Anatomy (CNS) · MU Sofia

145. General principles of the histophysiology of the nervous system

Covers the two principal cell types of nerve tissue, neurons and glial supporting cells, starting with the neuron as the structural and functional unit. It sorts neurons into sensory, motor and interneurons, describes the cell body, axon and dendrites, and then classifies neurons as bipolar, pseudounipolar or multipolar, with an example for each. The note closes with peripheral and central neuroglia, naming the four central types: astrocytes, oligodendrocytes, microglia and ependymal cells.

Inside: 3 sections · 3 labelled pictures · 12 flashcards · 3 min

Topic 3 of 34 in the MU Sofia syllabus for Anatomy (CNS) (Medicine, Year 2). The free AceMed note covers it in 3 sections, about 412 words (3 min of reading), with 12 flashcards.

In this note

  1. HISTOPHYSIOLOGY of the nervous system
  2. The Neuron:
  3. Supporting cells:

HISTOPHYSIOLOGY of the nervous system

Nerve tissue consists of 2 principal types of cells:

  1. 1. Neurons (nerve cell)
  2. 2. Supporting cells (glial cells).

The Neuron:

The neuron is the structural and functional unit of the nervous system.

Can be grouped into 3 general categories:

  1. 1. Sensory Neurons - convey impulses from receptors to the CNS.
  2. 2. Motor Neurons - convey impulses from the CNS or ganglia to effort cells.
  3. 3. Interneurons - form a communication between the sensory and motor neurons.

The functional components:

  1. 1. Cell body - contains the nucleus.
  2. 2. Axon - longest process extending from the cell body, transmits impulses away from the cell body to a specialized terminal (synapse).
  3. 3. Dendrites - shorter processes transmit impulses from the periphery towards the cell body.

Neurons are classified on the basis of the number of processes extending from the cell body.

1. Bipolar neurons :

  • Bipolar neurons have an oval-shaped cell body with two processes: one axon and one functioning as a distant dendrite.
  • These neurons serve as sensory neurons and are found in special sensory organs such as the olfactory epithelium, retina, and vestibulocochlear apparatus.
  • The terminal ramifications in the periphery receive signals from sensory organs and combine into one process that reaches the cell body. The axon then transfers the signal to the central nervous system (CNS).
  • Example: Olfactory neurons.

2. Pseudounipolar neurons :

  • Pseudounipolar neurons have a short axon that splits into two processes: one central and one peripheral.
  • These neurons are the most common sensory neurons in the PNS.
  • Example: Dorsal root ganglion neurons, which transmit sensory information from the body to the spinal cord.

3. Multipolar neurons

  • Multipolar neurons have multiple processes: a single axon and multiple dendrites.
  • They are the most abundant type of neurons in the CNS.
  • Example: Motor neurons, interneurons, and pyramidal cells in the cerebral cortex.

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