Cells of the nervous system Flashcards
What supports nuerons? Give the name for the group of cells
Supported by neuroglia
List 7 features of a nueron?
Large nucleus Prominent nucleolus Abundant rER Well developed Golgi (because of need to transport proteins over long distances) Abundant mitochondria Highly organised cytoskeleton HIGHLY ORGANISED METABOLICALLY ACTIVE CELL
Cellular structure of all neurons is similar. State what feature or features is different between nuerons?
Diversity is achieved by differences in the number and shape of their processes.
What determines the differences in morphology between nuerons?
Diversity of morphology determined by location and function
Why do nuerons have an extensive amount of golgi appuratus?
An extensive Golgi apparatus is in keeping with high amounts of protein trafficking via the secretory pathway.
List 5 main features for dendrites?
- major area of reception of incoming information - spread from cell body and branch frequently - greatly increase the surface area of the neuron - often covered in protrusions called spines - dendritic spines receive the majority of synapses - large pyramidal neurons may have as many as 30,000/40,000 spines
When will axons branch?
- may branch after leaving cell body and at target
What are axons prominent in?
prominent microtubules and neurofilaments
How many axons are there usually per cell?
- usually only one per cell
Where do axons emerge from?
- emerge at the axon hillock
What is the role of axons?
- conduct impulses away from cell body
What are axons abundant in?
axons contain abundant intermediate filaments and microtubules
What are varicosities?
Sometimes axons will synapse with many smooth muscle cells as it passes - so you have multiple swellings containing neurotransmitter called VARICOSITIES
What is a bouton?
terminal club-shaped enlargement of a nerve fiber at a synapse with another neuron
What is anterograde transport?
anterograde (forwards from the soma to the axon tip)
What are synapses abundant in?
- abundant mitochondria - 45% of total energy consumption is required for ion pumping and synaptic transmission - sensitivity to O2 deprivation
Name the two types of nuerotransmitters?
neurons use a diversity of chemical transmitters, excitatory and inhibitory
neurons receive multiple synaptic input Make a question
competing inputs are integrated in the postsynaptic neuron (neuronal integration)
Name the 3 types of synapses? State if they are excitory, inhibatory or modulatory?
- axo-dendritic (often excitatory) - axo-somatic (often inhibitory) - axo-axonic (often modulatory)
Draw an axo-dendritic synapse?
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Draw an axo-somatic synapse?
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Draw an axo-axonic synapses?
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What is the range of length for an axon?
in the human adult axons range in length from micrometers to up to a meter meter
What do nueorfilaments play a major role in for axons?
neurofilaments play a critical role in determining axon caliber (diameter)
What is retrograde transport?
moving vesicles containing various molecules back to the cell body
Why do the vesicle only move in one direction?
The microtubules are polarised (positive and negative) so the vesicles can only move in one direction
What are the differences between retrograde and anterograde transport?
retrograde moving vesicles are morpholgically and biochemically distinct from anterograde vesicles Anterograde (also called “orthograde”) transport is movement of molecules/organelles outward, from the cell body (also called soma) to the synapse or cell membrane. Retrograde transport shuttles molecules/organelles away from axon termini toward the cell body.
Axonal damage in multiple sclerosis Add question
Axonal Damage in Multiple Sclerosis If there is a restriction to the axon (e.g. traumatic injury or inflammatory disease) you begin to see SWELLINGS SWELLINGS - vesicles of neurotransmitter keep being transported down the axon and they accumulate because they have no where to go
Name some features of psuedounipolar nuerons?
Tend to be sensory neurons - sense pain often
They have two fused processes which are axonal in structure
The signal received passes directly to the axon terminal without going through the soma
Simplest nueron
Where are psuedounipolar cells located?
The soma (cell body) of each pseudounipolar neuron is located within a dorsal root ganglion
Where are bipolar cells found?
Found in the retina, cerebral cortex and white matter.
What are the types of nuerons according to their length?
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List some features of Golgi type 1 multipolar cells?
highly branched dendritic trees
axons extend long distances
Name some examples of Golgi 1 cells and state where they are found?
Pyrimidal cells of the cerebral cortex
Purkynje cells of the cerebellum
Anterior horn cells of the spinal cord
retinal ganglion cell
Where are purkinje cells found and sketch a purkinje cells?
Cerebellum
Where are pyrimidal cells found and sketch a pyrimidal cell?
