Overview
This lecture explains how the nervous system communicates using neurons, emphasizing electrical and chemical signaling, neuron structure, and how signals are transmitted rapidly.
Nervous System Overview
- The nervous system consists of the brain, spinal cord, and nerves.
- It communicates using both electrical impulses and chemical messages.
- The nervous system allows movement, sensation, pain perception, and thought.
Neuron Structure and Function
- The main cell type in the nervous system is the neuron.
- Neurons transmit electrical signals called nerve impulses.
- Each neuron has a cell body containing the nucleus and organelles.
- Dendrites are extensions that receive signals from the environment or other neurons.
- Signals travel from dendrites through the axon, a long projection.
Signal Transmission
- The axon carries signals to the axon terminal, where chemicals are released to the next neuron.
- Nerve impulses typically travel at about 1 meter per second.
Myelination and Rapid Impulse Transmission
- Schwann cells wrap around axons, creating an insulating myelin sheath.
- Myelin consists of multiple layers of phospholipid bilayers.
- Gaps between Schwann cells are called nodes of Ranvier.
- In myelinated axons, impulses "jump" from node to node, called saltatory conduction.
- Saltatory conduction enables impulses to travel up to 100 meters per second.
Key Terms & Definitions
- Neuron — a nerve cell that transmits electrical and chemical signals.
- Nerve Impulse — an electrical signal traveling along a neuron.
- Dendrite — neuron extension that receives signals.
- Axon — long fiber of a neuron that transmits signals to other cells.
- Axon Terminal — endpoint where chemicals are sent to the next cell.
- Schwann Cell — cell that forms myelin around axons.
- Myelin — insulating sheath around axons, made of phospholipids.
- Node of Ranvier — gap between Schwann cells on a myelinated axon.
- Saltatory Conduction — rapid impulse transmission by jumping between nodes of Ranvier.
Action Items / Next Steps
- Review the structure and function of neurons and related terminology.
- Study the process of saltatory conduction and its importance in nerve transmission.