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- ATP is produced in glycolysis, the Krebs citric acid
cycle, and electron transport yielding 36 ATP.^
- ATP is produced occasionally in the absence of
oxygen- in muscle cells during anaerobic respiration,
yielding only two ATP with a buildup of lactic acid
during strenuous exercise.^
- Muscle cells can also take up free fatty acids from
the blood and break those down into ATP.^
- Muscle cells also use phosphocreatine as a source of
phosphate to produce ATP.
The Muscle Twitch
- Laboratory analysis of a muscle contraction reveals a
brief latent period immediately following the stimulus
followed by actual contraction. Relaxation follows
contraction. This is called a muscle twitch.^
- The strength of a contraction depends on the strength,
speed, and duration of the stimulus as well as the
weight of the load and the temperature.^
- The all-or-none law states that a stimulus strong
enough to cause contraction in an individual mus-cle
cell will result in maximal contraction.
Muscle Tone
- Tone is that property of a muscle in which a state of
partial contraction is maintained throughout a
whole muscle.^
- Tone maintains pressure on the abdominal con-
tents, helps maintain blood pressure in blood
vessels, and aids in digestion. Tone gives a firm
appearance- to skeletal muscles.^
- There are two types of contraction: isotonic con-
traction occurs when muscles become shorter and
thicker as when lifting a weight and tension remains
the same; isometric contraction occurs when ten-sion
increases but the muscles remain at a constant length
as when we push against a wall.
The Anatomy of Smooth Muscle
- Smooth muscle is found in hollow structures like
the intestines, arteries, veins, and bladder. It is
under- the control of the autonomic nervous
system.^
- Smooth muscle cells are involuntary, uninucleated,
and nonstriated.
Chapter 9- In hollow structures, smooth muscle is arranged in
two layers: an outer longitudinal layer and an inner
circular layer. This results in material being pushed
forward in the tube by simultaneous contraction of
both layers.
The Anatomy of Cardiac Muscle- Cardiac muscle is found only in the heart and is
controlled by the autonomic nervous system.^ - Cardiac muscle cells are involuntary, uninucleated,
and striated. They also have intercalated disks for
coordinating contraction.^ - Cardiac muscle cells can receive an impulse,
contract,- immediately relax, and receive
another impulse. This occurs about 75 times a
minute.
The Naming and Actions
of Skeletal Muscle- Muscles can be named according to their action,
shape, origin and insertion, location, or the direc-
tion of their fibers.^ - The origin is the more fixed attachment; the
insertion- is the movable attachment of a
muscle.^ - Tendons attach a muscle to a bone. A wide flat
tendon- is called an aponeurosis.^ - Muscles that bend a limb at a joint are called
flexors; those that straighten a limb are called
extensors.^ - Abductors move a limb away from the midline;
adductors- bring a limb toward the midline of the
body.^
6.^ Rotators revolve a limb around an axis.^ - Muscles that raise the foot are dorsiflexors; those
that lower the foot are plantar flexors.^ - Muscles that turn the palm upward are supinators;
those that turn the palm of the hand downward are
pronators.^ - Levators raise a part of the body; those muscles that
lower a part of the body are depressors.^ - Prime movers are muscles that bring about an
action. Those that assist the prime movers are
synergists.