The Mammalian Circulatory System

Components of a CLOSED Circulatory System Pump: to circulate blood (i.e. heart) Vessels: along which fluid travels (arteries, veins, capillaries) Fluid: to carry substances around body (blood)

Flow of Blood in Circulatory System Divided into three main pathways: Pulmonary (lungs) Coronary (heart) Systemic (rest of body)

Coronary (Cardiac) Circulation Feeds heart muscle If blocked, leads to heart attack (cardiac infarction)

Structure of Heart

ELECTRICAL CONDUCTION Stimulation of the S.A. node causes the AV node to contract. From the AV node, impulses run through the Bundle of His to the Purkinje Fibres  these impulses cause ventricles to contract

CARDIAC CYCLE & ECG

Normal electrocardiograph The change in voltage produced by these electrical signals can be measured using a device called an electrocardioGRAM (ECG) The tracing produced by an electrocardiogram is called an electrocardioGRAPH Normal electrocardiograph Depolarization = contraction Repolarization = relaxation

Let’s play Doctor

Artificial Pacemakers They are useful if the SA node cannot transmit regular impulses It consists of: battery, timer and electrode These are inserted into heart region where the pacemaker would normally be Electrode sends out impulses at timed intervals to either speed up a slow heart or correct an erratic heart beat

Measurement of blood pressure Artery Rubber cuff inflated with air Artery closed 120 70 Pressure in cuff above120 Pressure in cuff below 120 Pressure in cuff below 70 Sounds audible in stethoscope Sounds stop Blood pressure Reading: 120/170

Blood Pressure Systolic pressure Diastolic pressure Is the pressure in the arteries during ventricular systole Is the highest pressure in the arteries Diastolic pressure Is the pressure in the arteries during diastole Is lower than systolic pressure

Blood pressure Blood pressure is determined partly by cardiac output C.O. = H.R. x S.V. And partly by peripheral resistance due to variable constriction of the arterioles

Mammalian Heart Each side of the pump has 2 chambers: atrium at the top; receive blood from veins ventricle (thick-walled) at the bottom; pump blood away from heart through arteries

Mammalian Heart Size of a fist Located between lungs Consists of cardiac muscle tissue Covered by pericardium (sac) Heartbeat is created by the pulling of the muscles in the organ against each other In an adult, 80 mL of blood is pumped at each beat Heart is divided into 4 chambers: 2 atria; 2 ventricles (i.e., two parallel pumps) separated by a thick partition called a septum

Structure of heart

Blood Flow through the heart The right atrium receives deoxygenated blood from the body via the vena cava The blood goes to the right ventricle and pumps to the lung (through the pulmonary artery)

Blood Flow through the heart The left atrium receives oxygenated blood from lungs (from pulmonary vein) The blood goes to the left ventricle, which pumps blood away from heart through the aorta to the rest of the body

Valves Maintain one-way flow of blood through heart 4 valves in total Atrioventricular (Atria  ventricles) tricuspid valve: from R.A. R.V. bicuspid (mitral) valve: from L.A. L.V. Semi-lunar valves (Ventricles  arteries) pulmonary SLV: R.V. pulmonary artery aortic SLV: L.V.  aorta

Valves

Sounds of the Heart Lub—AV valve close Dub—SL valve close

Systole vs. Diastole Systole Diastole contraction of heart chambers relaxation of heart chambers

VESSELS