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Brain and Behaviour > Neural Basis of Motor Control > Flashcards

Neural Basis of Motor Control Flashcards

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1
Q

Movements

A 
are brief unitary activities of muscle
Reflexes
Postural adjustments	
Sensory orientation
- hear something loud from other side of the room and turn to look and see
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2
Q

Actions

A

are complex, goal-oriented sets of movements (reaching and grasping)
Walking
Gestures
Acquired skills (speech, tool use, etc.)

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3
Q

Closed-loop movements:

A

Information flows from whatever is being controlled back to the device that controls it

  • a circuit is formed where feedback is coming in a adjustments can be made
  • picking up an object, there is full light outside you can see the object and can move towards it
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4
Q

Open-loop movements:

A

Ballistic movements where once movement is initiated, there is no opportunity for feedback – accuracy is controlled through anticipation of error
- throwing a dart in the dark once it leaves your hand you cant control it anymore

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5
Q

Overview of neural control of movement

A

Primary motor cortex -> brain stem -> muscles of head and neck/ spinal cord-> muscles of body

Primary motor cortex -> Basal ganglia modulation-> spinal cord -> muscles of body

Primary motor cortex -> Basal ganglia modulation-> brain stem-> spinal cord -> muscles of body

Primary motor cortex -> non primray motor cortex

Primary motor cortex -> cerebellar modulation
spinal cord -> muscles of body

Primary motor cortex -> cerebellar modulation -> brain stem-> spinal cord -> muscles of body

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6
Q

The neuromuscular junction

A

where the NS & the muscle connect and combine

site where a motor neuron excites a skeletal muscle fiber is called NMJ
- chemical synapse consisting of the points of contact between the axon terminals of a motor neuron & the motor end plate of a skeletal muscle fiber

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7
Q

List the steps of a neuromuscular junction

A
  1. AP travels length of axon of a MN to an axon terminal
  2. VG Ca2+ channels open & Ca2+ ions diffuse into terminal
  3. Ca2+ entry causes synaptic vesicles to release ACh via exocytosis
  4. ACh diffuses across the synaptic cleft & binds to ACh receptors, which contain ligand-gated cation channels
  5. Ligand-gated cation channels open
  6. Na+ ions enter muscle fiber & K+ ions exit muscle fiber
    - greater influx of Na+ ions relative to outward influx of K+ ions causes MP to become less (-)
  7. Once MP reaches a threshold value, an AP propagates along sarcolemma
    - neural transmission to a muscle fiber ceases when ACh is removed from the synaptic cleft (occurs in 2 ways)
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8
Q

What are the 2 ways ACh can be removed?

A
  1. ACh diffuses away from a synapse
  2. ACh is broken down by acetylcholinesterase to acetic acid & choline
    - choline is transported into axon terminal for resyn. of ACh
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9
Q

Effectors

A

e. g., the hands (distal) or neck (proximal).

- things muscle are moving

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10
Q

Eyes

A

effectors for vision.

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11
Q

Muscles

A

arranged in agonist / antagonist pairs

e. g., biceps and triceps.
- pairs have to be treated differently (1 stimulated & 1 inhibited) so they dont fight each other

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12
Q

alpha motor neurons

A

Primary site of interaction between muscles and the CNS is via..
- determines the strength of muscle contraction.

originate in the spinal cord, exit via the ventral root and terminate at extrafusal muscle fibres.

  • triceps are activated, biceps inhibited & vice versa
  • if not, muscles fight each other (more clicky clacky less smooth)
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13
Q

Acetylcholine

A

is the neurotransmitter released by action potentials in alpha motor neurons.

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14
Q

Intrafusal muscle fibres (muscle spindles)

A

– one sensory and one motor axon.

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15
Q

Describe Excitation and Inhibition

A

descending fibers can be excitatory or inhibitory and form the basis of voluntary movements.

excitation to the agonist muscle (e.g., biceps) is accompanied by inhibition of the antagonist muscle (e.g., the triceps) – in this example the elbow is flexed! (muscles are contracted, limbs are flexed).

this prevents the reflex action of the antagonist muscle overcoming the voluntary action of the agonist muscle.
- otherwise, will be rigid

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16
Q

Efferent signals

A

signals away from the CNS towards effectors (e.g. hand or eye).

