Transport Unit Part 2 Blood Fats, Heart Attacks, Blood Typing, Heart Transplants.
20-1 Functions of the Heart Generating blood pressure Routing blood –Heart separates pulmonary and...
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Transcript of 20-1 Functions of the Heart Generating blood pressure Routing blood –Heart separates pulmonary and...
![Page 1: 20-1 Functions of the Heart Generating blood pressure Routing blood –Heart separates pulmonary and systemic circulations Ensuring one-way blood flow –Heart.](https://reader030.fdocuments.in/reader030/viewer/2022032804/56649e455503460f94b3a04d/html5/thumbnails/1.jpg)
20-1
Functions of the Heart
• Generating blood pressure• Routing blood
– Heart separates pulmonary and systemic circulations
• Ensuring one-way blood flow– Heart valves ensure one-way flow
• Regulating blood supply– Changes in contraction rate and force match
blood delivery to changing metabolic needs
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20-2
Size, Shape, Location of the Heart
• Size of a closed fist• Shape
– Apex: Blunt rounded point of cone
– Base: Flat part at opposite of end of cone
• Located in thoracic cavity in mediastinum
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20-3
Pericardium
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20-4
Heart Wall
• Three layers of tissue– Epicardium: This serous membrane of smooth
outer surface of heart– Myocardium: Middle layer composed of
cardiac muscle cell and responsibility for heart contracting
– Endocardium: Smooth inner surface of heart chambers
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20-5
Heart Wall
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20-6
External Anatomy• Four chambers
– 2 atria– 2 ventricles
Major veins– Superior vena cava– Pulmonary veins
• Major arteries– Aorta– Pulmonary trunk
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20-7
Heart Valves
• Atrioventricular– Tricuspid– Bicuspid or mitral
• Semilunar– Aortic– Pulmonary
• Prevent blood from flowing back
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20-8
Function of the Heart Valves
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20-9
Blood Flow Through Heart
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20-10
Systemic and PulmonaryCirculation
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20-11
Heart Skeleton
• Consists of plate of fibrous connective tissue between atria and ventricles
• Fibrous rings around valves to support
• Serves as electrical insulation between atria and ventricles
• Provides site for muscle attachment
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20-12
Cardiac Muscle
• Elongated, branching cells containing 1-2 centrally located nuclei
• Contains actin and myosin myofilaments • Intercalated disks: Specialized cell-cell
contacts• Desmosomes hold cells together and gap
junctions allow action potentials• Electrically, cardiac muscle behaves as single
unit
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20-13
Conducting System of Heart
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20-14
Cardiac Arrhythmias
• Tachycardia: Heart rate in excess of 100bpm• Bradycardia: Heart rate less than 60 bpm• Sinus arrhythmia: Heart rate varies 5%
during respiratory cycle and up to 30% during deep respiration
• Premature atrial contractions: Occasional shortened intervals between one contraction and succeeding, frequently occurs in healthy people
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20-15
Cardiac Cycle
• Heart is two pumps that work together, right and left half
• Repetitive contraction (systole) and relaxation (diastole) of heart chambers
• Blood moves through circulatory system from areas of higher to lower pressure.– Contraction of heart produces the pressure
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20-16
Heart Sounds
• First heart sound or “lubb”– Atrioventricular valves and surrounding fluid vibrations
as valves close at beginning of ventricular systole
• Second heart sound or “dupp”– Results from closure of aortic and pulmonary semilunar
valves at beginning of ventricular diastole, lasts longer
• Third heart sound (occasional)– Caused by turbulent blood flow into ventricles and
detected near end of first one-third of diastole
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20-17
Mean Arterial Pressure (MAP)• Average blood pressure in aorta• MAP=CO x PR
– CO is amount of blood pumped by heart per minute• CO=SV x HR
– SV: Stroke volume of blood pumped during each heart beat– HR: Heart rate or number of times heart beats per minute
• Cardiac reserve: Difference between CO at rest and maximum CO
– PR is total resistance against which blood must be pumped
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20-18
Regulation of the Heart• Intrinsic regulation: Results from normal
functional characteristics, not on neural or hormonal regulation– Starling’s law of the heart
• Extrinsic regulation: Involves neural and hormonal control– Parasympathetic stimulation
• Supplied by vagus nerve, decreases heart rate, acetylcholine secreted
– Sympathetic stimulation• Supplied by cardiac nerves, increases heart rate and force of
contraction, epinephrine and norepinephrine released
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20-19
Heart Homeostasis• Effect of blood pressure
– Baroreceptors monitor blood pressure
• Effect of pH, carbon dioxide, oxygen– Chemoreceptors monitor
• Effect of extracellular ion concentration– Increase or decrease in extracellular K+ decreases heart
rate
• Effect of body temperature– Heart rate increases when body temperature increases,
heart rate decreases when body temperature decreases