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UWL BIO 312 - Ergoenic aids, control of skeletal muscle, and smooth muscle

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Lecture 23 Lecture Outline:1. Ergogenic aids2. Control of skeletal muscleo Motor neuron poolso Size principle3. Smooth muscleo characteristicsErgogenic Aids:- Caffeine: increase performance in both endurance exercise and high intensity exercise lasting about 5 mins.o CNS stimulant, saves muscle glycogen early in sub-max exercise, FFA mobilization- Blood doping: increasing the number of RBC’s in body thus increasing amount of oxygen in bloodo Remove RBCs about a month prior to event, body makes more, add blood cells back into bloodo Erythropoietin: hormone that stimulates bone marrow to produce red blood cells- Amphetamines: CNS stimulants (Adderall)- Growth hormone: stimulates protein synthesis- Anabolic steroids: stimulates protein synthesis, testosterone type drug, increase in muscle mass and strengtho Increased cholesterol, hypertension, liver disease, jaundice, increased sex drive, impotence, atrophy of testes, lowers testosterone and spermatogenesis, enlarged prostate, depression, aggressionControl of Skeletal muscle:- Innervated by somatic motor neurons originating in ventral horn of spinal cord and cranial nerve motor nuclei- Signals from alpha-motor neurons always excitatoryo Motor neuron nerve cell bodies are grouped together in motor neuron pool o Motor neuron pools extend over several spinal cord segments Axons from motor neuron pool exit spinal cord over several consecutive spinal roots (accounts for partial paralysis of muscle following certain types of spinal cord injury) Somatic motor neuron receives thousands of IPSPs and EPSPs from 1. Higher CNS areas 2. Somatosensory afferents 3. Muscle afferents (spindles)- What determines which motor units in a motor neuron pool get activated during contraction of whole muscle?o Only small portion of motor units within muscle’s motor neuron pool are activated for most contractionso Recruitment of motor units during contraction is governed by the size principle All three types of muscle fibers are represented in a typical skeletal muscle Smaller motor units require less EPSP’s to fire AP, more excitable Only during high level of descending excitatory input will larger motor units get activatedBio 312Smooth Muscle:- Non-striated: small spindle shaped cells, single nucleus, much smaller than skeletal muscle cells- Most is found in layers within walls of hollow tubular organs of digesive, circulatory, respiratory, urinary, reproductive systems as well as eyes and skin- Involuntary muscle: influenced by autonomic system- Contraction and relaxation periods longer and slower than in skeletal and cardiac muscle- Action is often rhythmical; some show ‘tone’- Very fatigue resistant, can maintain prolonged contractions with a low ATP cost- Can be stretched significantly beyond resting length and still be able to contract and generate tension- Capable of replication throughout life, whereas skeletal and cardiac muscle


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UWL BIO 312 - Ergoenic aids, control of skeletal muscle, and smooth muscle

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