BMS 108 Ch. 7 Nervous System Part 1 Flashcards
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What are the two kinds of cells that make up the nervous system?
neurons and glial cells
What are the two structural divisions of the Nervous System?
- Central Nervous System
2. Peripheral Nervous System
What are the functional units of the nervous system?
neurons
What do glial cells do?
Help maintain homeostasis and “help neurons”.
Glial cells are ___ times more common than neurons.
5
What are neurons?
Electrically excitable cells that gather and transmit information.
What are the three ways in which neurons gather and transmit information?
- Responding to stimuli (from other neurons or external inputs) “transduction”
- Producing and sending electrical impulses
- Releasing chemical messages
What are the two types of axons?
Myelinated and unmyelinated
What does myelin do?
electrically insulates the axon
What are the gaps inbetween myelin on a myelinated axon called?
Nodes of Ranvier
What glial cells are responsible for myelinating axons in the CNS?
Oligodendrocytes
Do oligodendrocytes myelinate just one axon?
No
What glial cell myelinates axons in the PNS?
Schwann cells
What are the glial cells in the CNS? in the PNS?
Astrocytes, oligodendrocytes, microglial cells, ependymal cells; Schwann cells and satellite cells
Why are some axons myelinated?
To increase conduction velocity
What are the reasons not to myelinate an axon?
- Myelin costs energy to produce
- Some very small unmyelinated fibers are actually faster than they would be if we myelinated them
In addition to myelin, what is another way to speed up electrical velocity?
Increased diameter of the axon
What is white matter?
Portion of the nervous system with myelinated axons
What is gray matter?
Portion of the nervous system with unmyelinated axons
What is the difference between a neuron, a nerve and a tract?
A neuron is 1 nerve cell; a nerve is a bundle of axons in the PNS; a tract is a bundle of axons in the CNS
How does an axon regenerated in the PNS?
- Schwann cells survive and form a regeneration tube.
- Tube releases chemicals (neurotropins) that attract growing axon
Can axons regenerate in the CNS?
Limited
Why is regeneration in the CNS limited?
Oligodendrocytes produce proteins that inhibit regrowth and form glial scar tissue that blocks regrowth.
Axons can be both _____ and _______.
long; short
What are the four special transport systems for axons?
- Axoplasmic flow
- Axonal transport
- Anterograde transport
- Retrograde transport
What is Axoplasmic flow?
Moves soluble compounds toward nerve endings away from the cell body (slow, nonspecific)
What is Axonal Transport?
Moves large and insoluble compounds bidirectionally along microtubules, uses cytoskeleton (fast, specific).
What is Anterograde Transport?
Moves materials away from the cell body.
What is Retrograde Transport?
Moves materials toward the cell body.