Muscular System Flashcards
all or nothing principle
when a muscle contractions it must contract with all possible force or none at all.
isometric contraction
muscle length remains the same but tension increases; they work but do not produce movement.
isotonic contraction
the tone or tension within the muscle remains the same; occurs usually when there is little or no resistance
motor unit
functional unit of skeletal muscle; composed of motor neuron and the attached muscle fibers
myofibril
fine fibers closely packed together
myofilament
proteins in the myofibers that are arranged into groups that cause striations to appear (bands)
neuromuscular junction
motor neurons attaching to a motor endplate,
sarcolemma
surrounds each muscle fiber; located in the plasma membrane.
sacromere
segment between 2 successive Z lines or discs.
ex. between thick and thin myofilaments
sarcoplasm
the cytoplasm of striated muscle cells
sarcoplasmic reticulum
a modified ER system for pumping Ca++ ions
t tubules
allow electrical signals to travel deeper into the cell
* a sandwiched t tubules is a triad.
tetanus
muscle that does not have enough time between contractions to completely relax; displayed by skeletal muscle
threshold stimulus
minimal level of stimulation needed to cause contraction
excitability
the ability to respond to a stimulus, which may be delivered from a motor neuron or a hormone.
contractility
the ability of muscle cells to forcefully shorten.
extensibility
the ability of a muscle to be stretched or extended.
motor neuron
neuronal cells located in the central nervous system (CNS) controlling a variety of downstream targets.
cross bridges
the “heads” of myosin
acetylcholine
neurotransmitter diffuses into the synapse in order to initiate an impulse. (contraction)
relaxation
occurs after Ca++ is released the SR begins to pump it back into sacs. when Ca++ is removed, it frees up the troponin molecules and shuts down the contraction.
grades strength principle
muscles get stronger when they are constantlly challanged.
visceral
(single-unit) form continuous sheets, is found in digestive, urinary and reproductive tracts, and exhibits peristalsis, autorhythmicity
peristalsis
a series of wave-like muscle contractions that move food through the digestive tract.
antagonist
muscles that directly oppose a movement
fixator
joint stabilizers that help maintain posture
synergist
muscles that assist prime movers
insertion
distal; the site where bone and muscle are attached and move during contraction.
lever
force weight, level balance.
includes 4 parts…
1) rigid rod or bar (bone) lever
2) fixed pivot (joint) fulcrum
3)weight or resistance that is moved load
4) force or pull (the contraction) effort
prime mover
muscle/group that performs specific movement.
endomysium
connective tissue membrane that covers individual muscle fibers. (inner)
perimycium
a tougher connective tissue membrane that holds fascicles together (middle)
tendon
strong tough cord that attaches muscle to bone
tendon sheath
tube shaped fibrous connective tissue
aponeurosis
broad flat sheet of connective tissue
fascicle
sheet/broad band of connective tissue.
origin
the site where bone and muscle are attached, but do not move during contraction
treppe
also known as the staircase phenomenon. shows that muscles contract more forcefully after they have been contracted a few times.
what are the basic functions of muscle?
1) contraction
2) heat production from movement
3) maintaining posture (standing, sitting, etc)
4) storing and moving substances throughout
the body.
what are the 3 types of muscle?
cardiac, smooth, and skeletal
how does each type of muscle differ structurally?
cardiac - involuntary, branched, stiriated.
smooth - involuntary
skeletal - voluntary, striated.
what are the three stages of a muscle contraction?
1) latent period
2) contraction phase
3) relaxation phase
what are the 3 types of levers?
1st class lever, 2nd class lever, 3rd class lever
how does the first class lever work?
joint is in the middle of the force and pull. like seesaw
ex. atlas of spine and skull
how does the second class lever work?
weight lies between fulcrum and joint. like wheelbarrow.
ex. standing on tippy toes.
how does the third class lever work?
pull exerted between fulcrum and weight. like lifting a shovel
ex. flexing biceps.
how are muscles named? provide an example
1) location- arm, brachialis
2) function- move towards, adductor
3) shape- triangle, deltoid
4) direction of fibers- straight, rectus
5) # of heads or divisions- two, biceps
6) points of attachment- sternocleidomastoid
what are the two types of tetanus?
fused and unfused
what is the difference between the two different types of tetanus?
fused - smooth, stiriated muscle contractions
unfused - sustained but wavering contraction
what is the graded strength principle influenced by?
1) metabolic condition of muscle fibers
2) # of muscle fibers contracting
3) # of motor units recruited
4) intensity and frequency of stimulation
what are the four types of proteins that make up myofilaments
myosin, acting, tropomyosin, troponin.
myosin
make up most of thick filament
actin
globular proteins; make bulk of thin filaments.
tropomyosin
blocks active sites of actin
troponin
holds tropomyosin in place at finding site
titin
accounts for most of the myofilaments elasticity and extensibility bc it can stretch to four times its initial length and return unharmed.
dysrophin
cytoskeletal protein that links thin filaments to the sarcolemma; help transmit tension.
tonic contraction
continued partial contractions
flaccid
muscles with less than normal tone are
considered
spastic
muscles with more than normal tone are
considered
concentric / eccentric
reduces the angle of the joint / increasing the angle and lengthening the muscle
stretch reflex
The amount of a load on muscles can also
influence contraction.
what is a length-tension relationship
the max strength a muscle can supply is
directly related to the initial length of its fibers.
intercalated discs
strong electrically coupled junctions
