L3 Cells Of The Nervous System Pt 2 Flashcards
How can we classify neurons?
By structure:
- Number of neurites
- Dendritic geometry
- Connections
- Axon length
By gene expression:
- Underlies structural differences
- Defines neurotransmitter expression
What are neurites?
Refers to any projections from the soma of a neuron.
What are the types of neurites by number?
- Unipolar
- Bipolar
- Multipolar
- Pseudo unipolar
If you wanted to find out the density of neurons in a given brain area which technique would you use?
Nissl staining
What is the difference between unipolar and pseudo unipolar?
Unipolar- a single process extending from cell body.
Pseudo unipolar - it has a single projection but each end branches out into something different. e.g. CNS or muscles
What is a bipolar neuron?
Bipolar neuron has two processes extending from it: one axon and one dendrite.
The axon is the process that transmits signals to other neurons, and the dendrite is the process that receives signals from others neurons
Where are bipolar neurons generally found?
Found in the retina of the eye
Give me 3 features of multipolar neuron
- Majority of neurons in the brain
- Large area for receiving synaptic input
- High levels of convergence
Give me 2 examples of other multipolar neurons
- Stellate
- Pyramidal neurons
What is a sensory neuron?
Also known as afferent neurons, are responsible for converting external stimuli into signals that the brain can interpret
What is a motor neuron?
Motor neurons are vital for our ability to move, breathe, and perform essential bodily functions. They are the link between the nervous system and our muscles and glands.
What are the 2 categories within interneuron?
- Relay or projection neurons (connect brain regions)
- Local interneurons
(Short axons and process information in local circuits)
Can glia proliferate throughout life?
Yes
What are the 3 functions that can be performed by different types of glial cells?
- Homeostatic
- Myelinating
- Phagocytic
Name the homeostatic glia cells of CNS and PNS.
CNS - Astrocytes
PNS - Satellite cells
Which glial cells are responsible for homeostatic function ?
CNS - Astrocytes
PNS - Satellite cells
ENS - Enteric glia
What glial cells are responsible for the function of myelinating?
CNS - Oligodendrocytes
PNS - Schwann cells
What glial cells are responsible for the phagocytic function?
CNS - Microglia
PNS - Schwann cells & Macrophages
What do astrocytes do? (5)
- They control environment surrounding neurons.
- They act as fuel suppliers
- They buffer extracellular potassium
- Form part of the blood brain barrier
- Couple neuronal activity to blood supply
Why do astrocytes act as fuel supplies?
They can take up glucose from the blood and convert it to lactate. Lactate is a fuel that neurons can use to generate ATP
What is the end feet of the astrocytes?
They are close association with blood vessels allowing them facilitate the transport of nutrients from the blood to the brain tissue which can be ultimately used for ATP for neurons in lactate form
What is the tripartite synapse?
Tripartite synapse expands on the traditional synapse (pre+postsynaptic membrane) by including the surrounding astrocyte
What happens at the tripartite synapse?
- Terminates neurotransmitter activity
- Recycles neurotransmitters to presynaptic terminals
Do astrocytes have receptors?
They have receptors.
What are microglia?
They are a type of glial cells that are found in the central nervous system
What is the role of microglia?
They have a key role in tissue surveillance and phagocytosis
They can also have harmful roles in neurodegeneration
What is the difference between oligodendrocytes and shwann cells?
Oligodendrocytes myelinate multiple neuron - axons.
Schwann cell myelinate a single neuron - axon.
What are oligodendrocytes?
They are a type of glial cell that are responsible for producing myelin sheaths of CNS axons
Can have 15-30 processes from cell body to myelin sheaths
What do Schwann cells do?
They form myelin sheath of PMS
One Schwann cell provides one myelin segment to a single axon
Describe the formation of the myelin sheath
Process of oligo cytoplasms wraps many times around the axons
Cytoplasm squeezed out of layers by compaction
Myelin sheath maintains contact with glial cells for nourishment
Imagine a swiss roll.
What is the function of myelin?
It’s primary function is to increase the speed of nerve impulse transmission
How does the myelin sheath increase the speed of impulse transmission?
1) Myelin acts as an eletrical insulator which wraps around the axon, preventing the leakage of ions across the axonal membrane
2) Gaps in the sheath called Nodes of Ranvier are essential for generating action potentials
3) Insulation provided allows current to ‘jump’ rapidly from one node to the next - saltatory conduction
Give me an example of a unipolar neuron
Dorsal root ganglion
