Have you ever thought about the sound you hear on a stethoscope. What is the “lub dub” sound?
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Transcript of Have you ever thought about the sound you hear on a stethoscope. What is the “lub dub” sound?
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Have you ever thought about the sound you hear on a stethoscope. What is the “lub dub” sound?
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Fig. 42-7
Pulmonary artery
Rightatrium
Semilunarvalve
Atrioventricularvalve
Rightventricle
Leftventricle
Atrioventricularvalve
Leftatrium
Semilunarvalve
Pulmonaryartery
Aorta
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The heart contracts and relaxes in a rhythmic cycle called the cardiac cycle
The contraction, or pumping, phase is called systole
The relaxation, or filling, phase is called diastole
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Fig. 42-8-1
Semilunarvalvesclosed
0.4 secAVvalvesopen
Atrial andventriculardiastole
1
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Fig. 42-8-2
Semilunarvalvesclosed
0.4 secAVvalvesopen
Atrial andventriculardiastole
1
2
0.1 sec
Atrial systole;ventriculardiastole
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Fig. 42-8
Semilunarvalvesclosed
0.4 secAVvalvesopen
Atrial andventriculardiastole
1
2
0.1 sec
Atrial systole;ventriculardiastole
3
0.3 sec
Semilunarvalvesopen
AV valvesclosed
Ventricular systole;atrial diastole
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Some cardiac muscle cells are self-excitable contract without any signal from the nervous
system
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Fig. 42-9-1
Pacemakergenerates wave ofsignals to contract.
1
SA node(pacemaker)
ECG
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Fig. 42-9-2
Signals aredelayed atAV node.
2
AVnode
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Fig. 42-9-3
Signals passto heart apex.
3
Bundlebranches Heart
apex
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Fig. 42-9-4
Signals spreadthroughoutventricles.
4
Purkinjefibers
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Velocity of blood flow is slowest in the capillary beds, as a result of the high resistance and large total cross-sectional area
Blood flow in capillaries is necessarily slow for exchange of materials
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• The critical exchange of substances between the blood and interstitial fluid takes place across the thin endothelial walls of the capillaries
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• Two mechanisms regulate distribution of blood in capillary beds:– Contraction of the
smooth muscle layer in the wall of an arteriole constricts the vessel
– Precapillary sphincters control flow of blood between arterioles and venules
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• Blood pressure is the pressure that blood exerts against the wall of a vessel
• Systolic pressure is the pressure in the arteries during ventricular systole; it is the highest pressure in the arteries
• Diastolic pressure is the pressure in the arteries during diastole; it is lower than systolic pressure
• A pulse is the rhythmic bulging of artery walls with each heartbeat
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Blood pressure is generally measured for an artery in the arm at the same height as the heart
Blood pressure for a healthy 20 year old at rest is 120 mm Hg at systole and 70 mm Hg at diastole
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Fig. 42-13-1
Pressure in cuffgreater than120 mm Hg
Rubbercuffinflatedwith air
Arteryclosed
120
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Fig. 42-13-2
Pressure in cuffgreater than120 mm Hg
Rubbercuffinflatedwith air
Arteryclosed
120 120
Pressure in cuffdrops below120 mm Hg
Soundsaudible instethoscope
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Fig. 42-13-3
Pressure in cuffgreater than120 mm Hg
Rubbercuffinflatedwith air
Arteryclosed
120 120
Pressure in cuffdrops below120 mm Hg
Soundsaudible instethoscope
Pressure in cuff below70 mm Hg
70
Blood pressure reading: 120/70
Soundsstop
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Vasoconstriction is the contraction of smooth muscle in arteriole walls; it increases blood pressure
Vasodilation is the relaxation of smooth muscles in the arterioles; it causes blood pressure to fall
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Blood is moved through veins by smooth muscle contraction, skeletal muscle contraction, and expansion of the vena cava with inhalation
One-way valves in veins prevent backflow of blood