Term
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Definition
- provide communication between other neurons
- do not exit the CNS (brain and spinal cord)
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Term
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Definition
- established between inside and outside cell
- ions have a tendency to flow to equalize "pressure"
- pumps move ions to increase gradient
- we turn on faucets to let ions floor in
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Term
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Definition
- in neurons, gradient is established using electrical charge and molecular density rather than gravity pulling on water
- using magnets, positive poles repel each other; whereas, opposite poles attract each other
- ions- atoms that have either lost or gained an electron (negative particle)
- causes them to acquire either positive or negative charge
- positive ions will repel other positive ions, but positive ions will attract negative ions
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Term
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Definition
- molecules tend to move from area of higher concentration to area of lower concentration to equalize the concentration
- analogy: tea bag in water
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Term
| electronephalography (EEG) |
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Definition
| sum of much neural activity within brain, produced by 'generators' |
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Term
| auditory brainstem response (ABR) testing |
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Definition
- audiologist records electrical activity of neurons to determine whether auditory pathway is intact
- he/she presents a stimulus such as puretone or click and then measure electrical emanations from brain stem area
- done when baby is sleeping
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Term
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Definition
- ease with which molecules may pass through a membrane
- tea bag is very permeable...plastic pouch is NOT
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Term
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Definition
| some ions may pass through it, given appropriate circumstances |
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Term
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Definition
- no energy is expended to move ions across the barrier
- rather, gradient established by inequalities between the two sides of membrane causes ion movement
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Term
| passive transport gatekeepers |
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Definition
- voltage-sensitive proteins serve as gatekeepers
- open channel when they receive adequate electrical stimulation
- channel proteins also serve as gatekeepers
- allow specific ions to pass through membrane
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Term
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Definition
- active pumping is required to move ions across barrier
- energy is expended to accomplish this task
- ion pumps role is to move sodium and potassium ions against gradient
- energy used by Na-K pump proteins is in form of ATP (adenosine triphosphate); a product of mitochondria of cell
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Term
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Definition
- operate continuously
- move 3Na+ ions out for every 2K+ ions moved in
- active transport is required to readjust balance of ions across membrane
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Term
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Definition
| minus signs indicate negative charge |
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Term
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Definition
- space between cells
- positive signs indicate positive charge
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Term
| resting membrane potential (RMP) |
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Definition
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Term
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Definition
| change in electrical potential that occurs when cell membrane is stimulated adequately to permit ion exchange between intra- and extracellular spaces |
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Term
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Definition
| when critical threshold of stimulation is reached (-55mv), Na+ ions gates open up causing large number of Na+ ions to flood intracellular space |
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Term
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Definition
| raising intracellular potential to +30mV very rapidly |
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Term
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Definition
- cell membrane is depolarized to threshold
- sodium gates open; Na+ is propelled into cell by its concentration and electrostatic gradient
- membrane potential goes positive
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Term
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Definition
- sodium gates close
- potassium gates open; K+ is propelled out of cell by its concentration and electrostatic gradients
- membrane potential drops rapidly
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Term
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Definition
- potassium gates begin to close
- sodium-potassium pump helps restore resting membrane potential
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Term
| absolute refractory period |
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Definition
- time during which cell membrane cannot be stimulated to depolarize
- no amount of stimulation will cause it to depolarize again
- potassium channels open and K+ ions flow out of intracellular space
- sodium inactivation- sodium gates spontaneously close and become inactivated
- sodium-potassium pump- removes most of Na+ ions, while increasing intracellular concentration of K+ ions
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Term
| relative refractory period |
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Definition
- period after absolute refractory period
- period during which membrane may be stimulated to excitation again, but it needs a greater than typical amount of stimulation
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Term
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Definition
- critical threshold (~ -55mV)
- for action potential to be generated, membrane channels have to break down
- AP is not generated until you reach this critical threshold
- if stimulation does not result in sufficient ion transfer to reach critical threshold, AP will not be triggered and sodium-potassium pump will restore RMP (-70mV)
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Term
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Definition
- RMP-->AP-->RMP ~ 1ms
- neuron may respond every 1/1000 of second, or 1000x per second
- even if stimulated 2000x per second, it will not be able to respond that rapidly because it won't have time to stimulate twice that rapidly
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Term
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Definition
| -70mV, resting membrane potential |
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Term
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Definition
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Term
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Definition
| depolarization has occurred ; note plus signs in cell (+30 mV) |
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Term
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Definition
| negativity is even greater than -70 mV; negative after potential (dips down below -70 mV) |
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Term
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Definition
| sodium-potassium pump has restored RMP (-70 mV) |
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Term
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Definition
- spreading effect of wave action
- wave of depolarization for APs
- larger axon diameter results in increased rate
- myelinated fibers facilitate an increased rate
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Term
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Definition
- neuron either depolarizes or it does not
- if neuron fails to depolarize, no AP is generated and no information is conveyed
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Term
| spike rate (rate of discharge) |
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Definition
| frequency with which neuron is "turned on" |
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Term
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Definition
- myelin is laid down on axon in "donuts" with nodes of exposed membrane between them
- voltage-sensitive channels are found within the membrane at nodes
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Term
| saltatory ('leaping') conduction |
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Definition
- propagating AP is "passed" from node to node
- in long fibers, precious milliseconds can be saved by skipping from node to node
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Term
| synapse between two neurons |
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Definition
- neurotransmitter travels across cleft very quickly (100 microseconds)
- activates receptor proteins on postsynaptic neuron
- presence of neurotransmitter in cleft triggers the ion channels to open
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Term
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Definition
| increase probability that neuron will depolarize |
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Term
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Definition
| decrease probability that neuron will depolarize |
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Term
| excitatory postsynaptic potential (EPSP) |
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Definition
- excitation causes depolarization; sum of their depolarizations will reach critical threshold
- can continue to send the messages to the rest of the body
- "voting" by neurons
- hundreds or even thousands of neurons may make synapse on a given neuron
- if sufficient number of these synapses are activated, then AP results
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Term
| inhibitory postsynaptic potential (IPSP) |
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Definition
- inhibition causes hyperpolarization
- greatly elevates threshold of firing
- generally inhibitory synapses are found on soma
- they stop message from continuing
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Term
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Definition
- some neurons require many near-simultaneous synaptic activations
- represents many points of contact arrayed over surface of post-synaptic neuron
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Term
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Definition
- two or more closely successive impulses arrive
- then synapse is established
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