Intro to Nervous System 2 Flashcards
Describe 4 aspects of an axon
Not tapered like dendrites.
Cylindrical rising from axon hillock.
Microtubule bundles with neurofilaments and mitochondria funnel into the initial segment of the axon.
No nissl bodies or substance.
What happens if the axon is separated from the soma?
The distal axon will die within 24 to 36 hours. This can cause a false reading if a severed nerve is measured within this timeframe.
Why is the initial segment of an axon’s excitability measure by an algebraic sum?
For depolarization. (to fire or not to fire)
Describe the function of a synaptic cleft.
10 - 20 nm wide.
The neurotransmitter is released from the presynapse and diffused across the synaptic cleft thereby binding to receptor molecules on the postsynaptic element.
When sufficient strength is reached, the postsynapse is depolarized.
What are the 2 variations of Schwann cell?
What is an internode?
Myelinated
Unmyelinated…the cell still wraps around the neuron, but there is no fat present.
Internode–myelin between the two nodes of ranvier
If a nerve is severed in the PNS, what has to happen to regenerate the cell?
If severed, the axons have to get back within the Neurilemma (outer layer) in order for regeneration to occur.
Where are the Neuronal Cell bodies of Sensory Neurons found?
Spinal and cranial nerve ganglia, some sensory epithelia.
What are autonomic ganglion cell bodies found?
Sympathetic, parasympathetic, enteric (near internal organs) ganglia.
Where are Schwann cells located?
Myelin sheaths, sheaths of unmyelinated axons.
What is the function of Satellite cells that surround neurons?
Maintain a homeostatic environment.
What was the original determined function of glial cells?
“Glue” Fill up the space between neurons and “hold them in place.”
Describe an Oligodendrocyte tree
Oligodendrocytes myelinate dozens of axons creating internodes on the axons. They are not found on unmyelinated axons because they produce fat. Most prominent in white matter but can be on grey matter.
**Promote axonal growth during development and prevent axonal regeneration/sprouting after an injury.
Describe Astrocytes 5 things.
Name basis
4 functions.
Named for star shape.
CNS metabolism and ionic concentration regulation.
Create gliotic scars after injury with intermediate filaments.
Maintains Blood brain barrier.
Does some signaling.
What are and Where are the 3 types of Astrocytes found?
Protoplasmic Astrocytes are found in grey matter.
Fibrous Astrocytes. are found in white matter.
Radial Astroglia are present during development and provide scaffolding that helps guide growth of neurons. Determines shape and function of neuron.
Describe Ependymal Cells (2)
Form the epithelial lining of ventricles and the central canal of the spinal cord.
Some are specialized as a secretory epithelium that produces cerebrospinal fluid in the choroid plexus.