Lectures 17-23 w/ corresponding chapters

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University of Toronto Scarborough
Biological Sciences
Catherine Nash

FINAL EXAM REVIEW Lecture 17 Skeletal Muscles o attached to bones of the skeleton by tendons (collagen) o positions and moves the skeleton o 40% total body weight o contracts in response to a signal from a somatic motor neuron o cannot initiate own contraction o contraction not influenced by hormones Smooth Muscle o primary muscle of internal organs (except heart) o influence the movement of materials around and in and out of the body o multiple levels of control o primary extrinsic control arises from autonomic nervous system (ANS) o some can contract spontaneously i.e without signals from CNS o modulated by endocrine system Cardiac Muscle o only found in the heart o moves blood through circulatory system o multiple levels of control o primary extrinsic control arises from autonomic nervous system (ANS) o some can contract spontaneously i.e without signals from CNS Skeletal Muscle o Origin: - point of muscle bone attachment closest to the trunk. - usually more stationary. o Insertion: - The point of muscle bone attachment more distal (distant) from the trunk. - usually more mobile Flexor and Extensor muscles www.notesolution.com o Flexor muscles: brings bones closer together e.g bicep o Extensor muscles: moves bones away from each other e.g tricep o Most joints have pairs of muscles: 1 flexor, 1 extensor o Antagonistic muscle groups: - flexor-extensor pairs exert opposite effects - when one contracts, the other relaxes Skeletal muscles are composed of muscle fibres o Muscle cells are the largest cells in body o Groups of muscle cells function together as a unit o Long, cylindrical with up to several 100 nuclei each muscle fibre (or cell) o Fibres arranged in parallel o Each muscle fibre is covered in connective tissue o Groups of adjacent fibres are contained in fasicles o Collagen, elastic fibres, nerves and blood vessels are found between the fasicles o Entire muscle is enclosed in connective tissue and tendons Components of muscle fibres o Muscle fibre: comprised of myofibrils, which contain thick and thin filaments - the contractile machinery of the muscle o Sarcolemma = Cell membrane o Transverse tubules (T-tubules) = Invaginations of the sarcolemma o Sarcoplasm = Cytoplasm (contains mitochondria and glycogen for muscle contraction) Sarcoplasmic reticulum (SR) = Modified endoplasmic reticulum - Wrapped around myofibrils - releases Ca during muscle contraction o Mitochondria : provides ATP for muscle contraction T Tubules allow conduction of the Action Potential www.notesolution.com
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