CIRCUITS AND THE CARDIAC CYCLE Pump It!. RECALL THE HEART A series of FOURS : 4 CHAMBERS: two ATRIA and two VENTRICLES 4 VALVES: two ATRIOVENTRICULAR.

CIRCUITS AND THE CARDIAC CYCLEPump It!

RECALL THE HEARTA series of FOURS:

4 CHAMBERS: two ATRIA and two VENTRICLES

4 VALVES: two ATRIOVENTRICULAR and two SEMILUNAR

4 BLOOD VESSELS: AORTA, VENA CAVA, PULMONARY VEIN, and PULMONARY ARTERY

PULMONARY CIRCUITDeoxygenated blood enters heart at the right atrium

It flows to the right ventricleIt flows from the right ventricle to the pulmonary trunk

The blood is pumped to the lungs by the pulmonary arteries

AT THE LUNGSBlood picks up

oxygen and releases carbon dioxide at the capillaries

Gas exchange at the capillaries occurs by DIFFUSION

PULMONARY CIRCUITOxygenated blood flows back to the heart through the pulmonary veins

The blood enters the heart through the left atrium

The blood flows to the left ventricle

The blood is pumped to rest of body through the aorta

SYSTEMIC CIRCUITOxygenated blood travels through the aorta which branches out to various parts of the body

Gas exchange occurs at capillaries O2 exchanged CO2

Deoxygenated blood from upper body enters heart by superior vena cava

Deoxygenated blood from lower body enters heart by inferior vena cava

CARDIAC CYCLEA continuous cycle of relaxation and

contraction of the heart muscles during a complete heartbeat.

The cycle has two parts:DIASTOLE: The period of the cycle

when the ventricles are relaxed, blood fills the ventricles.

SYSTOLE: The period of the cycle when the ventricle contracts, blood is ejected from the ventricles.

DIASTOLEThe heart is relaxedBlood flows into the atriaThe AV valves are pushed open; ventricles begin to fill

Diastole lasts for 0.4sBlood pressure lowDiastole ends with contraction of atria to fill the ventricles

SYSTOLEStarts with the contraction of the

ventriclesThe AV valves are forced closedThe ventricles contract fully forcing

the Semilunar Valves openBlood expelled forcefully from heartSystole lasts 0.3sBlood pressure is high

HEART SOUNDSThe LUBB-DUBB sound of the

heartbeat is caused by the closing of the valves.

LUBB sound: The ventricles begin to contract and AV

valves closeThe start of SYSTOLE

DUBB sound:The ventricles relax and the Semilunar

Valves closeThe end of SYSTOLE

SINOATRIAL NODE Acts as the pacemaker

of the heart It maintains the heart’s

intrinsic pumping rhythm

Sinoatrial node AV node Purkinje Fibres

BLOOD PRESSUREThe pressure exerted on walls of

arteriesIt’s generated as heart ejects

blood into aorta

SYSTOLIC PRESSURE: aorta expands and wave of pressure created

DIASTOLIC PRESSURE: aorta recoils propelling blood along arteries

TERMS TO KNOWCARDIAC OUTPUT: volume of

blood pumped from left ventricle to aorta per minute

STROKE VOLUME: amount of blood pumped by left ventricle when it contracts

HEART RATE: number of contractions per minute

DISEASESHYPERTENSION: “high” blood

pressure which can damage heart and blood vessels

ATHERSCLEROSIS: fatty deposits containing cholesterol and lipids accumulate in lining of blood vesselsPLAQUE: decreases the diameter

and elasticity of the blood vessels

DISEASESHEART ATTACK: clot completely

blocks a coronary artery leading to death of cardiac muscleThe heart forms scar tissueThe heart weakens and may not be able to

pump efficientlySTROKE: damaged blood vessel;

usually to the brainclot or vessel bursts due to high blood

pressure or weakness in blood vessel