Transcript 6-Nervous_Endocrine_Muscle_fallers-2010

Muscle, Endocrine and Nervous
Systems
A bit on structure and function (but not
a lot!)
Effects of Ageing
Differences in fallers
Effects of Training
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Main Communication
Systems
• NERVOUS SYSTEM
– rapid communications (seconds)
– Nerve Fibres
• ENDOCRINE SYSTEM
– Slow transmissions (mins to hours)
– Hormones
• CO-ORDINATION
– Nerves stimulate and inhibit hormones
– Hormones can stimulate/inhibit nerve electrical
impulses
• ACTION – Muscles !
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Function of Nervous
System
Control
Activation
Integration
Modification
Sensory Input
Central Processing
Motor Output
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Nervous System Structure
•
Central
– Spinal Cord
– Brain
•
Peripheral
– Spinal (31) and cranial (12) nerves
• Myelinated (faster) and unmyelinated
– Somatic (voluntary)
– Autonomic (involuntary)
• Sympathetic (speeding up)
• Parasympathetic (slowing down)
•
Sensory nerves
– ‘Away’ from receptors TO CNS
•
Motor nerves
– ‘Exiting’ CNS TO produce response
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Bridging the gap between
nerve cells and other cells
Synapses - ‘the connectors’
Action Potential crosses synaptic cleft
via chemical neurotransmitter release
Acetylcholine, Noradrenaline,
Dopamine - ‘neurotransmitters’
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SIMPLE OR REPETITIVE
MOVEMENTS
Spinal reflexes - Reflex Arc
(brain still informed!)
COMPLEX MOVEMENTS
Brain-stem reflexes complex reflexes
Balance
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Cortex
Cerebellum
Basal Ganglia
Brainstem
Spinal Cord
Multi-linked Musculoskeletal
System
Multi-sensory
Information
Vestibular
Visual
Proprioceptive
Cutaneous
Environment
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Sensory Input  Stability
Three main sources of input
•
Visual information
•
Vestibular information
•
Proprioceptive information
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Functions of ENDOCRINE
SYSTEM
• Affects bodily activities by releasing hormones into
the bloodstream
–
target organ or system function (metabolism)
– regulates chemical composition and volume
– responds to emergency situations
• Coordinates activities with the nervous system
–
–
–
–
nerves stimulate / inhibit hormones
hormones stimulate/ inhibit nerve impulses
nervous control = seconds
hormones = minutes to hours
• Tightly regulated
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Endocrine System
• Central nervous control
– hypothalamus produces ‘releasing’/’inhibiting’ chemical secretions
• Endocrine glands
(eg. pituitary, thyroid, adrenals)
• Hormones  bloodstream  target organs
– Anabolic (
tissue growth)
– Catabolic (
tissue loss)
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Anabolic Hormones
• Growth Hormone
• maintenance of muscle and bone in adulthood
• decreased levels - loss of muscle and bone and increase in fat
• Insulin
• influences blood sugar levels
• allows storage of sugars in muscle and fat cells
• Type I Diabetes Mellitus - insulin replacement
– Short term - ‘hypos’, muscle fatigue, neural control
– Long term - peripheral nerve damage
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Anabolic Hormones
•
Thyroid Hormones
• affect metabolic rate
• too much - hypersensitivity, weight loss, eventual bone loss
• too little - lethargy, weight gain
•
Oestrogens and Androgens control
– our gender
– the growth of muscle and bone
– the maintenance of muscle and bone in later life
– ‘menopause’
•
Parathyroid hormone (covered in Bone lecture)
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CALCIUM REGULATING
ANABOLIC HORMONES
• Major controllers
– Parathyroid Hormone (PTH) and active form of Vitamin D
– control serum levels of calcium - excitability
– ‘retrieve’ calcium from bone and
absorption in kidney
• Vit D from diet and sunlight
– produced in kidney
–
absorption of calcium from gut
– mineralisation of bone
•
Vit D = PTH released
– Long term PTH release leads to bone loss
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Catabolic Hormones
• Cortisol (in excess)
– reduces inflammatory reactions
– increases blood glucose levels
– produced as a response to stress
– causes muscle and bone loss
– causes fat gain
– central effects - depression
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CALCIUM / VIT D INTAKE
• Essential for
– Muscle contraction
– Bone density
– Teeth and nails
• The course recommendations for participants
– Calcium 1000 mg/day, Vit D 20g/day
• See foods handout
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Muscular System
• Functions
– Motion
– Maintenance of posture
– Immune Function
– Heat production
• Types
– Skeletal - striated and voluntary
– Cardiac - striated and involuntary
– Smooth - non striated and involuntary
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– Muscle bundle
Structure
– Muscle Fibres
– Connective Tissue
– Sarcomeres
– Sarcoplasmic reticulum
(Calcium)
– Cross-bridges
– Protein filaments
• actin (thin)
• myosin (thick)
– Mitochondria
– Rich blood and nerve supply
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Type 1
Type 2
Slow
Fast
Non-fatiguable
Fatiguable
Oxidative
Non-oxidative
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Power
• Product of strength (Type 2 fibres) and
speed
• Functionally relevant
• Affected by temperature changes
• Asymmetry in lower limbs of fallers
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Sedentary behaviour
• Immobilisation reduces muscle mass, muscle
strength and power
(Appell 1990)
• Lower limb muscles and faster Type 2
muscles fibres are particularly vulnerable
(Broomfield 1997)
• 27 days of bed rest has lead to the loss of 0.9%
of bone mineral density per week
(Frost, 1990).
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active, strength-trained
The same size difference is
seen between 30 yr old and
80 yr old
70 yr old
females
sedentary
(Adapted from Sipilä & Suominen
Muscle Nerve 1993;16:294)
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Ageing, falling……what are the
effects ?
