Question

Unipolar axons are found in (a) Respiratory epithelium (b) Retina (c) Embryo (d) Cerebral cortex

Short answer

The correct answer is (c) Embryo.

Step-by-step solution

Understand what unipolar axons are

Unipolar axons are a type of neuron that are common in the sensory pathways of vertebrates. These axons have a single process emerging from the cell body.

Evaluate each of the options provided

(a) Respiratory epithelium - This part of the body contains primarily pseudostratified ciliated columnar epithelium, not neurons. \n(b) Retina - The retina, part of the eye, contains bipolar cells but does not have unipolar neurons. \n(c) Embryo - In the early stages of development, the human embryo begins to form the neuronal system. It is in the dorsal root ganglia of the embryo where unipolar neurons are predominantly found. \n(d) Cerebral cortex - This is the part of the brain responsible for higher thought processes. It contains mostly multipolar neurons, not unipolar.

Choose the correct answer

Based on the evaluation in step 2, the correct answer is (c) Embryo, since this is where unipolar neurons are predominantly found in early stages of development.

Key concepts

Unipolar Neurons

Unipolar neurons are a distinct type of neuron primarily associated with sensory pathways in vertebrates. They are characterized by having a single process that emerges from the cell body. This process typically bifurcates into two branches: one acting as a dendrite, receiving sensory information, and the other functioning as an axon, transmitting signals to the central nervous system. This unique structure plays a crucial role in relaying sensory information efficiently. Unipolar neurons can commonly be found in the dorsal root ganglia within the sensory pathway framework. Understanding how these neurons function can help in comprehending broader neural networks in the body.

Sensory Pathways

Sensory pathways are essential networks within the nervous system that relay information from sensory receptors to the brain. These pathways begin at the receptors in various parts of the body and follow structured routes to ensure that the brain receives accurate and timely data. An important element in these pathways are unipolar neurons, which effectively carry signals like touch, temperature, and pain. The seamless transmission of these signals is vital for our interaction with the environment.
They help us interpret stimuli from the external world and are essential in daily functioning.

• They primarily involve the peripheral and central nervous systems.
• Relay stations, such as the dorsal root ganglia, modulate the flow of information.

Dorsal Root Ganglia

The dorsal root ganglia (DRG) are clusters of nerve cell bodies found in the dorsal part of the spinal cord. These ganglia serve as a primary hub in the sensory pathway system and house the cell bodies of unipolar neurons. The dorsal root ganglia play a critical role in the transmission of sensory signals from the peripheral to the central nervous system.
Due to their strategic position, they help mediate the communication between the body and the brain. In the context of embryonic development, the DRG is where unipolar neurons originate and begin to form connections.

• Each spinal nerve has a dorsal root ganglion.
• They contain sensory neuron cell bodies.
• Their location is pivotal for the sensory pathways' efficiency.

Embryonic Development

Embryonic development refers to the process by which embryos form and mature from a single cell into a fully developed organism. During this stage, the nervous system begins to develop rapidly. It's in this embryonic stage where the structure and function of neurons, including unipolar neurons, are established. Unipolar neurons first appear prominently in the dorsal root ganglia of the embryo.
As the embryo matures, these neurons lay the groundwork for efficient sensory pathways.

• The development of nervous tissue is a crucial aspect of embryogenesis.
• Proper formation ensures functional integration within the body.
• Neurons continue to specialize and form necessary connections.

Understanding embryonic development gives essential insights into how complex neural systems are designed and how potential abnormalities can affect an organism.