Movement

Question 1

What is the motor hierarchy (most important to least important)?

Answer 1

Cerebral cortex, basal ganglia, cerebellum, spinal cord

Question 2

How does the spinal cord connect to muscles?

Answer 2

Spinal cords has hundreds of specialised nerve cells called motor neurons which increase their rate of firing. The axons of these neurons project out to muscles where they activate contractile muscle fibres. The terminal branches of the axons of each motor neuron form specialised neuromuscular junctions on to a limited number of muscle fibres within one muscle

Question 3

What happens after motor neurons are connected to produce movement?

Answer 3

Each action potential in a motor neuron causes the release of neurotransmitter from nerve endings and generates a corresponding action potential in the muscle fibres. This causes Ca2+ ions to be released from the intracellular stores inside each muscle fibre which triggers contraction of muscle fibre, producing movement

Question 4

What is used to measure the level of electrical activity produced by muscles?

Answer 4

Electro-myographic recordings (EMGs)

Question 5

What important part does the spinal cord play?

Answer 5

It plays an important part in the control of muscles through several reflex pathways such as withdrawal reflex and stretch reflex

Question 6

What kind of reflex is knee-jerk?

Answer 6

Stretch reflex

Question 7

What type of nerve cell does knee-jerk involve?

Answer 7

Sensory neurons that signal muscle length, connected through synapses to motor neurons that cause movement

Question 8

How are complete behaviours formed?

Answer 8

Reflexes combine together with more complex ones in spinal circuits that organise behaviours

Question 9

What is the final common path to muscles that move your bones?

Answer 9

Motor neurons

Question 10

What happens in the cerebral cortex?

Answer 10

An large number of calculations have to be made by cells for each element of movement to ensure that movements are carried out smoothly and successfully

Question 11

What happen between the cerebral cortex and motor neuron of the spinal cord?

Answer 11

Critical areas in the brain stem combine information about the limbs and muscles ascending from spinal cord with descending information from the cerebral cortex

Question 12

Where is the motor cortex?

Answer 12

Thin strip of tissue running across the surface of the brain, directly in front of the somatosensory cortex

Question 13

What happens in the motor cortex?

Answer 13

There is a complete map of the body: nerve cells that cause movement in different limbs are topographically arranged, neurons may be found in any part of this map that are active about 100ms before activity in the appropriate muscles

Question 14

What is used to specify the actions by firing of an ensemble of neurons?

Answer 14

Population code

Question 15

What does the pre-motor cortex do?

Answer 15

It is involved in planning actions, preparing spinal circuits for movement and in processes that establish links between seeing movements and understanding gestures

Question 16

What are mirror neurons used for?

Answer 16

Imitating and understanding actions

Question 17

What happens in the parietal cortex?

Answer 17

A number of different cortical areas are concerned with the spatial representation of the body and of visual and auditory targets around us and where interesting targets are with respect to us

Question 18

What is parietal neglect?

Answer 18

Failure to notice objects (often on left side) or even ignore the left side of own body

Question 19

What happens if you damage right parietal lobe?

Answer 19

There is hemispatial neglect where the left side is ignored

Question 20

What is the basal ganglia?

Answer 20

A cluster of interconnected areas located beneath the cortex in the depths of the cerebral hemispheres

Question 21

What do basal ganglia do?

Answer 21

They are crucial in the initiation of movements

Question 22

How does basal ganglia act?

Answer 22

Like a complex filter, selecting information from amongst the enormous numbers of diverse inputs they receive from the anterior half of the cortex and the output feeds back to the motor cortical areas

Question 23

What regions are considered the anterior half of the cortex?

Answer 23

Sensory, motor, prefrontal and limbic regions

Question 24

What is Parkinson’s disease characterised by?

Answer 24

Tremor and difficulty in initiating movements

Question 25

What causes Parkinson’s disease?

Answer 25

Degeneration of neurons in the substantia nigra whose axons release dopamine into the basal ganglia, there is a precise arrangement of dopamine axons onto their target neurons in the basal ganglia

Question 26

What is the treatment for Parkinson’s disease?

Answer 26

Treatment with drug L-Dopa which is converted into dopamine in brain, restores dopamine levels and movement

Question 27

What else is basal ganglia important for besides the initiation of movement?

Answer 27

It is important in learning, allowing the selection of actions that lead to rewards

Question 28

What is the cerebellum important for?

Answer 28

It is crucial for skilful smooth movements

Question 29

What does damage to the cerebellum cause?

Answer 29

Poorly coordinated movements, loss of balance, slurred speech and cognitive difficulties

Question 30

What substance has a powerful effect on cerebellum?

Answer 30

Alcohol

Question 31

What else is cerebellum important for besides skilful smooth movements?

Answer 31

Motor learning and adaptation, almost all voluntary actions rely on fine control of motor circuits and cerebellum is important in their optimal adjustment

Question 32

How does the cerebellum work?

Answer 32

It has a very regular cortical arrangement and seems to have evolved to bring together vast amounts of information from the sensory systems, cortical motor areas, spinal cord and the brain stem. It generates a model fo how motor systems work and builds this model using synaptic plasticity that is embedded into this network

Question 33

What does the acquisition of skilled movements depend on?

Answer 33

Cellular learning mechanism called long-term depression which reduces that strength of some synaptic connections

Question 34

What does the Purkinje cell of the cerebellum look like and do?

Answer 34

It has an extensive branching of its dendritic tree which serves to receive the myriad of inputs required for the precise timing of skilled movements we learn

Question 35

What is the chemistry underlying actions and habits?

Answer 35

Neurotransmitter dopamine is released on to neurons in the basal ganglia where it acts at metrabotropic receptors

Question 36

What does dopamine serve as?

Answer 36

An incentive to act and a reward signal for acting appropriately

Question 37

When is the release of dopamine the highest?

Answer 37

When the reward is unexpected

Question 38

When do dopamine neurons fire the most strongly?

Answer 38

Dopamine neurons fire most strongly at a stage of learning when it really helps to give a strong reinforcement to motor system for having produced the right output

Question 39

How does movement get strung together?

Answer 39

They get strung together in a sequence through release of successive burst of dopamine

Question 40

What happens when complex movements become habitual?

Answer 40

System free-runs without dopamine reward

Question 41

What plays a role if movements have to be accurately timed?

Answer 41

Cerebellum