Muscle Test Review Questions
1. Give examples of each muscle type and how they are different.
Skeletal muscle is connected to a bone, voluntary, multinucleate, and striated;
cardiac muscle is found only in the heart, striated, shaped like a “y”, and
involuntary. Smooth muscle is involuntary and shaped like a spindle. It can be
found lining the digestive tract and in blood vessels.
2. How is muscle tissue is different from the other tissue types (think about what it’s
function is!) Muscles are contractile tissues, unlike other tissues. It is closely
associated with nervous tissue (to cause contractions), is supported by connective
tissues, and is covered by connective tissue in many cases.
3. What are origin vs. insertion points- what do these terms mean, not necessarily
examples. The origin of a muscle is the part of the muscle attached to the bone
that doesn’t move, and is closer to the midline of the body. The insertion is distal,
and is attached to the bone that moves when the muscle contracts. The muscle
must cross a joint, and moves the bone that is more distal.
4. What are antagonistic and synergistic pairs? Pairs that work antagonistically work
in opposition/ do opposite movements, like flexion and extension. Ex- quadriceps
femoris (all muscles on the front of the thigh) and hamstrings groups (all muscles
on the back of the thigh); biceps brachii and triceps brachii; tibialis anterior and
gastrocnemius. Pairs that work synergistically are working together to make a
motion- ex; quadriceps femoris group; hamstring group.
5. What is reciprocal innervation? What muscles (antagonists or synergists) exhibit
this? Reciprocal innervation is when a muscle in an antagonistic pair cannot work
while the other (in opposition) works. Reciprocal innervation is used to prevent
antagonistic pairs from “fighting” each other; since synergistic pairs work
together to perform the same job, it doesn’t help the body at all to “shut off” one
of the pairs.
6. Describe the structure of muscle from large to small units (down to sarcomeres
made from actin and myosin). All muscles are attached to bone via a tendon. The
muscle/ tendon are is covered in connective tissue called fascia. Connective
tissues line all muscle bundles. Those that cover the entire muscle are called
epimysium and perimysium lines all fascicles. Endomysium lines all muscle
fibers (muscle cells themselves). Each muscle fiber is covered by sarcolemma,
with sarcoplasmic reticulum (SR- whose role is to act as modified ER to deliver
Calcium ions (Ca2+) to the cell for contraction). The smallest bundle, the
myofibril, is multiple sarcomeres end to end bundled in parallel. Each myofibril
is composed of thick myosin filaments and thin actin filaments.
7. What are sarcomeres? How are they described? (Letters- specifically Z).
Sarcomeres are the smallest unit of muscle contraction. Multiple sarcomeres end
to end are bundled to form the myofibril. Sarcomeres are composed of actin and
myosin, which are parallel to each other. When muscle contracts, it is the
sarcomere itself that shortens, when the myosin binds to the actin and “walks
along” it, bringing the ends of the sarcomeres (the Z lines) together.
8. What is the sliding filament model? The sliding filament model is the term used to
explain how the muscle contracts. The filaments of actin and myosin slide along
each other, with the myosin grabbing along and attaching to the actin.
9. What is the all-or-none principal? The idea that a sarcomere contracts or does not.
There is no partial contraction of an individual unit.
10. Do all muscle cells in a muscle contract at once? Explain. No. When the whole
muscle contracts, only sections of motor units are in use (recruited). The larger
(more forceful) a muscle contraction is, the more motor units are in use.
11. What the role of ATP is in muscle movement is… ATP is used to attach myosin
to actin during cross bridge formation, and to remove calcium ions from the
extracellular fluid after contraction (active transport of Ca2+ back into SR).
12. What is rigor mortis? The “stiffness of death” that results when ATP is no longer
available to remove Ca2+ from the muscles and to unbind myosin from actin. It
sets in several hours after death and lasts up to 36 hours. The time lengths depend
upon the temperature of the body (therefore the surroundings). It stops when the
body’s muscles begin to deteriorate (decompose) from enzymatic action.
