170 Introduction to Anatomy and Physiology
Lesson 5.2 Review and AssessmentAssessment Lesson 5.2 Review and
Mini Glossary
Make sure that you know the meaning of each key term.
acetylch oline a neurotransmitter
chemical that stimulates muscle
action pote ntial the electric charge
produced in nerve or muscle fi ber by
stimulation
all-or-non e law the rule stating that
the fi bers in a given motor unit
always develop maximum tension
when stimulated
axon a long, thin fi ber connected to
the motor neuron cell body
axon term inals offshoots of the axon
that branch out to connect with
individual muscle fi bers
cross br idges connections between
the heads of myosin fi laments and
receptor sites on the actin fi laments
fast-t witch type of muscle that
contracts quickly
motor n euron a nerve that stimulates
skeletal muscle tissue
motor unit a single motor neuron
and all of the muscle fi bers that it
stimulates
neuromuscular jun ction the link
between an axon terminal and a
muscle fi ber
par allel a type of muscle fi ber
arrangement in which fi bers run
largely parallel to each other along
the length of the muscle
pe nnate a type of muscle fi ber
arrangement in which each fi ber
attaches obliquely to a central tendon
sarco meres units composed of actin
and myosin that contract inside the
muscle fi ber
slow-t witch type of muscle that
contracts slowly and is fatigue
resistant
synaptic cleft the tiny gap that
separates the axon terminal and
muscle fi ber
te tanus a sustained, maximal level
of muscle tension that occurs with
high-frequency stimulation
Know and Understand
1. Explain the role of acetylcholine in muscle
contractions.
2. Describe the parts of a motor unit.
3. Discuss the differences between a large and
small motor unit and their functions.
4. Describe parallel and pennate fi ber patterns.
Analyze and Apply
5. Which fi ber types do you think contribute to each
of the following: muscular strength, power, and
endurance? Explain your reasoning.
6. What would happen if you had no Na+ in your
body? no Ca++?
7. Why do temperature and humidity increase the
rate of muscle fatigue?
8. Do you think a soccer player has more fast-twitch
or slow-twitch muscle fi bers? Why?
9. Try an experiment. Get into and then hold a
squatting position for as long as you can while
a partner times you. Allow fi ve minutes to rest;
then continually move into and out of a squatting
position for as long as possible, again with your
partner timing you. Did you fatigue more quickly
holding a squatting position or while moving up
and down in a squatting motion? Why? Now
reverse roles with your partner.
In the Lab
d a
Assess
Build vocabulary with
e-fl ash cards and games
defi nition of muscular endurance is specifi c to
each physical activity.
In general, muscle fatigue can be thought
of as the opposite of muscular endurance. The
faster a muscle fatigues, the less endurance it
has. A variety of factors affect the rate at which a
muscle fatigues, including the nature of the work
or exercise being done, how often the muscle
is used, the muscle fi ber composition of the
muscle, and the temperature and humidity of the
environment.
1. What is measured to determine muscular
strength?
2. What is measured to determine muscular
power?
3. Is the strongest athlete the fastest? Why
or why not?
4. What is muscular endurance?
5. What infl uences muscular endurance?
Check Your Understanding