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Neurons (slides)
Neurons Powerpoint Slides
| Question | Answer |
|---|---|
| Interneurons | provide communication between other neurons; do not exit the CNS |
| Motor Neurons | efferent in nature (away from CNS); activate muscles or glandular response usually have long axons that are myelinated |
| Sensory Neurons | afferent in nature (towards CNS); identified by Roman numeral and a lower case letter |
| Alpha Motor Neurons | high conduction velocities (50 - 120 m/s); innervate majority of skeletal muscles (extrafusal muscle fibers); activate prime movers of motor act |
| Gamma Motor Neurons | slower velocity (40 m/s); innervate intrafusal muscles fibers within muscle spindle; responsible for maintaining muscle tone and muscle readiness for the motor act |
| Cell Gradients | established between inside and outside the cell; ions have a tendency to flow to equalize the charge; pumps move ions to increase the gradient |
| Two basic forms of gradients | Electrochemical gradients; Concentration gradients |
| Electrochemical Gradient | in neurons, the gradient is established using electrical charge and molecule density; ions are atoms that have either lost or gained an electron |
| Concentration Gradients | molecules tend to move from an area of higher concentration to an area of lower concentration to equalize the concentration; analogy: tea bag in water |
| Gradients: particle movement | within a cell: if charged particles move, it produces an electrical current; if ions move across a membrane to enter/leave a cell, the very act of moving creates an electrical current |
| Electroencephalography (EEG) | traces sum of much neural activity within the brain, produced by "generators" |
| Auditory Brainstem Response Testing (ABR) | an audiologist records the electrical activity of neurons to determine whether the auditory pathway is intact; he/she presents a stimulus such as a pure tone or click and then measures the electrical emanations from the brain stem area |
| Permeability | the with which molecules may pass through a membrane |
| Neuron membrane's permeability | semi-permeable: some ions may pass through it, given appropriate circumstances |
| Types of transport | Active transport, passive transport |
| Passive Transport | this type of ion movement is considered to be passive transport because no energy is expended to move the ions across the barrier; rather the gradient established by the inequalities between the two sides of the membrane causes the ion movement |
| Passive Transport Gatekeepers | voltage-sensitive proteins serve as gatekeepers; they open the channel when they receive adequate electrical stimulation; channel proteins also serve as gatekeepers; they allow specific ions to pass through the membrane |
| Active Transport | active pumping is required to move the ions across the barrier; energy is expended to accomplish this task |
| Active Transport | ion pumps: their role is to move sodium (Na) and potassium (K) ions against the gradient; energy used by the sodium-potassium pump proteins is in the form of ademosine triphosphate (ATP); a product of the mitochondria of the cell |
| Sodium-Potassium Pumps | operate continuously; they move 3 Na+ ions out for every 2 K+ ions moved in; this active transport is required to readjust the balance of ions across the membrane |
| Resting Membrane Potential (RMP) | -70 mV |
| Action Potential | change in electrical potential that occurs when a cell is stimulated adequately to permit ion exchange between the intra- and extracellular spaces |
| What is the critical threshold? What happens when it is reached? | -55 mV; depolarization begins: the Na+ ion gates open up causing a large number of Na+ ions to flood the intercellular space; membrane potential goes positive |
| What happens when the cell reaches its peak? | Na+ gates close, K+ gates open, K+ is propelled out of the cell by its concentration and electrostatic gradients; membrane potential drops rapidly |
| What happens when the cell reaches its lowest point? | K+ gates begin to close; sodium-potassium pump helps restore resting membrane potential |
| absolute refractory period | time during which the cell membrane cannot be stimulated to depolarized; no amount of depolarization will cause cell to depolarize again |
| relative refractory period | period after the absolute refractory period; period during which the membrane may be stimulated to excitation again, but it needs a greater than typical amount of stimulation |
| How long does an AP take? | > 1 ms in most neurons |
| propagation | refers to the spreading effect of wave action; the AP is "propagated" in a wave of depolarization |
| Nodes of Ranvier | nodes of exposed membrane along an axon between "donuts" of myelinated axon; necessary for saltatory conduction |
| saltatory conduction | "leaping" conduction; the propagating AP is passed from node to node (bypassing myelinated segments); in long fibers can save milliseconds |
| EPSP | Excitatory Postsynaptic Potential; excitation causes depolarization; begins as a micropotential (~3mV), a sufficient number of EPSPs will cause depolarization |
| IPSP | Inhibitory Postsynaptic Potential; inhibition causes hyperpolarization; does not change thresholds but lowers starting point |
| Two types of summation | 1. temporal, 2. spatial |
| Spatial Summation | represents many points of contact arrayed over the surface of the postsynaptic neuron; some neurons require many near-simultaneous synaptic activations |
| Temporal Summation | two or more closely successive impulses arrive, then a synapse is established (may occur with only one presynaptic neuron |
Created by:
sullivancl
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