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Ch. 11 Introduction to the Nervous System and Nervous Tissue
Amerman- Human Anatomy & Physiology 3e
Amerman3rd EditionHuman Anatomy & PhysiologyISBN: 9780138247201, 9780138247928, 9780138201814Not the one you use?Change textbook
All textbooksAmerman 3rd EditionCh. 11 Introduction to the Nervous System and Nervous TissueProblem L3.2
Chapter 11, Problem L3.2

During a surgical procedure, an anesthesiologist administers to the patient an inhaled anesthetic agent that opens Cl− channels in the postsynaptic membranes of neurons in the brain. Explain why this would put the patient 'to sleep' for the duration of the surgical procedure.

Verified step by step guidance
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Understand the role of Cl⁻ (chloride) channels in neuronal activity: Chloride ions are negatively charged. When Cl⁻ channels open, chloride ions flow into the neuron, making the inside of the neuron more negative (hyperpolarization). This makes it harder for the neuron to reach the threshold needed to fire an action potential.
Explain the importance of action potentials in brain activity: Action potentials are the electrical signals that neurons use to communicate. If neurons cannot fire action potentials, communication between neurons is disrupted, leading to a decrease in brain activity.
Connect hyperpolarization to reduced brain activity: By opening Cl⁻ channels, the anesthetic agent causes hyperpolarization of the postsynaptic membrane. This inhibits the ability of neurons to fire action potentials, effectively silencing neural communication in the brain.
Relate reduced brain activity to the anesthetic effect: The suppression of neural communication in key areas of the brain, such as those responsible for consciousness and sensory processing, leads to a loss of awareness and sensation, which is perceived as the patient being 'asleep.'
Summarize the mechanism: The inhaled anesthetic agent induces hyperpolarization by opening Cl⁻ channels, which inhibits neuronal firing and reduces brain activity, thereby putting the patient into a state of unconsciousness suitable for surgery.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Inhaled Anesthetic Agents

Inhaled anesthetic agents are volatile compounds used to induce and maintain general anesthesia during surgical procedures. They work by altering neuronal activity in the brain, leading to a reversible loss of consciousness and sensation. These agents are delivered through a vaporizer and inhaled, allowing for rapid onset and control of anesthesia depth.
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Chloride Channels and Neuronal Inhibition

Chloride channels are integral membrane proteins that allow the flow of Cl<sup>−</sup> ions across the neuronal membrane. When inhaled anesthetics open these channels, it leads to hyperpolarization of the postsynaptic neurons, making them less likely to fire. This inhibition of neuronal activity is crucial for inducing the state of unconsciousness associated with general anesthesia.
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Mechanism of Action in the Central Nervous System

The mechanism of action of anesthetics involves their interaction with various receptors in the central nervous system, including GABA receptors. By enhancing inhibitory neurotransmission and reducing excitatory signals, anesthetics effectively suppress brain activity. This results in the patient being 'put to sleep,' as the brain's ability to process sensory information and maintain consciousness is significantly diminished.
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Albert, the patient in question 3, takes the drug lithium, which reduces the permeability of the neuronal axolemma to Na+ (that is, it allows fewer Na+ to enter the axon). Predict the effect this would normally have on his neuronal action potentials. Do you think this drug would be beneficial or harmful, considering his condition?

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