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 PairsPairs 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.

BicepsBiceps 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 contractionscontractions 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 Assignment Use the anatomy books to identify the following human muscles on the worksheets. Zygomaticus major Orbicularis Oculi Frontalis Temporalis Masseter Orbucularis Oris Buccinator Sternocleidomastoid External Intercostals Deltoid Rectus abdominis External Oblique Internal Oblique Transversus abdominis Pectoralis major Sternocleidomastoid Trapezius Latissimus dorsi Deltoid Hamstrings (Biceps femoris, semimembranosus, semitendinosus) Iliopsoas Tibialis Anterior Gluteus maximus Adductor Group Quadriceps (Vastus lateralis, Vastus medius, Rectus femoris, Vastus intermedius) Gluteus medius Peroneus brevus and longus Gastrocnemius Deltoid Flexor carpi ulnaris Extensor digitorum Biceps brachii Flexor digitorum superficialis Triceps brachii

References D-Palmer/Lessons-on-Massage/images/fig-17-Showing- Action-of-Biceps.pnghttp://chestofbooks.com/health/body/massage/Margaret- D-Palmer/Lessons-on-Massage/images/fig-17-Showing- Action-of-Biceps.png pghttp:// pg advisor.com/images/actin_myosin.jpghttp:// advisor.com/images/actin_myosin.jpg