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