• Effects of ageing
• Differences in fallers
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Effects of Ageing on the
Nervous System
•  Neurones (somatosensory, vestibular and visual)
•  Spinal Cord Axons
•  Speed of transmission
•  Speed of central processing
• Changes in sensory input
–  Mass and strength in eye muscles,  Elasticity in lens,  Hydration of
the eye,  Eye Infections
–  Viscosity of fluid in inner ear,  medications that affect vestibular
system
–  number and efficiency of Proprioceptors,  medications that reduce
efficiency of proprioceptors,  oedema
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Functional Consequences of
an ageing nervous system
•
Poorer short term memory
•
Slower learning and performance
•
Poorer kinesthetic awareness
•
Poorer reaction / coordination integration
•
Poorer complex task performance
•
Difficulty comprehending floor patterns/textures
•
Simple movement tasks, repetition and rehearsal
•
Longer transition times
•
Effective verbal and visual cueing
•
Functional moves
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EFFECTS OF AGEING on the
ENDOCRINE SYSTEM
•
Hormones
– less well regulated
– Some glands produce less hormone
•
Target tissues and organs
– less responsive, poor circulation
•
↓ anabolic
hormone
production
System becomes more catabolic
–
Calcium intake reduced and sunlight exposure reduced
–
Cortisol release
–
Less anabolic hormone production
•
Metabolism and hormone diseases more prevalent
•
Side effects of medication (eg. Secondary osteoporosis)
↑ Cortisol
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FUNCTIONAL CONSEQUENCES of an
AGEING ENDOCRINE SYSTEM
•
Musculo-skeletal injuries
•
Fatigue
•
Dizziness / Fainting
•
Arrythmias
•
‘Hypos’
•
Dehydration
•
Longer warm up and warm-down
•
Fartlek training approach
•
Observation
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Effects of Ageing on MUSCLE
•
 No. & size of muscle fibres
– Preferentially type 2 fibres
•
 Muscle mass
•
 No. motor units &  size of remaining motor units (therefore loss
of fine control)
•
 Turnover of contractile proteins
•
 No. and size of mitochondria
•
 Proprioception in muscle and tendon
•
 Connective tissue and fat
•  heat production
•
 Susceptibility to injury and damage
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Functional Consequences of
Ageing of the Muscle System
•
Weaker muscles
•
Slower muscles
•
Fatigue
•
Poorer temperature maintenance
•
Poorer immune function
•
Poorer functional reserve
•
Target major functional muscle groups
•
Time for rest
•
Fartlek training approach
•
Effective warm-up, warm-down and stretches
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Differences in Fallers
NERVOUS SYSTEM / SENSORY INPUTS
•
•
Visual impairment a risk factor
–
–
–
–
Contrast sensitivity
Depth Perception
Visual Field
Visual acuity
Cognition a major risk factor
– Dementia
– Alzheimers
– Dehydration
Fallers have:
Worse balance
Larger sway
Worse gait
Difficulty in dual
tasking
•
Nervous System control of movement
•
•
Vestibular impairment = more falls
Peripheral neuropathy (eg. Lack of proprioceptive feedback) = more falls
– Parkinsons Disease
– Stroke
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Differences in Fallers
ENDOCRINE SYSTEM / DISEASE
• Those with metabolic / endocrine diseases are more
likely to fall
– Diabetes
– Hypothyroid
• Those with secondary bone loss due to endocrine disease
more likely to fracture if they do fall
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Differences in Fallers
MUSCULAR SYSTEM – STRENGTH
• Community dwelling frequent fallers have weaker ankle
dorsiflexion strength than non-fallers (Skelton 2002)
• Community dwelling fallers have reduced hip extensor
and adductor strength, they tend to weigh more and
have increased medio-lateral sway standing on foam
(Quinn 2003)
• Nursing home fallers are weaker in quadriceps and
hamstring strength than non-fallers (Whipple 1987)
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Differences in Fallers
MUSCULAR SYSTEM - POWER
• Explosive muscle power declines faster with increasing
age than isometric quadriceps strength
• Community dwelling frequent fallers are less powerful in
their lower limbs than non-fallers
(Skelton 2002)
– Fallers more asymmetrical in lower limb power than non fallers
– Average fallers power/kg is below the threshold level to step
confidently onto a 30cm step
– Power more predictive of risk of falls than strength
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But…the good news is…
• Training can help reduce the ravages of
age and sedentary behaviour…..
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Effects of Training on balance
and sensory inputs
•
Practice of specific functional movements and complex tasks =
–  dynamic balance
–  static balance
–  righting reflexes
–  proprioception
–  vestibular function
–  simple and complex reaction and movement times
–  visual function ?
–  body awareness
–  posture and gait
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Effects of Training on the
Endocrine System
• Improves
– circulation
– intake of nutrients (calcium, vitamins and proteins)
– cerebral function
• Releases growth hormone
– stimulates muscle and bone growth
•
Improves insulin sensitivity
•
Alters medication doses over time (insulin / thyroxine)
•
Decreased cortisol production in response to stress
– strength-training
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Effects of Training on Muscle
•
At any age
– Neural improvements in first 12 weeks then
muscle growth (Hypertrophy) so training has to
be of >12 weeks duration to improve muscle
size
–  strength (size of fibres, activation, increase in
protein turnover, speed of contraction,
relaxation time, agonist and antagonist coactivation etc)
–  power
–  posture and gait
–  blood supply
–  insulin sensitivity
0
3
6
9
12
15
Weeks
Muscle strength
Muscle size
–  neural control of movement
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• In over 75’s three months of strength
training rejuvenates up to 20 years
worth of lost strength. (Skelton, 1994)
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