specialist psi exercise module muscle, endocrine and nervous systems a bit on structure and function...

Specialist PSI Exercise Module

Muscle, Endocrine and Nervous Systems

A bit on structure and function (but not a lot!)

Effects of AgeingDifferences in fallersEffects of Training


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 !


Function of Nervous System

ControlActivationIntegrationModification

Sensory Input

Central Processing

Motor Output


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


Synapses - ‘the connectors’

Action Potential crosses synaptic cleft via chemical neurotransmitter release

Acetylcholine, Noradrenaline, Dopamine - ‘neurotransmitters’

Bridging the gap between nerve cells and

other cells


SIMPLE OR REPETITIVE MOVEMENTS

Spinal reflexes - Reflex Arc

(brain still informed!)

COMPLEX MOVEMENTS

Brain-stem reflexes - complex reflexes

Balance


Cortex

Cerebellum Basal Ganglia

Brainstem

Spinal Cord

Multi-sensory Information

VestibularVisual

ProprioceptiveCutaneous

Multi-linked Musculoskeletal System

Environment


Sensory Input Stability

Three main sources of input

• Visual information

• Vestibular information

• Proprioceptive

information


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


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)


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


• 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)

Anabolic Hormones


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


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


CALCIUM / VIT D INTAKE

• Essential for

– Muscle contraction

– Bone density

– Teeth and nails

• The course recommendations for

participants

– Calcium 1000 mg/day, Vit D 20g/day

• See foods handout


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


– Muscle bundle

– Muscle Fibres

– Connective Tissue

– Sarcomeres

– Sarcoplasmic reticulum (Calcium)

– Cross-bridges

– Protein filaments

• actin (thin)

• myosin (thick)

– Mitochondria

– Rich blood and nerve supply

Structure


Type 1 Type 2

Slow Fast

Non-fatiguable Fatiguable

Oxidative Non-oxidative


Power

• Product of strength (Type 2 fibres) and speed

• Functionally relevant

• Affected by temperature changes

• Asymmetry in lower limbs of fallers


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).


active, strength-trained sedentary

(Adapted from Sipilä & SuominenMuscle Nerve 1993;16:294)

The same size difference is seen between 30 yr old and 80 yr old

70 yr old females


Ageing, falling……what are the effects ?

• Effects of ageing

• Differences in fallers


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

Effects of Ageing on the Nervous System


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


• Hormones – less well regulated

– Some glands produce less hormone

• Target tissues and organs

– less responsive, poor circulation

• 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)

EFFECTS OF AGEING on the ENDOCRINE SYSTEM

↑ Cortisol

↓ anabolic hormone production


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


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

Effects of Ageing on MUSCLE


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


Differences in FallersNERVOUS SYSTEM / SENSORY INPUTS

• Visual impairment a risk factor– Contrast sensitivity– Depth Perception– Visual Field– Visual acuity

• Cognition a major risk factor– Dementia– Alzheimers– Dehydration

• Nervous System control of movement– Parkinsons Disease– Stroke

• Vestibular impairment = more falls• Peripheral neuropathy (eg. Lack of proprioceptive feedback) =

more falls

Fallers have:

Worse balance

Larger sway

Worse gait

Difficulty in dual tasking


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



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)



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


But…the good news is…

• Training can help reduce the ravages of age and sedentary behaviour…..


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


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


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 co-

activation etc)

power

posture and gait

blood supply

insulin sensitivity

neural control of movement

0 3 6 9 12 15

Weeks

Muscle strength Muscle size


• In over 75’s three months of strength training rejuvenates up to 20 years worth of lost strength. (Skelton, 1994)

specialist psi exercise module muscle, endocrine and nervous systems a bit on structure and function...

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