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Neuroscience > Voluntary Movement > Flashcards

Voluntary Movement Flashcards

1
Q

what are skeletal muscles innervated by?

A

alpha motor neurons

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2
Q

what is muscle contraction innervated by?

A

alpha motor neurons

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3
Q

describe the activation of skeletal muscles?

A
  • axons branch and innervated thousands of muscle fibres
  • axon exits the spinal cord via the ventral route
  • then innovates muscles
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4
Q

how do you get finer control of muscles?

A
  • the smaller number of alpha-motor neurons the finer control you have
  • typically a muscle fibre will receive innervation from one alpha motor neuron
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5
Q

how does the alpha-motor neuron control reflexes?

A

action potential - sensory - synapse - alpha-motor neurons - muscle - contraction

  • at the same will innovate an inhibitory interneuon in the spinal cord
  • triggers the alpha-motor neuron that controls the antagonist muscle
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6
Q

what did Fritsch and Hitzig find?

A
  • found that if you stimulate different parts of the brain it causes movement in the contralateral side of the animals body
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7
Q

what is meant by contralateral?

A

opposite side of the body

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8
Q

what are the parts of the gyrated brain?

A

gyprus - top part of the fold

- sulcus - invagination

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9
Q

what is the PMC?

A
  • the primary motor cortex, involved with voluntary movement
  • it is anterior to the primary sulcus
  • contains an orderly map of the contalateral body parts
  • there is dispropportionate mapping
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10
Q

when do action potentials fire from cortical motor neurons?

A

fire before and during movement

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11
Q

what can we see from graphs of action potentials of the cortical motor neurons?

A
  • can see theres action potential that happen much earlier than their initation of movement
  • silent during flexion
  • fire action potentials for movement
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12
Q

how many layers are there in the PMC?

A

6

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13
Q

which layer contains neurons that control movement?

A

5

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14
Q

what are pyrimidal neurons?

A
  • cell body like a pyramid

- dendritic branching and spines

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15
Q

what neurons do you find in layer 5?

A
  • giant pyramidal neurons called Betz cells

- they control movement

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16
Q

where do Betz cells project ot?

A
  • send axons from the PMC to the brain
  • go down the white matter tract through mid-brains and then medulla
  • once at the medulla-spinal cord junction it transverses to the other side of the spinal cord
  • synapses with an alpha-motor neuron
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17
Q

how is flexion and extension coordinated?

A
  • neurons terminate to coordinate flexion and extension

- coritcal motor neuron: synapse at the spinal cord, generally controls agonist muscle and the antagonist muscle

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18
Q

what do interneurons do?

A

indirectly suppress antagonist muscles

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19
Q

what do you need to initiate/control movement?

A
  • activation of the PMC isnt enough
  • need other sensory information
  • cerebellum and basal ganglia are needed
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20
Q

what is primary lateral sclerosis?

A
  • progressive weakness in voluntary muscle movement
  • loss of corticospinal motor neurons
  • generally effects legs first
  • not fatal but patients will be in a wheelchair
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21
Q

what is amyotrophic lateral sclerosis (ALS) caused by?

A
  • loss of corticospinal motor and alpha-motor neurons

- some motor neurons are spared

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22
Q

what are the features of ALS?

A
  • begins with trouble in executing fine movements of the hands
  • wont be able to stand, walk, use their arms or hands
  • retain cognitive abilities
  • ultimately affects muscles of respiration
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23
Q

how can you asses motor functions in rodents?

A

open filed and rotarod

24
Q

how does open field assessment work?

A
  • measure how much they move in the field
  • see profound changes when theres a disease model
  • can measure anxiety like behaviours
25
Q

how does rotarod assessment work?

A
  • central beam that spins mice try to cling on - may eventually fall off
  • if your studying disease, they wont hold on for as long
26
Q

what is the basal ganglia?

A
  • collection of different brain areas that receive input from the cortex, thalamus and brainstem
  • essential for controlling and regulating movement
27
Q

what is the striatum?

A

contains the candate nucelus and putamen

  • between the CN and P there are gaps, here the internal capsule is loacted
  • axons of white matter tract
28
Q

what is the globus pallidus?

