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The Muscular System. Chapter 1. The Muscular System: An Overview. 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:

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the muscular system an overview
The Muscular System: An Overview
  • 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
functions of muscles
Functions of muscles
  • 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
types of muscles
Types of muscles
  • 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.
how are musculoskeletal movements possible
How are musculoskeletal movements possible?
  • 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
flexion extension example
Flexion / extension example
  • 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?
types of muscular contractions
Types of muscular contractions
  • 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
anterior muscles
Anterior muscles
  • Frontalis (forehead)
  • Sternocleidomastiods (neck)
  • Obicularisoris (mouth)
  • Pectorals (chest)
  • Deltoid (shoulder)
  • Biceps (upper arm)
  • Rectus abdominis (abs)
  • Sartorious (inner thigh)
  • Quadriceps (thigh)
  • Tibialis anterior (shin)
posterior muscles
Posterior muscles
  • Trapezius (top of back)
  • Rhomboids (middle of back)
  • Triceps (upper arm)
  • Latissimusdorsi (middle / lower back)
  • Gluteus maximus
  • Hamstrings
  • Adductors
  • Gastrocnemius (calf)
  • Soleus (ankle)
  • Achilles tendon
arrangement of muscle fibres
Arrangement of muscle fibres
  • 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
types of penniform muscle fibres
Types of Penniform muscle fibres
  • Unipennate muscle fibres only branch out to one side of the tendon
  • Bipennatemuscle fibres branch out on both sides of the central tendon
  • Multipennate muscle fibres branch out repeatedly from a number of tendons
  • Page 15
muscle fibre types
Muscle Fibre types
  • 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
the effect of age and gender
The effect of age and gender
  • 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 20-30 and deteriorate by 1% each year after that
sliding filament theory
Sliding Filament Theory
  • Myofibrils have several sections called sarcomereswhich 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
the all or nothing principle
The “all or nothing” principle
  • 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