Neuroscience 2 - Cells of the Nervous System Flashcards
What are the main features of neurons? (6)
- Large nucleus.
- Prominent nucleolus.
- Abundant rER.
- Well developed Golgi.
- Abundant mitochondria.
- Highly organized cytoskeleton.
What are dendritic spines?
They are protrusions from thin dendrites and receive the majority of synapses.
How many spines do large pyramidal neurons have roughly?
30,000-40,000.
Where does the axon emerge from?
The axon Hillock.
How many axons per cell?
Usually only one.
Why do axons have an abundant of intermediate filaments?
To ensure the tensile strength that it needs.
What are branches of the axons called?
Axons collaterals.
Why are axons the same diameter throughout from the hillock to the end?
To maintain a constant speed of transmission of the action potential.
What is the paranode?
- The area where the binding end of myelin forms tight junctions with the neurone.
- Prevents leakage of current under the myelin sheath.
What is the juxtaparanode?
The area adjacent to paranode where K+ and Ca2+ channels are found.
What are the 2 forms of axon terminals?
- Boutons.
2. Varicosites - multiple swellings containing neurotransmitter - synapsing with many smooth muscle cells.
What is neural integration?
It is when competing inputs are integrated in the postsynaptic neurone.
What are the 2 types of synaptic inputs?
- Excitatory.
2. Inhibitory.
What are axo-dendritic synapses?
A synapse between the axon and dendrite - often excitatory.
What are axo-somatic synapses?
A synapse between the axon and the cell body - often inhibitory.
What are axo-axonic synapses?
A synapse between the axon and another axon - often modulatory.
How are proteins transported in the axon?
- Proteins are packaged into vesicles and then the vesicles attach to microtubules.
- The microtubules are polarized and hence the vesicles only move in one direction.
- Vesicles are moved using motor proteins that require ATP.
What is retrograde transport?
Moving molecules in vesicles back towards the cell body.
What happens when there is axonal damage?
- This results in swellings in the axon.
- This is because the vesicles of neurotransmitter keep getting transported down but accumulate at the point of injury as there is no where for them to go.
What are the morphological subtypes of neurons?
- Pseudounipolar - sensory neurons have two fused processes, which are axonal in structure., signal does not pass through soma.
- Bipolar - Involved in the white matter of cerebral cortex.
- Golgi type I Multipolar - highly branched dendrites, long axons. E.g. pyramidal, purkinje and retinal ganglion cells.
- Golgi type II Multipolar - highly branched, short axons. E.g. Stellate cells.
What are Neuroglia? Examples?
- Support cells of the nervous system.
- They have varied functions and are essential for the correct functioning of neurons.
- Examples include Astroglia, Oligodendroglia, Microglia and Schwann cells.
What are Astroglia?
- They are star-shaped cells and are the most numerous type of cell in the brain.
- They form gap junctions.
What are the functions of astroglia? (7)
- Scaffold for neural migration and axon growth during development.
- Formation of blood-brain barrier.
- Transport of substances from blood to neurons.
- Removal of neurotransmitters.
- K+ buffering.
- Synthesis of neurotrophic factors.
- Segregation of neuronal processes.
What are Oligodendroglia?
- The myelin forming cells of the CNS.
- There are 2 types - interfascicular and perineuronal.
- They are highly metabolically active and have a prominent ER and Golgi.
- Also have a small spherical nuclei.