A
  • internal segment (GPi)

- external segment (GPe)

29
Q

what is the STN?

A

subthalamic nucleus

30
Q

what is the susbtantia nigra?

A
  • pars compacta (SNpc)

- pars reticula (SNpr)

31
Q

where is the input from the basal ganglia from?

A

the cortex, from glutamatergic neurons

32
Q

where does the input initially go in the basal ganglia?

A

the striatum, make synapses with medium spiny neurons (MSNs)

33
Q

what are glutamatergic neurons?

A

release glutamate

34
Q

how can you record action potential firing in MSNs?

A
  • brain slice
  • microscope
  • see the cells
  • put a recording electrode for a whole cell recording
  • put a stimulatory electrode to activate the cortex and record action potientials
35
Q

what affect do cortical neurons have on MSNs?

A
  • depolarise MSNs as they release glutamate

- causes EPSPs - increases the probability of action potentials firing in the MSNs

36
Q

how can you record action potential in vivo?

A
  • have a mice brain - insert a recording electrode into the striatum - connect a computer and measure the extracellular action potential
37
Q

what happens if you activate the cortex?

A
  • get high activity in the striatum
38
Q

what are the 2 output nuclei of the basal ganglia?

A
  1. GPi
  2. SNpr
    - they serve different functions
39
Q

what are the 2 pathways from the striatum to the output nuclei?

A
  1. direct

2. indirect

40
Q

what does the direct pathway do?

A

facilitate of movement

41
Q

what does the indirect pathway do?

A

suppression of movement

42
Q

what neurotransmitters do MSNs release?

A

GABA

43
Q

how do MSNs affect the output nuclei in the direct pathway?

A
  • hyper-polarise their target cells
  • release GABA
  • IPSPs which decrease the probability of an action potential firing the target nuclei
  • the striatum inhibits the GPi and the SNpr
44
Q

how would you record the action of the direct pathway?

A
  • place the recording electrode in the GPi or record the SNpr
  • before stimulating the cortical neurons (AP firing in the GPi)
  • but as soom as they’re stimulated theres no AP fired
  • profound inhibitory effect on output nuclei
45
Q

where do the output nuclei send information?

A

to the thalamus

46
Q

what neurotransmitters do GPi and SNpr release?

A

GABA

47
Q

how is the thalamus effected in the direct pathway?

A
  • normally GPi and SNpr would inhibit the thalamus as they produce GABA
  • but theyve been inhibited
  • so there is increased firing in the thalamus (disinhibition of the thalamus)
48
Q

how is the cortex effected in the direct pathway?

A
  • thalamus has glutamatergic projections
  • sends it cortex back to the cortex
  • leads to further activation of the cortex
  • facilitates the thalamus
49
Q

what are the steps of the indirect pathway (draw an image)?

A
  • MSNs send their axons to the GPe
  • GPe release GABA and projects to the GPi/SNpr
  • leads to disinhibition of the GPi and SNpr
  • inhibition of the thalamus
  • decreased activation in the cortex
  • suppresses movment
50
Q

what are the 2 routes of the indirect pathway?

A
  • GPe also sends projections to the STN
  • decreased activity of GPe
  • less inhibition of the STN
  • STN action potentials will increase (they are glutamatergic actions that project to the output nuclei)
51
Q

what is the function of SNpc?

A
  • release dopamine
  • send their axons to the striatum
  • they activate the neurons and regulate the function of the striatum
52
Q

what is dopamine?

A
  • intermediate in the synthesis of noradrenaline

- also a neurotransmitter itself

53
Q

what is reserpine?

A
  • lead to movement problemsin animals
  • blocked the uptake of neurotransmitters into synaptic vesicles
  • movement problems could be rescued by dopamine but not noraadrenaline
54
Q

what is the process of making dopamine?

A

tyrosine
L-Dopa
Dopamine

55
Q

what do neurons in the SNpc release dopamine onto?

A
  • release it onto MSNs

- binds to postsynaptic receptors (GPCRs)

56
Q

what are the dopamine receptors?

A

D1-like in the direct pathway

D2-like in the indirect pathway

Neuroscience (11 decks)

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