Chapter 15 part 3 Flashcards
somatic motor pathways always involve at least _____motor neurons:
2:
upper motor neuron
lower motor neuron
where is the nucleus of the upper motor neuron and the lower motor neuron
nucleus of upper motor neuron lies in the CNS processing center
nucleus of lower motor neuron lies in a nucleus of the brain stem or spinal cord
explain how a single motor unit in a skeletal muscle is innervated
the upper motor neuron synapses on the lower motor neuron, which then innervates a single motor unit in the skeletal muscle
do the axons of the upper and lower motor neuron extend outside of the CNS?
NO
only the axon of the lower motor neuron does
what happens if a lower motor neuron is destroyed or damaged?
eliminates voluntary and reflex control over the innervated motor unit
activity in the upper motor neuron may ___ or ____ the lower motor neuron
facilitate or inhibit
conscious and subconscious motor commands control skeletal muscles by traveling over three integrated motor pathways.
what are they?
-the corticospinal pathway
-the medial pathway
-the lateral pathway
the output of these 3 motor centers stimulates or inhibits the activity of either _____ or _____
motor nuclei or the primary motor cortex
the corticospinal pathway provides…….
voluntary control over skeletal muscles
the corticospinal pathway is sometimes called the ____ system
pyramidal
what are the upper motor neurons of the corticospinal pathway?
pyramidal cells
explain how the corticospinal pathway is both direct and indirect
direct because the upper motor neurons synapse directly on the lower motor neurons that innervat skeletal muscle
indirect because the corticospinal pathway innervates centeres of the medial and lateral pathways
the corticospinal pathway contains _____ pairs of descending tracts:
-corticobulbar tract
-lateral corticospinal tract
-anterior corticospinal tract
the corticobulbar tract provides conscious control over..
skeletal muscles that move the jaw, phase, and some muscles of neck and pharynx (cranial nerves III-vii, ix, xi, xII)
what is a motor homunculus?
representation of the body’s motor functions in the brain.
shows which areas of the brain control different parts of the body
true or false
motor control is integrated at all levels through extensive feedback loops and interconnections
true
the components of the medial pathway help to control…
gross movements of the trunk and proximal limb muscles
the components of the lateral pathway help to control…
the distal limb muscles that perform more precise movements
which pathways innervate the SAME lower motor neurons?
the medial and lateral pathways innervate the same motor neurons as the corticospinal pathway
the medial pathway is primarily concerned with control of…
muscle tone and gross movements of the neck, trunk, and proximal limb muscles
the upper motor neurons of the _____ pathway lie within the red nuclei of the _________
lateral pathway, midbrain
the _ and ______ are responsible for coordination and feedback control over muscle contractions
BASAL NUCLEI AND CEREBELLUM
the basal nuclei provide the _ patterns of movement involved in voluntary motor activities
background — ie: the background position of the trunk or limbs, or direct rhythmic cycles of movement as in walking or running
explain how the basal nuclei work to perform their function
they do NOT exert direct control over the lower motor nuclei.
instead, they adjust the activities of the upper motor neurons based on input from all portions of the cerebral cortex, as well as the substantia nigra
