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

PULMONARY CIRCUIT Deoxygenated blood enters heart at the right atrium It flows to the right ventricle It flows from the right ventricle to the pulmonary trunk The blood is pumped to the lungs by the pulmonary arteries

AT THE LUNGS Blood picks up oxygen and releases carbon dioxide at the capillaries Gas exchange at the capillaries occurs by DIFFUSION

PULMONARY CIRCUIT Oxygenated 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 CIRCUIT Oxygenated blood travels through the aorta which branches out to various parts of the body Gas exchange occurs at capillaries O 2 exchanged CO 2 Deoxygenated blood from upper body enters heart by superior vena cava Deoxygenated blood from lower body enters heart by inferior vena cava

CARDIAC CYCLE A 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.

DIASTOLE The heart is relaxed Blood flows into the atria The AV valves are pushed open; ventricles begin to fill Diastole lasts for 0.4s Blood pressure low Diastole ends with contraction of atria to fill the ventricles

SYSTOLE Starts with the contraction of the ventricles The AV valves are forced closed The ventricles contract fully forcing the Semilunar Valves open Blood expelled forcefully from heart Systole lasts 0.3s Blood pressure is high

HEART SOUNDS The LUBB-DUBB sound of the heartbeat is caused by the closing of the valves. LUBB sound: The ventricles begin to contract and AV valves close The start of SYSTOLE DUBB sound: The ventricles relax and the Semilunar Valves close The 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 PRESSURE The pressure exerted on walls of arteries It’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 KNOW CARDIAC 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

DISEASES HYPERTENSION : “high” blood pressure which can damage heart and blood vessels ATHERSCLEROSIS: fatty deposits containing cholesterol and lipids accumulate in lining of blood vessels PLAQUE: decreases the diameter and elasticity of the blood vessels

DISEASES HEART ATTACK: clot completely blocks a coronary artery leading to death of cardiac muscle The heart forms scar tissue The heart weakens and may not be able to pump efficiently STROKE: damaged blood vessel; usually to the brain clot or vessel bursts due to high blood pressure or weakness in blood vessel