Question

When a visceral organ is denervated, a. it ceases to function. b. it becomes less sensitive to subsequent stimulation by neurotransmitters. c. it becomes hypersensitive to subsequent stimulation. d. no change occurs.

Short answer

When a visceral organ is denervated, it becomes hypersensitive to subsequent stimulation.

Step-by-step solution

Choice A

If a visceral organ is denervated, it ceases to function: This option might partly be true, as the organ can lose some of its nerve supply and automatic regulation by the autonomic nervous system. However, it doesn't mean that the organ will stop functioning entirely, as there might still be some residual activity.

Choice B

If a visceral organ is denervated, it becomes less sensitive to subsequent stimulation by neurotransmitters: This option is opposite of what happens after denervation. When an organ is denervated, it becomes hypersensitive to stimulation, and not less sensitive.

Choice C

If a visceral organ is denervated, it becomes hypersensitive to subsequent stimulation: This option is correct. When an organ loses its nerve supply, it compensates by becoming hypersensitive to stimulation from neurotransmitters. This increased sensitivity helps the tissue or organ adapt to its loss of nerve supply.

Choice D

If a visceral organ is denervated, no change occurs: This option is incorrect. As mentioned before, when an organ is denervated, it becomes hypersensitive to stimulation. In conclusion, the correct answer to this exercise is: c. When a visceral organ is denervated, it becomes hypersensitive to subsequent stimulation.

Key concepts

Autonomic Nervous System

The autonomic nervous system (ANS) plays a crucial role in the regulation of involuntary bodily functions such as heart rate, digestion, and respiratory rate. It functions largely unconsciously and includes both the sympathetic and parasympathetic nervous systems.
The sympathetic nervous system prepares the body for 'fight or flight' responses, increasing heart rate and blood flow to muscles.
Conversely, the parasympathetic nervous system promotes 'rest and digest' activities, slowing the heart rate and enhancing digestion.

When considering visceral organ function, the ANS provides the essential neural input that helps regulate and maintain homeostasis. It helps organs respond appropriately to changes in the body and environment. Without it, as in the case of denervation, organs may lose some of their regulation and adaptive response abilities, hence compensatory mechanisms such as hypersensitivity might come into play.

• Sympathetic and parasympathetic divisions act in balance.
• Denervation disrupts this regulation.
• Hypersensitivity may occur as a compensatory measure.

Neurotransmitter Sensitivity

Neurotransmitters are chemical messengers that transmit signals across a synapse from one neuron to a target cell, which could be another neuron or an organ. The sensitivity to neurotransmitters is an essential feature of how cells respond to signals.
This sensitivity ensures that the body's cellular responses are finely tuned and appropriate to the level of stimuli being received.
In visceral organs, sensitivity to neurotransmitters supports various functions such as contracting muscles or secreting substances.

In the case of denervated organs, there is often an increase in neurotransmitter sensitivity, contrary to what some might expect. This increase in sensitivity compensates for the lack of nerve input, enabling the organ to still respond effectively to the much-needed signals.

• Neurotransmitter sensitivity aids in cellular communication.
• Denervation leads to increased sensitivity.
• This compensatory mechanism ensures continued function.

Organ Hypersensitivity

When a visceral organ becomes hypersensitive, it responds more intensely to stimuli than it normally would. This is a common response after denervation, where the lack of regular neural input causes the organ to overcompensate by becoming more reactive to neurotransmitters.
Hypersensitivity is not always beneficial; while it can help maintain function, it may also lead to exaggerated responses that could potentially disrupt normal processes.
For instance, hypersensitivity in the digestive tract might lead to conditions like diarrhea or cramping due to overly active muscles or glands.

Understanding organ hypersensitivity is crucial because it highlights the body's innate ability to adapt, though sometimes with imperfect results.

• Hypersensitivity aids in compensation for denervation.
• Can lead to exaggerated responses.
• Reflects the body's adaptive mechanisms.