Quiz 2 (ch.12) Flashcards
astrocytes (CNS)
support & brace neuron (blood brain barrier), determine capillary permeability (CNS)
microgalia (CNS)
migrate toward injured neuron. phagocytize microorganisms & neural debris
ependymal cells (CNS)
line central cavities of the brain and spinal cord. separate CNS interstitial fluid from CSF in cavities
oligodendrocytes (CNS)
wrap CNS nerve fibers. forms insulating myelin sheath. can myelinate many axons
schwann cells (PNS)
insulate axons w/ myelin. vital to regeneration of damaged peripheral nerve fibers
relative refractory period
A period after firing when a neuron is returning to its normal polarized state and will fire again only if the incoming message is much stronger than usual
absolute refractory period
ensures that each AP is an all-or-none event. enforces one-way transmission of nerve impulses
graded potential
temporary changes in the membrane voltage, the characteristics of which depend on the size of the stimulus
theshold stimulus
push the membrane potential toward/beyond threshold
subthreshold stimulus
does not reach threshold
spatial summation
postsynaptic neuron is stimulated by a large number of terminals at the same time
temporal summation
one or more presynaptic neurons transmit impulses in rapid-fire order
cholinesterase
enzyme that breaks down acetylcholine
acetylcholine
a neurotransmitter that enables learning and memory and also triggers muscle contraction
axon hillock
Cone shaped region of an axon where it joins the cell body (soma).
ions involved in action potential
The principal ions involved are sodium and potassium.
Sodium ions enter the cell, and potassium ions leave, restoring equilibrium. Na+ and K+
EPSP
caused by the flow of positively-charged ions into the postsynaptic nerve. depolarization
IPSP
caused by the flow of negatively-charged ions into the postsynaptic nerve
depolarization
The process during the action potential when sodium is rushing into the cell causing the interior to become more positive.
repolarization
Return of the cell to resting state, caused by reentry of potassium into the cell while sodium exits the cell.
Continuous conduction
- Propagation along unmyelinated axon
- slow because there are always voltage-gated Na+ channels opening, and more and more Na+ is rushing into the cell
Saltatory conduction
- along the length of a myelinated axon
- faster because the action potential basically jumps from one node to the next (saltare = “to leap”), and the new influx of Na+ renews the depolarized membrane
Synaptotagmin protein
binds Ca2+ and promotes fusion of synaptic vesicles with axon membrane
