Neurons and Glia Flashcards
What is the size of a neuron?
10-40um
What are the three challenges associated with visualizing neurons?
- The size
- Obtaining nervous tissues that are sufficiently thin
- They are generally colorless
What types of stain helped along the study of neuron cells? What was the difference between the two types?
- Nissl staining only revealed parts of the cell
- Golgi staining with silver nitrate revealed two parts of the neurons, the soma and neurites (axons/dendrites)
- Ramon y Cajal improved the stain method to prove neurons were not in continuity
How wide is the synaptic cleft usually?
20nm or 0.02 um
What type of microscope is specially able to see the synaptic cleft?
Electron microscopes
What cells are generally found in the soma? What happens in this cell?
The Krebs cycle is undergone and the synthesis of ATP in the mitochondria found in the soma.
How can we tell the branches (collaterals) of the axon specially?
They are at a right angle to the axon hillock
What is the big function of the Axon hillock?
It is the site of the initiation of action potentials.
What are the two differences in the composition of axons and soma?
- The Endoplasmic Reticulum does not reach into the axon
- The protein composition of the axon is special
What are the 4 listed differences between the nerve terminals and axons?
- There are no microtubules in the nerve terminal
- There is the presence of synaptic vesicles in the nerve terminal
- There is an abundance of membrane proteins in the nerve terminal
- There is a large number of mitochondria found in the nerve terminal
What part of the cell makes up most of its surface area? What is its diameter?
The dendrites are 0.1-3um in diameter
What are dendritic spines? What neural processes are they associated with?
mushroom or spine shaped structures on dendrites that receive signals from other neurons. They are associated with memory and learning.
What are three regions of specialized cell membrane?
The presynaptic, postsynaptic, and axonal membranes
What are the three types of filaments in the neuron? What organelle are they found in?
In the cytoskeleton, microtubules, microfilaments, and neurofilaments are found
What are microtubules responsible for?
The movement of organelles, and it is a responsible for molecular motors
What are microfilaments responsible for?
Dynamic change of shape
What are neurofilaments responsible for?
support and stability
What are the two directions of axoplasmic movement?
Anterograde (soma to axon) and Retrograde (axon to soma)
What are the requirements for anterograde axoplasmic transport?
Kinesins interact with microtubules, ATP is used
What are the requirements for retrograde axoplasmic transport?
It requires dyneins and consumes ATP.
What do the different directions of nerve tracings tell us?
Anterograde tracing tells us what areas cell bodies innervate (labels cell terminals), and retrograde tracing tells us what cell bodies innervate which areas (labels the somas)
What are the categories of neuronal classification?
- Based on the number of neurites
- Based on cell morphology
- Based on the length of the axon
- Based on Connectivity
- Based on Secreted Transmitter
- Based on function
- Based on Molecular origin
How can we distinguish axons from dendrites?
Axons have 90 degree angle branches, no dendritic spines, and can grow to larger diameters above 3um.
What type of tracing would be used to determine which neurons send synaptic signals to an area?
Retrograde
What type of tracing would be used to determine which areas are innervated by a soma?
Anterograde
What are the classifications of neurons based on the number of neurites?
Unipolar, bipolar, and multipolar
What are the two classifications of cell based on morphology? What are the distinctions?
Somatic
-Oval/Spherical cells
-Pyramidal cells
Dendritic
-Lots of Dendrites
-Longer
-Branching pattern
What are the two classifications of cell based on length of the axon?
Golgi 1 neurons
-Longer axons (projection neurons)
Golgi 2 neurons
-short or no axons (Local neurons)
What are the three types of neuron based on connectivity? What are they attached to?
Sensory-sensory receptors
Motoneurons - muscles or glands
Interneurons - other neurons in the CNS
When classified by neurotransmitter, what is the suffix of the classification? What is an example of this?
ergic
eg. dopaminergic
What are the 3 types of neurotransmitter classification based on function?
Excitatory
Inhibitory
Modulatory (either)
What are glia?
Non-neuronal nervous system cells that are for neuronal support
What are the types of glia? (4)
Astrocytes
Oligodendrocytes
Schwann Cells
Microglia
What are the roles of astrocytes? (4)
-Fill the spaces between neurons in the brain
-influence neurite growth
-regulate extracellular ionic concentrations
-shape synaptic transmission
Which glia are responsible for the myelination of which subsections of the nervous system? What is different between them?
Oligodendrocytes wrap around multiple axons and are found in the Central Nervous System
Schwann Cells wrap around a single axon and are found in the Peripheral Nervous System
What is the role of myelin in neurons?
It insulates axons and increases the speed of transmission
What are the gaps in the myelin sheathes of axons called? What is its purpose?
The Nodes of Ranvier allows for saltatory transmission
What is the role of microglia?
They are phagocytes that are responsible for the immune system and the elimination of dead cells and waste
