The heart and circulation

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The heart and circulation

• Structure of the heart
• Regulation of heart activity
• The circulatory system- cardiovascular and
  lymphatic

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Structure of the heart Two atria, two
ventricles Atria receive blood from venous
system Ventricles pump blood into arterial
system Septum separates right from left side
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A double pump pulmonary and systemic circulation
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Valves embedded in fibrous skeleton AV valve
between right atrium and ventricle- tricuspid
valve AV valve between left atrium and
ventricle bicuspid (mitral) valve Semilunar
valves at base of pulmonary artery and aorta
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Cardiac cycle and heart sounds Contraction-
systole Relaxation- diastole Atria contract
simultaneously Then ventricles contract- with a
little overlap Stroke volume- amount of blood
ejected from ventricles during
systole end-systolic volume- whats left
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Electrical activity of the heart Myocardial
cells beat automatically Action potential is
usually originated in sinoatrial
node Spontaneous depolarization (pacemaker
potential) diffusion of calcium through slow
channels threshold- fast calcium channels open,
voltage regulated sodium channels
open repolarization produced through diffusion
of potassium
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Other parts of the heart can produce
pacemaker potentials Depolarize more slowly
than SA node usually stimulated by action
potentials from SA node before they could start
their own pacemaker potentials ectopic
pacemakers can set a rhythm if SA node
conduction is blocked pace will be slower
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Heart muscle cannot sustain contraction Long
refractory periods- heart cannot be stimulated
until it has relaxed from previous
contraction Arrhythmias- something affects the
cardiac cycle treatment depends on what it
is Fast Na channel blockers Slow Ca channel
blockers ?-adrenergic receptor blockers
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What does the ECG measure?
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The ECG and heart sounds
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Blood vessels- arteries and veins Arteries,
arterioles, capillaries Veins and
venules Arteries are more muscular Veins have
valves
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Capillaries deliver blood to cells Specialized
types of capillaries in different organs Fenestr
ated- kidneys, endocrine glands,
intestines Discontinuous- bone marrow, liver and
spleen Continuous- everywhere else
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Veins Veins can expand to accommodate
increasing amounts of blood arteries
cant Venous pressure is low compared to
arterial pressure Blood flow through veins is
facilitated by contraction of skeletal
muscles valves that prevent backflow
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Atherosclerosis

• Plaques block blood vessels
• Macrophages accumulate (fatty streaks)
• Inflammatory mechanism that accumulates damage
• Vasodilation function can be disrupted

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LDL, HDL, and cholesterol

• Cholesterol is carried to liver by LDL
• Recycled via LDL receptors on liver cells
• LDL (and cholesterol) can accumulate in blood
• HDL carries cholesterol away from arterial walls
• High HDL levels are beneficial

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Heart disease and EGC analysis
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Arrhythmias Bradycardia- slow rate (less than 60
bpm) Tachycardia- fast rate (more than 100
bpm) Can occur normally is abnormal if
rate increases during rest (ectopic
pacemakers) Flutters- extremely rapid
contractions Fibrillation- different groups of
fibers are activated so coordinated pumping of
chambers is not possible
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Lymphatic system Fluid transport from
tissues Fat transport from intestines Immune
response
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Summary

• Double pump enables heart to deliver oxygenated
  blood to the body- and recirculate it
• Valves regulate blood movement through the heart
• Electrical activity can be measured and monitored
• Arterial system delivers blood to the body, and
  the venous system returns it to the heart
• Lymphatic system helps regulate fluid levels
  among the body compartments