Human CirculationA closer look

Contents1. Cardiac cycle2. Maintenance of heartbeat3. Principles governing blood

circulation4. Cardiovascular disease5. Lymphatic system6. Blood composition and function

Cardiac cycle complete sequence of pumping and filling

Electrical activity of the heart

1 - Sinoatrial node (Pacemaker)2 - Atrioventricular node3 - Atrioventricular Bundle (Bundle of His)4 - Left & Right Bundle branches5 - Bundle Branches 6 - Purkinje fibers

AV valves

SL valves

Cardiac outputTotal volume of

blood pumped by the left ventricle per minute◦ Heart rate (HR)

# beats per minute

◦ Stroke volume (SV) mL

◦ Product gives the cardiac output (Q)

◦ Average adultQ = HR x SV

= 70 beats/min x 75 mL/beat

= 5.25 L/min

Maximum HR = 200-your ageTraining heart rate is 75% MHR

e.g. 200-15 = 185 * 0.75 =

139 beats/min 20 minutes, 3x a

week

Pulse Stretching of

arteries as an effect of heartbeat

Pressure waves moving the artery walls when blood moves into aorta

Usually accurate measure of heart rate

Normal resting pulse is 60-100 bpm

Common pulse points1. Temporal artery

3. Carotid artery

4. Brachial artery

5. Radial artery

Blood vessel structure

Physical principles governing blood circulation Blood flow velocity

◦ Aorta (30 cm/s)

◦ Capillaries (0.026 cm/s)

Law of continuity◦ Volume of flow per second must be constant through the

entire pipe

◦ Total cross-sectional area of the capillaries determines flow rate

◦ Blood flow slows down in capillary beds

Osmotic pressure – amount of pressure required to prevent diffusion of water

Blood pressureForce exerted by

blood on walls of vessels

Determined by cardiac output and peripheral resistance by arterioles

Arterial pressure measured by a sphygmomanometer

Systolic/Diastolic (mmHg)

Factors◦ Heart rate◦ Blood volume◦ Resistance of

vessels◦ Viscosity

Blood composition and function

Lymphatic SystemFunctions

◦ Returns excess body fluid to blood◦ Transports fats from intestines to blood◦ Defense

Anatomy◦ Lymph nodes scattered throughout body

(thymus, spleen)◦ Vessels

Cardiovascular disease Cardiovascular

disease (>50% of all deaths)

Heart attack- death of cardiac tissue due to coronary blockage

Stroke- death of nervous tissue in brain due to arterial blockage

Atherosclerosis: arterial plaques deposit

Arteriosclerosis: plaque hardening by calcium deposits

Hypertension: high blood pressure

Hypercholesterolemia: LDL, HDL