Neurophysiology Pt 2 Quiz

Glial Cells

• Glial cells lack axons and dendrites, making them smaller than neurons.
• Glial cells fill spaces in the nervous system not occupied by neurons or blood vessels.
• Glial cells can divide and are more numerous than neurons in nervous tissue.
• Glial cells do not produce action potentials and do not participate directly in synaptic interactions and electrical signaling.

Types of Glial Cells

• Microglial Cells

  • Act as macrophages, releasing NO to prevent viral replication.
  • Participate in phagocytosis to clear debris.
  • Protect the brain against injury and infection.
  • Aid brain development by helping to destroy unnecessary synapses.

• Astrocytes

  • Star-shaped cells with numerous long processes.
  • Make up 50% of the glial cell population within the CNS.
  • Provide structural and metabolic support to neurons.
  • Maintain neurons' working environment by controlling neurotransmitter levels and ion concentrations.

• Oligodendrocytes

  • Provide support to axons and neurons in the CNS.
  • Extend processes to form myelin around adjacent axons.

• Ependymal Cells

  • Cover brain ventricles, central canal of the CNS, and the choroid plexus in the 4th ventricle of the medulla oblongata.
  • Involved in creating CSF (cerebrospinal fluid).

• Schwann Cells (Neurolemmocytes)

  • Found in the PNS.
  • Form myelin sheath around axons, with each cell forming internodes of the myelin sheath.

Neurons

• Neurons are specialized in processing information.
• Neurons are the major functional unit of the nervous system.
• Neurons do not divide once they reach maturity, so any injury leading to neuronal death will permanently change the structure and function of the affected area.
• Neurons communicate via synapses.

Structure of Neurons

• Dendrites

  • Receive information from other neurons.
  • An information-receiving area of the cell membrane.

• Soma (Cell Body or Perikaryon)

  • Contains organelles.

• Axon

  • An information-carrying extension of the cell membrane.
  • Action potentials travel down the axon at a speed of 0.5-120 meters per second.

• Axon Hillock (Trigger Zone)

  • Where the axon originates, and action potentials originate.

• Presynaptic Terminal

  • Located at the end of the axon, used for information transmission.

• Myelin Sheath

  • A modified plasma membrane wrapped around the axon in a spiral fashion.
  • Enhances the speed of information transmission by acting as an electrical insulator and allowing saltatory conduction of impulses.

Classification of Neurons

• Multipolar

  • Have 1 axon and many dendrites.
  • The most common structure type.

• Bipolar

  • Have 1 axon and 1 dendrite.

• Pseudo-unipolar (Unipolar)

  • Have 1 single stem process that bifurcates to form 2 processes, where 1 process goes to the CNS and the other process goes to the PNS.

Function of Neurons

• Sensory (Afferent) Neuron

  • Send information from sensory organs towards the CNS.
  • Most sensory neurons are pseudo-unipolar.

• Motor (Efferent) Neuron

  • Send information to effector organs (muscles and glands) from the CNS.
  • All motor neurons are multipolar neurons.

• Interneuron (Association Neuron)

  • Connect motor and sensory neurons together.
  • Found in the CNS, usually multipolar or bipolar neurons.