What you will learn today . . .

• Muscles allow us to respond to a stimulus• Individual muscle fibers respond to a stimulus with an

all-or-none response. In other words, the muscle fiber contracts to its maximum potential or not at all

• Once a muscle has contracted , it must relax before it can contract again.

• Muscles work in pairs that have opposite functions• Muscle contractions can be weak and intermittent or

strong and permanent• Actin and myosin allow a muscle fiber to contract by

sliding across each other

Muscle Fatigue

Prolonged or repetitive use of a muscle group leads to muscle fatigue. Fatigue produces a sense of weakness and even discomfort. (EXAMPLE: Carrying a heavy load or walking up a flight of stairs)

Exercise improves muscular function and delays the onset of fatigue.

Make A Hypothesis:Continuous Grip

Make A Hypothesis:Repetitive Grip

The Muscular System

Check out those guns!

Muscles are largely responsible for our body weight and appearance

Skeletal Muscles

A. Muscles are effectors that allow us to respond to a stimulus.

B. Muscles work in pairs called flexors (bend a limb) and extensors (straighten a limb).

Muscles Work in Pairs

1. Muscles are attached to bones by tendons.

2. The middle of the muscle is called the belly and shortens when the muscle contracts.

3. The part of the muscle that is attached to stationary bone is called origin.

4. The part of the muscle that is on the bone that moves is called the insertion.

Biceps Brachii

All-or-none Law: a muscle fiber (cell) either

responds to a stimulus or it does not. Once

it responds, it will contract. The strength of

the contraction of a whole muscle depends

on the number of muscle fibers in that

muscle that are contracting.

Types of contractions

A. Muscle twitch: contraction for fractions of a second

B. Summation and Tetanus: maximal sustained contaction until muscle fatigues

C. Muscle tone: permanent contraction of muscles

Exercise increases the endurance and strength of muscles

The muscle fiber (cell)

A. Cell membrane = sarcolemma

B. Cytoplasm = sarcoplasm

C. Endoplasmic reticulum = sarcoplasmic reticulum

D. The SR encases myofibrils, which have contractile units called sarcomeres.

1. Actin

2. Myosin

Muscle Fiber

E. The Sliding-filament theory: Actin and myosin movement in relationship to each other causes the sarcomere to shorten

Your AssignmentUse the anatomy books to identify the following human muscles on the worksheets.Zygomaticus majorOrbicularis OculiFrontalis TemporalisMasseterOrbucularis OrisBuccinatorSternocleidomastoidExternal IntercostalsDeltoidRectus abdominisExternal ObliqueInternal ObliqueTransversus abdominisPectoralis majorSternocleidomastoidTrapeziusLatissimus dorsiDeltoidHamstrings (Biceps femoris, semimembranosus, semitendinosus)IliopsoasTibialis AnteriorGluteus maximusAdductor GroupQuadriceps (Vastus lateralis, Vastus medius, Rectus femoris, Vastus intermedius)Gluteus mediusPeroneus brevus and longusGastrocnemiusDeltoidFlexor carpi ulnarisExtensor digitorumBiceps brachiiFlexor digitorum superficialisTriceps brachii

References

• http://chestofbooks.com/health/body/massage/Margaret-D-Palmer/Lessons-on-Massage/images/fig-17-Showing-Action-of-Biceps.png

• http://www.daviddarling.info/images/biceps_and_triceps.jpg

• http://www.painfreefitness.com/images/freddy.png• http://www.ucl.ac.uk/~sjjgsca/MuscleCell.gif• http://www.sport-fitness-advisor.com/images/

actin_myosin.jpg• http://www.youtube.com/watch?v=EdHzKYDxrKc