EDKP 261

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EDKP 261
2012-10-09 17:27:37
Motor Development

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  1. Characteristics of Motor Development?
    • •Involves change in movement behaviorSometime changes are obvious some other they are less…
    • •Is sequential, age-related, continuous no stops
    • •Depends on underlying processes
  2. Motor learning
    relatively permanent gains in motor skill capability associated with practice or experience
  3. Motor Control
    the neural, physical, and behavioral aspects of movement
  4. Physical growth
    quantitative increase in size or body mass
  5. Physical maturation
    qualitative advance in biological makeup; cell, organ, or system advancement in biochemical composition
  6. Aging
    process occurring with passage of time, leading to loss of adaptability or full function and eventually to death
  7. Constraints
    • Limit or discourage certain movements
    • Permit or encourage other movements
    • “Shape” movement
  8. Types of Constraints
    • Individual: Functional and Structural 
    • Task Constraint 
    • Environmental
  9. Individual Constraints
    • •Inside the body (internal)
    • Structural constraints: related to the body’s structure–Height–Muscle mass etc…
    • Functional constraints: related to behavioral function–Attention–Motivation
  10. Environmental Constraints
    • •Outside the body: properties of the world around us
    • •Global, not task specific
    • Physical–Gravity–Surfaces
    • Sociocultural–Gender roles–Cultural norms
    • •External to the body
  11. Task Constraints
    • •Related specifically to tasks or skills
    • –Goal of task
    • –Rules guiding task performance
    • –Equipment
  12. Longitudinal
    • –An individual or group is observed over time.
    • –Study can require lengthy observation.
  13. Cross-sectional
    • –Individuals or groups of different ages are observed
    • –Change is inferred, not actually observed.
  14. Sequential or mixed longitudinal:
    mini-longitudinal studies with overlapping ages
  15. Precursor Period
    • Description of the movement: kids are smaller adults
    • “baby biographies”
    • “The mind of the child” (Preyer, 1909a, 1909b)
    • “A biographical sketch of an infant” (Darwin, 1877)

    No theories per se. Longitudinal studies only
  16. Maturational perspective (1928-1946)
    • Motor development driven by maturation of systems (neural system important)
    • –Genetics and biological time clocks are the major determinant of motor development

    •Minimal influence of environment

    • –Qualitative
    • –Discontinuous
    • •neuro-maturational
  17. History of the Maturational Perspective
    • •1930s: Gesell A, McGraw
    • •Suggested invariable, genetically determined sequence of development (individuals can have unique timing)
    • •Research: Co-twin control strategy
    • •McGraw (1935) associated motor behavior changes with development of nervous system.
    • •Posited that advancement in central nervous system triggers appearance of a new skill.
  18. Ecological Perspective
    • •Both branches reject CNS as executive controller of nearly limitless opportunities for movement.
    • •Control is distributed throughout the body, at both global and local levels.
    • •This challenging perspective allows for new types of experiments and new ways of thinking about old questions
  19. Universality
    Individuals in a species show great similarity in development.
  20. Variability
    Individual differences exist
  21. Descriptive Methodology in Motor Development
    •Use of quantitative scores to describe children’s average performance (Espenschade (1947), Glassow (1938), Rarick (1967))

    •Biomechanical descriptions of movement patterns in fundamental skills (Glassow (1938), Halverson (1973))
  22. Problematic Long-Lasting Beliefs From Maturation Theory
    • •Basic motor skills emerge automatically. Ex nihilo.
    • •There is no need for special training.
    • •Mild deprivation does not arrest development.
    • •The nervous system is most important.
  23. Information Processing
    •Also Bandura’s social learning (1986), Skinner’s behaviorism (1974)

