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