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KINESIOL 1A03 Study Guide - Final Guide: T-Tubule, Myocyte, Myofilament

16 pages102 viewsFall 2012

Department
Kinesiology
Course Code
KINESIOL 1A03
Professor
Maureen Mac Donald
Study Guide
Final

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Muscular System: Histology and
Physiology
Skeletal Muscle System Functions
- Body movement
o muscles are attached to bones, muscle attached to sclera of eye to help rotate eyeball,
muscle attached to skin in your face to help create facial expressions
oBones act as levers allowing body movement
- Maintenance of posture
o stabilize joints, maintain various body positions eg. Standing, sitting
oMuscles that maintain posture are always contracting
- Fainting – postural muscles relax and you can’t hold stay upright; sleeping – neck muscles relax
- Respiration – diaphragm, intercostal muscles help us breathe
- Production of body heat – main energy source is ATP, you get work out of it, majority of energy
is lost as heat during breakdown of ATP; muscles use so much ATP – main contributor to body
temperature – explains why exercise makes you hotter, why you shiver when you’re cold –
repeated contraction of muscles uses energy, produces heat to maintain body temp
- Communication
Properties of Muscle
-Contractility: the ability of a muscle to shorten forcefully
oShorten a muscle and create tension, that produces a force (tension is the force)
oMuscle attached to two bones , shortening it pulls on the bones, creates tension along
the length of the muscle and causes muscle to move the bone
-Excitability: capacity of muscle to respond to a stimulus; most cases we’re talking about
electrical excitability, electrical stimulus coming from the nervous system
oOn plasma membrane are voltage gated channels; when axon synapses with skeletal
muscle it sends a NT across which cause a change in resting potential and we can
propagate an AP across membrane
oCan respond to hormone, pH changes in addition to electrical impulse
1
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-Extensibility: muscle can be stretched beyond its resting length and still be able to contract
oEg. We can stretch muscles on anterior portion of joint beyond resting position but still
contract eg playing baseball swinging the bat
-Elasticity: ability of muscle to recoil to original resting length after its been stretched
- Muscle tissue can only be excited not inhibited, can contract or not, can`t inhibit it
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Skeletal Muscle Structure
- Composed of muscle cells (fibers), connective tissue, blood vessels, nerves
- Fibers are very long, cylindrical, multinucleated tube type of structure
- muscle fiber cell runs the length of the entire muscle in most cases
- nucleus is just under the plasma membrane
- nucleus is on the outside closer to plasma membrane because we don’t want it to interfere with
muscle protein properties which allow for contraction and are found on the inside
- striated appearance due to light and dark banding produced by proteins within muscle fiber
Picture 1
- outer layer – muscular fascia – fibrous sheath of CT surrounding muscle (very dense and thick_
- surrounds individual muslcles and sometimes groups with similar functions
- deep to fascia is the epimesium: dense, irregular connective tissue
- tightly adheres to fascia layer, also surroundsmuscle and is found on outer layer
-epimysium: bundles of muscle fibers (represented by red circles) are called fasiculus
- each fasiculus is surrounded by perimysium
- between muscle fibers in fasciululs is the endomysium – loose, areolar connective tissue which
fills in the spaces between muscle fibers in the fasiculus
- muscles have a very extensive blood and nerve supply –r every single muscle fiber has an
innervation by a nerve
- arteries and veins will penetrate all 3 layers to get into the level of the muscle fibres, when
arteries reach muscle fibers they form an extensive capillary bed network around the fibers
- as we train, we get more capillary beds so more O2 and oxygen  endurance improvement
- nerve supply enters the muscle, penetrate through -the connective tissue layers
- single axon divides up and innervates several muscle fibres
- single motor neuron and associated fibers is called the motor unit
3
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