    • •Basic tenet: brain like a complex computer
    • –The passive human responds to stimuli in the environment.
    • –Research investigates stimulus–response links, feedback, and knowledge of results (Schmidt).
    • •Young adults often studied first as basis of comparison for performance of children and older adults
    • Focus on the product of motor development rather than the underlying processes
    • •Study at one period of time rather than across time cross-sectional research study
  24. Perceptual-Motor Development
    • •Subfield exists within the framework of information processing.
    • •Early work (1960s) tried to link learning disabilities to delayed perceptual-motor development.
  25. A new period? Developmental Motor Neuroscience period
    • •This period was recently proposed as a post-dynamics systems period
    • •Two complementary and parallel trends occurring:
    • neuro-functional assessment
    • proposing models
  26. Ecological Perspective
    • •Development driven by interrelationship of individual, environment,and task (importance of multiple systems)
    • •Neural system one of many responsible for action
    • •Two branches1. Dynamic systems2. Perception–action
  27. Dynamic Systems
    • •Theory was advocated in early 1980s by Kugler, Kelso, and Turvey (among others). Following Bernstein’ theory in physiology
    • •Body systems spontaneously self-organize (not driven solely by CNS). And body structure guide toward movements (constraint to walk for Human)
    • •Body systems, performer’s environment, and task demands interact.
    • •Some systems may develop more slowly in the young or degrade faster in the old and thus control rate of development or change.
    • •Development is characterized by qualitative and discontinuous change.
    • •Change occurs across the life span.
  28. Dynamic Systems (continued)
    •Body does not develop at the same rate so each systems have rate limiter or controller that affect the movement.•Rate limiters are individual constraints that discourage motor skill until the system reach a critical level that allow the acquisition of the skill.
  29. Perception–Action
    • •Theory is based on the work of J.J. Gibson (1960s and 1970s)
    • .•Affordance is the function an environmental object provides to an individual.
    • –Characteristics define objects’ meanings.
    • –Object functions are based on individuals’ intrinsic dimensions (i.e., are body scaled) rather than object’s extrinsic, objective dimensions.
    • •Visual motion perception (Gibson JJ) helps to predict movement
    • •Body scaling: Example facing stairs
    • –A crawling infant: What the F… are the huge things
    • –Toddler: one step
    • –Adult; alternate step
    • –Arthritic elder: alternate footstep difficult so one step at a time
  30. Growth and Aging Change Individual Constraints
    • •Genetic and extrinsic factors combine to influence growth and aging.
    • •We observe patterns in growth and aging
    • .–Universality: patterns that hold for all humans
    • –Specificity: individual variation
    • •Educators and therapists can make tasks developmentally appropriate.
  31. Prenatal Development
    • •Early development is controlled by genes.
    • –Normal development
    • –Inherited abnormal development
    • •The embryo or fetus is sensitive to extrinsic factors.
    • –Positive effects
    • –Negative effects
  32. Embryonic Development
    • •Conception to 8 weeks
    • •Differentiation of cells to form specific tissues and organs
    • •Limbs formed at 4 weeks
    • •Human form noticeable at 8 weeks
  33. Fetal Development
    • •8 weeks to birth
    • •Continued growth by hyperplasia (cell number) and hypertrophy (cell size)
    • •Cephalocaudal (head to toe) and proximodistal (near to far)
    • •Plasticity (capability of taking on a new function)
  34. Fetal Nourishment structure
    • •The placenta: an interface between mother and fetus
    • •Multiple villi: increase of the surface of exchange
  35. Fetal Nourishment what goes through
    • •Oxygen and nutrients diffuse between fetal and maternal blood in placenta.
    • • Poor maternal health status can affect fetus as the fetus may receive toxic or teratogenic substances.
  36. Abnormal Prenatal Development
    • •Source of abnormal development can be genetic or extrinsic.
    • •Congenital defects (present at birth) can derive from genetic or extrinsic source.
  37. Genetic Causes of Abnormal Development
    • •Can be dominant disorders (defective gene from one parent) or recessive disorders (defective gene from each parent)
    • .•Can result from mutation of a gene.
    • •Effects on growth and maturation are variable.
  38. Extrinsic Causes of Abnormal Development
    • •Extrinsic factors can affect fetus through nourishment or physical environment.
    • •Teratogens delivered through nourishment system act as malformation-producing agents.
    • •Some teratogenic effects result from too much of a substance, some from too little.
    • •Placenta screens some substances (e.g., large viruses) but not all harmful ones.
    • •Harmful environmental factors include pressure, temperature, X and gamma rays, oxygen-deficient atmospheres, pollutants.
    • •Tissues undergoing rapid development at time of exposure are most vulnerable
  39. Extrinsic causes of abnormal development
    • •Age
    • –Frequency of Down syndrome if mother age more than 40
    • •Exercise
    • – Regular, moderate exercise is related toincreased birth weight.
    • – Frequent, vigorous exercise predicts lower birth weight. Drains resources away from baby
    • •Stress
    • –In humans, extreme maternal stress may be related to lower birth weight and children with emotional problems and behavioral disorders.
  40. Teratogens
    • • Teratogens are any agents from the environment that can cause harm to the developing fetus.
    • • Many harmful agents cause damage only if exposure occurs during a sensitive period of prenatal development.
    • • Critical factors that influence the degree of harm a teratogen will cause:
    • – The amount and length of exposure
    • – Individual differences in susceptibility
  41. Postnatal Development
    • •Overall growth follows sigmoid (S-shaped) pattern.
    • •Timing of spurts and steady periods can vary between individuals.
    • •Timing differs between the sexes.
  42. Height
    Follows sigmoid pattern.
  43. Velocity Curves for Height
    • • Long growth period of males contributes to absolute height differences.
    • Girls start 2year before their growth spurt
    • Girls
    • –Peak height velocity occurs at 11.5 to 12 years.
    • –Growth in height tapers off around 14, ends around 16.
    • Boys
    • –Peak height velocity occurs at 13.5 to 14 years.
    • –Growth in height tapers off around 17, ends around 18.
  44. Individual Variation
    • •Average ages for peak height velocity and tapering of growth are based on groups.
    • •Individuals can differ from the averages.
    • •In what ways can individuals vary from the average pattern?
  45. Weight
    • Follows sigmoid pattern
    • •Is susceptible to extrinsic factors, especially diet and exercise.variability

