Anatomy Chp 7

Strains

"pulled muscles" results when a muscle is stretched excessively. usually occurs when an antagonist has not relaxed quickly enough as an agonist contracts. hamstring are a common site

aponeurosis

a broad sheet of fibrous connective tissue that attaches a muscle to another muscle or connective tissue.

neurotransmitter

a chemical released by axon tips of neurons that activates a muscle fiber, gland, or another neuron; in this case called acetylcholine

creatine phosphate

a molecule that stores a small amount of energy in a muscle fiber

myoglobin

a molecule that stores a small amount of oxygen in a muscle fiber

motor unit

a motor neuron and all of the muscle fibers to which it is attached

tendon

a narrow band of fibrous connective tissue that attaches a muscle to a bone

muscle fibers

a single muscle cell

tetanic contraction

a sustained muscle contraction

recruitment

activation of more and more motor units

Fibrosis

an abnormal increase of fibrous connective tissue in a muscle. usually results from connective tissue replacing dead muscle fibers following an injury

latent period

brief interval before the muscle starts to contract

Botulism

caused by neurotoxin produced by the bacterium Clostridium Botulinum . Toxin prevents release of acetylcholine from the tips of motor axons.

isotonic contractions

causes movement at a joint

all or none response

characteristic of individual muscle fiber

myosin filament

composed of hundreds of myosin molecules each shaped like a double headed golf club

deep fascia

connective tissue covering a muscle

sarcomere

contractile unit of skeletal muscle , the smallest portion of a myofibril capable of contraction.

myogram

contraction recorded to produce a tracing

oxygen debt

develops as lactic acid accumulates. the debt is the amount of oxygen required to metabolize the accumulate lactic acid and to resupply the normal amount of ATP and creatine phosphate in the muscle cells.

Tetanus

diseased caused by the anaerobic bacterium Clostridium tetani which is common in soil. infection usually by punctured wounds. C tetani produces a neurotoxin that affects motor neurons in the spinal cord resulting in continous stimulation and tetanic contractions of certain muscles. first muscle affected is the ones that move the mandible.

acetylcholinesterase

enzyme which decomposes acetylcholine in the synaptic cleft

Myasthenia gravis

extreme muscular weakness caused by improper functioning of the neuromuscular junctions. an autoimmune disease in which antibodies are produced that attach to the acetylcholine receptors on the sarcolemma and reduce or block the stimulatory effect of acetylcholine

threshold stimulus

fiber will not contract until the stimulus reaches a certain minimal strength

Muscular dystrophy

general term for a number of inherited muscular disorders that are characterizes by the progressive degeneration of muscles. The affected muscles gradually weaken and atrophy (shrink) producing a progressive crippling of the patient .

agonist

group of muscles producing an action

hypertrophy

increase in muscle size and strength

isometric contractions

increase tension within a muscle

summation

increases force of contraction

Fibrositis

inflammation of the connective tissue especially muscle sheaths and fascia associated with muscles. produces soreness and stiffness that is commonly called muscular rheumatism

Cramps

involuntary painful sustained tetanic contractions of a muscle

insertion

movable attachment of a muscle

sarcoplasm

muscle cytoplasm

atrophy

muscle decrease in size due to lack of use

fascicles

muscle fibers that are arranged in small bundles that extend the full length of a muscle

myofibrils

one of many contractile fibers within a muscle cell; which extend the length of the fiber

maximal stimulus

one that activates all motor units.

antagonist

opposing group of muscles

hemoglobin

red pigment in red blood cells

three types of muscles tissues

skeletal, smooth , cardiac

muscle tone

state of constant partial contraction and keeps muscle ready to respond.

Spasms

sudden involuntary contractions of a muscle or a group of muscles.

neuromuscular junction

the connection between the terminal branches of an axon and the sarcolemma of a muscle fiber

origin

the immovable attachment

Myositis

the inflammation of muscle tissue. produces soreness and stiffness similar to fibrositis of the muscles.

sarcolemma

the plasma membrane of a muscle fiber

2 major kind of protein filaments

thin actin and thick mysosin

actin filament

thin and consist of two twisted strands of actin molecules joined together like a string of pearls.

synaptic cleft

tiny space between the axon terminal and the sarcolemma

two additional proteins found on actin filaments

troponin and tropomyosin ; play a role in muscle contraction

Poliomyelitis

viral disease of motor neurons in the spinal cord. destruction of the motor neurons leads to the paralysis of skeletal muscles.

fatigue

when a muscle is stimulate to contract for a long period its contractions will gradually decrease until it no longer responds to stimulation.

motor end plates

where the axon tips fit into depression in the sarcolemma