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Muscle has four major functional characteristics: | contractability, excitability, extensibility, and elasticity. |
Contractability is - | the capacity of muscle to contract or shorten forcefully |
Excitability is - | respond to stimuli |
Extensibility is - | stretching |
Elasticity is - | returning to its original shape |
When does lactic acid build up in our body? | Due to lack of excercise |
skeletal muscle | "voluntary muscle" generally attached to bone |
striated muscles | "striped" skeletal muscle |
smooth muscle | "involuntary muscle" functions automatically |
visceral muscle | smooth muscle generally found in the walls of the viscera; functions automatically |
non-striated muscle | smooth muscle that does not appear striped |
smooth muscle tone | a state of continuous partial contraction of smooth muscle |
cardiac muscle | found only in the heart, where it functions to pump blood throughout the body |
intercalated discs | junctions where cardiac muscle cells fit together tightly; Rings that provide a strong connection between cardiac muscle cells, to prevent tears and leaks in the heart. |
belly | the enlarged fleshy body of the muscle between the slender points of attachment; composed of thousands of muscle fibers (muscle cells) |
fascia | layers of tough connective tissue that surrounds large skeletal muscle |
epimysium | the outer layer of fascia; Connective tissue layer surrounding an individual muscle |
perimysium | a layer of connective tissue that surrounds smaller bundles of muscle fibers |
fascicles | bundles of muscle fibers |
endomysium | A layer of connective tissue that surrounds individual muscle fibers |
tendon | a line cordlike structure that connects muscle to bone |
compartment syndrome | "crush syndrome"; when the muscle and nerves are deprived of oxygen and nourishment and begin to die |
aponeurosis | a flat sheet-like fascia that connects muscle to muscle or muscle to bone |
sarcolemma | a cell membrane that surrounds the nucleus of a muscle cell |
transverse tubules | "T tubules"; Deep infoldings in the sarcolemma that help propagate a muscle impulse |
sarcoplasmic reticulum | a specialized endoplasmic reticulum within the muscle fiber |
myofibrils | long cylindrical structures that each muscle is composed of |
sarcomeres | a series of contractile units that each myofibril is made up of |
thin and thick filaments | a unique arrangement of contractile proteins |
thin filament | a unique arrangement of contractile proteins; composed of actin and the troponin-tropomyosin complex |
actin | a protein of a thin filament; contains binding sites for the myosin |
myosin | A type of protein filament that interacts with actin filaments to cause cell contraction; makes up nearly half of the proteins in muscle cells. |
troponin-tropomyosin complex | regulates contraction function of actin and myosin |
myosin heads | extends from the thick myosin filaments; are along the entire length of the filament in smooth muscle |
cross-bridges | temporary connections formed when the myosin heads make contact with the myosin-binding sites on the actin |
somatic motor nerve | the type of nerve that supplies the skeletal muscle |
motor neurons | a motor nerve composed of many nerve cells |
motor unit | consists of a single motor neuron and the muscle fibers that are supplied by the motor neuron |
recruitment | the consequences of activation of additional motor units |
neuromuscular junction | "NMJ"; the area where the motor neuron meets the muscle |
neurotransmitter | a chemical substance that fills membranous pouches |
acetylcholine | |
acetylcholinesterase | aka "cholinesterase"; an enzyme that is found within the NMJ, near the muscle membrane |
tetanus | "lockjaw"; sustained muscle contraction; a condition caused when the bacterium (Clostridium tetani) secretes a neurotoxin that causes excessive firing of the motor nerves. This causes excessive release of ACh, |
botulism | a very serious form of food poisoning; a disease caused by secretion of the bacterium (Clostridium botulinum) which appears most often when food has been improperly processed and canned. |
spastic paralysis | caused by an excess of ACh activity; a state of continuous muscle contraction |
flaccid paralysis | caused by a deficiency of ACh activity; a state in which the muscles are limp and unable to contract |
twitch | when a single electrical stimulus is delivered to a muscle fiber; the muscle fiber contracts and then fully relaxes |
tonus | muscle tone; refers to a normal continuous state of partial muscle contraction |
creatine phosphate | a storage form of energy that can be used to replenish ATP quickly during muscle contraction |
muscle fatigue | the inability of a muscle to contract forcefully following prolonged activity. |
origin | attaches muscle to the stationary bone |
insertion | attaches muscle to the more movable bone |
prime mover | "chief muscle" |
synergists | "helper muscles"; work with other muscles |
antagonists | muscles that oppose the action of another muscle |
hypertrophy | the response to overuse of a muscle |
atrophy | when prolonged inactivity results in the muscles getting smaller in size |
contracture | "frozen muscle" a abnormal formation of fibrous tissue within the muscle; freezes the muscle in a flexed position and severely restricts joint mobility |