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Questions and Answers
What is the enzyme responsible for degrading/hydrolysing Ach at the neuromuscular junction?
What is the enzyme responsible for degrading/hydrolysing Ach at the neuromuscular junction?
- Achase enzyme
- Acetylcholine oxidase
- Acetylcholine hydrolase
- Acetylcholinesterase (correct)
Which venom causes an explosive release of Ach leading to constant muscle contraction and potential respiratory failure?
Which venom causes an explosive release of Ach leading to constant muscle contraction and potential respiratory failure?
- Scorpion venom
- Black widow spider venom (correct)
- Cobra snake venom
- Black mamba snake venom
What effect does Botulinum toxin have on the neuromuscular junction?
What effect does Botulinum toxin have on the neuromuscular junction?
- Enhances the degradation of Ach
- Increases the release of Ach
- Blocks the release of Ach (correct)
- Promotes the synthesis of Ach
In comparison to EPSP, why is the end-plate potential (EPP) much larger in magnitude?
In comparison to EPSP, why is the end-plate potential (EPP) much larger in magnitude?
What happens when Ach is not degraded at the NMJ?
What happens when Ach is not degraded at the NMJ?
Which compound blocks the action of Ach at receptor channels?
Which compound blocks the action of Ach at receptor channels?
What is released from the axon terminals at the neuromuscular junction to stimulate muscle contraction?
What is released from the axon terminals at the neuromuscular junction to stimulate muscle contraction?
What structure forms when the terminal button of the motor neuron ends on the skeletal muscle fibers?
What structure forms when the terminal button of the motor neuron ends on the skeletal muscle fibers?
Which division of the nervous system controls skeletal muscles and is responsible for conscious movements?
Which division of the nervous system controls skeletal muscles and is responsible for conscious movements?
What is the final common pathway for influencing muscle activity by areas like the primary motor cortex and basal nuclei?
What is the final common pathway for influencing muscle activity by areas like the primary motor cortex and basal nuclei?
At the neuromuscular junction, what does each skeletal muscle fiber receive from one single motor neuron?
At the neuromuscular junction, what does each skeletal muscle fiber receive from one single motor neuron?
Which neurotransmitter is involved in stimulating muscle contraction at the neuromuscular junction?
Which neurotransmitter is involved in stimulating muscle contraction at the neuromuscular junction?
What type of potential is sent down the myelinated axon from the motor neuron to the skeletal muscle?
What type of potential is sent down the myelinated axon from the motor neuron to the skeletal muscle?
Which component of the neuromuscular junction forms a direct connection with the skeletal muscle fibers?
Which component of the neuromuscular junction forms a direct connection with the skeletal muscle fibers?
What specific type of receptor responds to acetylcholine at the neuromuscular junction?
What specific type of receptor responds to acetylcholine at the neuromuscular junction?
What is the role of acetylcholine at the neuromuscular junction?
What is the role of acetylcholine at the neuromuscular junction?
What happens when an axon fiber of a motor neuron loses its myelin sheath and reaches the muscle fiber?
What happens when an axon fiber of a motor neuron loses its myelin sheath and reaches the muscle fiber?
What is the purpose of voltage-gated calcium channels opening at the neuromuscular junction?
What is the purpose of voltage-gated calcium channels opening at the neuromuscular junction?
What effect does acetylcholine have on the motor end plate of skeletal muscle fibers?
What effect does acetylcholine have on the motor end plate of skeletal muscle fibers?
Which channel proteins are present at the motor end plate of skeletal muscle fibers for Ach binding?
Which channel proteins are present at the motor end plate of skeletal muscle fibers for Ach binding?
What is the main function of Action potentials at the neuromuscular junction?
What is the main function of Action potentials at the neuromuscular junction?
What occurs as a result of an end plate potential (EPP) at the motor end plate?
What occurs as a result of an end plate potential (EPP) at the motor end plate?
What happens when an action potential reaches the axon terminal of a motor neuron?
What happens when an action potential reaches the axon terminal of a motor neuron?
What is the primary function of the somatic nervous system?
What is the primary function of the somatic nervous system?
Explain the significance of motor neurons being the final common pathway.
Explain the significance of motor neurons being the final common pathway.
