BACKGROUND:
Muscle cells are part of a complex system involving
muscles, tendons, nerves, hormones, blood vessels, and sense organs.
Muscle contraction resembles a change in the elastic constraints of a spring.
In order for a muscle to pick up and lift some weight, the "spring" contracts
to accomplish the work. The energy from muscle contraction comes
from sugars and fats stored within the muscle.
The term involuntary muscle is used to indicate that this type
of muscle is not subject to our conscious control. Smooth and cardiac
muscles are involuntary. Imagine if we had to control our heart pumping
or food passage in order to live!
Voluntary muscles indicate that the muscle is under the conscious
control of that particular animal. Skeletal muscles are voluntary, in that
we control their actions and whether to make them more responsive.
Voluntary muscles in the body are usually attached to the skeleton in such
a way that they are stretched near their optimal length. Muscles
can pick up weight not directly but through a lever system.
PROCEDURE:
- In this activity, students will see if they
can improve their voluntary muscle reflexes by repeating a skill.
The skill involves preventing a meterstick from falling between two fingers.
- Go over directions on the lab sheet with students.
Tell them to make sure they remember where they started on the meterstick.
In order to avoid confusion it may be best to have the whole class begin
at one place on the meterstick.
- Have the students record their reflex times and then graph
them on the lab sheet. In most cases, there will be improvement from the
first trial to the last trial. You may want to discuss what happens
when a person does not have control of his muscles. There are several
diseases that are due to muscle disorders. Muscular dystrophy is
the wasting of the trunk and limb muscles. Poliomyelitis (Polio)
is a disease which involves the connective tissue and leads to the destruction
of the muscle fibers.
