Lecture 6: Cells of the Nervous System

Question 1

Why are neurons “special” cells?

Answer 1

• most pleomorphic cell type
• morphologically polarized
• electrically excitable
• cells communicate at synapses
• long processes require powerful transport mechanisms
• enormous energy requirements can only be met by oxidative metabolism
• post-mitotic => lost cells cannot be replaced

Question 2

How are neurons similar to other cells in the body?

Answer 2

they possess all characteristic organelles of eukaryotic cells (nucleus, ER, Golgi apparatus, mitochondria, cytoskeleton, etc) and have no organelle that is specific to them

Question 3

What are the defining features of neurons?

Answer 3

• derived from epithelial cells
• polarized, with dendrites corresponding to the basolateral compartment and axons to the apical compartment of epithelial cells
• typically have one or several dendrites, one cell body, and a single axon, and multiple axon terminals

Question 4

What types of cells are microglia?

Answer 4

• resident immune cells
• not derived from ectoderm, but mesoderm
• must migrate into brain before the blood-brain barrier forms

Question 5

What are the main categories of macroglia?

Answer 5

• astrocytes (CNS)
• oligodendrocytes (CNS)
• polydendrocytes (CNS)
• ependymal cells (CNS)
• satellite cells (PNS)
• Schwann cells (PNS)

Question 6

astrocytes

Answer 6

macroglial cells in CNS that perform the following general functions:

• ion homeostasis, K buffering
• transmitter removal/synapses
• energy supply and nutrition (maintain extracellular glucose and lactose levels)

Question 7

oligodendrocytes

Answer 7

macroglial cells in the CNS that function in myelination

Question 8

radial glial cells

Answer 8

guide neural migration during development

Question 9

Schwann cells

Answer 9

macroglial cells in the PNS that function in myelination

Question 10

In what important ways are glia different from neurons?

Answer 10

• cells are usually smaller: smaller volume, shorter branches, and less surface area
• often star shaped, but often non polar
• relatively lower energy requirement, function well under anaerobic conditions
• gliogenesis in adults
• can modify phenotype and morphology (gliosis)
• not directly involved in signaling (but modify it)
• not excitable cells

Question 11

nucleus

Answer 11

a brain structure (CNS) consisting of a relatively compact cluster of neurons

Question 12

tract (fasiculus)

Answer 12

• a bundle of axons within the CNS

- do not need connective tissue for protection

Question 13

Pyramidal tracts

Answer 13

• somatic motor output tracts
• go through pyramids structure
• 2 major tracts:
  
  • corticobulbar: motor cortex to brain stem
  • corticospinal: motor cortex to spinal cord
• control skeletal muscle movement