Cardiovascular System

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Cardiovascular System
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Heart Structure

• Hollow
• Located within the mediastinum of the thorax.
• Base is attached to several large blood vessels.
• Distal end extends downward and to the left
  forming a blunt apex at the fifth intercostal
  space.

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Pericardium or pericardial sac covers the heart.
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The inner layer of the pericardium is called the
visceral pericardium (epicardium) which covers
the heart. The parietal pericardium forms the
inner lining of the fibrous pericardium. The
fibrous pericardium is tough and composed of
mostly connective tissue. Between the layers is
the pericardial cavity which has pericardial
fluid that lubricates the membranes to reduce
friction when the heart moves.
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The heart consists of three different layers
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Mitral Valve Closed
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Mitral Valve Open
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Semilunar Valve Function
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Tricuspid Valve
Chordae Tendineae
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Pulmonary and Systemic Bloodflow
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Circumflex artery supplies the blood to the
walls of the left atrium and left
ventricle. Left anterior
descending artery supplies the walls of both
ventricles. Posterior interventricular artery
supplies the walls of both ventricles. Marginal
artery supplies the walls of the right atrium
and right ventricle.
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Heart Actions

• Atrial systole is when the atria contract while
  the ventricles relax which is called ventricular
  diastole.
• Thus systolic and diastolic blood pressure.
• This series of contraction and relaxation is
  called a cardiac cycle.

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Cardiac Cycle
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Heart Sounds

• Lubb heart sound occurs during the ventricular
  contraction when the A-V valves are closing.
• Dubb heart sound occurs during ventricular
  relaxation when the pulmonary and aortic valves
  are closing.
• A heart murmur is when the heart valves fail to
  close completely causing leakage.

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Sinoatrial Node
AtrioVentricular Node
Atrioventricular Bundle
Purkinje Fibers
Heart Conduction System
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Sympathetic Parasympathetic Nervous Systems

• Physical exercise, body temperature, and
  concentration of various ions affect heartbeat.
• Branches of sympathetic and parasympathetic nerve
  fibers innervate the S-A and A-V nodes.
• Parasympathetic impulses decrease heart action,
  sympathetic increases heart action.
• Cardiac center in the medulla oblongata regulates
  autonomic impulses to the heart.

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Effects of K Ca2

• Potassium and calcium are two ions that influence
  heart action and are the most important.
• Potassium affects the electrical potential of the
  cell membrane.
• Calcium ions are needed more for cardiac muscles

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Conditions

• Hyperkalemia (excessive potassium ions) decreases
  the rate and force of cardiac contractions.
• Very high amounts may block cardiac impulses.
• Hypokalemia is low potassium and can cause an
  abnormal arrhythmia.
• Hypercalcemia increases heart action causing a
  prolonged contraction.
• Hypocalcemia depresses heart action.

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Arteries are strong, elastic vessels adapted for
carrying blood away from the heart under high
pressure. Three distinct layers Endothelium
Inner most layer. Rich in elastic
and collagenous fibers. Called the tunica
interna. Middle layer Tunica media. Smooth
muscle fibers, thick layer of elastic
connective tissue. Outer layer Tunica
externa. Attaches the artery to tissues.
Contains vasa vasorum that gives Rise to
capillaries
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• Vasomotor fibers stimulate smooth muscle to
  contract, thus reducing the diameter of the
  vessel.
• This is called vasoconstriction.
• Vasodilation changes the diameter of the vessel
  that influences the blood flow and pressure.
• Arterioles are microscopic continuations of
  arteries that give off branches called
  metarterioles that join capillaries.
• If arteries are cut they spurt blood due to the
  high pressure of the heart.

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Venules are microscopic vessels That continue
from capillaries into To form veins. Veins have
valves and are Pushed back if blood begins To
back up in a vein. Valves aid in the return
of Blood to the heart. Arterial blood loss will
cause a sympathetic nerve impulse to stimulate
vein walls to return more blood to the heart to
maintain blood pressure.
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Capillaries exchanges nutrients, gases, and
metabolic by-products between the Capillary blood
and tissue fluid. Diffusion provides the most
important means of transport. The pathways
depend on lipid solubilities. Filtration causes
a net outward movement of fluid at the arteriolar
end of a capillary. Osmosis causes a net inward
movement of fluid at the venular end of a
capillary. Plasma proteins generally stay in the
blood.
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Blood Pressure

• Arterial blood pressure is produced by heart
  action it rises and falls with phases of the
  cardiac cycle.
• Systolic pressure occurs when the ventricle
  contracts diastolic pressure occurs when the
  ventricle relaxes.
• Heart action, blood volume, resistance to flow
  and blood viscosity influence arterial blood
  pressure.
• Blood pressure is controlled by cardiac output.
• The more blood that enters the ventricle the
  greater the stroke volume and the greater the
  cardiac output.

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Venous Blood Flow

• Not a direct result of heart action.
• Skeletal muscle contraction, breathing movements
  and vasoconstriction influence the flow.
• Venous constriction can increase venous pressure
  and blood flow.