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17
Q

afferent signals:

A

signals from effectors towards the CNS (e.g. sensory feedback from skin).

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18
Q

Monosynaptic stretch reflex

A

responding to weight of objects.
maintaining posture.
one synapse involved

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19
Q

Describe how Monosynaptic stretch reflex works in regaining posture

A

Standing upright; gastrocnemius muscle

leaning forward; muscle lengthens muscle spindles fire, alpha motor neurons are stimulated reflexively muscle contracts
force exerted at front of foot

upright posture

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20
Q

Polysynaptic reflexes

A

secondary reflexes inhibit alpha motor neurons.
- couple synapses included

protective mechanism – inhibits further action when the amount of stretch may cause damage to tendons.
- when going to the gym if you work out with to much weight to succeed you will have to overcome this mechanism

interneurons synapse on alpha motor neurons of antagonist muscle.

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21
Q

golgi tendon organ

A

sending info about how tight tendon is being pulled

- if tight it’ll send signal down operating thru an interneuron

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22
Q

motor plan

A

an abstract representation of an intended action.
specify a goal for the action.
outline the effectors needed to achieve that goal.
create the plan.
execute the movement.
compare executed movement with plan on-line.

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23
Q

efference copy

A

refers to a copy of the motor plan to be executed. This copy can be used to compare the plan with the outcome.
- like a blueprint; our brain uses this to compare how it should be going vs how it is going and make adjustments

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24
Q

Vocal motor plans

A

We start talking later when we are about to read a long sentence. Than we do for a short one.

This suggests that the entire vocal motor plan is generated before we begin speaking.

  • shorter sentence you can start quicker
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25
Q

Motor imagery

A

the time it takes to imagine moving shows the same patterns as for real movements.

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26
Q

Explain the boxes experiment

A

subjects made real movements where they touched one block and other and went back and fourth either did that for real or imagined to do it
- when the the 2 boxes were large they were closer together then the smaller boxes

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27
Q

deafferented patients

A

(no sensory feedback of moving limb) can perform simple motor tasks.(move hand up and down side to side)

movements are not as precise and multi-joint movements are particularly difficult. (moving finger one way and wrist the other way becomes difficult)

feedback plays a very important role in modifying motor plans on-line to improve accuracy.

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28
Q

Movement plans – effector independence

A

the particular goal of a movement specifies its control and execution.

movement endpoint may be the most crucial element specifying the goal (but direction, speed and form are important too).

29
Q

Supplementary Motor Area (SMA)

A

plays a role in planning, preparation and initiation of movements.

topographic connection with motor cortex.

ipsi and contralateral motor cortex projections and connections to opposite SMA.

primarily involved in complex movements and sequences (also active for imagined movements).

30
Q

Anterior Cingulate

A

involved in novel (new) motor plans.

single cell activity in monkeys shows increased firing prior to movement onset .(thought to be involved in planning)

fMRI shows the AC is involved in monitoring performance, error feedback and evaluation of possible response conflict (e.g. Stroop effect).

RED vs. RED (easier to colour of text is red then green bc its easier to read the text)

rough topography evident in the AC.
caudal (manual movements, e.g., hand movements), rostral (eye movements), speech – somewhere between the caudal and rostral regions.

31
Q

Internally and externally driven motor plans

A

may rely on different neural networks.

parietal, cerebellar and lateral premotor regions – spatially directed movements (novel situations).
-> reach out and pick up water bottle every time it will be positioned differently so its a novel movement

SMA, basal ganglia, temporal lobe (hippocampus) – internally driven, familiar sequences of movements.
- tying a shoelace walking

unlikely to be completely mutually exclusive.
- overlpap

32
Q

Motor strip

A

fine motor control has more area devoted

33
Q

Descending pathways - pyramidal and extrapyramidal tracts

A

all cortical motor tracts cross over at the medullary pyramids.
subcortical motor tracts can have ipsi and contralateral projections.

