Flashcards in Chapter 12 Deck (21):
Neuroglia of CNS
Neuroglia of the PNS
Form myelin sheath in brain and spinal cord.
Lines the brain and spinal cord, secretes and circulates CSF
Phagoctize that destroy microorganisms, foreign matter and dead nervous tissue
1. Cover the brain surface and non synaptic regions of neurons
2. From supportive framework in CNS
3. Induce formation of blood brain barrier
4. Nourish neurons
5. Produce growth factors that stimulate neurons
6. Communicate electrically with neurons and may influence synaptic signaling.
7. Remove K+ and some neurotransmitters fro ECF of the brain and spinal cord
8. Help to regulate composition of ECF from scar tissue to replace damaged nervous tissue.
Neuroglia of PNS
1. Schwann Cells
2. Satellite Cells
Form neurilemma around all PNS nerve fiber and myelin around most of them; aid in generation of damaged nerve fibers.
Surrounding somas of the neuron in the ganglia; provide electrical insulation and regulates chemical environment of neurons
Produced by gated channels on the dendrites and soma
Produced by voltage-gated channels on the trigger zone and axon.
Always begins with depolarization
All or non; either does not occur at all or exhibits the same peak voltage regardless of stimulus or strength.
May be a positive (depolarizing) or negative (hyperpolerizing) voltage charge Graded proportional to strength.
Irreversible, goes to completion once it begins
Reversible; returns to RMP if stimulation ceases before threshold is reached
Has effects for only a short distance from point of origin.
Decremental signal grows weaker with distance
Self-propagating; has effects a great distance from point of origin
Nondecremental' signal maintains same strength regardless of its distance