1.2.4 The muscular system

1.2.4 The muscular system

1. What does it do?

   • Causes movement through the contarction and relaxation ofmuscles
   • Defines body shape and helps maintain posture

2. Muscles

   • Muscles can work voluntary (conscious control by the body) or involuntary (in the internal organs)
   • Voluntary muscles
     • cause movement
     • consciously controlled
   • Muscles are attahed to bones by tendons and are made up of a number of muscle fibres
   • Muscle fibres contract causing movement - they pull against the skeleton but cannot push
   • Muscles are arranged in antagonistic pairs - as one contarcts the other relaxes
     • the muscle doing the work (contracting) and creating the movement is called the agonist
     • the muscle which is relaxing and letting the movement take place is called the antagonist
     • To flex the elbow, the bicep contracts and the tricep relaxes
       • Bicep = agonist
       • Tricep = antagonist
       • To extend the elbow, the bicep relaxes and the tricep contracts
         • tricep = agonist
         • bicep = antagonist
     • flexion at the knee joint, hamstrings contract (agonist) and quadriceps relax (antagonist)
       • extension at the knee joint, quadriceps contract (agonists), hamstrings relax (antagonist)

3. Muscles, position & action

   • Deltoids
     • abducts the upper arm, from the body
     • serve in tennis
   • Pectorals
     • Adduction of arm
     • swimming front crawl
   • Biceps
     • flexion of arm at the elbow
     • bending the arm to throw a cricket ball
   • Abdominals
     • flexion and rotation of the trunk
     • rowing
   • Quadriceps
     • extension of the leg at the knee
     • kicking a football
   • Trapezius
     • In the centre of the chest at the back of the body, spreading out
     • Rotates the shoulder blades backwards
     • Rowing
   • Triceps
     • extension of the arm at the elbow
     • straightening the arm to throw a cricket ball
   • Gluteals
     • extension of the upper leg
     • running and for maintaining good posture
   • Latissimus dorsi
     • At the back of the body, either side of the chest
     • Rotates upper arm at the shoulders
     • swimming butterfly
   • Hamstrings
     • flexion of the leg at the knee
     • sprinting: when leg bends
   • Gastrocnemius
     • plantar flexion of the foot
     • Running: pushing onto the toes

4. The immediate effects of exercise on the muscular system

   • Contract, lengthening and relaxing at an increased rate
   • Lactic acid builds up

5. Long-term effects of participation in exercise and physical activity on the muscular system

   • Increased muscle size (hypertrophy)

6. Isometric and Isotonic contractions

   • Isometric contractions: muscle contraction whihc results in increased tension but the length does not alter, for example when pressing against a stationary object
     • Hanstand
   • Isotonic contractions: muscle contraction that results in limb movement

7. Potential injuries to the muscular system

   • soft tissue injuries
     • tears, pulls and strains
   • RICE treatment
     • REST - for protection and recovery
     • ICE - to reduce swelling
     • COMPRESS - to prevent swelling
     • ELEVATE - to prevent swelling

8. Lifestyle, performance-enhancing drugs and the muscular system

   • Rest allows muscles to repair the damage caused by exercise, rebuild for the next session and strengthen
   • Diet is important to ensure the body receives proper nutrition, energy stores need to be replenished and protein is needed for growth and repair
   • Performance-enhancing drugs can be used to increase muscle size and strength eg: steroids