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47 terms

Muscle Structure and physiology

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Motor Unit
A motor neuron and all of the skeletal muscle cells it stimulates
Axon Terminals
The axon of each motor neuron has numerous endings
Synaptic cleft
The actual gap between an axonal ending and the muscle cell
acetylcholine
within the axonal endings are many small vesicles containing a neurotransmitter substance
Action potential
when it reaches the ends of the axon. the neurotransmitter is released, and it diffuses to the muscle cell membrane to combine with receptors there.
Tetanus
A continuous contraction that shows no evidence of relaxation
Isotonic concentration
A contraction in which the muscle shortens and work is done
Many Motor Units
To accomplish a strong contraction, these are stimulated at a rapid rate
few motor units
when a weak but smooth muscle contraction is desired, these are stimulated at a rapid rate
fatigue
when muscle is being stimulated but is not able to respond due to oxygen debt
Isometric Contraction
The muscle does not shorten but the tension in the muscle keeps increasing
perimysium
connective tissue surrounding a fascicle
Epimysium
connective tissue ensheathing the entire muscle
Sacromere
contractile unit of muscle
fiber
a muscle cell
endomysium
thin connective tissue investing each muscle cell
sacrolemma
plasma membrane of the muscle cell
myofibril
a long, filamentous organelle found within muscle cells that has a banded appearance
myofilament
actib or myosin containing structure
tendon
cord-like extension of connective tissue beyond the muscle, serving to attach it to the bone
fascicle
a discrete bundle of muscle cells
Smooth muscle tissue
cardiac muscle tissue
functions of the muscular system
movement,posture,stabilize joints, generate heat
Characteristics of skeletal muscle
1)most attached by tendons to bones
2)striated
3)voluntary
4)cells are surrounded and bundled by connective tissue
characteristics of Smooth Muscle
1) no striations
2) spindle shaped cells
3) involuntary- no conscious control
4) found mainly in the walls of hollow organs
Characteristics of Cardiac Muscle
1) has striations
2)usually has a single nucleus
3) joined to another muscle cell at an intercalated disc
4)involuntary
5)found only in the heart
Aponeuroses
sheet-like structure connecting muscle to bone
transverse tubules
transmit electircal impulses deep into cell
sarcoplasmic reticulum
specialized smooth endoplasmic reticulum stores and releases calcium
thick filament
with protein myosin, with atp enzymes
thin filament
with protein actin
irritability
ability to receieve and respond to a stimulus
contractility
ability to shorten when a stimulus is received
skeletal muscles must be stimulated by a nerve to contract
TRUE
neuromuscular junction
where nerve and muscle associate
synaptic cleft
gap between nerve and muscle- they do not make contact
(area between nerve and muscle is filled with interstitial fluid)
Action potential
(electrical impulse) triggers release of acetylcholine (a neurotransmitter) from the neuron
true
sodium rushing into the muscle fiber generates another action potential(electrical current) and the release of calcium from sarcoplasmic reticulum
contraction of a muscle cell
1)a single muscle fiber concentration is "all or none"
2)muscles have thousands of fibers, not all fibers may be stimulated at the same time
3)allows graded responses- different degrees of skeletal muscle shortening
3a)frequency of stimulation
3b)number of cells stimulated (more cells=greater force)
twitch
(not normal) single, brief contraction
tetanus
(summing of contractions)
1)one contraction is immediately followed by another
2) the muscle does not completely return to a resting state
3) the effects are added
unfused
incomplete tetanus some relaxation occurs between contractions
fused
complete tetanus no evidence of relaxation before the following contractions and the result is a sustained muscle contraction
energy for muscle contraction
ATP
muscles contract until they run out of energy. initially, muscles use stored ATP
breaking ATP bonds release energy
only 4-6 seconds worth of ATP is stored by muscles
after this initial time, other pathways must be utilized to produce ATP
Direct phosphorylation
muscle cells contain creatine phosphate(CP)
.) CP is a high energy molecule
.)Cp transfers energy to ADP, to regenerate ATP
.)1 CP yeilds 1 ATP
CP supplies are exhausted in about 20 seconds
Anaerobic glycolysis
.) glucose is broken down to pyruvic acis to produce 2 ATP (no oxygen needed)
.)pyruvic acid is converted to lactic acid
.) fast but innefficient (needs lots of glucose, and lactic acid causes muscle fatigue) 2 BATTERIES

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