Human Circulation

Human CirculationHuman CirculationA closer look

ContentsContents1. Cardiac cycle2. Maintenance of heartbeat3. Principles governing blood

circulation4. Blood composition and function5. Cardiovascular disease6. Lymphatic system

Cardiac cycle Cardiac cycle complete sequence of pumping and fillingcomplete sequence of pumping and filling

Electrical Electrical activity of the activity of the heartheart

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

PulsePulse 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

Cardiac outputCardiac output Total 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 adult

Q = 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

Blood vessel structureBlood vessel structure

Physical principles governing blood Physical principles governing blood circulationcirculation 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

Blood pressureBlood pressure Force exerted by

blood on walls of vessels

Pressure decreases from arteries to veins

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 Blood composition and functionfunction

Cardiovascular diseaseCardiovascular disease Cardiovascular disease

(>50% of all deaths) Hypercholesterolemia:

LDL, HDL Hypertension: high blood

pressure Atherosclerosis: arterial

plaques deposit Arteriosclerosis: plaque

hardening by calcium deposits

Heart attack- death of cardiac tissue due to coronary blockage

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

Lymphatic SystemLymphatic SystemFunctions

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

Anatomy◦ Lymph nodes scattered throughout body

(thymus, spleen)◦ Vessels

Check-up QuizCheck-up Quiz

1. What is ventricular systole?2. What makes the “lub dub” sound?3. Give one difference between an

artery, a capillary, and a vein.4. Name one factor that can raise

blood pressure.5. Name one substance that should

be present before a blood clot can form.