Describe the structure and function of a sensory neurone and a motor neurone and state that intermediate neurones connect sensory neurones and motor neurones

SouravNovember 1, 2024

Answer

Sensory neurons and motor neurons are two essential types of nerve cells in the nervous system, each with distinct structures and functions. Additionally, interneurons serve as connectors between sensory and motor neurons.

Structure and Function of Sensory Neurons

Structure:
Sensory neurons, also known as afferent neurons, are primarily characterized by their unique shapes. Most are classified as pseudounipolar, meaning they have a single axon that splits into two branches: one extending to sensory receptors and the other leading to the central nervous system (CNS). The cell bodies of these neurons are typically located in dorsal root ganglia outside the spinal cord. They possess specialized sensory receptors that respond to various stimuli, including light, sound, touch, taste, and internal body conditions like temperature and pain.

Function:
The primary role of sensory neurons is to transmit sensory information from the environment or internal body states to the CNS. They convert stimuli into action potentials, which are electrical signals that travel along their axons to the CNS for processing. This process is known as sensory transduction. For example, when touching a hot surface, sensory neurons detect the heat and send signals to the brain, resulting in the sensation of pain and a reflexive withdrawal from the source of heat.

Structure and Function of Motor Neurons

Structure:
Motor neurons, or efferent neurons, are primarily classified as multipolar, featuring one long axon and multiple dendrites. This structure allows them to integrate signals from various sources before transmitting impulses away from the CNS. The cell bodies of motor neurons are located in the CNS, specifically within the spinal cord for lower motor neurons that innervate skeletal muscles.

Function:
Motor neurons convey commands from the CNS to muscles and glands throughout the body. They play a crucial role in initiating voluntary movements by transmitting impulses that cause muscle contraction. There are two main types of motor neurons: upper motor neurons, which originate in the brain and connect to lower motor neurons in the spinal cord; and lower motor neurons, which directly innervate skeletal muscles. When activated, motor neurons release neurotransmitters at neuromuscular junctions, leading to muscle contraction.

Role of Interneurons

Interneurons act as intermediaries between sensory and motor neurons. They reside entirely within the CNS and facilitate communication between these two types of neurons. Interneurons process incoming sensory information before relaying it to motor neurons, allowing for complex reflexes and coordinated movements. This connection is vital for reflex arcs, where sensory input can lead to immediate motor responses without direct involvement from higher brain centers.