Voluntary Motion Flashcards
What are the main voluntary motion control areas in the brain?
Primary motor cortex
Supplementary motor cortex
Premotor cortex
What are the functions of the premotor cortex?
- Identifies the intent of the motion
- Decides if it is appropriate to move or not (dorsal aspect)
- Receives sensory information required to move
What are the 2 divisions of the supplementary motor cortex?
Supplementary motor area (SMA) and the
Pre-supplementary motor area (pre-SMA)
Function of the supplementary motor area?
Postural control
Function of the pre-supplementary motor area?
- Plans the motor sequence needed to make action occur
- Control to switch strategies or actions
What is the function of the primary motor cortex?
Controls specific movements –encodes the movements!
What cortex layer receives the sensory input?
Layer 4 - internal granular layer
What cortex layer outputs the info for the CST pathway?
Layer 5 - ganglionic layer
How are the neurons in the primary motor cortex arranged?
Into columns
What are the types of columns?
- On/off for agonist muscle
- Off/on for antagonist muscle
What are the types of neurons in the columns?
- 1 set to start motion
- 1 set to stop motion
Neighboring columns have what in common?
Control related motions!! (not neighboring muscles)
Stimulation of an area/column in the primary motor cortex that controls fine motion may result in what?
Contraction of a SINGLE muscle
Stimulation of an area/column in the primary motor cortex that controls general motion may result in what?
Contraction of a GROUP of muscles
Is there a homunculus for the precentral gryus?
Yes - fine motion (for example hands), takes up more of the topical map
When reaching for an object, what is the very first step?
The visual cortex (occipital) must see it and relay that axon to the parietal/frontal cortex
What are the areas in the parietal cortex that receive input from the visual cortex when reaching?
V6A, VIP, PEc, MIP
Function of VIP in the parietal cortex?
Create a rough map of the space around you
Where does the VIP project?
F4 in the premotor cortex
Function of F4?
Created a detailed map of the space around you
Describe the rate of firing in relation to F4 area in the premotor cortex?
Increased firing rate of action potentials the closer the object is to you
Function of V6A in the parietal cortex?
Tells you where your limb is in space
Where does the V6A project?
F2 in the premotor cortex
Function of F2?
Constructs a related map including the location of your limb in comparison to your body and the space around you
For grasping, what areas of the parietal cortex are important?
Anterior Intraparietal area (AIP) and the PFG
What can neurons in the Anterior Intraparietal Area and PFG respond to?
Seeing an object
Grasping an object
Seeing and grasping an object
Where does the Anterior intraparietal area and PFG project to?
F5 in the premotor cortex
Function of F5?
Neurons that fire the GOAL of the action!!
When trying to drink a cup of coffee, but the gripping is different what area of the premotor cortex is still firing the same?
F5 – goal is not changed just because the grasp of the cup is!
What area of the brain can sequence complex actions, correct force/direction, balance and eye movements and learn complex actions?
Cerebellum
What are the 4 functional (not anatomical) regions of the cerebellum?
Spinocerebellum (vermis) and Spinocerebellum (lateral)
Cerebrocerebellum
Vestibulocerebellum
Function of the Spinocerbellum (medial)?
Postural control of ongoing motions
Inputs to the spinocerebellum (Vermis)?
Efferent copy
Vestibular, hearing, auditory information
Outputs of the spinocerebellum (vermis)?
Fastigial nucleus, Interpositus nuclie to the rubrospinal tract of the SC
Interpositus
Globose nucleus + Emboliform nucleus
How are the outputs of the cerebellum communicated?
Deep cerebellar nuclei
Function of the Spinocerebellum (lateral)?
Force and direction of ongoing motion and ballistic motion control
Ballistic motion
Motion too fast with no time to correct it
Inputs of the spinocerebellum (lateral)?
Efferent copy and muscle afferent info
Outputs of the spinocerebellum (lateral)?
Interpositus nuclei to SC
Function of the cerebrocerebellum?
Planning complex motions and learning
Inputs of the cerebrocerebellum?
Cerebral cortex
Outputs of the cerebrocerebellum?
Dentate nucleus back to the cerebral cortex
Function of the vestibulocerebellum?
Future balance and eye movements
Input of the vestibulocerebellum?
Vestibular
Outputs of the vestibulocerebellum?
Vestibular nuclei that can ascend or descend
For repetitive actions such as walking, chewing, breathing; what initiates the movement?
Central pattern Generators (CPG)
What is necessary to activate the CPG?
Cerebral cortex
What is optional to activate the CPG but can help?
Sensory input helps to modify actions to be appropriate to the environment
What is the function of the Basal Ganglia?
Start and stop and modulate movement
What is the main NT released in the pathways within the Basal ganglia?
GABA - inhibitory
Another name for the direct pathway?
Straitonigral GABAergic
Describe the Direct pathway in detail
- Striatum projects to the SNPR/GPI and releases a lot of GABA
- This causes an IPSP and the neurons going from the SNPR/GPI do not release many action potentials
- This causes there to be less inhibition of the thalamic neurons and they will become excitatory and fire many action potentials to the cortex and release EAA
- Motion allowed
Purpose of the direct pathway in the basal ganglia?
Increase motor movements
Purpose of the indirect pathway in the basal ganglia?
Decrease motor movements
Describe the indirect pathway in detail
- Striatum projects to the GPE and releases a lot of GABA
- This causes an IPSP and few action potentials are generated on the neuron going from the GPE to the subthalamic nucleus
- GPE neurons will release less GABA so the subthalamic nucleus will be activated and increase its action potentials
- The subthalamic nucleus will release EAA to the SNPR/GPI and activate them
- The SNPR/GPI will then release a lot of GABA on to the thalamic neurons which will result in their inhibition and they will send less EAA to the cortex
- No motion allowed
What is the effect of dopamine on the direct pathway?
Amplifies movements and increases motor activity
Where does dopamine come from?
Substantia nigra pars compacta
What is the effect of dopamine on the indirect pathway?
Inhibits the indirect pathway from doing its original function of inhibiting motion
Overall effect of dopamine?
Initiation of motion! By activating the direct pathway and inactivating the indirect pathway
What is the dopamine receptor on the direct pathway and what is its response when bound to dopamine?
D1, excitatory
What is the dopamine receptor on the indirect pathway and what is its response when bound to dopamine?
D2, inhibitory
What is lost with parkinsons disease?
SNPC (substantia nigra pars compacta) - and consequentially dopamime
What is the result on each pathway when there is no SNPC and thus no dopamine?
The direct pathway is harder to activate
The indirect pathway is harder to inactivate
= Harder to initiate motion!
What are the 2 functions of the prefrontal cortex?
Planning of complex motor actions and carrying out “thought” processes
What areas are involved in planning complex motor actions?
Prefrontal cortex, premotor cortex, supplementary motor cortex and cerebrocerebellum - also basal ganglia (dopamine)
Once a motion is approved, what is activated?
The columns in the primary motor cortex
What must the brain activate for muscle contraction to occur in the agonist muscle?
It must activate the alpha AND gamma motor neurons
What must the brain inactivate for muscle relaxation/stretching to occur in the antagonist muscle?
It must inhibit the alpha AND gamma motor neurons
Once a motion has already started, what ensures the motion is correct?
Spinocerebellum