Chapter 1

 There are over 600 muscles in the human body which allow everyday movements  Without our muscles we would not be able to breathe, eat, walk or even keep our heart beating  The three major functions of the muscular system are: - Movement - Posture - Production of heat

 Movement: most muscles are under voluntary control and are responsible for bodily movements; others are involuntary and work without our conscious control  Posture: the position of our bodies is effected by gravity; our skeletal muscles are continually working to keep our bodies balanced and aligned  Body heat: muscles require energy to produce movement and this releases heat; muscles play a role in maintaining body temperature

 Skeletal muscles: attached to bones in the skeleton that are under conscious control making them voluntary muscles. They are striped (striated) in appearance.  Smooth muscles: found internally in blood vessels and the walls of organs. We have no control over them because they are involuntary muscles.  Cardiac muscle: makes up the wall of the heart and works involuntarily. It has a striped appearance.

 Muscular movements are controlled by the brain  For movement to happen muscles must cross a joint between two bones  Nervous impulses are sent from the brain to muscles which causes the muscle to contract  Muscles never work alone, often several are involved in producing one movement  The prime mover (agonist) is the muscle that directly causes the movement, therefore the opposite muscle is the antagonist

 The bicep muscle is the agonist that causes flexion of the arm  When you pull your arm up towards yourself in a bicep curl the bicep contracts and shortens  At the same time, the triceps muscle which is the antagonist relaxes and lengthens  Both of these muscles must work together in unison to produce flexion  What happens during extension?

 Isotonic: where the length of the muscle actually changes (e.g. sit-up). Concentric contractions shorten the muscle whereas eccentric contractions lengthen the muscle  Isometric: where the muscle length stays the same (e.g. pushing against a wall)  Isokinetic: when the tension within a muscle is maximal throughout a range of motion (only using machines). They work the muscle the most because they match the force that is exerted by the muscle

 Frontalis (forehead)  Sternocleidomastiods (neck)  Obicularis oris (mouth)  Pectorals (chest)  Deltoid (shoulder)  Biceps (upper arm)  Rectus abdominis (abs)  Sartorious (inner thigh)  Quadriceps (thigh)  Tibialis anterior (shin)

 Trapezius (top of back)  Rhomboids (middle of back)  Triceps (upper arm)  Latissimus dorsi (middle / lower back)  Gluteus maximus  Hamstrings  Adductors  Gastrocnemius (calf)  Soleus (ankle)  Achilles tendon

 The arrangement of muscle fibres determines how strongly they can contract  Fusiform muscle fibres run in the same direction as the tendon (lengthways)  Penniform muscle fibres run at angles to the tendon and make up about 75% of skeletal muscles  Penniform muscle fibres can be divided into three categories depending on how much they branch off the tendon

 Unipennate muscle fibres only branch out to one side of the tendon  Bipennate muscle fibres branch out on both sides of the central tendon  Multipennate muscle fibres branch out repeatedly from a number of tendons  Page 15

 Slow twitch fibres - Red colour - Contract slowly over a longer period of time - Best suited for aerobic and endurance activities - Exert less force but can contract repeatedly  Fast twitch fibres - White colour - Contract rapidly over a shorter period of time - Best suited for anaerobic and high intensity activities - Exert great force in bursts of power and speed

 Your size, gender, age and physical training will determine the power that can be exerted by your muscles  During puberty boys begin to produce more testosterone than females causing them to develop more muscle mass  Females generally possess about 65% of the strength of adult males  Muscles are at their strongest between and deteriorate by 1% each year after that

Muscle (e.g. bicep)Muscle Fascicle (small bundles inside the muscle)Muscle Fibre (smaller bundles inside the fascicles)Myofibril (section of the muscle fibre)Myofilaments (cause the release of energy)

 Myofibrils have several sections called sarcomeres which run the length of the muscle  Within each myofibril are two types of myofilaments called actin (thin filament) and myosin (thick filament)  The lighter section of the sarcomere only contains thin actin filaments and is called the I-band  The darker section is where both actin and myosin overlap and is called the A-band  There is a small section in where only myosin is found called the H-band  During physical activity the myosin glides in between the actin and releases energy so that muscles can contract

 When a motor unit (lots of muscle fibres) receives a message from the brain all the muscle fibres in the unit will contract providing the stimulus is of significant intensity  If the stimlus is not intense enough the muscle fibres won’t respond and the muscle won’t contract