What is a Neuron? Parts and Function

Introduction

  • Neurons are individual nerve cells that form the nervous system, enabling information travel throughout the body.

  • Neurons are essential for muscle movement, sensory detection, speech, decision-making, and understanding.

Parts of a Neuron

Dendrites

  • Function: Receive messages from other neurons.

  • Communication is through neurotransmitters, which are chemical signals.

  • Examples of neurotransmitters:

    • Dopamine: Reward-seeking and pleasure-related behavior.

    • Acetylcholine: Controls muscle actions.

    • Endorphins: Act as natural pain relievers.

  • Dendrites bind neurotransmitters like a lock and key at receptor sites.

Soma (Cell Body)

  • Function: Integrates and interprets messages received by dendrites.

  • Contains the nucleus, which holds genetic material to sustain the neuron's life.

Axon Hillock

  • Connects the soma to the axon.

  • If the incoming signal is strong enough, it generates an electrical charge called action potential.

Axon

  • The long tube that carries the action potential away from the soma.

  • Length can vary from a few millimeters up to several feet (e.g., from the spinal cord to the toes).

Myelin Sheath

  • Covers the axon, formed by glial cells (specifically Schwann cells).

  • Purpose: Acts as an insulator to speed up electrical impulses down the axon, similar to rubber tubing around a wire.

  • Destruction of myelin leads to conditions like multiple sclerosis, which disrupts communication through the nervous system.

  • Axons can be:

    • Myelinated: Most neurons in the central and peripheral nervous systems.

    • Unmyelinated: Some axons without myelin.

  • White matter in the brain corresponds to myelinated axons; gray matter corresponds to unmyelinated axons.

Nodes of Ranvier

  • Gaps between segments of the myelin sheath.

  • Increase the speed of action potentials through a process called saltatory conduction, where the action potential jumps from node to node.

Axon Terminal (Synaptic Buds)

  • The end of the axon containing synaptic vesicles filled with neurotransmitters.

  • Upon reaching the terminal, action potential causes neurotransmitters to be released into the synapse (the small gap between neurons) to bind with receptors on the next neuron.

Types of Neurons

Motor Neurons

  • Also known as multipolar neurons.

  • Function: Facilitate muscle movements by transmitting signals from the brain.

Sensory Neurons

  • Also known as unipolar neurons.

  • Function: Detect environmental stimuli such as temperature, smells, and sights.

Interneurons

  • Also known as bipolar neurons.

  • Function: Connect motor and sensory neurons, often found in areas like the retina, near ganglion cells.

Conclusion

  • Neurons may vary in appearance but share fundamental structures.

  • The interaction between different neuron types allows for complex nervous system functions.