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 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
• http://chestofbooks.com/health/body/massage/MargaretD-Palmer/Lessons-on-Massage/images/fig-17-ShowingAction-of-Biceps.png
• http://www.daviddarling.info/images/biceps_and_triceps.j
pg
• http://www.painfreefitness.com/images/freddy.png
• http://www.ucl.ac.uk/~sjjgsca/MuscleCell.gif
• http://www.sport-fitnessadvisor.com/images/actin_myosin.jpg
• http://www.youtube.com/watch?v=EdHzKYDxrKc