I) OVERVIEW
- A) Types of Muscle Tissue
1) Skeletal muscle
a) attaches to the skeleton
b) muscle fibers are striated
c) they're controlled voluntarily
2) Cardiac muscle
a) found only in the heart
b) muscle fibers are striated
c) they are involuntary
3) Smooth muscle
a) forms the walls of internal organs
b) not striated
c) involuntary
B) Muscle Functions
1) moves internal
and external body parts
2) maintain
posture
3) stabilize
joints
4) generate
heat
C) Functional Characteristics
1) excitability / irritability - muscles respond
to stimuli
2) contractility - muscles contract
3) extensibility - muscles can stretch
4) elasticity - muscles can return to their
normal size after stretching
A) Gross anatomy
1) Features
a) tendon - connects a muscle to bone
b) epimysium - connective tissue surrounding the entire muscle
c) fascicle - a bundle of muscle fibers; a number of fascicles make up the muscle
d) perimysium - connective tissue surrounding a fascicile
e) endomysium - connective tissue surrounding an individual muscle fiber
2) Skeletal muscle attachments may be direct or indirect by tendons or aponeuroses
B) Microscopic anatomy - skeletal musce fibers are long, striated, and multinucleate
1) Muscle fibers are made up of myofibrils.
2) Each myofibril is made up of a number of units called sarcomeres.
3) Each sarcomere contains thick (myosin) and thin (actin) myofilaments that slide against each other.
C) Contraction of Skeletal Muscle
1) Motor unit - 1 motor neuron and all the muscle cells it controls
2) Twitch - muscle response to a single brief threshold stimulus
3) The energy source for muscle contraction is ATP. When there is not enough oxygen for areobic production
of ATP, then anareobic respiration occurs, lactic acid is produced, and there is muscle fatigue. Oxygen debt is the
amount of oxygen needed to get rid of the lactic acid. Only 20-25% of the ATP energy is used for contracting the
muscles; the rest is released as heat.
4) 3 types of muscle fibers; most muscles are a mixture of muscle types
a) white fast twitch; more powerful, for short-term bursts of energy
b) red slow twitch - fatigue resistant, but not very powerful, but lots of endurance
c) intermediate fast twitch - fatigue resistant (though not as much as red slow twitch); for fast movements
D) Exercise and muscles
1) Regular aerobic exercise results in increased efficiency, endurance, and strength of muscles.
2) Regular aerobic exercise also results in more efficient cardiovascular, respiratory, and neuromuscular funtions.
3) Non-use of muscles causes muscle weakness and atrophy.
III) SMOOTH MUSCLE
A) Microscopic
anatomy
1) Smooth muscle fibers are small, spindle-shaped, and uninucleate.
2) They are usually arranged in sheets.
B) Contractions
of smooth muscle
1) Smooth muscle contracts for long periods of time using little energy
and without fatigue.
2) The pace of contraction may be set by pacemaker cells.
3) The contractions are energized by ATP and are activated by calcium pulses.
IV) MUSCLE DEVELOPMENT
A) Women's muscles
make up about 36% of their body weight.
B) Men's muscles
make up about 42% of their body weight.
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