Neurohistology Flashcards
What are the nervous tissues and neurons derived from?
They are ectodermally derived
Both the skin and nervous system are derived from the ectoderm, even though one is internal and one is external
Nervous tissue is one of the four basic types of tissue in the body. Its consists of two principle cell types, what are these?
Neurons are described as being excitable, what does this mean?
Neurons are excitable cells with long cytoplasmic extensions specialised for reception of stimuli and conduction of a nerve impulse (action potentials) via an axon
Tell me about neuronal cell division
Is there an exception to this?
Neurons do not undergo cell division and replication
The exception is Olfactory neurons. These are a minority and do undergo cell division and replication.
However, a majority of neuronal cells do not do this
Whats are dendrites and their role?
They recieve information from adjacent axons
(They sit close to cell body and are branched)
Whats the role of axons?
They send information from one end of the neuron to another (this transmission is faster if the axon is myelinated)
Whats the role of the axon hillock?
Signals from the cell soma are summated at the axon hillock. This hillock is considered the ‘trigger zone’ which must reach threshold potential to achieve an action potential
Tell me about the Hillock and axon initial segments (AIS)?
They are both rich in voltage-gated Na+ channels- where signals are summated
These do not have any myelin
What does the Nodes of Ranvier have an accumulation of?
Voltage gated Na+ channels
Label the structure of this neuron
What is used to identify dendrites and why is this used?
MAP2 (microtubule associated protein)
This is a neuron specific cytoskeletal protein which is found in dendrties
A good dendritic marker as it is only found here
Whats used to identify axons?
ßIV Spectrin
This is a cytoskeletal protein which is found in axons as well as some non-neuronal cells
Name some neuronal subtypes?
What is the role of each one?
- Motor neurons: Relay commands from brain and spinal cord to muscles and glands
- Sensory neurons: Are excited by specific stimuli
- Interneurons
Label this motor neuron
The arrows indicate the direction of signal transmission
Cell soma diameter: ranges from 5-135 µm
What is a Golgi stain used for?
The Golgi stain is a method using silver nitrate and potassium dichromate to densely stain an entire single neuron including its dendrite and axon branches.
It results in silver precipitation (from silver chromate) inside the neurons
Only a small subset of neurons are stained with the Golgi method, so the entire structure of those few neurons that are stained is visible for study
Cell bodies of multipolar motor neurons are found where and have what size?
They are large and found in the ventral horn of the spinal cord
How are motor neurons in the spinal cord displayed when stained?
They display a large pale staining nucleus and a prominent nucleolus and Nissl bodies
What does Nissl substance stain?
It stains rough endoplasmic reticulum and polyribosomes
The Nissl stain gives a good indication for what?
Protein synthesis
The Nissl substance is largely absent where?
In the axon
Label this sensory neuron
Arrows indicate the direction of signal transmission
Bring in afferent information
What are ganglia?
Aggregations of nerve cells (ganglion cells) outside the CNS
What are the dorsal root ganglia surrounded by?
A connective tissue capsule, which is continuous with the peripheral nerve
Where we find psudounipolar cells
Individual ganglion cells are surrounded by what?
A layer of flattened satellite (fibroblast) cells
