Voluntary Motion

Question 1

what areas of the cortex contribute to the production of voluntary motion?

Answer 1

• primary motor cortex
• supplementary motor cortex
• pre-motor cortex
• pre-frontal cortex
• parietal cortex

Question 2

dorsal pathway of visual input

Answer 2

• used for higher processing
• leaves the occipital cortex and goes to the parietal/frontal cortex and allows us to complete motor acts based on visual input

Question 3

reaching–maps

Answer 3

• need info about object’s location in relation to body
  
  • info is relayed from visual cortex–>parietal cortex–>…–>ventral inter parietal area (VIP)
    
    • VIP creates a rough map of space around you
  • info from VIP is sent to F4 in premotor cortex and this creates detailed map of space around you
• also need to rely on superior parietal cortex to get info about where your arm is in space and send the input to F2 in premotor cortex
  
  • so F2 constructs a map about where arm is in relationship to your body and things around you

Question 4

grasping

Answer 4

• need to know the features of the item we are picking up
• anterior interparietal and PFG of the inferior parietal cortex have neurons that respond to:
  
  • visually dominant–seeing an object to grasp
  • motor dominant–grasping an object
  • visuomotor neurons–either condition
• the anterior interparietal and PFG relay info to F5 which fire with the GOAL not motor act

Question 5

premotor cortex in motor control

Answer 5

• receives sensory info required to move–particularly F4 and F5
• dorsal component–applies the rules that determine whether it is appropriate to move
  
  • identifies intent of motion and decides what motion to produce

Question 6

supplementary motor cortex and motor control

Answer 6

• 2 parts:
  
  • supplementary motor area (SMA)–postural control–what body position does it take to accomplish the motion you want
  • pre-supplementary area (pre-SMA)–plans the motor program required to make action occur–more complicated the motion, the more involved
• fcns:
  
  • organize motor sequences
  • acquire motor skills
  • executive control–decision to switch actions/strategies

Question 7

primary motor cortex

Answer 7

• precentral gyrus
• controls specific movements
• regions of body that do fine motions have proportionally high representation
• arranged in columns

Question 8

columns of primary motor cortex

Answer 8

• stimulation of any give column produces a specific motion
  
  • if we are in an area that controls a more general motion, stimulation may produce contraction of a group of Ms
• layer 4: receives sensory input from M and joint proprioceptors
• layer 5: output for corticospinal pathway, so contain axons that travel down SC and activate alpha motor neurons
• 2 sets of neurons in each column: 1 to start motion and one to maintain it as long as necessary
• neighboring columns control related motions, NOT neighboring Ms
• 2 kinds of columns:
  
  • on/off for agonist M
  • off/on for antagonist M

Question 9

role of the cerebellum

Answer 9

• sequence complex actions
• correct force/direction
• balance and eye movements
• learning of complex actions

Question 10

spinocerebellum

Answer 10

2 regions:

• central–postural control
• either side of vermis–force and direction of an ongoing motion

Question 11

cerebrocerebellum

Answer 11

• lateral regions
• plan complex motions
• sequence

Question 12

vestibulocerebellum

Answer 12

-balance and eye movements of future NOT current actions

Question 13

outputs from cerebellum:

Answer 13

• via the deep cerebellar nuclei:
  
  • dentate nucleus
  • fastigial nucleus
  • interpositus: globes and emboliformis

Question 14

inputs and outputs of postural control

Answer 14

-uses spinocerebellum

inputs:

• vestibular
• visual and auditory
• efferent copy–pre motor neurons go to alpha motor neurons and send a branch to spinocerebellum so it can look at the incoming info and what the cortex wants to do an adjust to make that happen

outputs:

• interpositus n
• fastigial n
• to rubrospinal tract
  
  • all of this info goes straight down SC to work on motion happening now

Question 15

inputs and outputs of force and direction

Answer 15

-uses spinocerebellum and also controls ballistic motion

inputs:

• muscle afferent
• efferent copy

outputs:

• interpositus nucleus
• to rubrospinal tract–go straight down SC to work on motion happening now

Question 16

inputs and outputs of complex motions

Answer 16

-uses cerebrocerebellum–sequencing of rapid movement

inputs:
   -cerebral cortex
outputs:
   -dentate 
   -back to cortex

Question 17

inputs and outputs of planning balance

Answer 17

-uses vestibulocerebellum: control eye movement and balance

input:

