Week 9: Motor Control Development

Question 1

Define motor control and describe the primary structures involved.

Answer 1

Model Answer:
Motor control is the process by which the nervous system plans and executes movement. The CNS (central nervous system) is responsible for movement planning, while the PNS (peripheral nervous system) and musculoskeletal system execute the movement. Structures involved include sensory receptors, somatosensory cortex, association cortices, prefrontal cortex, supplementary motor cortex, basal ganglia, cerebellum, spinal cord, and motor units.

Question 2

2. Outline the stages of motor development progression and provide examples.

Answer 2

Model Answer:
Motor development follows three key progressions:
* Cephalo-caudal progression: control develops from head down (e.g., head/neck control before sitting).
* Proximal-distal progression: control develops from the trunk outward (e.g., shoulder before hand control).
* General to specific: broad movements precede fine motor control (e.g., holding with both hands before picking up small objects).

Question 3

3. List and describe the stages of nervous system development. Indicate which are prenatal and postnatal.

Answer 3

Model Answer:
1. Neuralation – neural tube formation (prenatal)
2. Proliferation – multiplication of neurons and glia (prenatal)
3. Cell migration – cells move to final locations (prenatal)
4. Differentiation – cells become specialized neurons (prenatal)
5. Synaptogenesis – formation of synapses (starts prenatal, continues postnatally)
6. Synaptic pruning – elimination of unused synapses (postnatal)
7. Myelination – development of myelin sheaths to increase signal speed (mostly postnatal, continues into adolescence).

Question 4

4. Explain the Neuronal Group Selection Theory and its significance in motor development.

Answer 4

Model Answer:
This theory includes two stages:
* Primary variability: spontaneous motor activity generates sensory input, not yet adapted.
* Secondary (adaptive) variability: uses sensory feedback from experience to select the most efficient motor strategies.
This theory highlights that motor development is not just genetically programmed but shaped by experience and trial-and-error learning.

Question 5

5. What are neural coalitions and why are they important?

Answer 5

Model Answer:
Neural coalitions are groups of neurons that work together to efficiently perform commonly encountered motor tasks. They are formed through dendritic refinement, myelination, and synaptic rearrangement. These coalitions allow for the development of complex and efficient motor sequences.

Question 6

6. Describe how motor control and reaction time change across the lifespan.

Answer 6

Model Answer:
* Children: slow reaction time in early years, improves through adolescence, peaks around age 15.
* Adults: reaction time decreases (improves) through young adulthood.
* Older adults: reaction time increases (slows) due to neural degeneration and decreased myelination.
Choice reaction time also reveals improved cognitive processing with age until decline in later life.

Question 7

7. What are primitive reflexes? Provide examples and their developmental significance.

Answer 7

Model Answer:
Primitive reflexes are involuntary responses present in neonates (e.g., rooting reflex, sucking reflex, stepping reflex). They are inhibited as voluntary motor control develops. Persistence beyond 2–3 months may indicate neurological abnormality. They can re-emerge in adults due to frontal lobe damage (frontal release).

Question 8

8. How does postural control and base of support evolve with motor development?

Answer 8

Model Answer:
* Postural control: Begins with head/neck stabilization and progresses to trunk and limb control. Crucial for visual attention and reaching.
* Base of support: Initially wide for stability. Narrows with improved balance and coordination, indicating neuromuscular maturation.

Question 9

9. What are the neural changes in ageing that affect motor control?

Answer 9

Model Answer:
* Decreased brain weight and myelination
* Loss of motor neurons and muscle mass (especially fast-twitch fibers)
* Increased reaction time, reduced strength, poorer balance, and less fine control
These changes affect gait, posture, and ability to perform quick, powerful movements.