13 Motor System Flashcards
-system that directs the voluntary control of muscles, from the simplest movements to the most complex.
-the simplest movement is highly integrated here and requires inputs from different areas of the central and peripheral nervous systems.
-It is the system behind the initiation and regulation of locomotion.
motor system
The motor system includes?
cerebral motor cortex
basal nuclei
cerebellum
brainstem
spinal cord
peripheral nerves
three key components of locomotion
voluntary
reflex
rhythmic
-is directed by the primary motor cortex
-Its task is to synthesize numerous signals into patterns of action in coordination with the cerebral cortex, basal nuclei, and cerebellum.
Voluntary movement
-The motor cortex and brainstem motor centers give rise to the ____ that control motor neurons innervating skeletal muscles.
-also act on the local reflex circuitries to maintain posture and muscle tone, and on the central pattern generator in the spinal cord to initiate, modify, or terminate the locomotor activity.
descending motor tracts
what initiates voluntary movements
Cerebral cortex
three descending motor tracts of the cerebral motor cortex:
corticonuclear
corticopontine
corticospinal
What tract descends to reach its target nuclei in the brainstem? This tract mediates such voluntary actions as eye movements, mastication, facial expression, swallowing, neck movement, and tongue movement.
Corticonuclear tract
What tract terminates in the pons and synapses with neurons that send their axons, as the pontocerebellar fibers, to the contralateral cerebellum. This is one of several ways the cerebellum monitors cerebral motor activities.
Corticopontine tract
What tract is a crossed pathway, as most of its fibers cross (75% or so in dogs) at the pyramidal decussation and descend as the lateral corticospinal tract in the contralateral side of the spinal cord. The remaining fibers stay in the ipsilateral side of the spinal cord and descend as the ventral corticospinal tract.
Corticospinal tract
Three key motor nuclei in the brainstem?
red nucleus of the midbrain
pontine and medullary reticular formation
vestibular nuclei in the medulla oblongata
gives rise to the rubrospinal tract, which is functionally similar to the lateral corticospinal tract. In animals, the rubrospinal tract is a key motor tract for voluntary movement. The primary role of this tract is to control the flexor motor system and fine movements of the extremities.
red nucleus of the midbrain
gives rise to the pontine and medullary reticulospinal tracts. These descending motor tracts maintain the muscle tone necessary for supporting the body against gravity, as well as postural adjustment and synergic movements of the body.
reticular formation
facilitates spinal motor neurons (alpha, gamma) that supply the extensor muscles, but it simultaneously inhibits motor neurons to the flexor muscles.
pontine reticulospinal tract
opposes the pontine reticulospinal tract by inhibiting spinal motor neurons (alpha, gamma) that supply the extensor muscles and simultaneously facilitate motor neurons for flexor muscles.
medullary reticulospinal tract
give rise to two descending tracts, the medial and lateral vestibulospinal tracts.
They descend in the ventral funiculus of the spinal cord. They maintain the balance of the body by facilitating lower motor neurons for extensor muscles and inhibiting lower motor neurons for flexor muscles.
vestibular nuclei in the medulla oblongata
Motor neurons are classified as
Upper motor neurons
Lower motor neurons
What motor neurons are responsible for voluntary muscle control, regulation of muscle tone, and maintenance of posture against gravity. They do not innervate the skeletal muscle directly but influence the lower motor neurons.
Upper motor neurons
What motor neurons leave the central nervous system (CNS) and innervate skeletal muscles
Lower motor neurons
The basal nuclei consist of
caudate nucleus
putamen
globus pallidus
-coordinates complex movements of the body by influencing the cerebral motor cortex and other major motor centers (e.g., red nucleus, reticular formation) in the brainstem.
-modulate cerebral motor outputs by acting on the primary motor cortex via the thalamus.
-regulates the learning of motor skills
Basal nuclei
-a relatively simple involuntary response to a specific sensory stimulus.
-an integral part of maintaining muscle tone and posture.
-is either monosynaptic or polysynaptic in type
Reflex
It is the simplest type reflex. It requires peripheral sensory neurons that bring sensory signals from sensory receptors to the spinal cord and central motor neurons that respond to sensory signals by triggering the contraction of skeletal muscles.
monosynaptic reflex
type of reflex that involves one or more interneurons connecting afferent (sensory) and efferent (motor) signals.
polysynaptic reflex
The voluntary and reflex motor control produce coordinated patterns of?
rhythmic activity
cycle that is used to describe the complex activity of locomotion, from the initial placement of the supporting heel on the ground to when the same heel contacts the ground for a second time.
Gait cycle
step cycle of locomotion consists of
the swing phase
the stance phase
Rhythmic pattern of walking relies on the central pattern generator in the:
Thoracolumbar spinal cord
