PhysioEx quiz Skeletal muscles
Terms in this set (49)
A motor unit consists of a _____ ____ and all of the ____ ____ it innervates
motor neuron + muscle fibers
Where do the motor neuron and a muscle fiber intersect?
Specifically, the _____ _____ is the location where the axon terminal of the neuron meets a specialized region of the muscle fiber's plasma membrane. What is this specialized region called?
neuromuscular junction ;
the motor end plate
The EVENTS that occur at the neuromuscular junction lead to the ?
An action potential in a motor neuron triggers the release of ______ from its terminal.
Acetylcholine then diffuses onto the muscle fiber's plasma membrane (_______) and binds to receptors in the motor end plate, INITIATING a change in ____ _______ that results in a graded depolarization of the muscle plasma membrane.
The end-plate potential triggers a series of events that result in the contraction of a muscle cell. This entire process is called ?
Excitation- contraction coupling
A _____ ____ is the mechanical response to a single action potential.
A muscle twitch has 3 phases: What are these?
latent period, contraction phase, relaxation phase
The period of time that elapses between the generation of an action potential in a muscle cell and the START of muscle contraction.
The _____ phase starts at the end of the latent period and ends when muscle tension peaks.
The ______ phase is the period of time from peak tension until the end of the muscle contraction
Skeletal muscles span 2 joints and attach to the skeleton via _____
Tendons attach to the ______ of the bone
Skeletal muscles are made of hundreds of thousands of individual cells called _____ _____
Muscle fibers produce muscle ______
When a skeletal muscle is isolated from an experimental animal and mounted on a FORCE TRANSDUCER, you can generate ____ _______ with controlled electrical stimulation
A skeletal muscle produces _____ (also known as muscle force) when nervous or electrical stimulation is applied
The force generated by a whole muscle reflects the number of active ___ ____ at a given moment
_____ muscle contraction = many motor units activated
_____ muscle contraction = fewer motor units activated
By increasing/recruiting the number of active motor units, we can produce a steady increase in muscle force, what is this process called?
Motor unit recruitment
Regardless of the number of motor units activates, a single stimulated contraction of whole skeletal muscle is called a muscle _____
Although NO force is generated during the latent period, chemical changed occur intracellularly in prep for contraction. (like the release of calcium from the sarcoplasmic reticulum)
True / false
During the ______ phase, the myofilaments utilize the cross-bridge cycle and the muscle develops tension
______ takes place when the contraction has ended and the muscle returns to its normal resting state and length
What is the SMALLEST stimulus required to induce an action potential in a muscle fiber's plasma membrane (sarcolemma)?
As the ____ voltage to a muscle is increased BEYOND the threshold voltage, the amount of force produced by the whole muscle also increases.
Maximal tension in the whole muscle occurs when all the muscle fibers have been activated by a sufficiently strong stimulus. What is this stimulus called?
Stimulation with voltages GREATER than the maximal voltage will not increase the force of contraction.
When a muscle first contracts, the force that it is able to produce is_____ than the force it is able to produce with subsequent stimulations within a relatively short time span.
_____ is the progressive increase in force generated when a muscle is stimulated in succession
Treppe (staircase effect)
(muscle twitches follow one another closely, each with successive twitch peaking slightly higher than the one before)
When a skeletal muscle is stimulated repeatedly, such that the stimuli arrive one after another within a short period of time, muscle twitched can ______ with each other and resume in a STRONGER muscle contraction than a stand-alone twitch.
(this process is wave summation)
____ ______occurs when muscle fibers that are developing tension are stimulated again before the fibers have relaxed
How is wave summation achieved? by increasing the ....
stimulus frequency, or rate that a stimulus is delivered to the muscle
Wave summation occurs because the muscle fibers are already in a partially contracted state when subsequent stimuli are delivered
If stimuli continue to be applied frequently to a muscle over a prolonged period of time, the maximum possible muscle force from each stimulus will eventually reach a plateau = ______ ____
If stimulus are then applied with even GREATER freq, the twitches will begin to fuse so that the peaks and valleys of each twitch become indistinguishable from one another = _____ ___
complete (fused) tetanus
When the stimulus frequency reaches a value beyond which no further increase in force is generated by the muscle, the muscle has reached its____ _____ ______
maximal tetanic tension
What are the 2 types of skeletal muscle contractions?
isometric or isotonic
When a muscle attempts to move a load that is equal to the force generated by the muscle, the muscle contracts ________
During an _____ contraction, the muscle stays at a fixed length. Ex: when you stand in a doorway and push on the door frame. Your muscles do not shorten even though they are actively contracting
____ force is generated by stretching the muscle and results from the elastic recoil of the tissue itself
____ force is generated when myosin thick filaments bind to actin thin filaments, engaging the cross bridge cycle and ATP hydrolysis.
Think of skeletal muscle as having two force properties: it exerts ____ force when it is stretched and ____ force when it is stimulated. _____ force is the sum of all forces
passive; active ; Total
During an _____ contraction, the skeletal muscle length CHANGES and the load moves a measurable distance
If the muscle length SHORTENS as the load moved, the contraction is called an isotonic ______ contraction
isotonic CONCENTRIC contraction
The speed of the contraction = muscle _____ ______
A light object can be lifted quickly (____ velocity) whereas a heavier object will be lifted with a slower velocity for a shorter duration
In an isotonic muscle contraction, one end of the muscle remains free
(this is unlike an isometric cont where both ends of the muscle are held in fixed position)