Problem 26 - Biological Psychology

Question

Is denervation supersensitivity a change in axons or dendritic receptors?

Step-by-Step Solution

Answer

Denervation supersensitivity is a change in dendritic receptors, not axons.

Step 1: Understanding the Concept

Denervation supersensitivity refers to the phenomenon where neurons or muscle fibers become more sensitive to neurotransmitters following the loss of innervation. This is a physiological response to maintain function when the usual nerve supply is reduced or eliminated.

Step 2: Identifying What Changes Occur

The change occurs at the level of dendritic receptors, not the axons. When denervation occurs, the number or sensitivity of receptors on the postsynaptic cell (such as a dendrite or muscle cell) increases to compensate for the lack of neurotransmitter release from the axonal terminals.

Step 3: Explaining Dendritic Receptor Changes

The loss of input from the presynaptic neuron causes an upregulation of postsynaptic receptors to try to capture any available neurotransmitter. This results in heightened sensitivity in the postsynaptic cell. The axons themselves do not change in terms of neurotransmitter release or structure in denervation supersensitivity.

Key Concepts

Neuron Sensitivity

Neuron sensitivity is a key feature of how neurons respond to the signals they receive. Think of neurons as highly sensitive messengers within your body. When the usual nerve communication gets disrupted, neurons have to adapt to maintain their function. This is where denervation supersensitivity comes into play.

After a neuron loses its usual nerve supply, it can become more sensitive to neurotransmitters. Neurotransmitters are like tiny chemical messengers that help transmit signals across synapses, which are the small gaps between neurons. To keep these signals strong, the affected neuron compensates by enhancing its responsiveness. This adaptation ensures that even minimal neurotransmitter presence can still trigger a sufficient response. Hence, neurons under this condition adapt to become more receptive, and this denotes an increase in neuron sensitivity.

Dendritic Receptors

Dendritic receptors are special protein structures found on the surface of dendrites. Dendrites are the branched extensions of neurons that receive signals. Imagine them as little docking stations waiting to capture neurotransmitter signals.

During denervation supersensitivity, when a neuron loses its normal input, the number or sensitivity of these dendritic receptors increases. This is the neuron's way of adapting to capture even the slightest amount of neurotransmitter that may float by. The dendritic receptors' heightened readiness allows the neuron to maintain communication, despite the reduction in neurotransmitter supply. It's like turning up the volume on your phone's ringer when expecting an important call — ensuring nothing gets missed, even if the signals are weak.

Neurotransmitters

Neurotransmitters play a pivotal role in neuron communication. These chemical substances are released by neurons to send signals across synapses to other neurons, muscles, or glands. There are different types of neurotransmitters, each serving unique functions, like serotonin for mood regulation or acetylcholine for muscle activation.

In the context of denervation supersensitivity, the importance of neurotransmitters becomes even more crucial. With the regular supply compromised, neurons become more attuned to the available neurotransmitters. They rely on these messengers to maintain functionality despite the decreased communication from axons. The adaptation of receptor sensitivity in response to neurotransmitter availability highlights how integral these chemical messengers are to maintaining neuronal communication in challenging situations.