Motor Function Of Spinal Cord Physiology Flashcards
building blocks for the movements
motor units.
final common pathway out of the CNS
motor neurons
Why are motor neurons the final common pathway of CNS
because all neural influences on skeletal muscle meet on the motor neurons and can only affect skeletal muscle through them.
The cell bodies of the motor neuron pool for a given muscle are close to each other either in
ventral horn of the spinal cord or in the brainstem.
Within the brainstem or spinal cord, the axons of many neurons synapse on a motor neuron, why
to control its activity.
Although no single input to a motor neuron is essential for contraction of the muscle fibers it innervates, a balanced input from all sources is necessary to
provide the precision and speed of normally coordinated actions
All body movements are achieved by
activation, in a precise sequence, of many motor units in various muscles.
To begin a movement, a general intention is generated attention
the highest level of the motor
control hierarchy.
Motor control of the skeletal system is orgainzed like ….. and the levels are
Pyramid
Highest level
Middle level
Local level
Highest levels
Higher centers (regions of the brain, including those involved in memory, emotions, and motivation)
Middle levels
Sensorimotor cortex Basal nuclei Thalamus Cerebellum Brainstem
Local levels
Brainstem and spinal cord
Receptors
Information is relayed from these higher-center “command” neurons to
parts of the brain that
make up the middle level of the motor control hierarchy.
The middle-level hierarchical structures are located in
parts of the cerebral cortex as well as in the cerebellum, subcortical nuclei, and brainstem and thalamus
The basal ganglia are
Cluster of sub cortical ganglia
The structures of the middle level have
extensive interconnections
The middle-level structures function
specify the individual postures and movements needed to carry out the intended action.
The neurons in the middle level of the hierarchy receive ……
from receptors in …….
afferent information
the muscles, tendons, joints, and skin, as well as from the vestibular apparatus and eyes.
middle level of the hierarchy relay information about
the nature of the space just outside the body in which a movement will take place.
The information determined by the motor program is transmitted via …… pathways to the………
descending
local level of the motor control hierarchy
In the local level of the motor control hierarchy the motor neurons to the muscles
exit the brainstem or spinal cord
The local level of the hierarchy includes what neurons
afferent neurons, motor neurons, and the interneurons whose function is related to them.
Local level neurons determine
exactly which motor neurons will be activated to achieve the desired action and when this will happen
The descending pathways to the local level arise only in
sensorimotor cortex and brainstem
Other brain areas exert their effects on the local level only indirectly, via the descending pathways from the cerebral cortex and brainstem. What are those brain areas
the basal nuclei (also referred to as the basal ganglia), thalamus, and cerebellum
The motor programs are continuously adjusted during
the course of most movements.
As the initial motor program begins and the action gets underway, brain regions at the middle level of the hierarchy continue to receive
a constant stream of updated afferent information about the movements taking place.
proprioception
Afferent information about the position of the body and its parts in space is called
