Anatomy 18.2 Heart Homestasis

Two conditions severely weaken heart:

-Incompetent Valve

-Valvular stenosis

Valvular stenosis

• Stiff flaps that constrict opening

• Heart needs to exert more force to pump blood

Defective valve can be replaced with

mechanical, animal, or cadaver (from another human)valve

Incompetent valve

Blood backflows so heart repumps same blood over and over

angina pectrois

-Thoracic pain caused by fleeting deficiency in blood delivery to myocardium

-cells are weakened

Myocardial infarction (heart attack)

-prolonged coronary blockage

-areas of cell death are reapired with noncontractile scar tissue

The heart relies mostly on

aerobic respiration (a chemical process that uses oxygen to convert glucose into energy, carbon dioxide, and water)

Cardiac muscle has more mitochondria than skeletal muscle so has greater dependence on

oxygen

-cannot function without it

-skeletal musclecan go through fermentation if without it

Both types of tissues can use other fuel sources including

-lactic acid (must have oxygen)

coordinated heartbeat is a function of

-Presence of gap junctions

-intrinsic cardiac conduction system (network of algorithmic (non-contractile) cells)

arrhythmias

-irregular heart rhythms

—uncoordinated atrial and ventricular contractions

Fibrillation

-rapid, irregular contractions

-heart becomes useless for pumping blood, causing circulation to cease, brain death

Fibrillation treatment

-defibrillation interrupts chaotic twitching, giving heart a “clean slate” to start regular, normal depolarizations

Changes in patterns or timing of ECG may reveal

-diseased or damaged hear

- problems with heart’s conduction system

problems that can be detected in the ECG pattern are

-enlarged R waves - can indiacte enlarged ventricles

-elevated or depressed S-t segment- indicates cardiac ischemia

Heart murmurs

abnormal heart sounds heard when blood hits obstructions

-indicates valve problems

Stetnotic valve during heart murmur

Fails to open completely, restricting blood flow through valve

Causes: high- pitched sound or clicking as blood is forced through narrow valve

imcompetent valve during heart murmur

Valve fails to close completetly, allowing backflow of blood

Causes: swishing sound as blood regurgitates backward from ventricle into atria

Tachycadia

abnormally fast heart rate

-if persistent can lead to fibrillation

bradycardia-

heart rate slower than 60 beats / min

-may lead to grossly inadequate blood circulation in nonathletes

congestive heart failure

-Progressive condition; CO is so low that blood circulation is inadequate to meet tissue needs

congestive heart failure is caused by

coronary atherosclerosis

-Clogged arteries from fat buildup, impairs oxygen delivery to cardiac cells

-heart becomes hypoxic

caused by blood pressure

Multiple myocardial infracts

heart becomes weak as contractile cells are replaced w/ scar tissue

-Drug toxicity or chronic inflammation may play a role

Left sided congestive heart failure results in

in pulmonary congestion

-blood backs up in lungs

Right- sided congestive heart failure results in

peripheral congestion

-blood pools in body organs, causing edema

Failure to either side of heart can

weaken the other side

-leads to decompensated, seriously weakened heart

Treatment for congestive heart failure:

Removal of fluid

-drugs to reduce afterload and increase contractility