Nervous System Histology Flashcards
What cells make up the nervous system?
- The neuron is a key cell supported by glial cells:
- Astrocytes
- Oligodendrocytes
- Schwann cells
- Ependymal cells
- Satellite cells of ganglia
- Immune cells = microglia
- Other cells = ependymal cells, choroid plexus
- Peripheral Nerves and ganglia
What is the CNS made up of?
–> The CNS is made up of white and grey matter with 6 layers of neurons and glia.
How are Neurons stained?
–> Neurons are stained using H&E and silver stains.
What is the ventricular system in the nervous system?
- Ventricular System
- Formation and passage of CSF
What is the choroid plexus?
- Choroid Plexus
- Vascular structure arising from the wall of each ventricle
- Forms CSF
Give some features of ependymal cells:
Ependymal Cells:
- Low columnar or cuboidal cells that line the central canal of the spinal cord and the ventricle within the brain.
- In some places have cilia on apical surface to aid CSF flow.
- Different to epithelial cells – non basal laminar
How do neurons differ from other cells?
- Neurons are specialized for signalling
- Morphologically distinct
- Electrically active
- Rapid communication
- Long distance
- Specialized (e.g., transduction mechanisms for the various senses)
- High level of protein synthesis
- Metabolically limited
- Terminally differentiated
- Neurons are able to be stained with Golgi stains and they are morphologically distinct
How is morphology regulated?
The cytoskeleton
What are the three components of the cytoskeleton?
- Neurons are specialized for signalling
- Morphologically distinct
- Electrically active
- Rapid communication
- Long distance
- Specialized (e.g., transduction mechanisms for the various senses)
- High level of protein synthesis
- Metabolically limited
- Terminally differentiated
- Neurons are able to be stained with Golgi stains and they are morphologically distinct
What is the soma of a cell?
- Metabolic centre of the cell
The Cell body gives rise to two types of processes, what are they?
- Dendrites
- Receive information from other neurons
- Axon
- Main conducting unit for carrying signals to other neurons
Explain the properties of volume distribution in the nervous system>
- High proportion of total cell volume is in axons and dendrites
- Axonal transport critical in supply cell-body derived elements
- Random damage often involves axon, not cell body
Explain how signalling is organised in the nervous system?
- Signalling is organized in the same way in all nerve cells.
- Membrane carries graded potentials.
- Unequal distribution of positively charged ions on either side of membrane
- Membranes contain Na, K-ATPase pumps; ion channels.
- Inputs to cell through dendrites.
- Passive electrotonic spread of current – local signal
- Outputs via action potential, propagates long distances.
Where does signalling take place between neurons?
Synapses
Explain the high level of protein production in neurons?
- Highly synthetic cell
- Protein required for ion channels, receptors, cytoskeleton
- Seen in cytology - large pale nucleus, Nissl bodies (rough ER, free ribosomes)
- Special problem of supplying protein to distal extremities
Give some features of the support cells (Glia) of the nervous system?
- Glial Cells include astrocytes, oligodendrocytes, Schwann cells and immune cells known as microglia.
What are some functions of astrocytes?
Passive support functions: - Neurotransmitter uptake and degradation - K+ homeostasis - Neuronal energy supply - Maintenance of the BBB. - Injury response and recovery Active functions: - Modulation of neuronal function - Modulation of blood flow.
Explain glutamate and GABA uptake?
- Glial cells express Glutamate transporters.
- When transporters are inhibited, cells are more depolarized.
How do glial cells modulate calcium levels in cells?
- Glia are excitable and so they have active functions:
- -> Glia show modulations in intracellular calcium (calcium waves)
- -> Initiated by:
- neurotransmitters such as ATP, glutamate
- Trauma
- Spontaneous
- Inflammatory mediators.
What is the method of communication between glial cells?
Mechanism of Glial Communication:
- Glial cells contain synaptic vesicles and show exocytosis.
How do glia regulate neuronal function?
- Neurons are inhibited by calcium wave.
- Mechanism involves release of ATP from glia
How do glial cells regulate vasculature?
- Astrocytes surround blood vessels
- Astrocytes regulate vascular tone.
- Calcium wave initiated within an astrocyte causes vasoconstriction or vasodilation.
Explain the process of myelination and its funciton?
- Oligodendrocytes cells are the predominant glial cell of white matter.
- They are responsible for myelinating axons in CNS. (Schwann cells do this in PNS)
- Provides electrical insulation for neurons Speeds up conduction (as does increased axon diameter)
Give some features of oligodendrocytes and Schwann cells?
- Each oligodendrocyte extend processes that wrap around parts of several axons.
- Schwann cell wrap around one axon.
- Myelin sheath does not cover entire axon. There are small gaps called Nodes of Ranvier.
