72 notecards = 18 pages (4 cards per page)
The narrow space between the axon terminal and the motor end plate is called the:
Stimulation of acetylcholine (ACh) receptors by ACh will primarily result in:
Sodium ions entering the muscle fiber
The end-plate potential is:
A depolarization caused by sodium ion movement into the cytosol
The neurons of patients with multiple sclerosis are unable to transmit action potentials down the axon. How will that affect skeletal muscle stimulation?
The muscle will not be stimulated and therefore will not contract
The active ingredient of Botox, botulinum toxin, blocks the release of ACh from the axon terminal. An overdose of Botox will most likely result in:
Muscle paralysis at the site of injection
When muscle fibers are stimulated so frequently they do not have an opportunity to relax, they are experiencing:
Fused or complete tetanus
The corticospinal pathways
Are descending motor pathways
The cross bridge cycle starts when ________.
Ca2+ from the sarcoplasmic reticulum binds to troponin
The sarcomere shortens when the myosin heads of thick filaments, in a cocked position, form cross bridges with the actin molecules in thin filaments. Steps that occur during a single cross bridge cycle in the correct order:
Clostridium botulinum is a bacterium that produces botulinum toxin that inhibits the release of acetylcholine. Which description best fits how muscle cells will respond to a lack of acetylcholine?
Muscle cells will become paralyzed when there is a lack of acetylcholine
Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?
Excitation, in this case, refers to the propagation of action potentials along the sarcolemma
Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?
Calcium release from the sarcoplasmic reticulum initiates the contraction
A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?
A series of proteins that control calcium release
What is the name given to the regularly spaced infoldings of the sarcolemma?
Transverse or T tubules
Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?
What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?
Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.
Increase in tension by increasing the number of motor units that are stimulated is called _______.
Latroxin, produced by the poisonous black widow spider, increases the release of acetylcholine. How do muscle cells respond?
Muscle cells will experience fused or complete tetanus when excess acetylcholine exists
What parts of the brain ultimately plan and coordinate complex motor activities?
Cerebellum and basal nuclei
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
Arrival of an action potential
The binding of calcium to which molecule causes the myosin binding sites to be exposed?
A myosin head binds to which molecule to form a cross bridge?
What causes the myosin head to disconnect from actin?
Binding of ATP
What causes the power stroke?
Release of ADP and Pi
The primary motor area
Contains a larger area for control of the hand and fingers than for control of the arm and elbow
What is the function of the muscle cell feature indicated by the arrow? (Pointing to the sarcoplasmic reticulum)
Storage of calcium
When a muscle cell generates tension but does not change length, a(n) _______ contraction occurs.
A drug that interferes with the active transport of calcium ions from the sarcoplasmic back into the sarcoplasmic reticulum would result in
Contraction with no relaxation
Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine?
Acetylcholine is degraded by acetylcholinesterase
The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction?
Acetylcholine is released by axon terminals of the motor neuron
Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.
Extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber
Calcium entry into the axon terminal triggers which of the following events?
Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine
Acetylcholine binds to its receptor in the sarcolemma and triggers __________.
The opening of ligand gated cation channels
Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?
The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffused inward along favorable chemical and electrical gradients.
The transverse tubules in a skeletal-muscle fiber
Provide a means of transmitting an action potential in the muscle plasma membrane to central portions of the fiber
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
Voltage-gated calcium channels
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
Binding of a neurotransmitter causes chemically gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma) and sodium enters the cell
How is acetylcholine (ACh) removed from the synaptic cleft?
Simple diffusion away from the synaptic cleft and acetylcholinesterase (AChE; an enzyme)
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?
Terminal cisterns (cisternae) of the sarcoplasmic reticulum
Place the following events of excitation in the correct
4, 3, 5, 1, 2
List the following structures in order from smallest to largest.
2, 3, 1, 4
A crossbridge forms when:
A myosin head binds to actin
Which of the following steps of the crossbridge cycle occurs immediately before the power stroke?
A cross bridge forms
As myosin heads complete the power stroke, actin filaments:
Slide toward the M line of the sarcomere
Which of the following causes myosin to detach from actin?
An ATP molecule binds to myosin
In the absence of ATP in the muscle, which of the following is most likely to occur?
Some myosin heads will remain attached to actin molecules, but are unable to perform a power stroke
If the Na+ voltage-gated channels in a muscle cell open, what will be the result?
In preparation for contraction, calcium ions bind to:
The protein that binds to actin when tropomyosin moves off of the active sites of actin, is:
What type of contraction is this? (Muscle stays the same length)
Heat released from contracting muscles functions to ________.
Maintain body temperature
Voluntary control over swallowing, defecation, and urination is provided by muscles that ________.
Guard entrances and exits
The permission surrounds a bundle of muscle fibers called a __________.
Which connective tissue layer wraps the entire muscle?
Which structure in a muscle fiber or muscle cell is continuous with the sarcolemma and carries the signal to contract deep into the muscle cells?
The repeating functional units seen on the myofibrils are ________.
Which of the following is NOT found in a thin filament?
Which of the following is the dark band seen on myofibrils?
The neurotransmitter required to trigger skeletal muscle contraction is __________.
What must bind to troponin in order to expose the active sites on actin?
In a twitch, what is the phase in which tension rises to a peak?
All the muscle fibers and the single motor neuron that innervates them are called a __________.
What is the type of contraction in which the muscle does NOT change length and the contraction does NOT produce tension that exceeds the load?
Which of the following produces ATP from glucose anaerobically?
When glycolysis produces pyruvic acid faster than it can be used by the mitochondria, pyruvic acid is converted to _________, which lowers the pH of body fluids.
What muscle fiber type contains abundant myoglobin and is specialized to contract for extended periods of time?
What is the name of the structure that contains gap junctions and desmosomes and joins the plasma membranes of two cardiac muscle cells together?
What is the term for the ability of cardiac muscles cells to contract without neural stimulation?
Which of the following is NOT a characteristic of smooth muscle tissue?
Presence of striations
What is the term for the ability to function over a wide range of lengths?