UWL BIO 312 - Skeletal muscle (2 pages)

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Skeletal muscle



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Skeletal muscle

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Lecture notes on muscle fatigue and the adaptations the body makes to fatigue.


Lecture number:
22
Pages:
2
Type:
Lecture Note
School:
University of Wisconsin-La Crosse
Course:
Bio 312 - Human Anatomy and Physiology I
Edition:
1

Unformatted text preview:

Bio 312 Lecture 22 Lecture Outline 1 Muscle Fiber types 2 Muscle fatigue a Synaptic fatigue b Conduction fatigue c Lactic acid buildup 3 Endurance training adaptations 4 Resistance training adaptations a CNS adaptations with resistance training Fiber Types Skeletal muscle is not homogeneous tissue not all muscle fibers are identical Fiber type distribution o Highly variable from species to species and within same species o Average active person is about 50 of each o The higher proportion of slow twitch muscle a person has the faster they can consume oxygen o Genetics is the biggest factor for fiber type distribution o Characteristics of motor neuron can play a role in determining muscle fiber type o All muscle fibers within a given motor unit are the same fiber type Muscle Fatigue decline in force producing ability as a result of previous contractile activity Dependent on fiber type intensity and duration of contractile activity state of fitness Muscle fatigue has multiple causes and varies based on activity Synaptic fatigue occurs at neuromuscular junction o Motor neuron being stimulated for long periods of time causes axon to run out of synaptic vesicles to push neurotransmitter into synaptic cleft o Can be shown in lab but not thought to be major factor for muscle fatigue in environment Conduction fatigue occurs in transverse tubules of sarcolemma o After extended periods of use action potentials do not penetrate all the way into the transverse tubules and do not stimulate deeper parts of muscle o Caused by buildup of K blocking AP s Lactic Acid Buildup lactic acid lactate H o Buildup of H in skeletal muscle alters protein conformation and activity Actin and myosin activity decrease Less Ca2 release from SR Decreases enzymatic activity less ATP production Decreased fatty acid mobilization Buildup of P from ATP ADP P slows the reaction decreasing rate of cycling Low intensity long duration exercise lactic acid conduction failure cross bridge cycling inhibition do



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