Motor System Flashcards
How are flexors and extensors arranged around the joint?
in an agonist/antagonist fashion
What are the 3 types of movement?
- voluntary (goal-directed)
- rhythmic motor patterns that require voluntary initiation and termination
- involuntary reflexes
What is the corticospinal tract?
the main tract for nearly all voluntary muscle activity
Where are neurons that supply the leg and foot muscles?
on the medial aspect of the hemisphere
Where are neurons that supply the hand and face?
on the lateral aspect of the hemisphere
What is the pathway of axons in the corticospinal tract?
- pass down through the internal capsule into the cerebral peduncles in the midbrain
- continue down the brainstem to reach the pyramids in the medulla oblongata
- cross to the opposite side and continue as the lateral corticospinal tract in the spinal cord
- at each level of the spinal cord, axons peel off and enter the ventral horn
- terminate by synapsing with lower motor neurons
What is the ventral corticospinal tract?
the axons that do not cross over at the medulla and continue down the spinal cord and peel off at each level to enter the ventral horn and terminate on the lower motor neurons
How do lower motor neurons send out their axons?
via the ventral roots
What are the corticospinal and rubrospinal tracts?
lateral systems that influence distal muscles
What are the vestibulospinal and reticulospinal tracts?
medial systems that influence axial and proximal muscles to maintain balance and posture
How do efferent fibres control different skeletal muscles and their movements?
on excitation, the efferent will release ACh at the synapse with the skeletal muscles which will act on nicotinic receptors leading to calcium influx and subsequent muscle contraction
What is the dorsal horn related to?
sensory activity (site of second order sensory neuron)
What is the ventral horn related to?
motor activity
What are the basal ganglia crucial for?
regulating and modulating motor functions, including movement initiation, coordination, and control
What are the 5 nuclei of the basal ganglia?
- caudate nucleus
- putamen
- globus pallidus
- subthalamic nucleus
- substantia nigra
What is the caudate nucleus involved in?
the regulation of voluntary movement and the integration of spatial information
What is the striatum?
caudate and putamen nuclei together
What is the putamen involved in?
regulation of autonomic and repetitive movements; also helps initiate and control gross motor activities
What is the globus pallidus involved in?
the regulation of voluntary movement, acting as a major output nucleus of the basal ganglia; influences the thalamus, which in turn modulates motor activity
What does the subthalamic nucleus do?
inhibit unwanted movements; important in the regulation of motor activity, particularly in modulating the activity of the globus pallidus and substantia nigra
What is the substantia nigra crucial for?
motor control, especially in the production of dopamine, which modulates the activity of the striatum
What is the order of motor hierarchy?
- cortex - voluntary movement
- brain stem - postural reflex and rhythmic motor patterns
- spinal cord - site of motor neurons that control muscle activity
What is the result of disrupting activity of the premotor cortex in humans?
the individual not knowing which series of actions to perform
What does increased activity of corticospinal neurons on flexor muscles do?
cause muscle contraction
