Nervous Tissue Overview

Purpose

• Receive and transmit electrical impulses.
• Found in brain, spinal cord, and nerves of the body.

Types of Cells

Neurons

• Electrically excitable cells.
• Send and receive signals.
• Structure:
  • Cell Body: Contains nucleus and organelles.
  • Dendrites: Extensions that receive signals.
  • Axon: Long part sending signals to synaptic end bulbs.
  • Myelin Sheath: Lipid-based wrapping on axon speeds up signal transmission.
  • Neurotransmitters: Released from synaptic end bulbs; examples include acetylcholine, dopamine, serotonin.

Neuroglial Cells

• Support and protect neurons.
• Not electrically excitable.

Types of Neuroglial Cells

Central Nervous System (CNS)

1. Astrocytes
   • Form blood-brain barrier.
   • Wrap around capillaries to protect neurons from harmful substances in the blood.
2. Oligodendrocytes
   • Form myelin sheath around multiple neurons.
   • Insulating material to speed up signal transmission.
3. Microglia
   • Act as macrophages (immune system cells).
   • Clean up damaged brain tissue and eliminate microbes.
4. Ependymal Cells
   • Produce cerebrospinal fluid.

Peripheral Nervous System (PNS)

1. Schwann Cells
   • Form myelin sheath around a single neuron.
   • Similar function to oligodendrocytes in CNS but envelop a single axon.
2. Satellite Cells
   • Form sensory ganglia of the autonomic nervous system.