Circulatory Responses

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Circulatory Responses
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Purpose

• transport oxygen to tissues
• transport of nutrients to tissues
• removal of wastes
• regulation of body temperature

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Organization

• arteries - away from heart (oxygenated)
• veins - to heart (deoxygenated)
• arterioles - branches
• capillaries - smallest arteries
• venules - smallest veins
• mixed venous blood - from entire body

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Structure of the Heart
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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

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The Myocardium
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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

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The Cardiac Cycle

• Systole
• Contraction phase

• Diastole
• Relaxation phase

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Pressure Changes During the Cardiac Cycle
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Insert fig 9.4

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

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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

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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)

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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

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Anterior View of the Heart
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Normal electrocardiogram at rest
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Use of ECG for Diagnosis (ST depression)
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Cardiac Output

• Q HR x SV
• Q cardiac output
• HR heart rate
• SV stroke volume
• Implications during exercise???

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Insert table 9.1
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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

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HR Regulation contd

• Sympathetic control
• cardiac accelerator nerves at SA and AV nodes
• norepinephrine released which increases HR and
  force of contraction
• responsible above 100 bpm

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Autonomic Control of HR
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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

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Factors Regulating Venous Return

• venoconstriction
• reduces volume capacity of veins to store blood
• sympathetic control
• muscle pump
• respiratory pump
• inspiration reduces intrathoracic pressure

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The Skeletal Muscle Pump
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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

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Hematocrit
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