The Cardiovascular System Heart-------Blood Vessels------Blood Cells
20-1 The Cardiovascular System The Heart. 20-2 Functions of the Heart Generating blood pressure...
-
Upload
stephen-moody -
Category
Documents
-
view
214 -
download
0
Transcript of 20-1 The Cardiovascular System The Heart. 20-2 Functions of the Heart Generating blood pressure...
20-1
The Cardiovascular System
The HeartThe Heart
20-2
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
20-3
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
20-4
Heart Cross Section
20-5
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
20-6
Heart Wall Layers
Heart Wall Layers
20-7
20-8
External Anatomy• Four chambers
– 2 atria– 2 ventricles
• Auricles– a small, muscular pouch
at the upper corner of the atrium
• Major veins– Superior vena cava– Pulmonary veins
• Major arteries– Aorta– Pulmonary trunk
20-9
External Anatomy
20-10
Heart Valves
• Atrioventricular– Tricuspid
– Bicuspid or mitral
• Semilunar– Aortic
– Pulmonary
• Prevent blood from flowing back
20-11
Heart Valves
20-12
Function of the Heart Valves
20-13
Blood Flow Through Heart
20-14
Systemic and PulmonaryCirculation
20-15
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
20-16
Conducting System of Heart
20-17
Electrical Properties
• Resting membrane potential (RMP) present
• Action potentials– Rapid depolarization followed by rapid, partial
early repolarization. Prolonged period of slow repolarization which is plateau phase and a rapid final repolarization phase
– Voltage-gated channels
20-18
SA Node Action Potential
20-19
Refractory Period
• Absolute: Cardiac muscle cell completely insensitive to further stimulation
• Relative: Cell exhibits reduced sensitivity to additional stimulation
• Long refractory period prevents tetanic (continuous) contractions
20-20
Electrocardiogram
• Action potentials through myocardium during cardiac cycle produces electric currents than can be measured
• Pattern– P wave
• Atria depolarization
– QRS complex• Ventricle depolarization
• Atria repolarization
– T wave: • Ventricle repolarization
20-21
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
• https://www.youtube.com/watch?v=Lc53tPyCzr8 • https://www.youtube.com/watch?v=VK20B7osr0s
20-22
Alterations in Electrocardiogram
20-23
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
20-24
Cardiac Cycle
20-25
Events during Cardiac Cycle
20-26
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
20-27
Location of Heart Valves
20-28
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
20-29
Factors Affecting MAP
20-30
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
20-31
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
20-32
Baroreceptor and ChemoreceptorReflexes
20-33
Effects of Aging on the Heart
• Gradual changes in heart function, minor under resting condition, more significant during exercise
• Hypertrophy of left ventricle
• Maximum heart rate decreases
• Increased tendency for valves to function abnormally and arrhythmias to occur
• Increased oxygen consumption required to pump same amount of blood