Class Notes (839,092)
Canada (511,185)
Kinesiology (1,408)
Lecture

L26 - Muscle Physiology Nov 12 Week.docx

6 Pages
95 Views

Department
Kinesiology
Course Code
KINESIOL 1A03
Professor
Tracy Mc Donald

This preview shows pages 1 and half of page 2. Sign up to view the full 6 pages of the document.
Description
Muscular System: Histology and Physiology Skeletal Muscle System Functions - Body movement – b/c attached to bone o Exception – muscle attached to sclera of eye o Skin in face - Maintenance of posture o Protect and stabilize joints o Maintain various body positions – standing, sitting o Muscles that maintain postures are always contracting - Respiration – diaphragm, intercostals muscles help us breathe - Production of body heat – main energy source is ATP, work out of it, majority of energy is lost as head – breakdown of ATP, muscles use so much ATP – main contributor to body temp – explains why you get hotter when you exercise - Communication – wouldn’t be able to write, speak, facial expression Properties of Muscle - Contractility: ability of a muscle to shorten forcefully o Muscle attached to 2 bones, when shortened, pulls on 2 bones, creates tension which causes muscle to move bone - Excitability: capacity of muscle to respond to a stimulus o Can it respond to electrical stimulus coming from NS? Yes! o Reason it has capability is b/c on its plasma membrane it contains voltage-gated channels o When axon synapses w/skeletal muscle, sends NT across which causes change in resting potential and propagate AP across membrane o Can respond to hormone, pH changes in addition to electrical impulses - Extensibility: muscle can be stretched beyond its resting length and still be able to contract o Normal resting position is anatomical position but can stretch muscles beyond normal resting position and still generate a force - Elasticity: ability of muscle to recoil to original resting length after its been stretched - Muscle tissue can only ever be contracted or not, cannot be inhibited – gravity has to take over and relax muscle, or opposing muscle group contracts while other relaxes Skeletal Muscle Structure - Composed of muscle cells (fibers), connective tissue, blood vessels (like bone), nerves - Fibers are long, cylindrical, multinucleated (tube type structure) o Cell is as long as the muscle – small muscles cell is short, large muscle cell is long o Nucleus is just under plasma membrane b/c we don’t want it to interfere w/muscle protein properties that allow for contraction - Striated appearance due to light and dark banding – striped appearance – bands created by proteins within muscle fiber Picture #1 - Outer layer – muscular fascia – fibrous sheath of CT surrounding muscle (very dense + thick) o Surrounds indiv. Muscles and sometimes groups w/similar functions - Epimysium – dense irregular CT and tightly adheres to fascia layer – deep to fasia – surrounds muscle too - Inside epimysium – bundles of muscle fibers – fasciculus (pl. fasciculi) - Each fasciculus is surrounded by perimysium - Btwn muscle fibers in fasciculus is endomysium (loose aereolar CT) - Muscles have a very extensive blood + nerve supply – every single muscle fiber is innervated by a nerve - Arteries + veins penetrate all 3 layers + fascia to get into level of muscle fibers where they reach muscle fibers and form extensive capillary bed around fiber – delivers nutrients + O 2 - As we train, more capillary beds are formed  receiving nutrients and O more suf2iciently, improves endurance - Single axon divides up and innervates several muscle fibers - Single motor neuron + associated fiber is motor unit – efficient way of signaling muscle fibers – send signal down 1 neuron causing reaction at several fibers - Every fiber has a synapse/neuromuscular junction - 1 axon/motor neuron goes to several fiber but each fiber only receives 1 branch – don’t wanna contract muscle fiber from diff ends at diff times – want coordinated contraction Picture #2 - Muscle fibers end where tendon is located - Tendon is continuation of 3 CT layers- attaches to bone (epimysium surrounds whole muscle, perimysium surrounds fasciculus, and endomysium surrounds muscle fibre in fasciculus) - Plasma membrane of muscle fiber – sarcolemma - Nuclei - # of them located on length of muscle fiber - Inside muscle fiber – transverse tubules (ttubules) – evaginations of sarcolemma – creates larger SA for AP to move along membrane – AP propogates along sarcolemma in little pore through ttubule – allows for faster response to the neural stimulation - Sarcoplasmic reticulum (SR) – smooth endoplasmic reticulum – stores calcium + when AP signals contraction, will release calcium into cytoplasm of muscle fibre - Sarcoplasm – cytoplasm of muscle fibre - Depending on fibre type, # of mitochondria located – endurance fibres have more mitochondria, less mitochondri
More Less
Unlock Document

Only pages 1 and half of page 2 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

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