    Individuals grow up, then fill out: Peak weight velocity follows peak height velocity (by 2.5–5 months in boys, 3.5–10.5 in girls).
  46. Relative Growth
    Body as a whole follows sigmoid pattern; specific parts, tissues, and organs have different growth rates.

    •Body proportions change from head-heavy, short-legged form at birth to adult proportions.

    •In adolescence, boys increase in shoulder breadth.
  47. Physiological Maturation
    • •As children and youth become older, they grow in size and mature.
    • •Children vary in maturation rate. An early maturation will stop the growth.
    • •It is difficult to infer maturity from age alone, size alone, or age and size together.
  48. Secondary sex characteristic as an indicator of maturation..women
    • Maturational changes in women:
    • Key stages:
    • Breast
    • B2: beginning of breast development
    • B5: adult formPubic development
    • P3:intermediate pubic hair development
    • P5 : adult formMenarche: first menstrual cycle
    • •Decrease in velocity as body matures
  49. Secondary sex characteristic as an indicator of maturation
    • • Maturational changes in men: not that easy
    • • Key stages are more difficult to identify:
    • 1) Growth of testes and scrotum
    • 2) Pubic hair appears
    • • No clear landmark: the production of sperm is a gradual process and constant through life although quality of sperm may decline.
  50. Secondary Sex Characteristics
    • •Characteristics appear as a function of maturation.
    • •They appear at a younger age in early maturers.
    • •Have you seen variations among a group of preteens in appearance of secondary sex characteristics? Which ones?
  51. Implications of Maturation Rate
    How should we counsel parents of an early maturer and star athlete about the child’s future in athletics?