34
Q

Corticospinal pathway

A

lateral tract – controls distal muscles (arms, fingers, lower legs, feet).

lateral tract completely crosses over at the medulla (i.e., completely contralateral).

ventral tract – important for posture and locomotion (projects both ipsilaterally and contralaterally).

35
Q

Corticobulbar pathway

A

important for the control of the face and tongue.

crosses midline at the pons.

synapses on the pons at the:
V (trigeminal – chewing, pain & touch for face and mouth),
VII (facial – facial expressions),
IX (glossopharyngeal – tongue movement),
X (vagus – digestion, taste) and
XII (hypoglossal – tongue movements) cranial nerves.

36
Q

Describe how the Corticobulbar pathway is organized

A

upper part of face represented both ipsi- and contralaterally (after unilateral cortical damage both eyebrows and eyelids can still be controlled).

lower part of face is exclusively contralateral (after unilateral cortical damage a facial droop is seen).

  • opposite side get the droop
  • left hemisphere damage droop on the right side of face eyes and eybrows are okay

damage to the facial nerve (VII) leads to Bell’s Palsy.

37
Q

Rubro-spinal pathway

A

originates in the red nucleus of the midbrain.

receives input from motor cortex and cerebellum.

projects mainly to the cerebellum.

modulates motor control and co-ordination.

38
Q

Ventromedial Pathway

A

originates in brain stem nuclei (including the superior colliculus, pontine and medullary reticular formation).

important for co-ordination of eye, head and trunk movements (tecto-spinal).

involved in posture control

39
Q

Brain stem disorders

A

damage to the cranial nerves will lead to various neurological signs (e.g., facial nerve palsy or Bell’s palsy – from VII nerve damage).

40
Q

locked-in syndrome

A

refers to a complete paralysis due to bilateral lesions of motor pathways and lower cranial nerves in the pons and medulla – the oculomotor nerve (III) is spared allowing patients to communicate with eye movements and blinks – cognition is unimpaired and EEG is normal.

41
Q

ALS

A

motor neuron disease or amyotrophic lateral sclerosis
affects motor neurons in the cortex, brain stem and spinal cord.

aggressively progressive disorder that generally leads to death within 2 – 4 years after onset (which is typically in the 40’s).

42
Q

Cerebellum

A

10% of brain’s mass.

more than half the brain’s neurons!

cerebellum Latin for “little brain”.

receives sensory input from somatosensory, vestibular, visual and auditory sensory modalities.

also receives input from association cortices.

motor feedback loops (mechanics garage) are also important in the cerebellum – for motor learning, modulation of movements, matching the executed to the planned movement, etc.

  • > if something is disturbing visual system it can help adapt
  • > ppl can live without it
43
Q

How is the cerebellum organized?

A

ipsilateral organization.

so movements of the right hand involve the left motor cortex and the right cerebellum.

44
Q

What is the cerebellum important for?

A

important for motor learning and modulation of motor control.

45
Q

What are the 3 sections of the cerebellum?

A

three sections – vermis, intermediate and lateral zones.

46
Q

deep cerebellar nuclei include;

A

fastigial nucleus, interpositus nucleus and the dentate nucleus.

47
Q

vermis

A

(incl. fastigial nuclei) receives somatosensory and kinesthetic information.

projects to the ventromedial pathway and is important for posture.

48
Q

intermediate zone

A

(incl. interpositus nucleus) receives information from the red nucleus and the spinal chord.

forms a loop with the red nucleus.

49
Q

lateral zone

A

(incl. dentate nucleus) receives information from motor and association cortices via the pons.

projects back to motor cortex via the red nucleus and the ventrolateral thalamus.

50
Q

What happens if the vermis is damaged?

A

walking and balance are affected by damage to the vermis while fine motor control of distal muscles remains intact.

51
Q

What does damage to the intermediate zone lead to?

