Chapter 7
The
Muscular
System

Myo means muscle
Sarco means
Flesh (muscle)
Remember the 3 types of muscle tissue?
Skeletal
Smooth
Cardiac

All muscle cells are called muscle

Skeletal Muscle fibers
They can range up to 1 foot in length
Voluntary or Involuntary
Striated or nonstriated
Single nucleus or multinucleated

Skeletal Muscle Fibers
Attached to The
Skeleton
(bones)

Skeletal Muscle Fibers
Contract rapidly with great force.
Fatigues easily

Skeletal Muscle Fibers
Fascia
Sheet or band under skin or around muscles

Skeletal Muscle Fibers
Each muscle fiber is enclosed in a protective sheath called an endomysium

Skeletal Muscle Fibers
Each endomysium is grouped and wrapped by the perimysium which forms a bundle called a fascicle

Fascicles are grouped by a epimysium which covers the entire muscle

epimysium perimysium fascicle endomysium

Skeletal Muscle Fibers
Fiber Each muscle cell
Endomysium
Perimysium
Fascicle
Covers each fiber
Wrapped around groups of fibers
Muscle fiber bundle or group
Epimysium
Fascia
Warpped around groups of fascicles
Wrapped around entire muscle

Anchor muscles
Provide durability
Conserve space
Small, can easily pass over a joint

Smooth Muscle
Voluntary or Involuntary
Striated or nonstriated
Single nucleus or multinucleated

Smooth Muscle
Walls of hollow organs like stomach, bladder, uterus, intestines, around blood vessels

Smooth Muscle
Arranged in sheets or layers
Contraction is slow and sustained
Slow to fatigue

Cardiac Muscle
Found only in the
_____________
Arranged in spiral or S shaped bundles

Cardiac Muscle
Voluntary or Involuntary
Striated or nonstriated
Single nucleus or multinucleated

Cardiac Muscle
Contraction is slow and steady
Slow to fatigue
(hopefully not for about 90 -
100 years

Functions of the Muscles
Skeletal muscles move the body
Smooth muscles force fluids and other substances through the body
Cardiac muscles circulate blood

Functions of the Muscles
Skeletal muscles constantly work against gravity

Functions of the Muscles
Especially muscle tendons

Functions of the Muscles
to power muscle contraction
¾ of its energy escapes as heat

Skeletal Muscle Microscopic Anatomy
Muscle cells are called fibers instead of cells because of their threadlike shape.

Skeletal Muscle Microscopic Anatomy
Sarcolemma Same as cell membrane
Sarcoplasm Same as cytoplasm
Sarcoplasmic
Reticulum (SR)
Similar to endoplasmic reticulum (ER)

Skeletal Muscle Microscopic Anatomy
Many mitochondria and many nuclei

Skeletal Muscle Microscopic Anatomy
Myofibrils Bundles of fine fibers.
Made of myofilaments
Sarcomere
T-tubules
Segment of myofibrils.
Many in each myofibril
Runs transverse. Allows electrical current to run deep into the cell
Triad SR t-tubule SR
Myofilaments Thick and thin. Make up the myofibrils

Skeletal Muscle Microscopic Anatomy
Myofilament
Made of 4 protein molecules:
Myosin
Actin
Attracted to each other
Tropomyosin
Tropin
Covers myosin when at rest
Holds tropomyosin in place.
Effected by Calcium

•Myofilament
•Myofibril
•Fiber
•Endomysium
•Perimysium
•Epimysium
•Fascia
Makes a fassicle

Cross bridges
Heads of myosin molecules lean toward actin and form a bridge for messages to cross over
Acetylcholine
A neurotransmitter secreted at the motor end plates of skeletal muscle.
These cause an electrical current called an action potential

Cross bridges
Arrange from smallest to largest: fiber
3 myofilament
1 myofibril
2
What is the energy source for muscle contraction?