• vestibular apparatus–direct or indirect
  output:
• fastigial nucleus to vestibular nucleus
• ascend or descend

Question 18

basal ganglia

Answer 18

• involved in the planning and programming of movement
• input is particularly important in initiation of movement
• they are the mother may I of motor control–takes the plan the cortex makes and evaluates it and says no or yes
• subthalamic nucleus
• substantia nigra: pars compacta and pars reticularis
• striatum: caudate and putamen
  
  • striatum receives the inputs to basal ganglia
• globus pallidus: internal (medial) and external (lateral) segment

Question 19

nigrostriatal dopaminergic system

Answer 19

• from: substantia nigra pars compacta
• to: nuclei of striatum
• effects:
  
  • D1 receptors: when dopamine binds, the neuron is activated
  • D2 receptors: when dopamine binds, the neuron is inhibited

Question 20

intrastriatal cholinergic system

Answer 20

• b/w the nuclei of the striatum–cell bodies within the nuclei of striatum
• release ACh and causes an excitatory effect

Question 21

striatonigral GABA-nergic pathway

Answer 21

• from: striatum
• to: substantia nigra pars reticularis and internal globus pallidus
• “the direct pathway”
• leads to initiation of movement

Question 22

inputs/outputs thru the basal ganglia

Answer 22

inputs:
-subtantia nigra pars compact receives inputs and relays them to striatum

outputs:

• info leaves the basal ganglia via the substantia nigra pars reticularis and the internal globus pallidus
• SNPR and the GPi project to the thalamus and release GABA within the thalamus
• inhibit the thalamus

Question 23

what and how does the basal ganglia work?

Answer 23

• control beginning and the end of the movement

- basal ganglia work by inhibition and withdrawal of that inhibition to start the movement

Question 24

direct pathway vs. indirect pathway of the basal ganglia

Answer 24

• direct:
  
  • D1 Rs
  • excited by dopamine
  • allows motion
• indirect:
  
  • D2 Rs
  • inhibited by dopamine
  • excited by EAA/ACh
  • inhibits motion

Question 25

Direct Pathway

Answer 25

• from striatum to substantia pars reticular and internal part of globus pallidus
  
  • SNPC dopaminergic inputs excite the striatal cells by releasing dopamine which binds to D1 receptors on the striatum
  • striatum releases more GABA to the SNPR and GPi which is inhibited by the greater amount of GABA, so less GABA is released
  • to thalamus which excites cortex–since less GABA is released to it, this allows us to move

Question 26

indirect pathway

Answer 26

• input from SNPC is inhibitory to stratal neurons that are part of indirect pathway due to D2 receptors
• to activate the indirect pathway, we must use input from the cortex and intrastriatal pathway
  
  • striatal neurons synapse on external globus pallidus and release more GABA to bind to GPe
  • GPe is inhibited by the high GABA, so it releases less GABA to the sub thalamic nucleus
  • subthalamic nucleus releases more EAA, b/c there was less GABA, it is activated
  • EAA binds to SNPR and GPi which activates it and this causes it to release more GABA to the thalamus
  • this inhibits the GABA b/c of the high conc of GABA and this inhibits movement

Question 27

association cortex and voluntary motion

Answer 27

• 2 major areas of fcn:
  
  • planning of complex motor actions
  • carrying out of thought processes

Question 28

prefrontal cortex and higher fcns of the brain

Answer 28

• plan complex motor actions
  
  • interacts with parieto-temporal-occipital association area and all levels of motor cortex
  • planning of a complex motor act requires the frontal association area, supplementary motor cortex, premotor cortex, and cerebrocerebellum
• interactions b/w frontal, premotor, SMC, and basal ganglia determine IF the motion will occur
• once the motion is planned, sequenced, and approved, the appropriate columns in the primary motor cortex is activated
• APs then travel down the corticospinal tract and activate the alpha motor neurons that innervate the Ms needed to complete the motion

Question 29

muscle spindle and voluntary motion

Answer 29

-M spindle could be a problem b/c it could oppose every motion b/c every motion we make stretched one or more Ms
-brain solves the problem by using the gamma motoneurons to trick the M spindle into believing that the M is not changing length
-to make motion occur, if the brain activates alpha motor neuron, and it activates the gamma motor neuron for spindles in the contracting (agonist) M–alpha gamma coactivation
to make motion occur, if the brain inhibits the alpha motor neuron, it also inhibits the gamma motor neuron for spindles in the stretching (antagonist) M