Motor /Muscular System This system acts as a supporting scaffold within your body Allows you to carry out a variety of coordinated tasks affecting circulation, digestion, respiration and excretion

Motor /Muscular System There are over 600 muscles in the human body that can be divided up into 3 basic types

1. CARDIAC MUSCLES Only in the heart Involuntary contractions and relaxations

2. SMOOTH MUSCLES Lining of organs Involuntary contractions and relaxations e.g. move food through the digestive system, push baby out of vagina during birth

3. SKELETAL MUSCLES Attached to the bones by tendons Voluntary contractions and relaxations Shorten to contract, lengthen to relax Arranged in pairs that work against each other (antagonistic muscles) like your bicep and triceps Skeletal muscles are made of several bundles of cells called fibres e.g. permits movement, enables smiling, helps you keep warm

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Skeletal Muscles Fibres are enclosed in a delicate sheath membrane Within each fibre there are threads of contractile proteins bundled together (called myofilaments) 2 types of myofilaments in the muscle ACTIN which is thin and MYOSIN which is THICK. Pg 300

Voluntary Muscle Contraction Muscle twitches or contractions occur when nerve impulses stimulate several muscle cells Upon contraction actin and myosin fibres slide over one another causing the muscle to shorten Muscles will relax when the fibres return to their original length This is the sliding filament theory

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Muscle Disorders Skeletal muscles are subject to fewer disorders than other organ systems Muscles are more vulnerable to injury than disorders

Common Ailments ConditionDescription CrampsPainful muscle spasms triggered by strenuous exercise, extreme cold, dehydration, salt imbalance, low blood glucose or reduced blood flow FibromyalgiaChronic muscular pain and tenderness often associated with fatigue and sleep disturbances; can be caused by infectious diseases, meds or physical/emotional trauma Delayed onset muscle soreness Pain, stiffness and tenderness felt after strenuous exercise; associated with trauma to the muscles, disruptions in the myofilaments and increased levels of muscle fibre enzymes in the blood AtrophyReduction in size, tone and power of muscle from inactivity; fibres decrease in size and become weaker initially is reversible but dead or dying muscle fibres cannot be replaced