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Questions and Answers
What is the primary function of the nucleus in relation to cellular protein substances?
What is the shape and length of an axon?
What is the characteristic of the cytoplasm of the axon?
What is the function of the myelin sheath in relation to nerve impulse transmission?
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What is the term for the bottleneck in the myelin sheath at regular distances?
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What is the term for the axons surrounded by the myelin sheath?
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What is the likely function of the myelin sheath in relation to the cylindrical axis?
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What is the significance of the final branches of the axon?
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What is the function of Schwann cells in relation to the axon?
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What is the characteristic of the diameter of the axon?
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Study Notes
Nerve Tissue Components
- Nerve tissue consists of two principal types of cells: neurons and supporting cells.
- The human brain contains approximately 100 billion neurons.
Neuron Types
- Neurons are classified based on their anatomic structure and function as:
- Sensory neurons
- Motor neurons
- Interneurons
Neuron Structure
- A neuron consists of:
- Dendrites (to receive signals)
- Cell body (to drive cellular activities)
- Axon (to conduct impulses to target cells)
- Synaptic junctions (specialized junctions between neurons that facilitate the transmission of impulses)
Supporting Cells
- Supporting cells are called neuroglial cells and are located close to the neurons.
- In the CNS, there are four types of glial cells:
- Oligodendrocytes
- Astrocytes
- Microglia
- Ependymal cells
- Each glial cell has a different function.
- In the PNS, supporting cells are called peripheral neuroglia and include:
- Schwann cells
- Satellite cells
- Various other cells with specific structures and functions.
Schwann Cells
- Schwann cells surround the processes of nerve cells and isolate them from adjacent cells and the extracellular matrix by producing a lipid-rich myelin sheath.
- This ensures the rapid conduction of nerve impulses.
Satellite Cells
- Satellite cells are similar to Schwann cells, but they surround the nerve cell bodies.
Oligodendrocytes
- Oligodendrocytes produce and maintain the myelin sheath in the CNS.
Nerve Composition
- A nerve is composed of a collection of bundles of nerve fibers.
- Within the CNS, the brain and spinal cord tissue can be classified as:
- Gray matter (made up of neuronal cell bodies)
- White matter (composed of myelinated nerve fibers)
Cell Body Components
- The cell body contains:
- Mitochondria (participate in the regulation of cell respiratory mechanisms, metabolic processes, and energy homeostasis)
- Golgi apparatus (functions as a factory in which proteins are further processed and sorted for transport)
- Nissl's granules (rough endoplasmic reticulum with rosettes of free ribosomes, site of protein synthesis)
- Lysosomes (contain digestive enzymes and devour foreign particles that enter the cell body)
- Nucleus (contains DNA and controls the formation of RNA, synthesis, and composition of cellular protein substances)
Axon Structure
- The axon is the primary appendage that emerges from the body of the nerve cell.
- The axon is cylindrical in shape, with a constant diameter throughout its length.
- The axon is either branched or single and ends with the final branches that form the synapse area.
- The axon is surrounded by the myelin sheath, which is secreted by Schwann cells, and contains Ranvier's nodes.
- Axons can be classified as:
- Myelinated fibers (surrounded by the myelin sheath)
- Non-myelinated fibers (not covered by the myelin sheath)
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Description
Learn about the basic structure and function of neurons, the building blocks of the nervous system. Discover the different types of neurons and their roles in the human brain.