    Should parents expect the same performance form their early maturer kid later in age?
  52. Extrinsic Influences on Postnatal Growth
    • •Individuals are especially sensitive during periods of rapid growth.
    • • Catch-up growth demonstrates extrinsic influences on kids with chronic renal failure.
    • •Recovery depends of
    • •Timing
    • •Duration.
    • •Severity of the environmental condition
    • •What extrinsic factors are most likely to affect growth during infancy?
    • •During the adolescent growth spurt?
  53. Adulthood and Aging
    • •Height is stable in adulthood but may decrease in older adulthood.
    • –Compression of cartilage pads
    • –Osteoporosis
    • •Average adult starts gaining weight in the 20s.
    • –Diet and exercise
    • –Loss of muscle mass
    • –Aging of body’s systemsProduction of hormoneschanges
  54. Growth, Maturation, and Aging: Summary
    • •Prenatal development is influenced by genetic and extrinsic factors.
    • •Most extrinsic factors are influential through the nourishment system.
    • •Growth abnormalities can be caused by genes, environment, or both
    • •Whole-body growth follows sigmoid pattern (with timing differences between the sexes and between individuals).
    • •With advancing age, extrinsic factors contribute more to individual variability.
  55. Assessment of Prenatal Growth
    • •Invasive prenatal assessments
    • –Amniocentesis–Chorionic villus sampling
    • •Noninvasive prenatal assessments
    • –Ultrasound (most common)
    • –3-D images (using new imaging software)
  56. Assessment of Extent and Rate of Postnatal Growth
    • •Distance curves show extent of growth.
    • •Velocity curves show rate of growth.
    • •Peaks on velocity curves show ages at which rate of growth changes from faster to slower.
  57. The concept of Body Systems
    • •Body systems are influenced by extrinsic factors
    • •It is important to know
    • –the average pattern of change within each system
    • –the range of individual variations for a system
  58. Rate-Limiting Constraints
    • •A system that lags in development can be a developmental rate limiter.
    • •Development lag in patients with muscular dystrophies caused by genetics mutations. Affects muscle strength.
  59. Skeletal System
    • •The embryo has a cartilage model of the skeleton
    • • Ossification begins at primary centers in the mid-portions of long bones.
    • •Growth in bone length occurs at secondary centers at the ends of bones.
    • • These centers are called epiphyseal plates, growth plates, or pressure epiphyses.
    • •Increase in bone girth is called appositional growth.
    • • Traction epiphyses are where muscle tendons attach to bones. Traction shapes bones: ex of clavicle
  60. Cessation of Bone Growth
    • •Growth at the epiphyseal plates stops at different times for different bones.
    • •All typically close by age 18 or 19.
    • •Closure occurs at a younger age in girls. What does this reflect about the connection between skeletal growth and maturation?
  61. Skeletal System in Adults
    • •Bone undergoes remodeling throughout the life span.
    • •Constant need of calcium and VitD
    • •Old bone is absorbed, new bone formed.
    • In adulthood, bone growth slows, fails to keep pace with re-absorption.
    • •Bone becomes more brittle. High content in minerals and less in organic material (cells)
  62. Skeletal Structure in Adulthood
    • •Structure itself changes little unless one has osteoporosis.
    • •Osteoporosis leads to rib cage collapse, stooped posture, and reduced height. Detected by bone density.
    • •Extent of bone loss is influenced by hormone levels, diet, and exercise.
  63. Factors inducing osteoporosis
    • •Hormone levels: menopauses and andropause (Drop of Oestrogenes and testosterone)
    • •Bed confinement/ medical conditions
    • •Medication
    • •Alcohol and smoke
  64. Development of the muscular system
    • •Prenatal growth involves hyperplasia and hypertrophy.
    • •Postnatal growth mainly involves hypertrophy.
  65. Muscle development
    • •Muscle growth follows sigmoid pattern.
    • •At Birth 25% of body weight
    • •Muscles increase in diameter and length by addition of sarcomeres.
    • Differences between the sexes become marked in adolescence (especially in upper body musculature)
    • •Effect of testosterone: Testosterone affects muscle growth. Binding to receptors that results in protein synthesis.You need constant production in order to maintain muscle mass
    • dependence
  66. Muscle Fiber Type
    • •Adult muscle is composed of type I (endurance), type IIa, and type IIb fibers (strength).
    • •At birth, 15 to 20% of fibers are undifferentiated.
    • •By age 1, distribution of muscle fiber type is similar to adult distributions.
    • •Exact proportions vary between individuals
  67. Muscular System in Adults
    • •Loss of muscle mass is minimal until age 50.
    • •By 80, average 30% of muscle mass is lost.
    • •Loss occurs in number and size of muscle fibers (the latter usually after age 70).
    • •Whether type II fibers undergo greater loss is unclear.
  68. Cardiac Muscle
    • •Heart and blood vessel size is appropriate for body size in childhood and adolescence.
    • •In old age, heart can lose elasticity and valves can become more fibrotic (depending partly on lifestyle).
  69. Adipose System
    • •Some fat is needed for energy storage, insulation, and protection.
    • •Brown fat deposits of brown fat, between the shoulder blades, around the nape of sternum. Mitochondria rich. 55% of body mass
    • •White fat: storage
    • •Fat increases rapidly until age 6 months, then gradually until age 8 years.
    • •In adolescence, girls increase fat more dramatically than boys do.
    • •Growth is by hyperplasia and hypertrophy (the latter more dramatic in adolescence).
    • •Individual variability is great
  70. Fat Distribution
    • •Body fat distribution changes with growth.
    • •Children have more internal than subcutaneous fat.
    • •Subcutaneous fat increases from age 6 or 7 years until age 12 or 13 in boys and girls.
    • •Subcutaneous fat then continues to increase in girls.
    • •Body fat distribution changes with growth.
    • •Fat distribution has an impact on movement
  71. Adipose Tissue in Older Adults
    • •Both men and women tend to gain fat during adulthood, but this is not inevitable
    • •Increases in trunk fat are notable, but subcutaneous fat on limbs tends to decrease.
  72. Endocrine System
    • •Plays role in regulating growth and maturation through chemical substances called hormones.
    • •Excess or deficiency can alter growth.
    • •Major hormones involved in growth include
    • –pituitary growth hormone,
    • –thyroid hormones, and
    • –two gonadal hormones

