Myelin Sheath - ANSWERS-Whitish, fatty (protein-lipid) segmented coating around most (not all) long
axon that is made out of other cells that are not neurons.
,Functions of the Myelin Sheath - ANSWERS-1. Protect the axon
2.Electrically insulate fibers
3. Increase speed of nerve impulse transmission
Fascicles - ANSWERS-Bundles of axons
Types of neuroglia cells in the CNS - ANSWERS-1. Astrocytes
2. Microglia
3. Oligodendrocyte
4. Ependymal Cells
* These cells CANNOT generate action potential
Astrocytes - ANSWERS-Support and brace neurons, and control the chemical environment
Microglia - ANSWERS-The immune cells of the CNS. They phagocytose.
Oligodendrocytes - ANSWERS-The insulators of the thick neurons. Responsible for the myelin sheath of
the CNS.
Ependymal Cells - ANSWERS-Cells responsible for circulating the CSF. Line the central cavities of the brain
and spinal column. Bring in nutrients and filter out waste.
Hydrocephalous - ANSWERS-A condition in which there is excess cerebropspinal fluid in the brain. The
result of ependymal cells not functioning properly.
Types of neuroglia cells in the PNS - ANSWERS-1. Schwann Cells
2. Satellite Cells
* These cells CANNOT generate action potential
,Schwann Cells - ANSWERS-Surround and insulate the axons of the PNS
Satellite Cells - ANSWERS-Support insulate and nourish cell bodies of the PNS
Voltage (V) - ANSWERS-The measure of differences in electrical potential energy generated by separate
charges. (Potential across the membrane)
Current (I) - ANSWERS-The flow of electrical charges between two points. (Ions)
Resistance (R) - ANSWERS-Hindrance to charge flow. (Membrane permeability)
Types of Ion Channels - ANSWERS-1. Leak Channels
2. Chemically (ligand)-gated Channels
3. Voltage-gated Channels
4. Mechanically-gated Channels
Leak Channels - ANSWERS-Ion channels that are always open.
Chemically (ligand)-gated Channels - ANSWERS-Ion channels that opens when a specific ligand bonds to
it. Closed in a resting state. Can be ion-specific or not.
Voltage-gated Channels - ANSWERS-Ion channels that are opened if the voltage outside the cell changes.
Always ion selective. Gates can be opened or closed at different speeds.
Mechanically Gated Channels - ANSWERS-Ion channels that physically open up in the presence of a
stimulus (temp, touch, vibration, etc). Found in sensory receptors.
Sodium/Potassium Pump - ANSWERS-Brings two molecules of K+ in and three molecules of Na+ out. Acts
to reserve an electrical gradient. It works against the the gradient and thus requires ATP.
, Depolarization - ANSWERS-Making the cell less potential
Hyperpolarization - ANSWERS-Making the cell more polarized
Graded Potential - ANSWERS-A short range change in a membrane potential upon a stimulus.
Proportional to the stimulus size. Can spread locally. The site next to the original depolarization event
will also depolarize, creating another graded potential
Axon Hillock - ANSWERS-Trigger zone for action potential
Absolute Refractory Period - ANSWERS-The time after an action potential has been fired and the Na+
channels have not yet reset to their resting positions and a new AP cannot be formed.
Relative Refractory Period - ANSWERS-The time after an action potential has been fired when only some
of the Na+ channels have reset
Multiple Sclerosis - ANSWERS-An autoimmune disease in which the blood brain barrier is essentially
broken. Cells in the immune system are killing the oligodendroglial sites and gradually the myelin sheath
disappears due to current leakage.
Presynaptic Neuron - ANSWERS-Conducts impulses toward the synapse. Can form different synapses
with a postsynaptic neuron. Three different kinds of these synapses.
Axodendritic Synapse - ANSWERS-Synapse between a presynaptic neuron and the postsynaptic neuron's
dendrites
Axosomatic Synapses - ANSWERS-Synapse between a presynaptic neuron and the postsynaptic neuron's
cell body (soma)
Axoaxonic Synapses - ANSWERS-Synapse between a presynaptic neuron and the postsynaptic neuron's
axon
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