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Unformatted text preview: Lecture 6 Skeletal Muscle Skeletal Exercise
Thursday 12810 Outline Outline
– – – – – Friday, January 29 Dr. Jesse Witt Assistant Professor Psychological Sciences Performance affects perception: Evidence form size, shape, and speed judgments Lecture Skeletal Muscle Turn in Grant Assignment #1 Discuss Grant Assignment #1 – ARMS B061, 1:30 P.M. Overview of muscle contraction Overview
Motor neuron ________________ Ttubule Sarcoplasmic reticulum _____________________ _____ Relaxation Exercise Physiology, McArdle, Katch & Katch Motor Neuron Motor
Transmit electrical signals from spinal cord to muscle fibers. ____________________ ____________________ ___________. A motor neuron and all muscle fibers it innervates is known as motor unit. Exercise Physiology, Brooks, Fahey & Baldwin Exercise Physiology, McArdle, Katch & Katch Motor Neuron Motor
Axon Presynaptic Terminal
– _____________ – ___________________________________ Exercise Physiology, McArdle, Katch & Katch Neuromuscular Junction Neuromuscular
Action potential Release of _________ into neuromuscular cleft ACh binds to muscarinic receptors located on postsynaptic membrane ________________________ Signal: electrical → _________ →electrical Exercise Physiology, Brooks, Fahey & Baldwin Neuromuscular Junction Neuromuscular
ACh is degraded by __________________ rapidly (5ms) End products of acetylcholinesterase (_________________) taken up by motor neuron to be resynthesized into ACh. Exercise Physiology, Brooks, Fahey & Baldwin T-tubules T-tubules
Transverse tubules (Ttubules) are channels that extend into ____________. Wave of depolarization moves across membrane and ____________ into muscle fiber. Exercise Physiology, Brooks, Fahey & Baldwin Sarcoplasmic Reticulum Sarcoplasmic
_____________ Wave of depolarization down Ttubules cause voltage gated Ca++ channels on Ttubule to physically interact with__________________ _________ on SR. Confromational change of ____________ release Ca++ from SR
Exercise Physiology, McArdle, Katch & Katch Sarcoplasmic Reticulum Sarcoplasmic
Ttubule ________________ cause ryanodine receptors to close. Ca++ taken up in____________________ _______________________ Many different __________ of SERCA. Exercise Physiology, Brooks, Fahey & Baldwin Excitation-Contraction Coupling Excitation-Contraction
Intracellular concentrations of Ca++ rise. Ca++ binds to __________ on actin protein. Activated troponin causes_________ to shift and expose myosin binding sites Exercise Physiology, Brooks, Fahey & Baldwin Excitation-Contraction Coupling
Ca++ binding allows myosin to Ca attach to actin “__________________” ADP and Pi are released and myosin slides actin inward ATP attaches to myosin head and breaks actinmyosin bond “_________________” ATPase hydrolyzes ATP to ADP +Pi + energy. Energy used to cock myosin head and myosin reattaches to actin “___________________”. Cycle continues until Ca++ is taken up by _______. Fig 8.10 Excitation-Contraction Coupling Excitation-Contraction http://www.youtube.com/watch?v=gJ309LfHQ3M Describe skeletal muscle relaxation from nerve to sarcomere? from Are there any differences between the Are there any differences between the excitationcontraction coupling process for a ___________ (shortening) versus __________ (lengthening) contraction? Length-Tension Curve Length-Tension
Electrically stimulating muscle fiber from _____(1970s) Maximal ______________ interactions produces greatest tensions Optimal sarcomere length is between ____________. Above or below optimal length decreases crossbridge interactions. Lengths of above _______ no tension can be developed
ACSM’s Advanced Exercise Physiology Length-Tension Curve
At rest sarcomere in vivo is at ____ length! Fig 8.17 How does skeletal muscle adapt to chronic exercise? chronic
Fiber type? Hypertrophy? Hyperplasia? Fiber Type Distribution Fiber
Distance Runner Track Sprinter Nonathletes Type I
7080% ______% 4753% Type IIx and IIa
___30% 7075% ______%
Table 8.2 Fiber Type Distribution and Exercise Exercise
16 weeks of endurance exercise at 5060% VO2max. Fiber type changes from __________ Type __________
2 4 6 5% 2% Fig 8.13 Experimental Model
Plantaris adopts Type I phenotype when Plantaris adopts Type I phenotype when gastroc and soleus are removed Slow Slow Fast
ACSM’s Advanced Exercise Physiology Can fiber types change from Can fiber types change from slow to fast? Fiber Type Distribution and Exercise Exercise
Exercise conditions ____________ conditions
Slow → Fast Buller and Eccles 1960 Surgically switched nerves that innervated ____________ and _____________________ _________ – Slow ↔ Fast – – – – Slow → Fast Buller and Eccles, J Physiol 1960 Hypertrophy Hypertrophy
Increase in fiber size. Fiber size increase is associated with ________________ __________ in parallel. Not associated with an increase in fibers ______.
Untrained Trained Mechanisms of Hypertrophy Mechanisms
____________ __________________ _____ ________
– IGF1 overexpression results in hypertrophy – Increase nuclei – Increases PKC, CaMK, Calcineurin
Increase transcriptional activity ACSM’s Advanced Exercise Physiology Hyperplasia
Increase in number of muscle fibers. Increase in number of muscle fibers. Direct evidence suggests _____________ _________ occur with exercise. Adult skeletal muscle fibers are terminally differentiated Indirect evidence suggests that hyperplasia may occur with exercise.
– ____ increase in muscle mass – ____ increase in fiber crosssectional area. – Where did the other 13% come from. Mechanisms for Hyperplasia Mechanisms
____________ – Protein that restricts muscle growth – Gene mutation leads to increase in muscle size through _________ (Belgian Blue) Myostatin in Humans Myostatin Morphology of leg ...
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This note was uploaded on 02/17/2011 for the course HK 458 taught by Professor Newcomer during the Spring '10 term at Purdue University-West Lafayette.
- Spring '10