    • •These hormones stimulate protein anabolism (tissue building).
    • •Endocrine–neurological feedback loops regulate hormone levels.
    • •Each hormone may have a critical role in development at specific phases in life span.
    • •Insulin plays indirect role, is vital for carbohydrate metabolism.
  73. Growth Hormone
    • •Growth hormone is secreted by anterior pituitary gland. Under the control of somatotrophic hormones
    • •Peptide
    • •It is necessary for normal growth.
    • •Action:
    • –Direct effects: growth hormone binds to its receptor on target cells. Adipocytes`: break down triglyceride
    • –Role in anabolism: stimulation of Fat, Protein and carbohydrate metabolism–Indirect: action on the Liver which is induces the release
    • • Insulin-like-growth factor1:
    • Stimulates the proliferation of chondrocytes
    • Stimulates the proliferation of myoblasts
  74. Growth Hormone
    • •Deficiency can result in growth abnormality.
    • –Giangantism
    • •Modulation of GH release by exercise, sleep, stress, nutrition
    • •But mainly secreted under the control of:
    • •hypothalamic hormones
    • •hormone from the stomach
  75. Thyroid Hormones
    • •These are secreted by thyroid gland.
    • •Triiodothyronine (T3) and thyroxine (T4)
    • •Synthesis stimulated by TSH produced by the axis pituitary gland and hypothalamus
    • •They influence whole-body growth.
    • •One plays a role in skeletal growth.
    • •Need T3 in order to develop brain structures
    • •Need of T3 from the mother during prenatal development (production starts at 20weeks)
  76. Thyroid Hormones
    • •Thyroid Hormones play a role in neuromediator efficiency. Potentiate the effect of serotonin and acetylcholine
    • •Goitre
    • •PathologyHashimoto's Thyroiditis (hypothyroidism
    • :Fine Motor Movement Problems - Coordination of arms, hands, fingers.
    • Tremors
    • depression
  77. Goiter 
    Hypo or hyperthyroidism
  78. Hashimoto's Thyroiditis(hypothyroidism):
    • Fine Motor Movement Problems - Coordination of arms, hands, fingers.
    • Tremors
    • depression
  79. Gonadal Hormones
    • •Influence on growth, sexual maturation (sex organs, secondary sex characteristics)
    • •Androgens
    • –Secreted by testes (boys), adrenal glands (boys, girls).
    • –Hasten epiphyseal growth plate closure.
    • –Promote growth of muscle mass.
    • •Estrogen
    • –Secreted by ovaries (girls), adrenal cortex (girls, boys).
    • –Hastens epiphyseal growth plate closure.
    • –Promotes accumulation of fat.
  80. Endocrine System in Older Adults
    • •Imbalances may develop between nervous, endocrine, and immune systems.
    • •Thyroid disorders are more prevalent.
    • •Decreasing gonadal hormone levels are associated with loss of bone and muscle tissue.
  81. Nervous System
    Genes direct its development. 84% of all genes are expressed somewhere in the human brain

    •Extrinsic factors exert influence, especially in the formation of synaptic connections. Variability and extrinsic factor can influence.