A

damage leads to rigidity and action or intention tremor (distinct from resting tremor).
-> doesn’t exist when person is at rest only happens when person does action

finger – nose test.

52
Q

What does damage to the lateral zone lead to?

A

damage affects ballistic movements (leading to overshoot), co-ordination of multi-joint movements, learning new movements.

damage also leads to impairments in timing of motor and cognitive functions.

53
Q

Describe what happens when the lateral cerebellum is damaged?

A

damage to the lateral cerebellum impairs the ability to recalibrate movements in response to visual perturbations.

normals adjust movements to accommodate change induced by prisms.

normals then show an after-effect that indicates they made a compensation for the prisms – adjustments are very rapid.

cerebellar patients fail to adjust and therefore do not show an after effect.

54
Q

List some Cerebellar Disorders

A

ataxia

gait ataxia

55
Q

ataxia

A

a (without) taxia (to order, or arrange).

ataxia is a disorder of the co-ordination of movements including directional errors, decomposition of movements into sub-components.

56
Q

gait ataxia

A

lurching, unsteady or wide based gait (widely moving legs) – typical of midline cerebellar lesions or chronic alcoholism.
-> diff then parkinsons movement

57
Q

Basal Ganglia

A

input mainly to the striatum – caudate and putamen.

output is almost exclusively via the internal globus pallidus and part of the substantia nigra.

output is mainly ascending (via the thalamus).

58
Q

Circuitry of the basal ganglia

A

excitatory and inhibitory connections within the basal ganglia allow for fluid control of movement.

preparation for voluntary movements, auto-pilot for well-learned movements, timing and switching, planning, learning and execution.

59
Q

What do direct and indirect routes connect to?

A

direct route connects striatum with GPi (inhibitory connection).

indirect route connects striatum to GPe, STN and the GPi (eventual excitatory pathway).

60
Q

What happens if we increase amount of inhibition to thalamus?

A

we decrease excitation of cortex we slow voluntary movements
- parkinsons

61
Q

direct route

A

leads to less inhibition of the thalamus (i.e., striatum inhibits GPi which in turn inhibits its normal (inhibitory) action on the thalamus), thus leading to greater excitation from the thalamus to the cortex.

direct route allows sustained action or initiation of action.

62
Q

indirect route

A

excites the GPi thereby increasing its inhibition of the thalamus.
- damage to this system causes to many unwanted movements

indirect route suppresses unwanted movements.

63
Q

What can the basal ganglia thought of as?

A

can be thought of as a trigger center for movements – through the balance between the inhibitory and excitatory connections one movement plan is executed over a myriad of other possible actions.

64
Q 
1) The strength of contraction of a muscle is determined by activity of
A) intrafusal muscle fibers.
B) golgi tendon organs.
C) afferent fibers.
D) gamma motor neurons.
E) alpha motor neurons.
A

E) alpha motor neurons.

65
Q 
2 ) A \_\_\_\_\_\_\_\_ is formed by the synapse of an efferent nerve terminal onto a muscle fiber.
A) myofibril tangle
B) motor unit
C) neuromuscular junction
D) intrafusal contact
E) muscle spindle
A

C) neuromuscular junction

66
Q

3 ) One function of the monosynaptic stretch reflex is to
A) coordinate the movements of the flexors on each limb.
B) smooth out muscle contractions.
C) provide feedback to the brain about motor activity.
D) alter the speed with which an arm moves while throwing a ball.
E) help maintain posture.

A

E) help maintain posture.

67
Q 
4 ) Which of the following pathways controls movements of the fingers?
A) lateral corticospinal tract
B) rubrospinal tract
C) tecto-spinal tract
D) nigrostriatal bundle
E) corticobulbar pathway
A

A) lateral corticospinal tract

68
Q 
5 ) Which of the following pathways controls movements of the tongue, face and some eye
muscles?
A) lateral corticospinal tract
B) ventral corticospinal tract
C) spinothalamic tract
D) rubrospinal tract
E) corticobulbar pathway
A

E) corticobulbar pathway

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