Neuromuscular System

NEUROMUSCULAR SYSTEM

MUSCULAR SYSTEM

Anterior Posterior

Smooth Muscle

Cardiac Muscle

MUSCULAR SYSTEM

Skeletal Muscle

Smooth Muscle

Found in the digestive, circulatory, urinary and reproductive systems

Controlled by the autonomic nervous system

Smooth in appearance

Involuntary controlled

MUSCULAR SYSTEM

MUSCULAR SYSTEM

Cardiac Muscle

Found in the heart

Contraction of the heart is controlled by the sinoatrial node (SAN)

Striated (striped) in appearance

Involuntary controlled

MUSCULAR SYSTEM

Skeletal Muscle

All attached either directly or indirectly to the skeleton

Controlled by the somatic nervous system

Striated in appearance

Voluntary controlled

MUSCLE PROPERTIES

The main constituents of skeletal muscle are:• Water 70%• Protein (myofilaments)23%• Minerals (calcium and phosphorus) and substrates

(glycogen and fatty acids) 7%

SKELETAL MUSCLE ANATOMY

Skeletal muscle is made up of fibres:• Made up of smaller myofibrils

• Within each myofibril are strands of myofilaments (actin and myosin)

• Fibres grouped together are called fasciculi

• Fasciculi are then grouped together to form the muscle


• Endomysium – surrounds each muscle fibre

• Perimysium – surrounds each fasciculi

• Epimysium – covers entire muscle


myofibrilmuscle filament

fasciasurrounds the muscle

connected to periosteum (bone)

Epimysiumthe outer layer

perimysiumaround each bundle of fibres

muscle fibre

endomysiumaround each muscle fibre

SLIDING FILAMENT THEORY

• Myofilaments actin (thin) and myosin (thick) do not decrease in length when a muscle contracts.

• They simply slide over each other thus shortening the entire muscle.

• The myosin filaments have golf club shaped heads which attach onto the actin and pull the actin closer together (as detailed in picture on next slide)

SLIDING FILAMENT THEORY

actin

myosin

myosin cross-bridges attach to the actin filaments

actin is pulled together and sarcomere length is reduced

NEUROLOGICAL SYSTEM

The nervous system consists of two primary

divisions, the central nervous system (CNS) and the peripheral nervous system (PNS)

NEUROLOGICAL SYSTEM

The Central Nervous System

The Brain and Spinal Cord

The PeripheralNervous System

THE REFLEX ARC

Central Nervous SystemSensory Receptor

Sensory Nerve

Motor Nerve

Muscle responds to nerve impulses

MUSCLE FIBRE RECRUITMENT

Motor units and muscle fibre recruitment:

A motor unit consists of a motor neuron (nerve fibre) and all the fibres it innervates

‘All or none law’ – when a motor neuron is stimulated, ALL of the muscle fibres are activated

The more motor units that are recruited for a task, the greater the force will be developed

ROLES OF MUSCLES

Agonist- A muscle that carries out a voluntary movement

Antagonist- The opposing muscle that relaxes in order to allow the movement to occur

Synergist- A muscle that assists the agonist in producing movement

Fixator- A muscle that stabilises a body part whilst the agonist is contracting

Muscular Contractions

TYPES OF MUSCLE CONTRACTION

Concentric (positive); the muscle contracts and shortens to overcome a resistance E.g. Lifting a dumbell during a bicep curl

Eccentric (negative); the muscle contracts and

lengthens to control a resistance E.g. Lowering a dumbell during a bicep curl

Isometric (static); the muscle contracts toovercome a resistance but without any change in length

MUSCLE FIBRE TYPES

Slow-twitch or Type 1

MUSCLE FIBRE TYPE

STRUCTURAL FEATURES

Smaller diameter fibre Large myoglobin content (carry oxygen) Many mitochondria (where energy is produced) Many capillaries (blood vessels) Red in colour

MUSCLE FIBRE TYPE

FUNCTIONAL FEATURES

Increased oxygen delivery Produce less force Long-term contractions Resistant to fatigue

MUSCLE FIBRE TYPE

ACTIVITIES-

Maintaining posture Endurance-based activities – long-distance running etc.

MUSCLE FIBRE TYPE

Fast-twitch or Type ll

MUSCLE FIBRE TYPE

STRUCTURAL FEATURES

Larger diameter fibre Smaller myoglobin content Fewer mitochondria Fewer capillaries White (pale) in colour

MUSCLE FIBRE TYPE

FUNCTIONAL FEATURES

Decreased oxygen delivery Produce more force Short term contractions Less resistant to fatigue

MUSCLE FIBRE TYPE

ACTIVITIES-

Rapid, intense movements


Responses of the neuromuscular system to exercise

Short term response:

Vasodilation (diversion of blood) to the muscles



Long term adaptations to aerobic exercise:

Increase in the number and size of mitochondria in the muscle fibres

Increase in the number of capillaries surrounding these fibres

Increase in the number of aerobic enzymes, stored glycogen and triglycerides (fats)



Long term adaptations to strength training:

Decrease nervous inhibition (increased nervous stimulation!)

Increase in the diameter of the recruited fibres Increase in work performed under anaerobic

conditions or high stress conditions

Principles of Training

PRINCIPLES OF TRAINING

OVERLOAD

In order to challenge the muscle you need to work outside of your comfort zone. The degree of extra challenge depends upon the aims and fitness level of the individual


SPECIFICITY

Training that is relevant to the desired outcome


REVERSIBILITY

You cannot store fitness – if you don’t use it you will lose it!

Muscles which are not regularly stimulated will suffer muscle wastage or “atrophy”


PROGRESSION

As you adapt to a workload and can complete it without feeling challenged, the next step is to increase the workload in order to progress


ADAPTATION

An anatomical or physiological change that occurs in the body, such as getting stronger, losing fat or increasing muscle size.

The body will adapt to any new stresses by protecting and strengthening the area.


HYPERTROPHY

An increase in cross-sectional diameter of trained muscle fibres


ATROPHY

An decrease in cross-sectional diameter of muscle fibres due to lack of use

Documents

Neuromuscular System