heart: length-tension relationships starling’s law of the heart
DESCRIPTION
Heart: Length-tension relationships Starling’s law of the heart reflex control of heart contraction Smooth muscle Anatomy Contraction mechanism Contraction regulation. Length-tension relationships. There is an optimal sarcomere length for generating a maximal force during contraction. - PowerPoint PPT PresentationTRANSCRIPT
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• Heart:– Length-tension relationships– Starling’s law of the heart– reflex control of heart contraction
• Smooth muscle– Anatomy– Contraction mechanism– Contraction regulation
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Length-tension relationships
• There is an optimal sarcomere length for generating a maximal force during contraction.
• As blood enters the ventricle, it expands and the sarcomere length increases
• The stroke volume increases when the force of contraction increases
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Starling’s law of the heart
• The relationship between stretch and force in the intact heart.
• The force of contraction (stroke volume) is proportional to the end-diastolic volume.
• Within physiological limits, the heart pumps all the blood that returns to it.
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Starling’s Law of the Heart
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Understand:
• Integration of factors that regulate heart activity
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Smooth muscle
• Blood vessels, G-I tract, urinary tract, reproductive tract,iris, etc.
• Slow, sustained contraction
• No sarcomeres
• Yes, contractile filaments
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Example of smooth muscle
• Sphinctors
• Smooth muscle is tonically contracted
• Sphinctor relaxes when material leaves a hollow organ (eg. Esophagus stomach)
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Smooth muscle cells
• Single nucleus
• Actin and myosin are located diagonally around periphery and single nucleus
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Proteins associated with actin
• Actin
• Tropomyosin
• Actin filaments attach to dense bodies of protein
• Actin filaments terminate in protein plaques of cell membrane
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Myosin
• Myosin thick filaments located between actin filaments
• Myosin heads line thick filament surface
• Slow ATPase activity
• Myosin light chain kinase phosphorylates myosin head (activates ATPase, stimulating cross-bridge cycling)
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CaM is calmodulin
MLCK is myosin light chain kinase
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Sometimes,dephosphorylatedmyosin remains attached to actinlatch state, contractionis maintainedMaintain contraction without ATP.
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Source of calcium
• Pacemaker potentials
• Depolarization through Ca++ entry
• In single unit smooth muscle, gap junctions spread Ca++
• Ca++ induced Ca++ release
• Myogenic contraction