13. How do muscles contract? (From action potential in the neuron to relaxation).
Muscle contraction begins with a nerve impulse that releases acetylcholine (Ach)
into the space between the nerve and the muscle (called the neuromuscular
junction). ACh is absorbed by the muscle (not the whole thing, but the motor unit
that it reaches), and this causes Ca2+ to be released by the SR and flood into the
muscle unit. The Ca2+ binds to the troponin on the thin filament (made up of
actin, troponin, and tropomyosin), and this pulls the tropomyosin (the chaperone)
away from the myosin binding site on the actin. The myosin then can attach to the
actin, forming a cross bridge. The myosin pulls the thin filaments (the power
stroke) and walks along the actin using ATP to unbind from it, and move to the
next attachment site. This walking along continues as long as there is ATP
available, and as long as there is Ca2+ in the muscle cell. Ach needs to be removed
by the action of acetylcholinesterase, and the calcium removed back to the SR via
active transport.
14. Where ATP comes from during sustained and short-term activity? ATP is
normally created from cellular respiration in the mitochondria of the muscle cells.
This is when oxygen is readily available. When oxygen levels are low (during
periods of high use), ATP may be obtained from lactic acid fermentation, a
process that results in lactic acid build up. ATP may also be regenerated from
creatine phosphate in the muscles.
15. Why muscles are reddish brown? Due to the presence of myoglobin, and protein
that holds extra oxygen for periods of time when it will be needed.
16. Where muscle cramps come from? Muscle cramps results from a build up of
lactic acid and from small tears in the muscle that occur as a result of challenging
the muscles as a part of growth and repair.
17. What is the role of calcium in muscles? See question #13
18. Compare and contrast slow twitch v. fast twitch muscle fibers (the red and white
stuff). Slow twitch muscle fibers are red muscle fibers; they are resistant to
fatigue as they have more myoglobin to supply oxygen (to create ATP). They are
darker and more prevalent in muscles that are used often/ heavily. Fast twitch
muscle fibers are lighter, called white, have less myoglobin and are easier fatigue
due to the lower amount of myoglobin. They are more likely to be found in
muscle that is used less frequently. The ratio of fast to slow twitch fibers in a
muscle can be altered through use/ disuse.
19. What are isotonic v. isometric contractions of muscle? Isotonic contractions do
not shorten the length of the muscle (think of planks). Isometric contractions do
shorten the muscle , which is when there is any motion made; the muscle must
shorten to pull on the bone and move it.
20. What is muscle tone? (Are your muscle really ever at rest?) Muscle tone is the
base-line level of contraction that is always occurring in our muscle. They are
responsible for posture and keeping us upright. Our muscles are never fully at
rest. Even a normal contraction of a muscle uses only 20% of the muscle cells at
one time.
21. How is muscle like a rope? Ropes are made up of fibers, just as muscles are.
However, the main thing is that muscles can only act to move a muscle by pulling
on the bones, just as a rope can only be used to pull things. Neither can be used to
push an object.
22. Know the muscles of the face and those from the project.
23. What is polio? Causes and effects. Poliomyelitis (Polio) is a viral disease that
damages the nerves that connect to muscles. What results from the illness is an
inability to contract the muscles connected to the affected nerves. This can result
in paralysis or death.
24. What is myasthenia gravis? Myasthenia gravis is an autoimmune disorder that
results in damage to the ACh receptors, resulting in weakness or fatigue to
affected muscles. The disease can be treated but not cured.
25. How does our muscular system change as we age? Myosin, ATP, and creatine
phosphate levels decrease. Muscle mass decreases (by 50% at age 80); Adipose
and other connective tissues take the place of muscle. Exercise reduces the
effects of these changes.
26. What is muscle fatigue? When muscles are running low on ATP (due to lack of
oxygen, for whatever reason, from lack of blood flow to not being able to pump
blood fast enough), they fatigue and become unable to contract. ATP must be
replaced in order for them to become functional again. Low minerals, such as
calcium and magnesium, also play a role in fatigue, as does a build up of lactic
acid. Cramping- sustained, strong muscle contraction- is a result.
27. What is muscle strain? Muscles strain occurs when there is damage to the
connective tissues within the muscle (the –mysiums), and to the muscle fibers
themselves. This causes pain in the muscle.