muscles Flashcards
Skeletal muscle tissue
attached to bones- or for face muscles skin.
-packaged in skeletal muscle that attach and cover bony skeleton
-has striations
-controlled voluterily
contracts rapidally but tires easliy
extremely adaptable, can exart force 0.001 to 30kg
Sooth muscle tissue
Mostly in walls of visceral organs.
- maintains blood pressure
- propels substances (food, faaeces) through internal pathways
- not striated
- involuntery
cardiac muscle tissue
walls of heart.
- contracts at steady rate
- neural control allows heart to respond to bodies needs
- pumps blood through body
- some striated
- involuntary
Structure of muscle tissue (all 3 tissue type sum up)
Each muscle is a discrete organ composed of muscle tissue, blood vessels nerve fibres and connective tissue
Endomysium
First layer - fine sheath of connective tissue composed of reticular fibres surrounding each muscle cell….en-side-inner most layer
Perimysium
Second layer- fibrous connective tissue that surrounds groups of muscle cells called fascicles
Epimysium
3rd layer- an overcoat of dense regular connective tissue that surrounds the entire muscle.
Sacromere
Is the smallest contractile unit of muscle- it is the region of myofibril between two successive Z disks- it is made up of myofilaments and contractile protiens.
microscopic structure of skeletal muscle structure
myofibrilis- densely packed rod organelles within muscle cell
- arrangement of myofibrilis is perfectly aligned- dark A bands and light I bands repeat
- This banding occurs because of thick (myosin) and thin (actin) protien filaments within a myofibril.
- Thick and thin myofibril attach to Z disk
- A single segment of thick and thin filament and inbetween Z discs is called a sacromere
- Sacromeres are arranged in a series along the length of skeletal muscle.
Neuromuscular Junction= somatic motor neuron
the region where the motor neuron comes into close contact with a skeletal muscle cell—– equivalent of a synapse in nerve cell
Motor Unit
A motor neuron and all the cells attached to it is called a motor unit.
Small- motor unit only connected to to a few muscle cells, for fine movement
Large-motor unit connected to many muscle fibres-generates higher forces.
Sliding Filament theory
- Thin filaments slide past thick filaments so that actin and myosin filaments overlap more.
- In a relaxed state only overlap slightly
- Upon stimulation myosin heads bind to actin and sliding begins
- Each myosin heads binds and detaches throughout contraction, this acts as a ratchet to generate tension and propel the thin filaments to the center of the sacrome.
- As this event occurs throughout the sacromes the muscle shortens.
Flexion
Decrease angle of joint, brings 2 bones closer together
Abduction
movement away from midline
circumduction
combination of flexion adduction and abbduction
order of muscle structure
muscle fibre> enclosed in endomysium> bunch of muscle fibres> enclosed in Perimysium> this is called a fasicle> a group of fasicles is enclosed in epimysium
crossbridge
myosin head attached to an actin is called a crossbridge- the more crossbridges the heavier strain the muscle can endure.
why skeletal cells are multinuclenated
because cells are so big
sacrolemma
plasma membrane of muscle cells
myofibrils
bundles of myofilaments
myofilaments
actin and myosin
very short muscle length compared to stretched muscle
short- lots of actin-actin crossover so not to many places myosin can attach. Long- muscles so stretched myosin heads may pop up but can not always attach
what does a striped muscle pattern mean
very organised- skeletal muscles…… cardiac kind of organised……..smooth not very organised
isotonic and isometric
isometric- muscle stays the same
isotonic- muscle shorTens
