfer of action pot. via an electrical synapse

*branched cells and intercalated discs allow heart to contract in a rhythmic pattern w/ rest periods

-left side pumps high O2 blood to the systemic circuit (all tissues of body)

-right side pumps low O2 blood to pulmonary circuit (lungs)

-each side has an atrium and ventricle 

atrium (top)

receives blood from the venous sys and aids in filling the ventricles

-

ventricles (bottom)

forcefully pump blood out of heart into arteries

2 atrioventricular valves (AV valves)

-left AV valve--aka mitral valve

-right AV valve--aka tricuspid valve

2 valves b/w the ventricles and major arteries 

-aortic valve-- aka left semilunar valve

-pulmonary valve-- aka right semilunar valve

-all valves keep blood flowing in the right direction

major blood vessels

-major arteries- carry away

-aorta--high O2 blood out to systemic circuit

-pulmonary artery--low O2 blood, carriesCO2 to lungs

-major veins- to heart

-superior and inferior vena cava--carries low O2 blood to heart from systemic circuit 

-pulmonary veins--carry rich O2 blood back to heart

order of blood flow

1.deoxygenated blood from body flows through superior and inf. vena cava

2.enters right atrium

3.flows through right AV valve into right ventricle

4.pumped through pulmonic valve into pulmonary artery

5blood in oxygenated in lungs

6.returns to heart via pulmonic veins

7.enters left atrium

8.flows through left AV valve into left ventricle

9.pumped through aortic valve into aorta and out to rest of body

cardiac cycle def and 2 types

-one complete cycle of contraction and relaxation of the heart

-systole and diastole

systole

the contraction phase

-AV valves (aortic and pulmonic) open THE FIRST HEART SOUND

-semilunar valves (aortic and pulmonic) open

-the ventricles contract forcing blood into the major arteries

diastole

-the relaxation phase-

-starts after the ventricles relax

-semilunar valves close 2ND HEART SOUND

-AV valves open

-all chambers are relaxed being filled w/ venous blood

-the atria contract to force more blood into the ventricles just before the end of diastole

blood supply to the myocardium

**coronary arteries and veins supply blood to myocardium

-coronary arteriesbranch off at the base of aorta

-coronary veins enter the right atrium through the inferior vena cava

conduction system has 2 basic structures...nodes and fibers.  explain nodes and the 2 types

set the pace for heart rate by generating an action potential at a certain rhythm

-2 types-

-synoatrial node (SA node)- main pacemaker that starts action potential

-atrioventricular node (AV node)- secondary pacemaker, slows conduction from the atria to the ventricles

steps in conduction

1. SA node generates action potential

2. action pot. travels through mm of atria causing them to contract.  at same time action pot. travels to AV node.

3. AV node is stimulated and slows conduction allowing atria to finish contracting

4. action pot. travels down bundle of his and bundle branches

5.action pot. spreads down purkinje fibers to contract muscular walls of ventricles starting at apex