Podcast
Questions and Answers
Which mechanism ensures a rapid and efficient removal of acetylcholine?
Which mechanism ensures a rapid and efficient removal of acetylcholine?
- Acetylcholine is stored in vesicles.
- Acetylcholine is transported into glial cells.
- Acetylcholine is reabsorbed into axon terminals.
- Acetylcholine is degraded by acetylcholinesterase. (correct)
Which statement describes a critical event that occurs at the neuromuscular junction?
Which statement describes a critical event that occurs at the neuromuscular junction?
- ATP is hydrolyzed.
- Calcium is released by the muscle fiber.
- Acetylcholine is released by axon terminals of the motor neuron. (correct)
- Myosin binds to actin.
These motor neurons __________.
These motor neurons __________.
extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber.
What triggers synaptic vesicles to release acetylcholine?
What triggers synaptic vesicles to release acetylcholine?
Acetylcholine binds to its receptor in the sarcolemma and triggers __________.
Acetylcholine binds to its receptor in the sarcolemma and triggers __________.
Why do sodium and potassium ions not diffuse in equal numbers through ligand-gated cation channels?
Why do sodium and potassium ions not diffuse in equal numbers through ligand-gated cation channels?
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum?
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum?
The binding of calcium to which molecule causes the myosin binding sites to be exposed?
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?
A myosin head binds to which molecule to form a cross bridge?
What causes the myosin head to disconnect from actin?
What causes the myosin head to disconnect from actin?
What causes the power stroke?
What causes the power stroke?
How is the opposite action (extension at the elbow) produced?
How is the opposite action (extension at the elbow) produced?
Which of the following is an effect of the parasympathetic nervous system?
Which of the following is an effect of the parasympathetic nervous system?
What happens when calcium binds troponin?
What happens when calcium binds troponin?
How is the energy released by ATP hydrolysis used during the contractile cycle in skeletal muscle?
How is the energy released by ATP hydrolysis used during the contractile cycle in skeletal muscle?
What is the function of transverse tubules?
What is the function of transverse tubules?
What is the function of the titin protein?
What is the function of the titin protein?
In order for high force crossbridges to form in contracting skeletal muscle, calcium must
In order for high force crossbridges to form in contracting skeletal muscle, calcium must
Each myosin head has a binding site for
Each myosin head has a binding site for
What happens as ATP binds to the myosin head at the beginning of a muscle contraction cycle?
What happens as ATP binds to the myosin head at the beginning of a muscle contraction cycle?
What is the molecular event that occurs immediately after the power stroke?
What is the molecular event that occurs immediately after the power stroke?
What does the hydrolysis of ATP cause myosin to do?
What does the hydrolysis of ATP cause myosin to do?
The action potential traveling along the T-tubule is detected by the
The action potential traveling along the T-tubule is detected by the
What channel opens when acetylcholine binds to its receptor at the neuromuscular junction?
What channel opens when acetylcholine binds to its receptor at the neuromuscular junction?
The contraction cycle is triggered by the rise in ________ released from the sarcoplasmic reticulum (SR).
The contraction cycle is triggered by the rise in ________ released from the sarcoplasmic reticulum (SR).
The brief period of time between the beginning of the action potential in the muscle and the beginning of contraction is referred to as the
The brief period of time between the beginning of the action potential in the muscle and the beginning of contraction is referred to as the
________ is the backup energy molecule that can be rapidly converted to ATP in active skeletal muscle.
________ is the backup energy molecule that can be rapidly converted to ATP in active skeletal muscle.
Which is a characteristic of slow-twitch oxidative skeletal muscle fibers?
Which is a characteristic of slow-twitch oxidative skeletal muscle fibers?
A motor unit consists of
A motor unit consists of
Which fibers fatigue sooner?
Which fibers fatigue sooner?
Calcium, released by the sarcoplasmic reticulum, binds to ________ to move the ________, which allows actin to form a high-force crossbridge with myosin.
Calcium, released by the sarcoplasmic reticulum, binds to ________ to move the ________, which allows actin to form a high-force crossbridge with myosin.
In order to contract and relax, muscle cells require energy in the form of ________. The immediate backup energy source is ________ that requires the enzyme ________.
In order to contract and relax, muscle cells require energy in the form of ________. The immediate backup energy source is ________ that requires the enzyme ________.
Asynchronous activation of motor units is important because it functions to prevent
Asynchronous activation of motor units is important because it functions to prevent
Smooth muscle cells lack which protein(s)?
Smooth muscle cells lack which protein(s)?
Which of the following is NOT a correct comparison of cardiac myocytes to other muscle cell types?
Which of the following is NOT a correct comparison of cardiac myocytes to other muscle cell types?
In smooth muscle cells, Ca2+ binds to ________ which activates the enzyme ________ to phosphorylate myosin and increase force.
In smooth muscle cells, Ca2+ binds to ________ which activates the enzyme ________ to phosphorylate myosin and increase force.
In comparison to skeletal muscle, smooth muscle cells function over a ________ range of muscle lengths and exhibit a speed of contraction that is ________ than skeletal muscle.
In comparison to skeletal muscle, smooth muscle cells function over a ________ range of muscle lengths and exhibit a speed of contraction that is ________ than skeletal muscle.
What does excitation-contraction coupling refer to?
What does excitation-contraction coupling refer to?
What specific event initiates the contraction of a skeletal muscle fiber?
What specific event initiates the contraction of a skeletal muscle fiber?
How are components of a triad connected?
How are components of a triad connected?
What name is given to the regularly spaced infoldings of the sarcolemma?
What name is given to the regularly spaced infoldings of the sarcolemma?
Which is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?
Which 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?
What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?
