Muscles

Naming of Skeletal Muscles•Direction of muscle fibers▫Example: rectus (straight)

•Relative size of the muscle▫Example: maximus (largest)

• Location of the muscle▫Example: many muscles are named for bones (e.g., temporalis)

•Number of origins▫Example: triceps (three heads)

Naming of Skeletal Muscles• Location of the muscle’s origin and insertion▫Example: sterno (on the sternum)

•Shape of the muscle▫Example: deltoid (triangular)

•Action of the muscle▫Example: flexor and extensor (flexes or extends a

bone)

Head and Neck Muscles

Figure 6.15

Superficial Muscles: Anterior

Figure 6.21

Superficial Muscles: Posterior

Figure 6.22

On Page 54 in your INBMake a list and describe the function of the muscles:

• Buccinator• Frontalis• Masseter• Orbicularis oculi• Orbicularis oris• Sternocleidomastoid (together

and alone)• Temporalis• Trapezius• Zygomaticus• Biceps brachii• Triceps brachii• Deltiod

• Extensor Digitorum• Flexor Digitorum • Pectoralis major• Diaphragm• Latissimus dorsi

• Define these terms:▫ Flex-▫ Extend-▫ Adduction-▫ Abduction-▫ Pronate-▫ Supinate-▫ Synergist-

The Muscular System•Muscles are responsible for all types of body

movement•Function of a muscle is contraction (shortening)•Three basic muscle types are found in the body▫Skeletal muscle▫Cardiac muscle▫Smooth muscle

Function of Muscles•Produce Movement▫Allow us to escape danger, move, manipulate things,

express emotion•Maintain Posture▫Muscles function constantly making tiny adjustments to

maintain erect or seated posture despite gravity•Stabilize Joints▫Muscle tendons reinforce joints at their articulating

surface•Generate Heat▫ATP is used to power muscle contractions 75% of this

energy escapes as heat▫It maintains our body temperature

Skeletal Muscle• Muscle fibers are bundled

together by connective tissue called endomysium

• Groups of muscle fiber are then wrapped again by a coarser fiber called perimysium which forms bundles of fibers called a fascicle

• Many fascicles are wrapped together by a connective tissue called the epimysium which covers the entire muscle.

• The epimysia blend in to make the tendons which connect muscle to bone

Microscopic Anatomy of Muscle•Multinucleate•Sarcolemma—Plasma

membrane of the muscle cell

• In the muscle cell are long ribbon like fiber called myofibrils.

•Very little cytoplasm in a muscle cell—filled with myofibrils

Microscopic Anatomy•Myofibrils are chains of contractile

units called sarcomeres aligned end to end

• In a sarcomere there are myofilaments •There are 2 types of myofilaments •Thick filaments which contain a

protein called myosin▫Myosin splits ATP which gives power for

muscle contraction▫End has projections which connect the

thick and thin fibers during contraction•Thin filaments called actin

Nerve Stimulus •Skeletal muscles are stimulated to move by nerve cells•The nerve and the muscles it stimulates are called a

motor unit•The axons of a nerve reaches the muscles at the

sarcolemma it is called a neuromuscular junction•There is a gap called a synaptic cleft filled with

interstitial fluid

Nerve Stimulus--Physiology •When the nerve impulse reaches the terminal a

neurotransmitter is released•Neurotransmitter is a chemical called acetylcholine

(Ach)• It attaches to proteins in the sarcolemma (which causes

Ca+2 ions to be released) and the sarcolemma becomes temporarily more permeable to sodium and potassium ions (called depolarization of the membrane)

• Lots of sodium ions enter and some potassium ions leave

•This causes an upset in the electrical conditions –this upset is called an action potential

Nerve Stimulus--Physiology •This action potential sends

electrical current from one end of the cell to another

•This causes muscle contraction•Myosin heads attach their tiny

“oars” and slide the actin together= muscle contraction

•To relax myosin detach from Actin filament and actin slides apart

•Then Ca+2 reabsorbed, Na+/K+ pump starts to reset muscle so it can contract again

Nerve Stimulus--Physiology •Remember ATP is made in aerobic respiration

(breaking down glucose with oxygen to form ATP) •The ATP that the myosin uses is made using oxygen• If you don’t have enough oxygen body will break down

glucose through anaerobic respiration (you are repaying oxygen debt when you start to breath deeper and faster)

•Anaerobic respiration also forms lactic acid—this causes sore muscles•Cramps will occur if a muscle is depleted of water and ions—a spastic contraction

Other Muscle Stuff• Even when skeletal muscles appear to be relaxed you maintain

a small sustained contraction that allows for posture and muscle tone.

• Standing requires more effort than sitting and sitting requires more than lying down

• Hypertrophy—when muscles are used a lot and they add new muscle fibers causing an increase in mass and diameter

• Atrophy—When a muscle is not used the protein fibers are “borrowed” for other bodily processes. This causes a decrease in mass and diameter

Muscle Diseases--Poliomyelitis•Polio•Caused by a viral infection

with poliovirus•The infection affects the

brain and spinal cord •Results in muscle weakness

or paralysis•Caused a world wide

epidemic in the early 1900’s•All children in the US are

now immunized against this

Amytrophic Lateral Sclerosis (ALS)• Aka Lou Gehrig’s Disease• 17 Major League seasons with Babe Ruth

for New York Yankees• .340 batting average• hit 493 homeruns and 1,995 RBIs. • Played 2, 130 consecutive games • On September 6, 1995, Cal Ripken Jr.

played in his 2,131st consecutive game breaking Lou Gehrig’s record

• May 2, 1939, will forever be the day when Gehrig "hung 'em up." Two month's later, on July 4, Gehrig would make his famous Farewell speech at Yankee Stadium.

Amytrophic Lateral Sclerosis (ALS)•Unknown cause•Degeneration of motor

neurons of spinal cord and brain stem causing muscle weakness and eventual paralysis leading to death.

•Death usually occurs 2-5 years after onset

•Usually seen in men 45-55•Stephen Hawking has ALS

Multiple Sclerosis (MS)• Unknown cause—possibly a

virus• Disease of the central nervous

system where nerve fibers break down leading to muscle weakness and eventually permanent paralysis

• Slow progressing • Usually seen in women 30-50• Montel Williams• Teri Garr• Lena Horne• Annette Funicello

Tetanus•Caused by a bacterial infection•Aka Lockjaw•Usually enters through wounds•Causes paralysis of muscles in face and neck•Get a tetanus shot!

Myasthenia gravis•Muscles do not get

enough Ach•Could me an auto

immune disease because blood contains an antibody to Ach

•Disease characterized by drooping of the upper eyelids, difficulty swallowing and talking

•Generalized muscle weakness and fatigability

Muscular Dystrophy •Congenital disease•Cause: diseased muscle fibers

lack a protein called dystrophin that maintain the sarcolemma

•Group of muscle destroying diseases that affect specific muscle groups

•Muscles enlarge due to fat and connective tissue deposits but the muscle fibers degenerate and atrophy

Muscular Dystrophy •Most common

Duchenne’s muscular dystrophy

•Mostly in males—diagnosed at 2-6 years old

•Children become clumsy—starts in extremities and quickly moves to head and chest muscles

•Most are in wheel chairs by 12 and don’t live beyond young adulthood.