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8 - Contraction of Motor units


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motor units
What are the groups of muscle cells called, within a muscle, that are innervated by one motor neuron and contracted together and stimulated by that motor neuron?
The size & # of motor units being stimulated
What important factors determine the strength of contraction of a muscle
motor unit
a motor nueron

& all of the muscle cells it stimulates
neuromuscular junction
What is the junction between the branch of an neuron and a muscle cell called?
all of the muscle cells which are stimulated by that one neuron will contract.
When a motor neuron fires, how many muscle cells are stimulated?
The more motor units there are, the stronger the contraction will be.
What is the relationship between the strength of the muscle contraction and the number of motor units which are stimulated?
The stimulation of additional motor units to increase strength of a contraction.
it generates precise movements
What is the general function of motor units that contain only a few muscle cells?
1. # of motor units firing
2. # of cells per motor unit
What two factors effect the strength and degree of muscle movement?
Have large motor units in which a single neuron is connected to a large # of muscle cells
Describe the motor units in large muscles which exhibit gross movements.
The eye has more complex movements (small, but important) compared to muscle movement in the thigh, which is gross movement.
What did the virtual professor mean when she said "small precise muscles that cause fine movements, like those of the eye, have a huge number of motor fibers controlling them, comparatively speaking.?"
a. small
b. large
c. large
d. small
Tell if the following muscles would have small or large motor units:

a. muscles of the fingers
b. biceps brachii muscle
c. gastrocnemius muscle
d. muscles of the throat involved in speech
A neuron within the brain or spinal cord that lies between sensory and motor neurons. Also called an association neuron.
muscle tone
The nearly constant state of low-level tension and resistance to stretch in a muscle.
activities of the spinal cord & result in firmness of the muscle
What causes muscle tone?
They become flaccid & briefly contract by nerve impulses.
they stretch by the weight of the muscle.
What happens to a muscle if all the motor neurons to that muscle are cut?

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