PowerPoint: Part 2
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Transcript of PowerPoint: Part 2
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The HeartPart 2
Circulatory System:
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Cardiac Cycle
• One complete contraction and relaxation of all 4 chambers of the heart
• Atrial systole, Ventricle diastole
• Atrial diastole, Ventricle systole
• Quiescent period
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• Resistance opposes flow– great vessels have
positive blood pressure– ventricular pressure must
rise above this resistance for blood to flow into great vessels
Principles of Pressure and Flow
• Pressure causes a fluid to flow – ____________________________ - pressure difference
between two points
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Heart Sounds
• ____________________ - listening to sounds made by body
• First heart sound (S1), louder and longer “_______”, occurs with closure of _______ valves
• Second heart sound (S2), softer and sharper “_______” occurs with closure of __________________ valves
• S3 - rarely heard in people > 30
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Phases of Cardiac Cycle• ________________ period– all chambers relaxed– AV valves open and blood
flowing into ventricles• _____________ systole– _____ node fires, depolarize– atria contract, force
additional blood into ventricles
– ventricles now contain ____-___________________ (____) of about 130 ml of blood
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___________________ of Ventricles
• Atria repolarize and relax
• Ventricles depolarize
• Ventricles contract
• Rising pressure closes AV valves - ___________________
• No ejection of blood yet (no change in volume)
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Ventricular Ejection
• Pressure opens ________________ valves
• Blood ejected
• Stroke volume: amount ejected, _____ ml at rest
• SV/EDV= ejection fraction, at rest ~ ____%, during vigorous exercise as high as ____%, diseased heart < ______%
• ___________________: amount left in heart
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Ventricles- Isovolumetric Relaxation
Ventricles repolarize and relax (begin to expand)
• _______________ valves close (__________ notch of aortic press. curve) - heart sound S2 occurs
• AV valves remain closed
• Ventricles expand but do not fill (no change in volume)
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Ventricular Filling - 3 phases
1. Rapid ventricular filling • AV valves first
open
2. ________________• sustained lower
pressure, venous return
3. ______________ • filling completed
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Major Events of Cardiac Cycle• __________ period
• __________ filling
• Isovolumetric contraction
• _______________ ejection
• _______________ relaxation
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Rate of Cardiac Cycle
• Atrial systole, 0.1 sec
• Ventricular systole, 0.3 sec
• Quiescent period, 0.4 sec
• Total 0.8 sec, heart rate 75 bpm
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Ventricular Volume Changes at Rest
End-systolic volume (ESV) 60 ml
Passively added to ventricle during atrial diastole +30 ml
Added by atrial systole +40 ml
End-diastolic volume (EDV) 130 ml
Stroke volume (SV) ejected by ventricular systole -70 ml
End-systolic volume (ESV) 60 ml
Both ventricles must eject same amount of blood
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________________ (CO)
• Amount ejected by ventricle in 1 minute• Cardiac Output = ____________ x
________________– ~ 4 to 6L/min at rest– _____________________ CO to 21 L/min for
fit person and up to 35 L/min for world class athlete
• ____________________: difference between a persons maximum and resting CO with fitness, with disease
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Heart Rate• ___________ = surge of pressure in artery– infants have HR of 120+ bpm – young adult females avg. _______ bpm– young adult males avg. ________ bpm– HR rises in the elderly
• ____________: resting adult HR above 100– stress, anxiety, drugs, heart disease or body
temp.
• _____________: resting adult HR < 60– in sleep and endurance trained athletes
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Chronotropic Effects
• ____________ chronotropic agents HR
• ____________ chronotropic agents HR
• ____________ of medulla oblongata– an autonomic control center with two
neuronal pools: a cardioacceleratory center (sympathetic), and a cardioinhibitory center (parasympathetic)
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Chronotropic Chemicals• _______________• Neurotransmitters - cAMP 2nd messenger– catecholamines (NE and epinephrine) • ______________________
• _______________ – caffeine inhibits cAMP breakdown– nicotine stimulates catecholamine secretion
• _______________– TH adrenergic receptors in heart,
sensitivity to sympathetic stimulation, HR
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• Electrolytes– _____ has greatest effect• hyperkalemia
– myocardium less excitable, HR slow and irregular
• ______________________– cells hyperpolarized, requires increased stimulation
– ___________• ______________________
– decreases HR
• hypocalcemia – ____________________
Chronotropic Chemicals
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Sympathetic Nervous System
• _______________________- center– stimulates sympathetic nerves to SA node,
AV node and myocardium– nerves secrete _________________, binds to
-adrenergic receptors in the heart(positive chronotropic effect)
– CO peaks at HR of 160 to 180 bpm– Sympathetic n.s. can HR up to 230 bpm,
(limited by refractory period of SA node), but SV and CO (less filling time)
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Parasympathetic Nervous System
• Cardioinhibitory center stimulates _________ nerves
• right vagus nerve - SA node• left vagus nerve - AV node
– secretes ACH which binds to receptors• nodal cells hyperpolarized, HR slows
– vagal tone: background firing rate holds HR to sinus rhythm of 70 to 80 bpm• severed vagus nerves (intrinsic rate-100bpm)• maximum vagal stimulation HR as low as 20 bpm
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Inputs to Cardiac Center
• Higher brain centers affect HR– cerebral cortex, limbic system, hypothalamus • sensory or emotional stimuli (rollercoaster, IRS audit)
• ___________________ – inform cardiac center about changes in
activity, HR before metabolic demands arise
• ________________ signal cardiac center– aorta and internal carotid arteries • pressure , signal rate drops, cardiac center HR• if pressure , signal rate rises, cardiac center HR
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Inputs to Cardiac Center
• ____________________________– sensitive to blood pH, CO2 and oxygen
– aortic arch, carotid arteries and medulla oblongata
– primarily respiratory control, may influence HR
CO2 (hypercapnia) causes H+ levels, may create acidosis (pH < 7.35)
– Hypercapnia and acidosis stimulates cardiac center to HR
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Stroke Volume (SV)
• Governed by three factors:1. _________________
2. contractility
3. _________________
• Example preload or contractility causes SV afterload causes SV
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Preload
• _________________________________________
________________________________________• ____ preload causes ___ force of contraction– exercise venous return, stretches
myocardium ( preload) , myocytes generate more tension during contraction, CO matches venous return
• ______________________________ - SV EDV– _____________________________________• _________ they are stretched ( preload) the
______ they contract
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Contractility
• Contraction force for a given preload
• ______________ inotropic agents – factors that ____ contractility• hypercalcemia, catecholamines, glucagon, digitalis
• _____________ inotropic agents – factors that ____ contractility are• hyperkalemia, hypocalcemia
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Afterload
• Pressure in arteries above semilunar valves opposes opening of valves
afterload SV– any impedance in arterial circulation _____
afterload
• Continuous in afterload (____________, atherosclerosis, etc.) ________________ of myocardium, may lead it to weaken and fail
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Exercise and Cardiac Output
• Proprioceptors– HR ____ at beginning of exercise due to signals from
joints, muscles
• Venous return– muscular activity ____ venous return causes ______
SV
HR and SV cause CO• Exercise produces ventricular hypertrophy– _______ allows heart to beat more slowly at rest cardiac reserve