Week 8 - Controlling Movement

Question 1

Explain what is important to analyse when looking at Organised movement, instead of how complex it is?

Answer 1

To assess organised movements, the degree of sensitivity to online feedback is important to observe, to determine how reflexive or corrected the sequences of motor movements is.

Question 2

Outline what ballistic movements are? are they open-loop or closed-loop control mechanisms?

Answer 2

The motor movements that have no external feedback (once started they wont stop), so they are open-loop.

Question 3

Explain the difference between open-loop and closed-loop motor mechanisms?

Answer 3

OL are concerned with speed and have no external feedback, CL are concerned with accuracy, and has continual feedback to correct the movement/behaviour.

Question 4

Explain what a motor plan / organised movements? What is two example (one in humans, and one in animals)

Answer 4

They sequences of muscle movements that are previously organised into actions (reflexes that are action). Playing a piano, and a goose re-collecting eggs for nesting.

Question 5

Explain the function of Flexor withdrawal muscles why they function?

Answer 5

Designed to protect you, they are simple reflexes that send a protective signal to the spinal cord, and using excitatory interneurons to send messages to Flexor muscles to contract and protect the body. For example, stepping on a nail.

Question 6

What is a fixed action pattern?

Answer 6

A reflex of complex motor sequences that is induced by a sign stimulus, as seen in geese chicks when they try to peck their mothers red dot on the bill for food.

Question 7

How is the proprioceptive system used for reflexes? Relate to the Golgi tendon organs

Answer 7

The proprioceptive system has sensory receptors in the joints and muscles of the body. These send reflexive feedback to the brain, resulting in generated compensatory stretch reflexes to maintain stretch and tension of limbs. Sensory neurons send to spine, motor neurons response. The Golgi tendon organs is one of these receptors in tendons that reports tension to the CNS.

Question 8

Identify three types of muscles, and example, and how

do they all function?

Answer 8

Skeletal muscles - control all movements when interacting with the world (most complex), e.g. limbs
Smooth muscles - autonomic NS that controls viscera and other organs, e.g. urine and stomach.
Cardiac Muscles - also autonomic NS, controls heart and blood pressure, requires stronger muscles.
All muscles use contraction to function.

Question 9

What are antagonistic and synergistic muscles? examples of each? Do some muscles just relax after contracting.

Answer 9

Muscles that work against or together to function. Bicep and tricep work antagonistically, muscles below the elbow to lift the arm work synergistic-ally. Some muscles, like the sphincter just relax after contacting, instead of using another muscle.

Question 10

Muscles are composed of muscle fibres, but explain what are they are, how are they activated? explain how fine and gross motor control activate?

Answer 10

Muscle fibres are single large cells with many nuclei, they contract when acetylcholine is released at neuromuscular junction (which are specialise terminal buttons of axons). Fine motor control will occur when each axon only synapses with a few fibres, gross and fine use different neurons.

Question 11

What are “voluntary” movements and what parts of the brain are used?

Answer 11

Movement that are directed at a goal, and require cortical controls from M1, SMA, PMA prefrontal cortex, cerebellum, basal ganglia, and posterior parietal lobe.

Question 12

Outline what the basal ganglia made up of?

Answer 12

A group of interconnected forebrain nuclei: Caudate Nucleus, putamen, globus pallidus, and two associated parts of the midbrain, substantia nigra and subthalamic nucleus.

Question 13

Explain how the basal ganglia used is movement?

Answer 13

(1) Excitatory connection between the frontal lobes and putamen exist. (2) When excited the putamen inhibits the globus pallidus which releases VLo from inhibition (two negatives). (3) The VLo activity influence the SMA, which activates the PMA and M1.

Question 14

In short, how does the basal ganglia influence movement?

Answer 14

Basically, mediates motor action via releasing action from inhibition (by releasing VLo).

Question 15

Explain how the posterior parietal cortex used for movement?

Answer 15

Receives information from three areas: visual (dorsal stream), proprioceptive, and auditory areas, which then send information (axons) to the frontal lobes for movement decisions.

Question 16

Explain what the basal ganglia used for in movement? An example?

