Advanced Biology: Myology

Three types of muscle tissue

smooth, skeletal, cardiac

Skeletal Muscle tissue

attaches to bone and is under conscious control

components of skeletal muscle tissue

nervous tissue, blood, connective tissue

Fascia

layers of fibrous connective tissue

function of connective tissue in skeletal muscle tissue

separates individual muscle tissues, surrounds each muscle, forms tendons

aponeuroses

connective tissue forms broad fibrous sheets, attach to the coverings of adjacent muscles

Layers of connective tissue

epimysium, perimysium, fasiculi, edomysium

epimysium

layer that surrounds the skeletal muscle

perimysium

extend inward from the epimysium

fasciculi

bundles of skeletal muscle fibers

endomysium

thin covering over each muscle fiber in fasciculi

Skeletal muscle fibers

a single cell that contracts in response to stimulation and then relaxes when the stimulation ends (All or None Law)

myofibrils

contain protein filaments vital in muscle contraction

myosin

thick; A bands or dark bands

actin

thin; I bands or light bands

striations

alternations of the two filaments

neuromuscular junction

connection between motor neuron and muscle fiber

motor neuron

where a muscle fiber connects to a fiber from a nerve cell

muscle only contracts when

stimulated by neuron

motor end plate

muscle fiber, nuclei, and mitochondria are abundant and cell membrane is extensively folded

neurotransmitters

chemicals released when a nerve impulse is sent from the brain

muscle contractions

filaments of acting and myosin sliding past one another

myosin

two twisted protein strands

actin

globular structure with a binding site to which the myosin cross-bridge attaches

stimulus for contraction

acetylcholine; neurotransmitter that stimulates a muscle impulse

acetylcholine is rapidly decomposed by (relaxation)

acetylcholinesterase enzyme

creatine phosphate

helps cells regenerate ATP from ADP

hemoglobin

loosely binds O2 and carries to muscles

myoglobin

stored in muscles and picks up O2 from hemoglobin

when muscles run out of oxygen, they require energy from

lactic acid fermentation

oxygen debt

amount of oxygen cells require to convert the accumulated lactic acid into glucose

muscle fatigue

a muscle exercised strenuously and loses its ability to contract

muscle cramp

muscle undergoes a sustained involuntary contraction

threshold stimulus

minimal strength required to cause a contraction

All or none response

If the threshold is met, the muscle contracts completely. If not, the contraction doesn’t occur

Myogram

record or graph of muscle contraction

twitch

single contraction that only lasts a fraction of a second

Latent period

the delay between a stimulus and muscle response

summation

when the frequency of the stimulus increases so that the muscle cannot relax before the next stimulus

tetanic contraction

forceful, sustained contraction lacks even partial relaxation

recruitment of motor units

increases the number of motor units being activated by increasing the stimulus

large motor units

thicker fibers, respond later but more forceful

muscle tone

even at rest, a certain amount of sustained contraction is occurring; stimulation of few muscle fibers

smooth muscle

elongated cells with tapering edges, no striations, actin and myosin

cardiac muscle

found only in heart, striated cell joined end to end forming fibers, longer twitches than skeletal

Origin

end of muscle fastens to a fixed part

Insertion

end of muscle attached to a moveable portion

flexion

decrease angle of joint

extension

increase angle of joint

prime movement

muscle that provides most of the movement

synergists

muscles that contract and assist the prime mover

antagonist

muscles that resist a prime mover’s action and cause movement in an opposite direction