Circulatory Responses

Purpose

• transport oxygen to tissues

• transport of nutrients to tissues

• removal of wastes

• regulation of body temperature

Organization

• arteries - away from heart (oxygenated)

• veins - to heart (deoxygenated)

• arterioles - branches

• capillaries - smallest arteries

• venules - smallest veins

• mixed venous blood - from entire body

Structure of the Heart

The Heart has Two Pumps

• pulmonary - pumps blood to the lungs and back to the left side of the heart from the lungs

• systemic - pumps blood to the rest of the body and back to the right side of the heart

The Myocardium

Cardiac Cycle

• Systole– contraction phase– 0.3 sec at rest down to 0.2 sec during heavy

exercise

• Diastole– relaxation phase– 0.5 sec at rest down to 0.13 sec during heavy

exercise

The Cardiac Cycle

• Systole– Contraction phase

• Diastole– Relaxation phase

Pressure Changes During the Cardiac Cycle

Insert fig 9.4

• two heart sounds– 1st closing of the atrioventricular valves– 2nd closing of the aortic and pulmonary valves

Blood Pressure

• arterial blood pressure estimated using sphygmomanometer– systolic/diastolic– males 120/80– females 110/70

• Hypertension– resting BP of 140/90– primary or secondary

Blood Pressure Determination

• Pulse pressure– difference between systolic and diastolic

• Mean arterial pressure (MAP)– product of cardiac output and total vascular

resistance (sig?)– average pressure during cardiac cycle– determines rate of blood flow through system– MAP = DBP +.33 (pulse pressure)

Factors Affecting Blood Pressure

• Blood pressure can be increase by– increase in blood volume– increase in heart rate– increase in blood viscosity– increase in stroke volume– increased peripheral resistance

Anterior View of the Heart

Normal electrocardiogram at rest

Use of ECG for Diagnosis (ST depression)

Cardiac Output

• Q = HR x SV– Q = cardiac output– HR = heart rate– SV = stroke volume

• Implications during exercise???

Insert table 9.1

Regulation of Heart Rate

• Parasympathetic control– cardiovascular control center (medulla

oblongota)– vagus nerve– acetylcholine decreases activity of both SA and

AV nodes– can increase HR by removal

HR Regulation cont’d

• Sympathetic control– cardiac accelerator nerves at SA and AV nodes– norepinephrine released which increases HR

and force of contraction– responsible above 100 bpm

Autonomic Control of HR

Regulation of Stroke Volume

• end diastolic volume (EDV) - volume of blood in ventricles at the end of diastole– Frank-Starling Law– increase in contractility increases volume

pumped per beat– venous return

• average aortic blood pressure• strength of ventricular contraction

Factors Regulating Venous Return

• venoconstriction– reduces volume capacity of veins to store blood– sympathetic control

• muscle pump

• respiratory pump– inspiration reduces intrathoracic pressure

The Skeletal Muscle Pump

Components of Blood

• Plasma– Liquid portion of blood– Contains ions, proteins, hormones

• Cells– Red blood cells

• Contain hemoglobin to carry oxygen

– White blood cells– Platelets

• Important in blood clotting

• Hematocrit– Percent of blood composed of cells

Hematocrit