NEUROGLIA CELLS

Synapses

• Definition: Connection between a neuron and another cell (typically another neuron).

Types of Synapses

• Axodendritic Synapse:

  • Common type where an axon connects to a dendrite.

• Axosomatic Synapse:

  • Occurs when an axon connects to the soma (cell body) of a neuron.

• Axoaxonic Synapse:

  • An axon connects directly to another axon, bypassing dendrites and soma.

• Neuromuscular Junction:

  • A synapse between an axon and a muscle, enabling motor function and muscle contraction.

• Neuroglandular Synapse:

  • A connection between a neuron and a gland, facilitating the release of substances.

Synapse Examples

• Examples visually displayed in diagram:

  • Axodendritic: Connection shown on the diagram.

  • Axosomatic: Identified by soma connection.

  • Axoaxonic: Illustration of axon to axon connection.

  • Neuromuscular: Demonstrates motor neuron synapse.

  • Neuroglandular: Illustrates neuronal connections with glands.

Neuroglia

• Definition: Support cells that assist neurons.

Functions of Neuroglia

• Provide framework and structural support for neural tissue.

• Maintain the intercellular (interstitial) environment.

• Act as phagocytes, consuming waste and pathogens.

• Capable of reproduction and division (mitosis).

Types of Neuroglia

• Peripheral Nervous System (PNS):

  • Satellite Cells: Protect neurons and facilitate the exchange of materials between the neuron and its environment.

  • Schwann Cells: Form myelin sheath around axons in PNS.

• Central Nervous System (CNS):

  • Oligodendrocytes: Create myelin in the CNS, providing insulation for axons.

  • Astrocytes: Star-shaped glial cells that maintain the blood-brain barrier and interstitial environment.

  • Microglia: Phagocytic cells that remove waste and debris.

  • Ependymal Cells: Line the ventricles of the brain and central canal of the spinal cord, involved in the production and monitoring of cerebrospinal fluid.

Central Nervous System Overview

• Spinal Cord Structure:

  • Transverse section reveals a butterfly shape, with gray matter (cell bodies) and white matter (axon pathways).

Astrocytes

• Structure: Typically star-shaped with numerous cytoplasmic processes that interact with different neural components.

• Function: Regulate the interstitial environment, maintain blood-brain barrier; prevent harmful substances from affecting neurons.

Oligodendrocytes

• Structure: Have cytoplasmic extensions that contact axons and form myelin sheath.

• Function: Increase the speed of nerve impulses via myelination.

Microglia

• Structure: Small cells with feathery processes.

• Function: Act as the immune defense in the CNS; they engulf bacteria and debris.

Ependymal Cells

• Location: Line the ventricles of the brain and central canal of the spinal cord.

• Function: Produce and monitor cerebrospinal fluid (CSF); crucial for cushioning the brain and spinal cord.

Peripheral Nervous System Overview

• Satellite Cells: Support and protect neuron cell bodies.

• Schwann Cells: Similar function to oligodendrocytes in CNS; responsible for forming myelin sheath around peripheral axons.

Summary of Myelination

• Function of Myelin Sheath: Increases speed of action potentials; myelinated axons conduct impulses faster (up to 40 m/s) compared to unmyelinated axons which conduct slower (less than 1 m/s).

Conclusion

• Summary of neuroglia types completes the overview of nervous tissue, paving the way for learning about the brain in subsequent topics.