Neural Structure and Signaling (6/23/15) Flashcards
Neurons make up _____% of all CNS cells.
10%
Myelin _____ action potential speed.
Increases!
______ is the trigger zone for action potentials.
Axon hillock (Intial segment)
True or false, neurons are Terminally differentiated
True, they are non-dividing
What is the Soma of a neuron?
Contains the nucleus and is used for protein synthesis.
Where are vesicles stored?
Axon terminals
What are the 3 main classes of Neurons?
- Afferent = Sensory/Input transmit info to CNS
- Interneurons = Located within CNS and function as integrators and switches.
- Efferent = Motor/output Neurons transmit commands to effector cells. (cell bodies within CNS but axons project outside.
* SAME = sensory afferent/Motor Efferent
____ make up 90% of cells in CNS.
Glial Cells
What are the Gilal cells of the CNS?
Ogliodendrocytes and Microglia (Provide myelination)
What are the Gilal cells of the PNS?
Schwann cells (Provide myelination)
What is a Microgila?
(Glial cell) A macrophage like cell that has phagocytic role.
Has:
- Unreactive (resting state)
- Reactive state
What is an astrocyte?
A CNS Gilial cell that:
- Regulates extracellular fluid (Remove K+ and neurotransmitters) buffering role.
- Provide neurons metabolically (such as glucose)
- Surround brain capillaries (form blood-brain barrier)
Schwann cell provides myelin to ________.
One axon (Many schwann cells per axon)
Oligodendrocytes provide myelin to ______.
many axons
What Clinical condition is associated with Peripheral demyelination?
Guillian-Barre Syndrome (Demylenation of motor neurons)
Nerve damage
Describe the Neuron to Microglia interaction….
- Neuron keeps Microglia Unreactive with neuron glycoprotein CD200.
- Neuronal injury releases intracellular ATP inducing motility (Reactive)
- Microglia move to site of injury.
Describe the Microglia to Neuron interaction….
Not well understood, but they make physical contact with healthy neurons and are involved in “Pruning” unused dendrites.
______ is transport of material (Nutrients, enzymes, neurotransmitters) away from the cell body down the axon.
Anterograde transport
- Fast rate around 400mm/day (Neurotransmitter vesicles)
- Slow transport 2-2.5 mm/day (Structural proteins)
_______ is transport of materials towards the cell body of neuron.
Retrograde transport
- Fast 400 mm/day (motor protiens “Dyneins”)
Viruses are commonly transported via _______.
Retrograde transport
- Herpes
- Rabies
- Polio
_______ plays a large role in nerve regeneration.
Axonal transport
- Retro & Antero
Nerve growth and regeneration in CNS vs PNS, Go!
CNS = neurons do not regenerate! Axons “Sprout” but do not reach targets due to Scar formation.
- Astroycytes also make Chondroitin sulfate proteoglycans that inhibit nerve growth.
PNS = axons DO regenerate here! Which is important for dental procedures such as extractions.
- Functional recovery can take place depending on severity.
What is a “Severe Nerve injury” and what is the response to it?
A severe nerve Injury tends to be close to the cell body in the Nerve trunk.
- We will see Anterograde and terminal degeneration of injured portion of neuron.
- Cell death may occur - at this point regeneration is impossible.
- Transganglionic degeneration = degeneration of central process of axon.
- Transsynaptic Degeneration = Induces degeneration on 1st central neuron that cell synapsed on.
What is a “Less severe Nerve injury” and what is the response to it?
A less severe nerve injury is further away from the cell body.
* All that happens here is Anterograde and Terminal degeneration (Terminal degeneration is the degeneration of axon terminals specifically)
Describe the Roll of Schwann cells in regeneration…..
Schwann cells produce Laminin for substrate for regenerating axons.
They also secrete NGF (nerve growth Factor) that is transported to the Ganglion body.
What does NGF (Nerve growth factor) do?
It regulates gene expression and promotes sprouting.
How does Collateral sprouting occur?
NGF moves via Retrograde Transport and then collaterals sprout off of axon since NGF promotes sprouting.
Do teeth allow rein nervation of nerves?
No!