MODULE 12: Motor Development

role of the nervous system in movement

the nervous system..

• allows cognitive processing (planning, decision-making)

• transmits sensory signals (what the body feels)

• sends motor signals to activate muscles

role of the musculoskeletal system in movement

the musculoskeletal system..

• generates the force needed for movement

• maintains posture + stability

• allows body parts to move through joints/muscles

how do these systems develop

movement abilities improve as the brain matures and as muscle grow

• meaning motor skills develop in parallel with nervous system development

how do the systems contribute to movement

their interaction determines HOW and WHY the body moves effectively

why is motor development considered a lifelong process

because motor skills change across the entire lifespan..

• improve in childhood

• stabilize in adulthood

• and may regress in older age

why is motor development considered “multidimensional”

because developments involves several interacting areas

• biological development - changes in physical characteristics (physical growth, body changes)

  • ex. brain maturation improves coordination

• cognitive development - changes in information processing + knowledge

  • ex. understanding rules helps someone play a sport correctly

• socio-emotional development - changes in relationships, emotions + personality

  • ex. a confident child tries new movements, encouragement improves practice

why is motor development considered “multi-directional”

because development includes both gains and losses

• improvement in early life and possible regression later in life

why is motor development considered interconnected across dimesions

because biological, cognitive, socio-emotional and environmental factors constantly influence each other

• ex. genes → influence the person → influence society → which then shapes the person again

• ex. better brain → understand game better → more confidence → joins a team → regular practice strengthens muscles/neural pathways

how does the brain develop in early life

• it forms ~250,000 neurons per minute (before birth)

  • the connections (synapses) is what changes

• reach peak synaptic density at age 2

how do the changes during brain development occur

1. synaptic proliferation - building more neural connections

2. synaptic pruning - removing unused connections

   1. which makes the brain faster + more efficient

what influences brain development

it is heavily influenced by genes + environment

• ex. experience, learning, stimulation

• it continues through adolescence → early adulthood

when does prenatal movement begin

1. 7-8 weeks - gross whole-body movement

2. 10-11 weeks - limb movement starts

3. 14-18 weeks - mothers feels the first “kicks”

what happens to fetal movement after 28 weeks

the fetus can respond to stimuli (specifically pressure, sound)

• therefore movement patterns become an important indicator of fetal health

characteristics of motor development during infancy

movement is mostly reflexive, involuntary, and triggered by specific stimuli

• which means reflexes occur through simple pathway

  • sensory (afferent) → CNS → effector

  • if any part is missing = reflex doesn’t occur

• they develop without thinking

what are reflexes in inflancy

involuntary, stereotypes movements

• which depend on specific neural networks

• only occurs if this pathway is intact

why do reflexes appear and disappear

1. appearance - all required neural components are functioning

2. disappearance

   1. the networks are inhibited (as voluntary movement develops)

   2. the reflex becomes unnecessary and is replaced by voluntary control

3. reappearance

   1. only happens if inhibitory signal fails (common in certain neuroological disorders)

importance of reflexes

1. survival of the individual

   1. feeding + protections

   2. preparation for future (voluntary) behaviours

      1. as it enhances neural connections

      2. builds muscular strength

2. diagnostic tool - abnormal expression can indicate a presence + cause of neurological disorders

what is the moro (startle) reflex

ex. pretending to drop a baby

1. stimulus: sudden loud noise or movement

2. response: back/head/arms extend then arms/legs quickly flex

3. purpose: it helps infant cling to caregiver

4. disappears: 3-4 months

what is the rooting reflex

1. stimulus: stroke cheek or corner of mouth

2. response: infant turns head toward the touch

3. purpose: it helps locate nipple for feeding

4. disappears: 3-4 months

what is the sucking reflex

1. stimulus: object placed in mouth

2. response: infant sucks

3. purpose: feeding (it works w/ rooting reflex)

4. disappears: 3-4 months

what is the grasping reflex

1. stimulus: object touches infant’s palm

2. response: strong grip

3. purpose:

