Questions and Answers
What triggers the exocytosis of synaptic vesicles at the sympathetic neuroeffector junction?
How does norepinephrine (NE) affect the target cell?
What happens after NE binds to its adrenergic receptor?
What role do voltage-gated Ca2+ channels play in the sympathetic neuroeffector junction?
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Which process is responsible for the removal of norepinephrine (NE) from the synapse?
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What initiates the action potential at the varicosity of an axon?
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What is the primary role of norepinephrine in the sympathetic nervous system?
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Why is the process of neurotransmitter removal important?
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Which component is essential for the entry of Ca2+ during the action potential at the varicosity?
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What is the immediate effect of Ca2+ entry into the varicosity?
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What is the primary ion involved in creating the neuronal action potential?
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During the latent period of a muscle twitch, which phase occurs before tension develop?
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What is typically the resting membrane potential in a muscle fiber?
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Which structure transmits the action potential from the Central Nervous System to muscle fibers?
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What occurs during the contraction phase of a muscle twitch?
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What triggers the exocytosis of synaptic vesicles in the axon varicosity?
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What happens to norepinephrine (NE) after it has activated the adrenergic receptor?
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What is the role of monoamine oxidase (MAO) in the context of norepinephrine?
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What triggers the opening of voltage-gated calcium channels?
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Which type of receptors do postganglionic parasympathetic target cells predominantly utilize?
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How is norepinephrine removed from the synapse?
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What occurs when norepinephrine binds to an adrenergic receptor?
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Which of the following is NOT a characteristic of muscarinic receptors?
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What main effect does the influx of calcium ions have in the context of neurotransmission?
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How does receptor activation in the sympathetic nervous system cease?
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What is the primary characteristic of somatic pathways?
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Where is the cell body of a somatic motor neuron typically located?
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What are varicosities primarily responsible for in autonomic synapses?
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What triggers the exocytosis of synaptic vesicles in sympathetic neuroeffector junctions?
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What neurotransmitter is released at the neuromuscular junction?
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Which neurotransmitter is released at sympathetic neuroeffector junctions?
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What type of receptors are found on the postsynaptic membrane of skeletal muscle fibers?
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How does receptor activation cease after norepinephrine binds to its receptor?
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How does relaxation of skeletal muscles occur?
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Where are the primary autonomic neurotransmitters synthesized?
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What occurs when an action potential reaches the axon terminal of a somatic motor neuron?
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What role does voltage-gated Ca2+ channels play in neurotransmitter release?
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What role does calcium play at the axon terminal in somatic motor pathways?
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Which statement about somatic motor neurons is true?
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What is the primary function of adrenergic receptors in postganglionic sympathetic target cells?
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What is the purpose of the motor end plate on skeletal muscle fibers?
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What is the primary role of monoamine oxidase (MAO) at the sympathetic neuroeffector junction?
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In somatic motor pathways, what would likely happen if the neuronal pathways were blocked?
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Study Notes
Autonomic Synapses
- Varicosities are swollen areas at the distal ends of autonomic axons containing neurotransmitters for release.
- Neurotransmitters diffuse across the synapse and attach to receptors on target cells.
- Primary autonomic neurotransmitters include acetylcholine and norepinephrine, both synthesized in the axon varicosities.
Neurological Function at Sympathetic Neuroeffector Junction
- Action potentials reach varicosities, which causes depolarization and the opening of voltage-gated Ca²⁺ channels.
- Entry of Ca²⁺ ions triggers the exocytosis of synaptic vesicles containing norepinephrine (NE).
- NE binds to adrenergic receptors on target cells, leading to various physiological responses.
- Activation of adrenergic receptors ceases when NE diffuses away and is removed via reuptake into synaptic vesicles or metabolism by monoamine oxidase (MAO).
Receptor Types
- Adrenergic receptors respond to norepinephrine and have multiple subtypes.
- Muscarinic receptors, present in postganglionic parasympathetic cells, are G protein-coupled with various second messenger pathways and at least five subtypes.
Somatic Motor Division
- Somatic pathways are primarily voluntary and always excitatory, with no antagonistic innervation for relaxation.
- The cell body of somatic motor neurons is located in the ventral horn of the spinal cord or the brain, projecting directly to skeletal muscle.
- Activation of somatic motor neurons leads to contraction of skeletal muscles through acetylcholine (ACh) binding to nicotinic receptors.
Neuromuscular Junction
- An action potential at the axon terminal causes calcium channels to open, permitting Ca²⁺ influx.
- This calcium entry causes synaptic vesicles to fuse with the presynaptic membrane, releasing ACh into the synaptic cleft.
- ACh binds to nicotinic receptors on the motor end plate of the skeletal muscle fiber, leading to muscle fiber excitation.
Muscle Contraction Dynamics
- The process of muscle twitch consists of three phases: latent period, contraction phase, and relaxation phase.
- The development of tension varies during each of these phases, and recording electrodes can measure changes in membrane potential in response to action potentials.
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Description
This quiz explores the structure and function of autonomic synapses, specifically focusing on varicosities and their role in neurotransmitter release. Understand how these swollen areas facilitate communication with target cells through diffusion and receptor binding.