Answer 16

Select appropriate movement behaviour based on biological needs. Also used for amplitude, direction and initiation of movement, and movements influence by memories.
For example, you see a bottle of water, and your basal ganglia says you are thirsty, so you move to get water (by releasing inhibition).

Question 17

What is the posterior parietal cortex used for in motor commands?

Answer 17

Helps direct attention (visual/audio to objects) and guide action towards it (smooth and controlled with proprioception).

Question 18

How is the cerebellum used for movement? What does the sequential nature allow?

Answer 18

Many Inputs (sensory and cortex), stimulate slow, unmyelinated parallel fibres which activated purkinje cells (sequentially). This sequential nature allows ‘timing’ movements to be performed by the cerebellum.

Question 19

What is the cerebellum used for in motor movement? Example of learning by cerebellum?

Answer 19

Helps generate coordinated, well-timed, targeted action, especially for well-learned and rapid movement. For example, riding a bike: learning starts in the frontal cortex, whereas when it is second nature, it is stored with new connection in the cerebellum.

Question 20

Explain the behaviour of neurons when moving in particular directions?

Answer 20

Much like the tilt-effect, M1 controls movement in a distributed fashion (different neurons (and networks of neurons) are prone to particular direction). M1 remembers both muscles and direction of movement. E.g. Monkey Experiment.

For example, if you reach out leftwards, this is the result of a pooled output of a network of neurons that code for that direction, and nearby that direction. Code is a distributed fashion.

Question 21

Explain the lateral pathway of the descending spinal tracts?

Answer 21

Pathway from cortex to controlling limbs:

(1) M1 axons fire to the,
(2) Red nucleus in the midbrain,
(3) Pyramid in the medulla
(4) Swap to the contralteral side of the spinal cord
(5) Allowing control of movements of (hands, arms and feet) for reaching grasping and manipulating.

Question 22

What is the lateral pathway of the descending spinal tracts function?

Answer 22

Make direct manipulation of the world by controlling movements.

Question 23

What is the vetromedial pathway of the descending spinal tracts function?

Answer 23

Move/get to objects, for movement.

Question 24

Explain the vetromedial pathway of the descending spinal tracts?

Answer 24

(1) start at M1, firing axons that go down,
(2) and join with neurons from the vestibular nucleus, basal ganglia, tectum, reticular formation, and cerebellum, etc…
(3) Via the medulla
(4) then split in two to both sides of the spinal cord.
(5) Controls trunk, neck, posture, and locomotion-based movements - e.g. keeping up and moving around from one place to another.

Question 25

Difference between vetromedial pathway and lateral pathway of the descending spinal tracts? Why are they both important?

Answer 25

Vetromedial path allows us to keep upright and move around, the lateral path allows us to actually manipulate and interact with the world. Both required for goal directed behaviour.

Question 26

What are the four cortical motor areas, and their basic function?

Answer 26

(1) primary motor cortex (M1) - execution, everything is initiated here.
(2) Premotor cortex (PMA)- Tactical, locations/direction of targets
(3) Supplementary motor area (SMA) - Longer tactical planning and inhibition of movements
(4) Prefrontal cortex - strategic planning.

Question 27

What is the role of M1 in motor control?

Answer 27

(start) - Generating/executing actions of particular body parts. It has a map across is to do this.

Question 28

What is the role of PMA premotor cortex? What other neuron exists here.

Answer 28

(active before response- used for directions/location)

Used for direction of movements in response to external cues

Mirror Neurons exists here (active when moving and observing other moving). e.g. locating something to grasp it.

Question 29

What is the difference between PMA and SMA?

Answer 29

Both used for tactics (short term planning) but PMA is active before response, used for body posture and locations of targets, where as SMA is used for immediate planning of movements and inhibition of habitual movements.

Question 30

What is the role of the (SMA) supplementary motor area? Where is it located?

Answer 30

used for immediate planning of movements that are Internally generated, and inhibition of habitual movements

e.g. stop yourself from throwing a bottle at someone when you think about doing it.
Anterior to PMA and more medial (down the middle of the brain).

Question 31

Outline the role of the prefrontal cortex in motor activity?

Answer 31

Long-term planning of movements to achieve long-term goals.

Question 32

Explain how we process and control movement direction, for example, moving right arm in left direction?

Answer 32

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