Chs. 7-11, 19, 22-24

26 Pages
81 Views
Unlock Document

Department
Biological Sciences
Course
BIOD27H3
Professor
Catherine Nash
Semester
Fall

Description
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 Transverse tubules (T-tubules): invaginations of the sarcolemma, closely associated with terminal cisternae to form a triad. - membrane of t tubules is continuous with muscle fibre - lumen of t-tubules are continuous with extracellular fluid - allow depolarisations of sarcolemma to quickly reach interior of a muscle fibre. - transport Action Potentials from NMJ to interior of fibre 2+ Sarcoplasmic reticulum (SR): releases Ca ions from the terminal cisternae - terminal cisternae gathers and stores Ca 2+ Myofibrils are the contractile units of muscle fibres - highly organised bundles of contractile and elastic proteins that carry out work for contraction - one muscle fibre contains a 1000 or more myofibrils Components of myofibrils Sarcomere: fundamental contractile unit of myofibril that repeats throughout the length of the myofibril Sarcomeres contain: Myosin (thick filaments) Actin (thin filaments) Two Z lines per sarcomere Actin (thin) and Myosin (thick) filaments are sandwiched between Z lines Z lines: Zig-zag protein structures Attachment site (anchor) for thin (actin) filaments M line: proteins that form attachment sites for thick (myosin) filaments - equivalent to Z disk for thin filaments A Band: Darkest band Encompasses entire length of thick filament www.notesolution.com H zone: Central region of A band lighter Only contains thick filaments I band: brightest in colour on fibre Contains only thin filaments Z disk runs through middle of I band Occupies space between A bands of adjacent sarcomeres Structure of Myofibrils: thick filaments o Myosin heads are clustered at end of filament o The hinge region allows the heads to swivel at point of attachment o Myosin is the motor protein of the myofibril o Composed of protein chains that intertwine o Form a long tail and pair of tadpole-like heads 250 myosin molecules join to form a thick filament Structure of Myofibrils: thin filaments o Single actin molecules = g actin globular protein o Polymerise to form f actin (fibrous). 2 polymers twist creating thin filament Tropomyosin and troponin: start and stop contraction Tropomyosin: long fibrous molecule - extends over many actin molecules - blocks myosin binding when muscle at rest Troponin complex: actin, tropomyosin, Ca2+ www.notesolution.com
More Less

Related notes for BIOD27H3

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit