Nervous System Cell Types and Functions

Oligodendrocytes vs. Schwann Cells

• Oligodendrocytes are found in the central nervous system (CNS) and can insulate multiple axons (up to 50).
• Schwann cells reside in the peripheral nervous system (PNS) and wrap around a single axon.

Microglia

• Microglia are a type of glial cell in the central nervous system.
• They provide immune defense and function similarly to macrophages by engulfing pathogens.

Glial Cells

• Glial cells are non-excitable cells that do not fire action potentials.
• They support neurons physically and metabolically.

Functions of Glial Cells

• Glial cells insulate axons with myelin, offer protection, and help maintain the extracellular environment.
• They also participate in neurotransmitter release and clearance.

Macrophages

• Macrophages are large white blood cells responsible for engulfing pathogens, including bacteria.

Nervous System Cell Types

• The nervous system consists of two main cell categories: neurons and glial cells (glia).

Central vs. Peripheral Nervous System

• The central nervous system includes the brain and spinal cord.
• The peripheral nervous system comprises all other neural components.

Functions of the Nervous System

• The nervous system rapidly responds to environmental changes and facilitates cell communication for homeostasis.

Evolutionary Aspects of the Nervous System

• The human nervous system has evolved to enhance cognition and emotion.

Synaptic Transmission

• At a synapse, the presynaptic neuron sends the signal, while the postsynaptic neuron receives it.

ATP Synthase vs. ATPase

• ATP synthase is responsible for synthesizing ATP, whereas ATPase hydrolyzes ATP for energy use.

Myelination of Neurons

• Not all neurons are myelinated; for instance, multipolar interneurons lack myelin.

Action Potentials and Nodes of Ranvier

• Action potentials "jump" between nodes of Ranvier due to the electrical conductivity of the axon cytoplasm and the insulating properties of myelin, allowing faster transmission.

Myelin Structure

• Myelin is formed by glial cell outgrowths and serves as an electrically insulating layer around axons.

Common Glial Cells

• The most prevalent type of glial cell is the astrocyte.

Functions of Astrocytes

• Astrocytes play key roles in maintaining the blood-brain barrier, regulating blood flow, neurotransmitter dynamics, and interstitial fluid composition.

Simple Nervous Systems

• A nerve net is a basic network of neurons found in some organisms, facilitating direct communication from sensory cells to effectors.

Neuronal Clusters

• Groups of neurons are referred to as ganglia.

Brain Structure

• The brain is a massive collection of ganglia that coordinates higher processing.

Nervous System in Simple Organisms

• Sea anemones possess a nerve net, while sponges do not have a nervous system.

Earthworm Nervous System

• Earthworms have a segmental nerve cord equipped with pairs of ganglia.

Complexity in Nervous Systems

• Squids exhibit more complex nervous systems than earthworms due to specialized ganglia that process and integrate information.

Divisions of the Peripheral Nervous System

• The PNS is divided into two main parts:
  • Afferent (sensory) division
  • Efferent (motor) division.

Explore the differences between oligodendrocytes and Schwann cells, and the crucial roles of microglia and other glial cells in the nervous system. This quiz will test your understanding of how these cells support neurons and maintain homeostasis in the nervous system. Dive into the essential functions of both glial cells and macrophages in immune defense.