Muscular System

1
Muscular System

• Muscle fibers (cells) grow during prenatal period
• Birth muscle mass is 25 of body weight
• Gender differences are minimal in children
• Males 54 of body weight, females 45 of body
  weight
• Type I slow twitch (endurance)
• Type II fast twitch (anaerobic)
• At birth 20 of muscle cells are undifferentiated
• Early activities may affect proportion but fixed
  by age 1

2
Motor Units

• All muscle fibers are attached to by a nerve
  (innervated) which is a motor unit
• Fast or slow twitch (depending on speed of
  contraction and relaxation)
• Older Adults
• Compared to young adults of muscle decreases
  (training can alter effects)
• Old age number and size of fibers decreases
• Muscle mass is influenced by genetic
  inheritance, insulin level, growth hormone level,
  nutrition, activity and training level

3
Cardiac Muscle

• The heart is made up of muscle tissue and goes
  through same growth process as the rest of the
  body
• Left ventricle starts off smaller but catches up
• Has same growth pattern as body

4
Adipose System

• Plays a vital role in energy storage, insulation,
  and protection
• Appears at 3.5 months and increases rapidly the
  final 2 months of pregnancy
• Fat mass increases until age 8
• Girls experience more dramatic increase during
  adolescence
• After 8, fat levels are generally maintained
• Adipose increases most in first 6 postnatal
  months and puberty
• Older Adults
• Both genders increase, body weight decreases
  after 50

5
Endocrine System

• Hormones play important role in regulating growth
  and maturation
• Interaction of hormones, genes, nutrients and
  environment
• Interact together in feedback loops and work
  together to regulate the levels of hormones in
  the body
• 3 types
• Pituitary growth hormone
• Thyroid hormones
• Two gonadal hormones

6
Hormones

• Excess or deficiency will alter process
• Stimulate protein anabolism
• Results in retention of substances needed to
  build tissue
• Growth hormone
• Important during childhood and adolescence
• Under control of CNS
• Secreted by anterior pituitary gland
• Enhances mobilization of stored fat and conserves
  carbohydrates

7

• Thyroid Hormones
• Thyroid gland is in anterior neck region
• Increases the oxygen consumption in the tissues
• Decreases circulating calcium, promotes calcium
  deposition in bones
• Gonadal Hormones
• Most active during adolescence
• Stimulate the development of secondary sex
  characteristics and sex organs
• Androgens hasten the fusion of the growth plates
• Increase muscle mass
• Women have more estrogens which speed up growth
  plate closure and increase fat accumulation
• Genders have both types but in very different
  quantities

8

• Insulin
• Indirect role in growth
• Produced in pancreas
• Vital to carbohydrate metabolism and necessary
  for full function of growth hormone
• Older Adults
• Regulation of cardiovascular performance
• Mobilization of fuel
• Synthesis of new protein
• Base levels of GH are stable
• Exercise causes larger increase in GH levels than
  in younger people
• Thyroid function decreases
• Decreased levels of gonadal hormones
• Dont utilize insulin as effectively

9
Nervous System

• Early development genetically determined
• Cell growth occurs early but cells mature
  postnatally
• Many nervous cells have tremendous plasticity
• Brain
• Develops rapidly
• Increase in myelin and glial cells
• Increase in size of neurons and arborization
• Connections established with other neurons in 1st
  yr
• Form synapses with each other increases firing
  which is crucial for brain development

10

• Lower brain centers
• Respiration, food intake, reflexes, reactions
• Automatic movements dominate fetus and newborn
  movements
• Onset of goal directed movement sign of higher
  brain function
• Most mature at birth
• Myelin
• Insulation around nerve cell
• Interrupted by nodes of Ranvier
• Impulse jumps from node to node
• Unmyelinated cells slower and fire less frequently

11
Spinal Cord

• Small and short at birth
• Myelinization 2-3 weeks after birth
• 2 motor pathways
• Extrapyramidal tract (reactions)
• Pyramidal tract (intentional)
• Older Adults
• Decreased number of neurons
• Decreased brain weight
• Decreased signal strength and number of neural
  connections

12
Factors Affecting Postnatal Dev.

• Important to recognize environmental influences
• May affect critical periods of learning
• Birth process
• Traumatic for fetus
• Umbilical cord important for oxygen
• Low birth weight is indicative of greater health
  risks
• If improve environment, catch up growth may occur

13
Postnatal Nutrition

• Body needs energy that food provides to grow and
  maintain body functions
• Important for maintenance and repair of tissues
  through life
• Proteins, carbohydrates, and fat are all
  important
• Proteins amino acids and building material for
  various tissues
• Carbohydrates chief source of fuel and energy
• Fats energy storage and insulation from heat
  loss
• Also contributing are water, vitamins, and
  minerals

14
Nutrition

• Malnutrition
• Decrease in stature and may not attain potential
  height, delay puberty
• Can decrease CNS function
• Occurs everywhere, not just underdeveloped
  nations
• May be caused by heavy physical training
• Overnutrition
• Due to too much sugar and fat and not enough
  activity
• Most prevalent in affluent areas
• Obesity increases growth and development but also
  cholesterol and tryglicerides

15
Physical Environment

• Climate
• Tall, and thin are more common in hot climates
• Short and stocky are more common in cold climates
• Seasons
• Greater weight gains in fall than spring
• Greater height gains in spring than fall
• May be due to nutrition and exercise patterns
• Altitude
• High altitude leads to smaller bodies and growth
  rates
• Other
• Radiation cell mutations, damage to NS
• Lead poisoning decreased neurological growth

16
Physical Activity and Training

• Everyone needs some minimum to support growth
• Must keep in mind level of training and emphasis
• Skeletal growth
• Physical activity doesnt affect length
• Evidence that it increases diameter and density
• Body weight
• Increases lean body mass and decreases fat weight
• Body physique and maturation
• Doesnt affect much

17
Capacity for Exercise

• Decreases with age
• Stronger skeletons, stronger muscles, increased
  endurance, flexibility, decreased fat weight,
  faster reaction times, increased brain function
• If excessive, may lead to injury