What is a cross bridge?
What is a cross bridge?
What structure is the functional unit of contraction in a skeletal muscle fiber?
What structure is the functional unit of contraction in a skeletal muscle fiber?
Where are calcium ions stored within the muscle fiber?
Where are calcium ions stored within the muscle fiber?
What causes cross bridge detachment?
What causes cross bridge detachment?
How does the myosin head obtain the energy required for activation?
How does the myosin head obtain the energy required for activation?
What specific event triggers the uncovering of the myosin binding site on actin?
What specific event triggers the uncovering of the myosin binding site on actin?
When does cross bridge cycling end?
When does cross bridge cycling end?
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
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?
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
What occurs when the neurotransmitter binds to receptors on the motor end plate?
What occurs when the neurotransmitter binds to receptors on the motor end plate?
How is acetylcholine (ACh) removed from the synaptic cleft?
How is acetylcholine (ACh) removed from the synaptic cleft?
Where are calcium ions stored in the muscle cell?
Where are calcium ions stored in the muscle cell?
What role does calcium play in the cross bridge cycle?
What role does calcium play in the cross bridge cycle?
What role does tropomyosin play in the cross bridge cycle?
What role does tropomyosin play in the cross bridge cycle?
How does troponin facilitate cross bridge formation?
How does troponin facilitate cross bridge formation?
What, specifically, is a cross bridge?
What, specifically, is a cross bridge?
Which event causes cross bridge detachment?
Which event causes cross bridge detachment?
Where in the cross bridge cycle does ATP hydrolysis occur?
Where in the cross bridge cycle does ATP hydrolysis occur?
How/when does the myosin head cock back to store energy for the next cycle?
How/when does the myosin head cock back to store energy for the next cycle?
What effect would BMD have on the cross bridge cycle?
What effect would BMD have on the cross bridge cycle?
During contraction, what prevents actin myofilaments from sliding backward when a myosin head releases?
During contraction, what prevents actin myofilaments from sliding backward when a myosin head releases?
Which fibers generate more force?
Which fibers generate more force?
Which ion signals the beginning of skeletal muscle contraction?
Which ion signals the beginning of skeletal muscle contraction?
Slow-oxidative muscle fibers (type I) are characterized by the presence of myoglobin and
Slow-oxidative muscle fibers (type I) are characterized by the presence of myoglobin and
How does the process of smooth muscle contraction differ from contraction in skeletal muscle?
How does the process of smooth muscle contraction differ from contraction in skeletal muscle?
How are cardiac muscle cells similar to smooth muscle cells?
How are cardiac muscle cells similar to smooth muscle cells?
Study Notes
Action Potential and Acetylcholine
- Action potential propagation ceases when acetylcholine (ACh) is removed from the synaptic cleft.
- Acetylcholine is rapidly degraded by the enzyme acetylcholinesterase.
Neuromuscular Junction Function
- Critical event at the neuromuscular junction involves the release of acetylcholine from motor neuron axon terminals.
- Action potentials travel from the brain or spinal cord to the sarcolemma of skeletal muscle fibers.
Calcium and Muscle Contraction
- Calcium entry into axon terminals triggers synaptic vesicles to release acetylcholine.
- When ACh binds to receptors on the sarcolemma, ligand-gated cation channels open, allowing ion flow.
- The arrival of an action potential causes calcium release from the terminal cisternae of the sarcoplasmic reticulum.
- Calcium binds to troponin, exposing myosin-binding sites on actin.
Myosin Functionality
- Myosin heads bind to actin, forming cross bridges.
- The binding of ATP to the myosin head causes it to detach from actin.
- Power stroke is initiated by the release of ADP and inorganic phosphate (Pi) from the myosin head.
- Myosin head's rotation (cocking) is powered by the hydrolysis of ATP.
Muscle Structure and Function
- Muscles move bones at joints; antagonistic muscles allow opposing movements.
- Muscle cells utilize ATP for contraction and relaxation, with phosphocreatine serving as a rapid energy backup.
Muscle Fiber Types
- Slow-twitch oxidative fibers have long contraction durations and high capillary densities, while fast-twitch fibers fatigue sooner and generate more force.
- Myosin heads require actin and ATP binding sites; asynchronous activation of motor units prevents fatigue.
Smooth and Cardiac Muscle
- Smooth muscle cells lack troponin and obtain Ca2+ from both extracellular fluid and the sarcoplasmic reticulum.
- In cardiac muscle, contractions are under autonomic control, and cardiac cells are electrically linked.
Cross Bridge Cycle
- Calcium ions couple excitation of muscle fibers to contraction, stored in the sarcoplasmic reticulum.
- Tropomyosin displacement exposes active sites on actin, facilitating cross bridge formation.
- The cycle ends when calcium is actively transported back into the sarcoplasmic reticulum.
Muscle Cell Activation and Control
- Voltage-gated calcium channels open upon action potential arrival at the axon terminal.
- Exocytosis is the method for releasing neurotransmitters into the synaptic cleft.
Muscle Contraction Dynamics
- Calcium ion binding to troponin alters its shape, allowing muscle contraction.
- ATP binding to myosin is essential for cross bridge detachment, allowing continuous cycling.
Summary of Muscle Conception
- Each motor unit consists of one motor neuron and all muscle fibers it innervates.
- The sarcomere serves as the functional unit of contraction, with muscle contractions triggered by calcium ion release from the sarcoplasmic reticulum.
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Description
This quiz focuses on key concepts from Chapter 12 of your Physiology exam. Explore critical events in neuromuscular junctions and the mechanisms behind action potential propagation in skeletal muscle fibers. Test your understanding and retention of essential physiological processes related to acetylcholine function.
