What is the spinal cord involved in?
- processing commands from the brain
- reflexes
- rhythmic motor patterns
What organs generate basic patterns of rhythmic muscle activity?
Spinal cord and brainstem circuits
What are rhythmic muscle patterns used for?
- locomotion
- breathing
- chewing
- swallowing
What kind of commands does the brain give the spinal cord and brainstem circuits?
- stop/start
- speed
- force
- direction
What is in the primary motor cortex?
An ordered map of the body (somatotopy)
What is the corticospinal (pyramidal) tract?
A pathway used for For regulation of spinal cord motor systems by the primary motor cortex.
output from motor cortex controls spinal neurons for fine movements (crosses over to opposite side).
What is the secondary motor cortex involved in?
Planning of movements
What is somatotopy?
Body parts are represented roughly sequentially across the cortex. The area devoted to each part is dependent on level of fine control and extent of use.
What happens if damage occurs to the primary motor cortex?
Problems with movement, particularly with fine voluntary control in specific parts of the body
What is the role of brainstem pathway?
In charge of coordinated activity in large muscle groups for posture, locomotion, and routine activities (can be crossed or uncrossed).
What are the roles of the primary motor cortex?
- controlling force of muscle contraction
- controlling direction of movements (steering occurs around the joints)
Where do most motor cortex axons synapse
interneurons
What is the role of motor cortex neurons which synapse onto alpha-motor neurons?
- mostly for control of distal limbs
- direct, fast and powerful effect
What are motor programs?
sequences about what muscle contracts which are put in place prior to the action. actions are worked out in detail before they are put forwards
What is the planning loop?
sensorimotor cortex –> basal nuclei –> thalamus
What happens during the planning stage?
Dopamine is released to confirm a plan is going to be successful, and central motor neurons send down the input in order to generate movement
What are the roles of basal ganglia?
- monitors and helps plan cortical activity involved in movement
- helps cortex select combinations/sequences of muscle activation
- cycle through loop occurs during preparation for movement
- positive feedback to cortex for selected motor output pathways
- needed for initiation of movements
- dopamine input vital to allow proper functioning
What occurs due to death of dopamine neurons?
Parkinson’s disease
What are symptons of Parkinson’s disease?
- difficulty beginning movements
- slowed movements
- tremor
What are possible treatments for Parkinson’s?
- dopamine replacing drugs
- deep brain stimulation
- transplantation of dopamine cells
What is the role of the cerebellum and brainstem feedback loop?
It incorporates sensory information from planning as well as sensory feedback from the environment to decide how to best execute the motion.
What are the roles of the cerebellum?
- helps plan ,execute, and learn motor programs
- integrates sensory information with planned motor programs
- organises timing of individual muscle contractions around joins
- compares the intended results of a planned movement with the actual result, and modifies ongoing activity
What happens if the cerebellum is injured?
Movements become slow and uncoordinated. Tend to have a drunken gait.
How does alcohol affect the cerebellum?
The cerebellum has a lot of GABA receptors. Alcohol inhibits those receptors, so individuals tend to sway and stagger when walking.