   1. it prepares for voluntary grasping

   2. it increases strength + coordination

4. disappears: 3-4 months (it is replaced by voluntary grasp)

what is the (asymmetrical) tonic neck reflex

1. stimulus: infant’s head is turned to one side

2. response: arm extends (ipsilateral), arm flexes (contralateral)

3. purpose:

   1. it prepares for reaching + crawling

   2. helps w/ strength + coordination

4. disappears: 2-4 months

what is the babinski reflex

1. stimulus: stroke sole of the foot

2. response: toes fan/extend (opposite happens in adults)

3. purpose: it may be a evolutionary remnant from quadrupedal walking

4. disappears: 9-12 months

what is the stepping reflex

1. stimulus: infant held upright w/ feet touching a surface

2. response: to create a rough stepping pattern

3. purpose:

   1. preparation for walking

   2. it activates the neural circuitry (for walking)

4. disappears: 2 months (because the legs become too heavy)

major developments that occur from infancy → toddler

from ages 0-2 years, there’s a rapid increase in..

• musculoskeletal development - strength & endurance

• neural development

  • sensory systems

  • learning

    • observational (imitation)

    • associative (conditioning)

    • understanding action-effect relationship - where movement changes the environment

• multidimensional development - where cognitive and motor grow in parallel to one another

motor development trends

1. cephalocaudal trend

2. proximodistal trend

what is the cephalocaudal trend

where motor development progresses from HEAD → DOWNWARD

• order: head/neck → arms/trunk → legs

• ex. babies gain neck control during tummy time before they can sit or walk

what is the proximodistal trend

where motor development progresses from the CENTRE → OUTWARD

• order: neck → trunk → arms → hands → fingers

• ex. a child can move their whole arm before they can hold a pencil properly

what are the major gross milestones (0-6 months)

to explore the environment, the child must be able to..

1. 6 months - holds head steady when upright

2. 2 months - lift head on stomach; roll side → back

3. 4 months - roll back → side

4. 6 months - arm only crawl

what are the major gross milestones (7-12 months)

to explore the environment, the child must be able to..

1. 7 months - full crawl; sit unassisted

2. 8 months - pulls to stand

3. 11 months - stand unassisted

4. 12 months - walk unassisted

what are the major gross milestones (12-24 months)

to explore the environment, the child must be able to..

1. 16 months - walk up stairs w/ help

2. 23 months - jump in place

what are the major fine motor milestones

1. 7 weeks - poorly coordinated pre-reaching

2. 3 months - reaches for objects

3. 4 months - ulnar grasp (no thumbs)

4. 4-5 months - transfers objects hand ↔ hand

5. 9 months - pincer grip (thumb + finger)

motor development in childhood

• further milestones achieved (~7-8 years)

• learning of novel fine/gross motor skills

  • tool use

  • increasing cognitive complexity

motor development in young adulthood

from 18-30 years..

• peak performance

• improved accuracy

• improved RT and movement times (bc strong, efficient motor control)

what happens to the nervous system in middle adulthood

from ~30-65 years - sensorimotor controls begins to slow

• nervous system

  • decrease in resolution/sensitivity

  • processing begins to slow

    • reduced neuronal activity

    • loss of myelin (slower transmission)

what happens to the musculoskeletal system in middle adulthood

from ~30-65 years - sensorimotor controls begins to slow

• musculoskeletal system

  • sarcopenia - loss in muscle fibre size + #

    • which causes lower endurance + strength

what happens to the nervous system in older adulthood

• a decrease in neural connections

• slowing of neural transmission

  • more variable force generation

  • less accurate + efficient processing

  • slower movements used to compensate

  • possible reappearance of inhibited reflexes (ex. babinski)

what happens to the musculoskeletal system in older adulthood

• strength + endurance continue to decrease

• movements may be reduced or become less effective

stages of older adulthood

1. youngest-old (65-74) - neural + sensory changes; sarcopenia

2. middle-old (75-85) - decline accelerates

3. oldest-old (85+) - most rapid decline

what does neural + muscular decline lead to

leads to..

• reduced mobility

• reduced balance

• increased risk of falls and fractures