Electrocardiography Electrocardiogram (ECG or EKG): a composite of all the _ Three waves 1.P wave:...
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Electrocardiography
• Electrocardiogram (ECG or EKG): a composite of all the _
• Three waves1. P wave: 2. QRS complex: 3. T wave:
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Heart Sounds
• Two sounds (lub-dup) associated with ____________________________________– First sound occurs as
____________________________________ and signifies beginning of systole
– Second sound occurs when __________________________________________ at the beginning of ventricular diastole
• Heart murmurs– abnormal heart sounds most often indicative _
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Mechanical Events: The Cardiac Cycle
• _________________________________: all events associated with blood flow through the heart during one complete heartbeat– Systole— – Diastole—
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Phases of the Cardiac Cycle
1. Ventricular filling—takes place in mid-to-late diastole– – 80% of blood
_______________________________ flows into ventricles
– ________________________________ occurs, delivering the remaining 20%
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Phases of the Cardiac Cycle
2. Ventricular systole– Atria relax and ventricles begin to contract
– Rising ventricular pressure results in _
– In ejection phase, ventricular pressure exceeds pressure in the large arteries, forcing the _
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Phases of the Cardiac Cycle
3. Isovolumetric relaxation occurs in early diastole– Ventricles relax– Backflow of blood in aorta and pulmonary trunk
closes _
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Cardiac Output (CO)
• Volume of blood pumped by each ventricle in one minute
• CO = – HR = number of beats per minute– SV = volume of blood pumped out by a ventricle
with each beat
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Autonomic Nervous System Regulation
• Sympathetic nervous system is activated by _
– _________________________________ causes the pacemaker to fire more rapidly and at the same time increases contractility
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Autonomic Nervous System Regulation
• Parasympathetic nervous system opposes sympathetic effects – Acetylcholine
__________________________________ cells by opening K+ channels
• The heart at rest exhibits _________________________________ (parasympathetic)
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Chemical Regulation of Heart Rate
1. Hormones– Epinephrine from
_____________________________________ enhances heart rate and contractility
– Thyroxine increases heart rate and enhances the effects of norepinephrine and epinephrine• Takes longer to act, but causes a _
– Can lead to weakened heart in hyperthyroid conditions
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Chemical Regulation of Heart Rate
2. Intra- and extracellular ion concentrations (e.g., __________________) must be maintained for normal heart function
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Chemical regulation
• Ion imbalances: – Hypocalcemia•
– • Increase heart _• Spastic heart contractions
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Chemical regulation
• Ion imbalances: – Hypokalemia•
– Hyperkalemia• Interferes with depolarization• Can lead to _
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Other Factors that Influence Heart Rate
• • Gender• • Body temperature
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Homeostatic Imbalances
• – abnormally fast heart rate • Above _• If persistent, may lead to fibrillation
• – heart rate slower than _• May result in grossly inadequate blood circulation• May be desirable result of _
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Congestive Heart Failure (CHF)
• Progressive condition where the ___________________________ is so low that blood circulation is inadequate to meet tissue needs
• Caused by– – Persistent high blood pressure– – Dilated cardiomyopathy (DCM)
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Developmental Aspects of the Heart
• Fetal heart structures that _
– __________________________________ connects the two atria
– __________________________________ connects the pulmonary trunk and the aorta
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Developmental Aspects of the Heart
• Congenital heart defects– Lead to mixing of _
– Involve _____________________________ or vessels that increase the workload on the heart
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Age-Related Changes Affecting the Heart
• ____________________________ and thickening of valve flaps
• Decline in _• ______________________________ of
cardiac muscle•
End Chapter 18, begin Chapter 19
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Blood Vessels
• Delivery system of dynamic structures that _– Arteries:
• carry blood _________________________________________; oxygenated except for pulmonary circulation and umbilical vessels of a fetus
– Capillaries: • contact tissue cells and _
– Veins: • carry blood _
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Structure of Blood Vessel Walls
• Arteries and veins– Tunica _– Tunica _– Tunica _
• – Central blood-containing space
• Capillaries– ___________________________________ with
sparse basal lamina
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Tunics
• Tunica intima– Endothelium
_________________________________ of all vessels
– In vessels larger than 1 mm, a connective tissue basement membrane is present
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Tunics
• Tunica media– ___________________________________ and
sheets of elastin
– ___________________________________ nerve fibers control vasoconstriction and vasodilation of vessels
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Tunics
• Tunica externa (tunica adventitia)– _________________________________ fibers
protect and reinforce
– Larger vessels contain __________________________________ to nourish the external layer
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Elastic (Conducting) Arteries
• Large thick-walled arteries with _
• ___________________________ and its major branches
• Large lumen offers low resistance • Act as _– expand and recoil as blood is ejected from the
heart
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Muscular (Distributing) Arteries and Arterioles
• ______________________to elastic arteries; deliver blood to body organs
• Have ________________________________ with more smooth muscle
• Active in _
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Arterioles
•
• Lead to capillary beds
• ________________________________ beds via vasodilation and vasoconstriction
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Capillaries
•
• Walls of thin tunica intima, _
• Size allows only a _________________________________ at a time
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Capillaries
• Present in all tissues except for – – – –
• Functions: exchange of gases, nutrients, wastes, hormones, etc.
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Capillaries
• Three structural types1. _____________________________ capillaries
2. _____________________________ capillaries
3. Sinusoidal capillaries (sinusoids)
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Continuous Capillaries
• Abundant in the _– _____________________________ connect
endothelial cells – Intercellular clefts allow the passage of fluids and
small solutes• Continuous capillaries of the brain– Tight junctions are complete, forming the _
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Fenestrated Capillaries
• Some endothelial cells contain pores – _
• _____________________________ than continuous capillaries
• Function in _
– small intestines, endocrine glands, and kidneys
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Sinusoidal Capillaries
• Fewer tight junctions, _________________________________, large lumens
• Usually _• Allow ____________________________ and
blood cells to pass between the blood and surrounding tissues
• Found in the _______________________, bone marrow, spleen
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Blood Flow Through Capillary Beds
• ________________________________ regulate blood flow into true capillaries
• Regulated by local chemical conditions and vasomotor nerves
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Venules
• Formed when _• Very porous– allow _
• Larger venules have one or two layers of smooth muscle cells