Cardiovascular System

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Cardiovascular System

• Chapter 30

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Blood Flow

• Vena Cava Right Atrium Tricuspid
• Right Ventricle Pulmonic Pulmonary
• Artery Lungs Pulmonary Veins Left
• Atrium Mitral Left Ventricle Aortic
• Valve Aorta

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Conduction Pathways

• Sinoatrial (SA) node
• primary pacemaker
• regular rate of 60-100 BPM
• Atrioventricular (AV) node
• rate of 40-60 BPM
• Bundle of His
• 20-35 BPM
• Purkinje fibers

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Electrophysiologic Properties

• Automaticity
• spontaneous initiation of electrical impulse
• Excitability
• capacity to respond to electrical impulses
• Conductivity
• ability to transmit impulses cell to cell
• Contractility
• ability of myocardial fibers to shorten

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Cardiac Cycle

• Contraction (depolarization)
• systole
• first heart sound
• lubb louder than dub at the apex
• Caused by closure of AV valves
• Relaxation (repolarization)
• diastole
• second heart sound
• Closure of aortic and pulmonic semilunar valves

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Cardiac Output

• Amount of Blood Ejected from the Left Ventricle
  in 1 Minute
• Average resting CO is 5 to 6 L

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Ejection Fraction

• Measure of ventricular efficiency
• Usually about 60
• Lower values indicate ventricle is not pumping as
  forcefully
• Therefore, more blood remains in ventricle at end
  of systole

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Electrical Impulse

• Heart generates own electrical impulse
• Begins in SA node
• Changes in response to environmental
  circumstances
• Sympathetic nerve impulses
• Increase rate and force of contraction
• Causes gt HR and force of contraction dilates
  coronary vessels
• Parasympathetic nerve impulses
• Decrease heart rate

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Hormones and Heart

• Epinephrine
• Sympathetic in nature
• Increases
• Heart Rate
• Force of Contraction
• Cardiac Output
• Systolic BP

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Hormones and Heart

• Aldosterone
• Regulates Sodium/Potassium
• Atrial Natriuretic Peptide
• Secreted by atria of heart when gt BP stretches
  walls of atria
• Excretes Sodium and therefore, loss of water in
  urine
• Therefore, lt blood vol and BP

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Blood Vessels

• Arteries/arterioles
• Carry blood from heart to capillaries
• Thick walled
• Carry blood under high pressure
• Veins/venules
• Carry blood from capillaries to heart
• Thin walled
• Capillaries
• Carry blood from arterioles to venules
• Blood pressure from 30 mm Hg to 15 mm Hg
• Pressure low enough to prevent rupture but high
  enough to permit filtration

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Factors affecting BP

• Peripheral resistance
• Venous return
• Elasticity of large arteries

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Renin-Angiotensin-Aldosterone Mechanism
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Blood Pressure

• Blood Force Against Blood Vessel Walls
• Normal
• Systolic 90 to 135 mm Hg
• Diastolic 60 to 85 mm Hg

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Aging and the Cardiovascular System
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Aging and the Cardiovascular System

• Atherosclerosis
• Arteriosclerosis
• Blood Pressure Increases
• Vein Valves More Incompetent
• Heart Muscle Less Efficient
• Dysrhythmias Common