Nervous System Overview

Nervous System Overview

• The nervous system consists of two categories of cells: neurons (nerve cells) and glia (glial cells)
• Neurons generate and transmit electrical signals, while glia provide support and maintain the extracellular environment
• A common neural stem cell gives rise to all cells in the nervous system

Structure of a Typical Neuron

• Neurons have a basic structure consisting of dendrites, cell body, axon, and terminals
• Dendrites receive signals, the cell body integrates the signals, the axon transmits the signal, and the terminals release neurotransmitters

Types of Glial Cells

• Macroglia: oligodendrocytes, astrocytes, and Schwann cells
  • Oligodendrocytes produce myelin and insulate axons in the CNS
  • Astrocytes contribute to the blood-brain barrier and provide nutrients to neurons
  • Schwann cells insulate axons in the PNS
• Microglia provide immune defenses in the CNS

Neuron Communication

• Neurons communicate with each other and with other cells through electrical and chemical signals
• Electrical signals: action potentials, ion channels, and ion transporters
• Chemical signals: neurotransmitters, synapses, and receptors

Action Potentials

• Action potentials are rapid, large, and transient changes in membrane potential
• The sodium-potassium pump establishes concentration gradients and generates the resting potential
• Voltage-gated Na+ channels open and close to generate the action potential
• The refractory period is the time during which the neuron cannot generate another action potential

Synapses

• Chemical synapses: release of neurotransmitters from the presynaptic cell, binding to receptors on the postsynaptic cell
• Electrical synapses: direct electrical connection between neurons through gap junctions
• The neuromuscular junction is a chemical synapse between motor neurons and skeletal muscle cells

Neurotransmitters and Receptors

• Neurotransmitters bind to specific receptors to elicit a response
• Ionotropic receptors: ligand-gated ion channels, fast and excitatory
• Metabotropic receptors: G-protein coupled receptors, slower and longer-lived
• Examples of neurotransmitters: ACh, glutamate, GABA, dopamine

Neural Networks

• Neurons are organized into neural networks for information processing
• Afferent neurons carry sensory information, efferent neurons carry commands, and interneurons integrate information
• The central nervous system (CNS) consists of the brain and spinal cord, while the peripheral nervous system (PNS) consists of neurons and support cells outside the CNS

Learn about the unique cells of the nervous system, how neurons generate and transmit electrical signals, and how they communicate with other cells.