Describe the innervation pattern of motor neurons on skeletal muscle fibers.
Describe the innervation pattern of motor neurons on skeletal muscle fibers.
What is the structure formed when the axon terminal of a motor neuron connects with a skeletal muscle fiber?
What is the structure formed when the axon terminal of a motor neuron connects with a skeletal muscle fiber?
Explain the role of the neural component at the neuromuscular junction.
Explain the role of the neural component at the neuromuscular junction.
What is the function of the muscular component at the neuromuscular junction?
What is the function of the muscular component at the neuromuscular junction?
Why can't a single muscle fiber have connections with two neuromuscular junctions?
Why can't a single muscle fiber have connections with two neuromuscular junctions?
What is the significance of the myelinated axon of a motor neuron in transmitting action potentials?
What is the significance of the myelinated axon of a motor neuron in transmitting action potentials?
Explain the role of acetylcholine in muscle contraction at the neuromuscular junction.
Explain the role of acetylcholine in muscle contraction at the neuromuscular junction.
What differentiates the function of the somatic nervous system from the autonomic nervous system in muscle control?
What differentiates the function of the somatic nervous system from the autonomic nervous system in muscle control?
Each skeletal muscle fiber can be innervated by multiple motor neurons.
Each skeletal muscle fiber can be innervated by multiple motor neurons.
The motor end plate is a structure formed when the axon terminal of a motor neuron connects with a skeletal muscle fiber.
The motor end plate is a structure formed when the axon terminal of a motor neuron connects with a skeletal muscle fiber.
Neuromuscular junctions have only a neural component and no muscular component.
Neuromuscular junctions have only a neural component and no muscular component.
The myelinated axon of a motor neuron sends action potentials down to smooth muscles.
The myelinated axon of a motor neuron sends action potentials down to smooth muscles.
In the neuromuscular junction, one single motor neuron can innervate more than one skeletal muscle fiber.
In the neuromuscular junction, one single motor neuron can innervate more than one skeletal muscle fiber.
Study Notes
Neuromuscular Junctions (NMJ)
- NMJ consists of multiple terminal buttons, each containing thousands of vesicles to store Ach
- Each terminal button releases more neurotransmitter than a pre-synaptic bulb in response to an action potential
- Motor end plate has a higher surface area and more density of receptors than a post-synaptic membrane, resulting in greater influx of positive ions and larger depolarization
- EPP (end plate potential) is larger than EPSP (excitatory post-synaptic potential)
Somatic Nervous System
- Somatic nervous system is the efferent division that controls skeletal muscle
- 1 motor neuron localized in the ventral horn of the spinal cord
- Myelinated axon sends action potential down to the skeletal muscle
- Axon terminals release Ach to stimulate muscle contraction
- Exception: muscles that control the head are localized in the brain, not spinal cord
- Motor neurons are the final common pathway, influenced by upper areas in the brain such as primary motor cortex and basal nuclei
- Somatic nervous system only produces excitation, whereas autonomic nervous system can produce excitation or inhibition
Chemicals/Agents that Act on NMJ's
- Black widow spider venom causes explosive release of Ach, leading to constant muscle contraction and respiratory failure
- Botulinum toxin blocks release of Ach, preventing muscle contraction and leading to respiratory failure
- Curare blocks action of Ach at receptor channels
- Organophosphates prevent inactivation of Ach, resulting in constant muscle contraction
- Myasthenia gravis inactivates Ach receptor-channels
Motor Units
- Motor unit = 1 motor neuron + all skeletal muscle fibers it innervates
- Process of how information is carried from nerve to muscle fiber:
- Action potential travels along axon fiber of motor neuron
- Axon loses myelin sheath and ends in a terminal button near muscle fiber
- Action potential causes voltage-gated Ca2+ channels to open, releasing Ach via exocytosis
- Ach enables communication between axon terminal and skeletal muscle fiber
- Receptors at motor end plate are nicotinic receptors, causing depolarization and muscle contraction
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Description
Explore the process of neurotransmission at the neuromuscular junction, including the influx of Na+ leading to action potential formation and the role of acetylcholinesterase. Learn about the differences between end plate potentials (EPP) and excitatory post-synaptic potentials (EPSP) in neuronal communication.
