BM 1041:03 Lecture Notes - Lecture 6: Neuromuscular Junction, Sarcomere, Myosin
23 May 2018
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Describe how a muscle contracts and explain how the nervous
system controls skeletal muscle contraction
Screen clipping taken: 7/03/2018 8:39 PM
Thin filaments
Actin
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Troponin - binding sites for actin, tropomyosin and Ca ions
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Tropomyosin - covers myosin binding sites
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Thick filaments
Actin binding sites on myosin heads
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Consists of head and tail
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Myosin
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Sarcomere
Basic unit of muscle contraction
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Titan filaments
Provides elasticity and recoil
H zone
Zone of thick filaments that is not superimposed by the thin filaments
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M line
Disc in the middle of the sarcomere
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I band
Where thin filaments are
A band
Where thick filaments are
Stimulates contraction
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Stored in terminal cisterns of sarcoplasmic reticulum
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Released into sarcoplasm on activation via T-tubules
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Start action potential
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Ca2+
Ca2+ released from SR by action potential
1.
Ca2+ interact with tropnin to expose myosin binding sites on actin
2.
Requires ATP, as moving against concentration gradient
Motors neurons send signal which initiates release of Ca2+ from SR
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Motor neuron interacts with muscle membrane
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Neuromuscular junction
L1 and 2 - muscle physiology
Wednesday, 7 March 2018
8:28 PM
Week 3 Page 1
Sends signalling molecules Acetylcholine (Ach)
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Acts with Ach receptor on membrane to activate action potential (releasing Ca2+)
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Motor neuron interacts with muscle membrane
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Nerve impulse causes Ach release at neuromuscular junction, Ach binds to receptors on motor
end plate
1.
Action potential propagates along Sarcolemma and down T-tubules
2.
Calcium ions released form sarcoplasmic reticulum
3.
Calcium binds to troponin, removes blocking action of tropomyosin
4.
Active site exposed on actin filament, myosin head binds
5.
Contracts, sarcomere shortens, requiring ATP
6.
Screen clipping taken: 7/03/2018 10:17 PM
Discuss how the energy for a muscle contraction is obtained
3 sources of ATP for skeletal muscle cell
Creatine
phosphate
Screen clipping taken: 7/03/2018 10:18 PM
Week 3 Page 2
Document Summary
Describe how a muscle contracts and explain how the nervous system controls skeletal muscle contraction. Troponin - binding sites for actin, tropomyosin and ca ions. Zone of thick filaments that is not superimposed by the thin filaments. Ca2+ interact with tropnin to expose myosin binding sites on actin. Motors neurons send signal which initiates release of ca2+ from sr. Acts with ach receptor on membrane to activate action potential (releasing ca2+) Nerve impulse causes ach release at neuromuscular junction, ach binds to receptors on motor end plate. Action potential propagates along sarcolemma and down t-tubules. Calcium binds to troponin, removes blocking action of tropomyosin. Active site exposed on actin filament, myosin head binds. Discuss how the energy for a muscle contraction is obtained. 3 sources of atp for skeletal muscle cell. Transfers high-energy phosphate group to adp, catalysed by creatine kinase. Production of pyruvic acid from glucose via glycolysis, glucose catabolised. Krebs cycle, electron transport chain (oxygen-requiring reactions) produce.
