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Essentials Human Anatomy/ Phys 7e & Brief Atlas Hum Body:
Human Anatomy & Physiology Laboratory Manual with PhysioEx 8.0, Main Version, Update (8th Edition)
A motor neuron and all the muscle cells it innervates
Stimulation of additional motor units will increase the strength of contraction
Where is the interneuron located?
Where is the motor neuron located?
Traveling to the muscle
The synapse between a motor neuron and the muscle it innervates is called..
Variables affecting the strength and degree of muscle movement
Number of motor units firing
Number of muscle cells per motor unit
Small motor units create ___ movement
Large motor units create ___ movement
Random, asynchronous motor unit contractions that provide a low level tension and resistance to stretch
What will happen to a muscle if the motor unit is cut?
It will become flaccid
A muscle contraction in respinse to a single stimulus of adequate strength
What are the phases of a single muscle twitch?
Latent, contraction, relaxation
Latent period (3 things)
Sarcolema and T tubules depolarize
Calcium ions released into cytosol
Cross bridges begin to cycle but there is no visible shortening
Contraction period (2 things)
Sarcomeres shorten because of myosin cross bridge cycling
Speed depends on weight and fiber type
Relaxation period (3 things)
Calcium ions transported back into terminal cisternae
Cross bridge cycling decreases and ends
Tension is reduced, muscle returns to original length
Conditions for treppe (2)
Relaxation phase of previous twitch must be completed before a new stimulation
New stimulation must be close enough that the muscle is still warmed up from the first stimulation
The voltage at which the first perceptible contraction is seen
Lowest stimulation that produces maximum contraction
Max force of contraction of muscle. All motor units are firing.
An increase in the strength of the stimulus will cause an increase in tension development caused by
recruitment of more motor units
When a second stimulus is applied before complete relaxation, there is a greater development of tension. What is this called?
During the initial phase of muscle contraction, each successive stimulus produces a slightly stronger contraction because of increased muscle warming and efficiency of enzymes. This stage is called:
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