Muscle System (a)
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Essay: Steps of muscle contraction
- 1. Acetylcholine released from the axon terminal binds to receptors on the sarcolemma.
- 2. An action potential is generated and travels down the T tubule
- 3. Ca2+ is released from the sarcoplasmic reticulum in response to the change in voltage
- 4. Ca2+ binds troponin; Cross-bridges from between actin and myosin
- 5. Acetylcholinesterase removes acetylcholine from the synaptic cleft.
- 6. Ca2+ is transported back into the sacroplasmic reticulum
- 7. Tropomyosin binds active sites on actin causing the cross-bridge to detach
The capacity of a muscle cell to shorten forcefully is known as
Muscles exhibit the property of excitability.
This means that the muscle
responds to stimulation by the nervous system
Identify the general functional characteristics of muscle
Muscle tissue shortens forcefully but lengthens passively
Acetylcholine binds to a membrane bound receptor and causes ligand-gated sodium channels to open and results in
Which of the following actions caused by contraction of skeletal muscle
moving your feet in walking
Smooth muscle and cardiac muscle are similar in that they are both
- A calcium-calmodulin complex initiates cross bridge formation
- Multiunit smooth muscle is located wall of blood vessels
- depolarizes when both sodium and calcium ions diffuse into the cell.
Hypertrophy of skeletal muscles from weight lifting is caused by an increase in the
size of muscle fibers
Skeletal muscle fibers develop from
is surrounded by perimysium
surrounds individual muscles
surrounds each muscle fiber
Lack of acetylcholinesterase in the synaptic cleft would result in
continuous stimulation of the postsynaptic membrane
List the following structures in order from smallest to largest
myofilament --> myofibril-->muscle fiber--> muscle fasciculus
Which of the following will respond to a threshold stimulus with an all-or-none contraction?
A & B a single muscle fiber & a single motor unit (d)
Which of the following is called the thin myofilament?
has a calcium-binding site
Which of the following is composed of myosin molecules
The active sites to which cross-bridges attach are found on the
You are hired to work in a laboratory to measure the rate of human muscle contraction. Which of the following might decrease in quantity in muscle cells undergoing contractions?
T tubules are invaginations of the
conduct action potentials deep into the muscle cell
stores calcium ions
Sliding filament model
Both actin and myosin myofilaments shorten during contraction (false statement)
If sodium ions cannot enter a muscle fiber in response to a stimulus,
contraction cannot occur
(Neuromuscular junctions) The
sites where a chemical substance is transmitted from the presynaptic terminal
of an axon to the postsynaptic membrane of a muscle fiber are called
A drug that interferes with the active transport of calcium ions from the sarcoplasm back into sarcoplamic reticulum would result in
contraction with no relaxation
ATP molecule is required
- (*e*) A, B, C
- A)for formation of the cross-bridge.
- B) for movement of the cross-bridge.
- C) for release of the cross-bridge.
After contraction has occurred,
released from troponin
Depolarization of the cell membrane occurs when there is a rapid influx (inflow) of
synaptic vesicles in the neuromuscular junction contain
Curare blocks acetylcholine receptors at the motor end plate. This would result in
inability of the muscle fiber to respond to nervous stimulation
Arrange these structures as they participate in excitation
sarcolemma, T tubules, sarcoplasmic reticulum, calcium ions
Arrange the following list of biochemical events in the correct sequence
- 1. An action potential is conducted deep into the muscle fiber by the T tubule
- 3. The membranes of the sarcoplasmic reticulum become more permeable to calcium ions.
- 4. Calcium ions diffuse into the sarcoplasm around the myofibril.
- 2. Calcium ions bind to troponin.5. The troponin-tropomyosin complex moves exposing active sites
Movement of the myosin molecule while the cross bridge is attached in a ________
During the contraction phase of a muscle twitch
actin-myosin cross-bridges form.
Tetanus of a muscle is thought to be caused by
high calcium ion concentrations in the sarcoplasm
Rigor mortis occurs after death because
cross-bridges form but can't release.
amount of oxygen that cells need to replenish ATP supplies after exercise.
Consider the following four phrases and select the one that does not belong with the others
fuels runner in a marathon
Which of the following correctly describes myoglobin's special function in muscle tissue?
acts as a reservoir for oxygen
is characterized by a decrease in muscle size
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