bio chap 9 terms

contractility

ability to shorten

extensibility

ability to stretch

elasticity

ability to return to original length after contraction or extension

irritability

ability to respond to a stimulus

epimysium

connective tissue covering that wraps each skeletal muscle (continuous with tendons)

fascicle

bundle of muscle fibers

perimysium

connective tissue membrane that wraps each fascicle

endomysium

connective tissue sheath that covers each individual fiber

sarcoplasm

the cytoplasm of a muscle fiber

myofibrils

individual protein strands

myofilaments

fine strands of protein (actin & myosin)

actin

thinner myofilaments

myosin

thicker myofilaments

mitochondria

cell powerhouses

sarcomeres

functional units of muscle contraction

z-lines (membranes)

dark lines that separate one sarcomere from another

myosin filaments

center of sarcomere

actin filaments

partially overlap myosin filaments and extend to where they are anchored to z-lines

a-bands

dark regions of the sarcomere where actin and myosin overlap

i-bands

light areas of the sarcomere that consist of actin only

m-line

dark line at center of each a-band that consists of myosin only

t-tubules

system of tubes that run perpendicular to the sr and open through the sarcolemma

calcium triad

t-tubules plus cisternae of sr on either side

cisternae

fused i-bands tubules (end sacs)

transmembrane potential

the charge difference (voltage) maintained between the inside and outside of a cell membrane

the motor unit

a motor neuron plus all the muscle fibers it stimulates

the neuromuscular junction

a small gap that exists between the end of a motor neuron and the sarcolemma

action potential

reversal of charges

hypertrophy

an increase in muscle size resulting from activity (muscle contraction or use)

atrophy

a loss in the size and strength of a muscle due to the disuse

contraction

the generation of tension or pulling force

isotonic

the muscle changes in length and moves the resistance

concentric contractions

the muscle shortens as it develops tension and overcomes the resistance

eccentric contractions

the resistance overcomes the active muscle and the muscle lengthens as it develops tension

isometric

muscle develops tension but does not shorten

muscle tone

the slightly contracted state of muscles

flaccid

soft, flabby; result of decreased stimulation

initial heat

the heat released during muscle contraction

recovery heat

the heat produced for up to 30 minutes after exercise

latent period

time between the application of a stimulus and the start of the contraction (ab 10 ms for human muscle)

contraction phase

time during which the muscle shortens (different muscles, different amounts of time)

relaxation phase

time from removal of the stimulus to relaxation (return to original resting length)

absolute refractory period

the time period during which a muscle will not respond to a second stimulus

relative refractory period

time period during which a second stimulus will bring about summation

summation contraction

a contraction of greater magnitude, resulting from the application of a second stimulus before the end of a contraction

treppe/ warm-up phenomenom

a long series of summations results in a stair-step increase in magnitude, due to heat production (aka bowditch effort)

tetanus contraction

result when a muscle received a series of stimuli in rapid succession and muscle remains in a constant state of contraction

incomplete tetanus contraction

muscle partly relaxes between application of stimuli

complete tetanus contraction

stimuli are applied so quickly that the muscle does not relax at all

contracture

extremely slow relaxation of a muscle due to the over stimulation and the accumulation of wastes

fatigue

the inability of a muscle to contract (respond to a stimulus) due to the depletion of necessary chemicals

starling’s law

a muscle will contract with even greater force when its fibers are stretched

visceral organs

organs located inside the body in the abdominopelvic cavity (mostly digestive organs)

tourette’s syndrome

nervous system disorder involving repetitive motion or unwanted sounds

acteylcholine

a compound which occurs throughout the nervous system, in which it functions as a neurotransmitter.

all or none principle

muscle fibers contract to the full extent of their ability or not at all

\#? skeletal muscles

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