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16 Cards in this Set
- Front
- Back
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What 3 factors help determine the number of synapses a cell receives?
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1. Surface area (determined by Soma size)
2. Dendritic arborization 3. Axonal features |
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What do dendritic spines do? (3)
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1. Increase cell surface area
2. Create restricted volume for local signaling 3. Sites of excitatory synaptic contact |
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How are dendritic spines dynamic structures?
What are the implications? |
Spines are constantly being deleted or created, so synaptic contacts change
Basis for learning, memory, and overall plasticity of nervous system |
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What are the 3 classifications of synaptic contact?
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1. Axo-dendritic
2. Axo-somatic 3. Axo-axonic |
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What ultimately determines whether a postsynaptic cell will fire an AP?
Why is this the determining region? What is located here that helps create an AP? |
The axon hillock of the postsynaptic cell
Has the lowest threshold for AP generation Has many voltage-gated Na channels |
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What parts of the neuron are considered the 'input' side?
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Dendrites, soma
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What parts of the neuron are considered the 'output' side?
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axon
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What happens to the synaptic potential as it spreads from dendrite to soma to hillock?
What accommodation must synaptic inputs far out on dendrites have to generate APs? |
Synaptic potential decreases in magnitude, delay at soma
If signal is inputed far out on dendrite, it must be larger |
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What is the difference between passive and active membranes?
Where is each found in neurons? |
Passive = incapable of generating AP, found in dendrite and soma
Active = capable of generating AP, found in axon |
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What is synaptic integration and why does the timing matter?
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Synaptic integration = neuron integrates inhibitory and excitatory inputs --> AP or no AP
All inputs arriving at the same time are summed, but if at different times, not summed |
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How can stretch reflex measure clinically the level of demyelinating in peripheral nerves?
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If receptor axons are activated synchronously (w/a reflex hammer) --> synchronous signal to postsynaptic cell --> AP --> reflex
If demylination in some axons --> asynchronous signal --> no AP --> no reflex |
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What is the size principle of neuronal recruitment
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Smaller cells --> less surface area --> lower conductance --> higher resistance --> voltage changes more for given current (V=IR) --> more AP
Smaller neurons recruited first |
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How does the size of motorneurons activated determine the type of muscle fiber activated?
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Smaller cells activated first --> slow-twitch oxidative
Medium neurons next --> fast fatigue-resistant Large neurons last --> fast fatiguable fibers |
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What does increased intensity in synaptic input translate to?
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Higher firing rate of APs
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What determines the max firing rate of APs?
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The time required for Na channels to recover from inactivation
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What is phase locking of AP spikes?
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AP more likely to fire at the same phase of the stimulus
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