Structure and Types of Neurons

STRUCTURE OF NEURONS

Functional Units of the Nervous System

  • Neuron (nerve cell)

    • Neurons serve as the fundamental units for communication in the nervous system, sending messages to various parts of the body.

    • They receive information from other neurons and pass it along to subsequent neurons.

Components of Neurons

  • Cell Body

    • Contains the nucleus and other organelles that are integral for neuron function.

    • Usually located centrally within the neuron.

  • Dendrites

    • Structures that connect the neuron to receptor cells or other neurons.

    • Information is transmitted along the dendrites towards the cell body.

  • Axon

    • Responsible for carrying information away from the cell body toward other neurons or effectors (e.g., muscles, glands).

  • Myelin Sheath

    • A protective and insulating layer that coats the axon.

    • Functions:

    1. Increases the speed of transmission of electrical impulses.

    2. Prevents interference between signals in neighboring neurons.

  • Synaptic Knob

    • The part of the neuron that can form a junction (synapse) with the dendrites of other neurons or with effector organs.

TYPES OF NEURONS

Sensory Neurons

  • Function: Carry information about sensory stimuli to the central nervous system (CNS).

  • Types:
    A. Some sensory neurons receive sensory stimuli directly and convert this information into electrical impulses.
    B. Other sensory neurons receive information from receptor cells.

  • Structure:

    • Most sensory neurons possess one long dendrite that typically divides into shorter branches at the end, allowing for multiple connections with receptor cells.

Motor Neurons

  • Function: Transmit electrical impulses from the central nervous system to effectors (muscles or glands).

  • Structure:

    • Motor neurons typically feature short dendrites and a long axon to send information over distances to effector cells.

Relay Neurons

  • Found exclusively in the central nervous system.

  • Function: Transmit impulses between sensory and motor neurons.

  • Information flow: Sensory information is transferred from sensory neurons to relay neurons in the brain, often passing through multiple relay neurons before reaching motor neurons.

  • Structure:

    • Relay neurons generally consist of many short axon terminals that carry nerve impulses from the cell body to motor neurons.