Overview
This lecture covers the basic structure, classification, and function of neurons, the fundamental units of the nervous system.
Neuron Structure and Function
- Neurons are the basic functional units of the nervous system.
- Humans have about 100 billion neurons, mainly in the brain and spinal cord.
- Each neuron consists of a cell body (soma) containing the nucleus and organelles.
- Dendrites are extensions from the cell body that receive signals from other neurons.
- The axon transmits electrical impulses away from the cell body toward other neurons.
- Axons often end in terminals that connect to other neurons via synapses.
- Myelin sheath, produced by Schwann cells, insulates axons and speeds up signal transmission.
- Neurons communicate through action potentials and neurotransmitters at synapses.
Types of Neurons: Structural Classification
- Multipolar neurons have one axon and multiple dendrites; most common type in humans.
- Bipolar neurons have one axon and one dendrite; found mainly in the retina and nose.
- Unipolar (or pseudounipolar) neurons have a single fused axon-dendrite; common in sensory pathways.
- Anaxonic neurons lack a distinct axon and are found mainly in the brain.
Types of Neurons: Functional Classification
- Sensory (afferent) neurons transmit information from sensory receptors to the central nervous system (CNS).
- Motor (efferent) neurons carry commands from the CNS to muscles or glands (effectors).
- Interneurons connect sensory and motor neurons within the CNS.
Key Terms & Definitions
- Neuron — basic cell of the nervous system that processes and transmits information.
- Cell body (soma) — main part of a neuron containing the nucleus and organelles.
- Dendrite — branch-like structure that receives signals from other neurons.
- Axon — long extension that transmits electrical signals away from the cell body.
- Myelin sheath — insulating layer that speeds up signal transmission along the axon.
- Synapse — junction between two neurons for signal transmission.
- Sensory neuron (afferent neuron) — neuron carrying information to the CNS.
- Motor neuron (efferent neuron) — neuron sending information from the CNS to effectors.
- Interneuron — neuron connecting other neurons within the CNS.
Action Items / Next Steps
- Review neuron parts and types for identification practice.
- Watch linked videos for deeper understanding of action potentials and synapse function.