Cerebral Cortex
Where are anterior horn cells found?
Spinal cord
Name some features of golgi type 2 cells?
- highly branched dendritic trees
- short axons
- axons terminate quite close to cell body of origin
Give an example of a golgi type 2 cells and state where it is found?
stellate cells of the cerebral cortex and cerebellum
What are nuerons that have both cell bodies and axons inside the CNS known as?
Internuerons
What are nueroglia and what are they essential for?
support cells of the nervous system
essential for the correct functioning of neurons
Name some examples of 7 neuroglia cells?
astroglia
oligodendroglia
microglia
immature progenitors
ependymal cells
Schwann cells
satellite glia
What is the most numerous cell type in the CNS?
Astrocytes
Glial fibrillary acidic protein (GFAP) is a protein that is encoded by the GFAP gene in humans. Glial fibrillary acidic protein is an intermediate filament (IF) protein that is expressed by numerous cell types of the central nervous system (CNS).
What are these cells?
astrocytes and ependymal cells.
Gap junctions are found in Astrocytes.
What does this suggest?
gap junctions suggest astroglia-astroglia signalling
What nueroglia cell make up the blood brain barrier?
Astrocytes
List features of astrocytes?
- Scaffold for neuronal migration and axon growth during development.
- Formation of blood-brain barrier.
- Transport of substances from blood to neurons- important for nutrition of the brain- transport substances -glucose
- Segregation of neuronal processes (synapses).
- Removal of neurotransmitters.
- Synthesis of neurotrophic factors-In the nervous system, neurotrophic factors play a role during development, especially for the differentiation of neuronal and glial cells. Moreover, they promote cell survival of neurons, axons, and oligodendrocytes,
- Neuronal-glial and glial neuronal signalling
- Potassium ion buffering
- Form scars when the CNS tissue is damaged
What are the barrier functions of the CNS?
That thick red line at the top is a stack of astrocyte processes that forms a barrier between the brain and the CSF surrounding the brain. That is called the glia limitans, the brain CSF barrier. The cell bodies are located below the thick red line
-Regulate the transport of anything in the csf and into the brain, and anything in the brain extracellular fluid back into the CSF.
Name the two types of astrocytes and sketch them?
Fibrous and Protoplasmic
Describe the image below
Astrocytes
A very important function of these cells are to control the level of pottasium, water and nuerotransmitters. So when a nuerotransmitter is released from a presynaptic membrane to the postsynaptic membrane something has to stop the action of that nuerotransmitter otherwise it continues to stimulate the receptors- leading to an epilieptic type event. So the nuerotransmitters are either broken down enzymatically or removed by astrocytes processes (glutamate). That is why they have a fuzzy morphology because they have thousands of tiny processes that insert themsleves almost in the synapse.
What is the function of oligodendrocytes?
- the myelin forming cells of the CNS
List some features of oligodedrocytes?
- small spherical nuclei
- few thin processes
- prominent ER and Golgi
- metabolically highly active
Name two disease which are results of loss of myelin?
- Multiple Sclerosis (MS)
- Adrenoleucodystrophy
Why do neonates with very poor nutrition have hypomyelination?
It requires a fast amount of energy for oligodendrocytes to for the multiple myelin sheaths. This process occurs mostly in the forst two years. If there is a restriction of nutritional supply in neonates, there is a lack of myelin. If you look at mri you can see clear indications in a child if he is malnourished.
Why do you have multiple symptoms for Multiple Scelorosis?
The loss of myelin can occur anywhere in the brain, and conduction of Action potential will be slowed down in that area?
Where are microglia cells derived from?
- derived from bone marrow during early development.
State the roles of microglia cells?
resident macrophage population of the CNS
- involved in immune surveillance
- present antigens to invading immune cells
- first cells to react to infection or damage
- role in tissue modelling
- synaptic stripping
Synaptic pruning, which includes both axon and dendrite pruning, is the process of synapseelimination that occurs between early childhood and the onset of puberty in many mammals, including humans. Pruning starts near the time of birth and is completed by the time of sexual maturation in humans.
Name an example of a peripheral glia cell?
Schwann cells
How many myelin sheaths do one schwann cell produces?
- each Schwann cell produces only one myelin sheath
What can schwann cells promote?
Promote axon regeneration
What is synaptic integration
Synaptici ntegration is the computational process by which an individual neuron processes its synaptic inputs and converts them into an output signal.