    The nervous system...especially post natal is driven by genesYou have a good basis then you need to model it
  82. Prenatal Neural Development
    • Process generally includes neuron formation, differentiation into general type, and migration.
    • Other cell types (glia) are of importance:
    • oAtrocytes
    • oOligodendrocyte
    • oMicroglia
    • oSchwann cells
  83. Different shaded cells have different morphology they are also polorizedThey have big nuclei and have paraya...axon-specialized to conduct imputs(proecess info)synaps connect to muscles or other things..myelin is an important fat...insulates axon and for sytatolic action
  84. glia1)provide nutrients2)3)defend nervous cells4)insulate the axon...we have two systems, one is central and peripheral made of schwann cells
  85. Prenatal Neural Development
    • •Once in place, neurons develop an axon to carry signals to neurons, glands, organs, muscles.
    • •Teratogens might disturb normal migration and branching. Broad spectrum of foetal alcohol syndrome–Ex: Alcohol and migration of Purkinje cells in cerebellum
  86. First carry axonthen extand the axon to get the info..the fatal alcohol syndrom is desterbance of the neuron.. so the system does not work properly b/c the axons dont migrate properly
  87. Early Neural Development
    • •Late in prenatal period, neurons start to fire electrical impulses (first at random, then forming circuits).
    • •Experience might play role in synaptic proliferation (strengthening some connections, weakening others).
    • •Neural network becomes more efficient with experience.
  88. The neurons connects to make a synaptsAt first it seems like the neurons want to connect to everything..so you start to get rid of the synaps you create.Synergenic energy happends to the elimination of synaps
  89. Give impulse to make sure they are ready to fire.. they start to for a circultry to make sure they can walk
  90. At first you have less cells mainly neural cellsthen after the neural cell are made thats when u start makeing glia cells to support the nourishments
  91. Postnatal Neurological Growth
    • •Brain growth increases rapidly after birth
    • •Growth involves these factors:
    • –Increases in size of neurons
    • –Prolific branching to form synapses
    • –Increases in glial cells for support and nourishment of neurons
    • –Increases in myelin to insulate axons
    • Stimulation of learning increases number of synaptic connections.
    • •The majority of brain synapses or connections form by age 3, and 85% of a child’s brain development is completed by age 5
  92. Waves of development
    • •Development of synapse correlated with hormones.
    • When increasing the size of the cells in the brain it increases the amount of synapse
    • overproduction of dopimine
  93. Motor Neuron Structure
    • The alpha motor neuron: Motor neuron connecting to muscle
    • Found in spinal cord and that what innervates are muscle.connects nervous system and muscle
  94. Brain Structures
    • Brain structures involved in Motor control.
    • Brain stem is important for all the autonomic systems
    • Frontal system develops very late, it is the one that does all the movement planning..control the motor system 
  95. Motor pathways
    • •Hierarchy
    • •Cortico-spinal: direct
    • •Extrapyramidal: Indirect pass through filters (cerebellum, basal ganglia…)
  96. If you have a problem in your cerebellum you have problem its the fine tuning.. like if a patient wants to touch hi nose he will have trouble fine tuning the placement 
  97. Brain Structures
    • •Spinal cord and lower brain centers are relatively advanced at birth.
    • •Their function is correlated with survival reflexes ( primitive period of Clark)
    • mylenated axons..mylein is kind of fat thats why its white
    • Cerebral cortex gradually becomes more functional after birth.
    • •Development of brain cortex: The pattern of human evolutionary expansion is remarkably similar to the pattern of human postnatal expansion
    • •Myelination of axons allows faster conduction of neural impulses.
    • •Direction of myelination tends to follow direction of conduction
  98. Neonads
  99. mportant for the motor development of movement If you stike the mylenation..can cause damage*the direction of mylenation goes in same direction as conductions..You will promote schwann cell mylenation... some type of exercise promotes mylenation
  100. Nervous System in Older Adults
    • •Aging involves loss of neurons, dendrites, synapses, neurotransmitters, and myelin.
    • •One theory of aging suggests that breaks in neural network links cause detours and therefore slowing.
    • •Exercise promotes improved cognitive function.
  101. You also have many intermidiates to get to it.. which makes things much slower
  102. You can release neural transmitter but the receptor might be the problemmulitplescoloris; often see motor developement One of the theories is that you can use you synaps nand neurons...the plastity of your system will help you innervated you..because you need to stimulate it and have the "muscle memory" i guess..
  103. sensory neuronit has lots of receptors especially in the joint...proprioceptionIt fine tunes movement
  104. Development and Aging of Body Systems: Summary
    • •Systems interact as they develop and age.
    • •During periods of rapid change, a system might be more sensitive to extrinsic factors
    • •Extrinsic factors play a greater role (genetic factors lesser role) as one moves through life.
    • •Model of constraints shows that a system can act as rate limiter (during growth) or as accelerator (of aging).
  105. As you age you are more susceptible to extrinsic factors...at the beginning its more genetics