ch 48 bio
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Glia vs. Ganglia
- glia function in Neuron support, Nourish neurons, Insulate axons, and Regulate
- extracellular fluid surrounding neurons
ganglia- cluster of neurons that carry out high order processing
where axon joins cell body
What are the major classes of neurotransmitters?
- Think of the acrostic: All Boys Are Not Good
- 1. Acetylcholine
- 2. Biogenic amines
- 3. Amino acids
- 4. Neuropeptides
- 5. Gases
Graded potential vs action potential
- Graded - changes in the membrane potential of a neuron where the magnitude of the change varies with the strength of the stimulus. Graded potentials are not the nerve signals that travel along an axon, but do influence their generation.
- action potential - nerve impulses that occur when the membrane voltage reaches a certain value, known as the threshold. Action potentials are considered an "all-or-nothing" phenomenon, there is no variance in their strength - it either occurs, or does not. Unlike graded potentials, action potentials have a constant magnitude and can regenerate in adjacent regions in the membrane. Action potentials arise because some ion channels in neurons are voltage-gated ion channels, meaning that they open when the cell's membrane potential passes a certain level. If a depolarization causes voltage-gated sodium channels to open, sodium ions flow into the neuron causing further depolarization. This depolarization causes more voltage-gated sodium channels to open, allowing sodium ions to flow in, which causes even more sodium channels to open. The result is a process of positive feedback which triggers the opening of all voltage-gated sodium ion channels and the production of the marked change in membrane potential that characterizes an action potential.
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