Lesson 3: Cells of the Nervous System and Organization of Tissues Flashcards
Two(2) Principal Kinds of Cells are:
Neuroglia
Neurons
are the “nerve glue” or the cells that support the neurons of the CNS.Their name originates from the idea of early histologists that they were the “glue” that held nervous tissue together
Neuroglia Cells / Supporting Cells
Neuroglia Cells / Supporting Cells provides:
SPIN
Support
Protection
Insulation
Nutrition
They are smaller but they greatly outnumber neurons, perhaps by as much as 5 to 25 times and they do not generate action potentials. They continue to divide throughout an individual’s lifetime.
Neuroglia Cells / Supporting Cells
Six types of Neuroglia:
Found in CNS:
Astrocytes
Oligodendrocytes
Microglia
Ependymal Cells
Found in PNS:
Schwann Cells
Satellite Cells
Type of Neuroglia:
- are star-shaped cells with many processes. The processes make contact with blood capillaries, neurons and the pia matter
Astrocytes (astro- = star; -cyte = cell)
2 types of Astrocytes:
Protoplasmic Astrocytes
Fibrous Astrocytes
Type of Astrocytes:
with many short branching processes (location:gray
matter)
Protoplasmic Astrocytes
Type of Astrocytes:
with long unbranched processes (location: mainly
white matter)
Fibrous Astrocytes
consists of cellular structure that selectively inhibit certain substances in the blood from entering the interstitial spaces of the brain or CSF, thus making the nervous system impermeable to large & potentially harmful molecules.
Blood Brain Barrier - BBB
A component of BBB:
- encircle the capillaries-secrete chemicals that maintain the permeability characteristics of the tight junctions
Astrocytes & astrocytic feet/processes
A component of BBB:
- Pericytes cover the basal lamina of the endothelium and contribute to the structural integrity of the BBB.
The capillary basement membrane/basal lamina with embedded pericytes.
A component of BBB:
- consists mainly of tight junctions that seal together the
endothelial cells of brain blood capillaries and a thick basement membrane that surrounds the capillaries.
The tight JUNCTION between the OVERLAPPING endothelial cells of the brain capillaries
Type of Neuroglia:
- These resemble astrocytes but are smaller and contain fewer processes.
- Give support by forming semi-rigid connective tissue rows between neurons in the CNS
- Produce phospho-lipid for the myelin sheath around axons of neurons in the CNS - responsible for forming and maintaining the myelin sheath around CNS axons.
Oligodendrocytes - (oligo- = few; -dendro- = tree)
Type of Neuroglia:
- These neuroglia are small cells with slender processes that give off numerous spinelike projections.
- Act as macrophages – they engulf & destroy microbes and cellular debris/act as macrophages formed during normal development of the nervous system and phagocytize microbes and damaged nervous tissue.
Microglia or Brain Macrophages or Microglial Cells
Type of Neuroglia:
- are cuboidal to columnar cells arranged in a single layer that possess microvilli and cilia. These cells line the ventricles of the brain and central canal of the spinal cord (spaces filled with cerebrospinal fluid, which protects and
nourishes the brain and spinal cord).
- Form a continuous epithelial lining for the ventricles of the brain & the central canal of the spinal cord
- Assist in the formation & circulation of CSF in the ventricles of the brain & the central canal of the spinal cord
Ependymal Cells or Ependymocytes - (epen-= above; -dym- = garment)
Type of Neuroglia:
- Form myelin sheath around axons of neurons of the peripheral nervous system
o myelinates a single axon
o A single Schwann cell can also enclose as many as 20 or
more unmyelinated axons (axons that lack a myelin
sheath)
- participate in axon regeneration, which is more easily
accomplished in the PNS than in the CNS.
Schwann Cells
Type of Neuroglia:
- these flat cells surround the cell bodies of neurons of PNS ganglia
- Provides structural support,
- Regulate the exchanges of materials between neuronal cell bodies and interstitial fluid.
Satellite Cells
- are the basic functional unit of the nervous system
- they are the primary cells of the nervous system.
- its primary function is the conduction of impulses from one part of the body to another.
- it has the ability to respond to a stimulus and convert it into action potential (electrical excitability).
Neurons or Nerve Cells
The fuel source for neurons is predominantly…
Glucose
responsible for most special functions of the nervous system like perception, rationalization, memory, muscle control and glandular secretion regulation.
Neurons
- they are irreplaceable
- they are highly specialized cells, most have lost the ability to undergo mitotic divisions
Neurons
Parts of Neuron:
Cell Body
Dendrite
Axon
The main portion of a neuron and contains a nucleus surrounded by
cytoplasm where organelles such as lysosomes, mitochondria & Golgi
complex are found.
Cell Body
- are clusters of rough Endoplasmic reticulum and free ribosomes.
- are the site of protein synthesis in neurons and are used to substitute cellular components, as material for growth of neurons, and to restore damaged axons in the PNS.
Nissl bodies
cytoskeleton; for cell shape and support
Neurofibril