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39 Cards in this Set
- Front
- Back
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Compare flexors and extensors
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Flexors decrease the angle of a joint, whereas extensors increase the angle of a joint.
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Compare location of sensory and and motor neuron projections in the spine.
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Sensory neurons are located in the dorsal root ganglia, and motor neurons are in the ventral root ganglia.
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Why are muscles generally reciprocation activated? What kind of neuron is responsible for allowing this to happen?
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Because reciprocal activation is essential for locomotion. Interneurons allow this to happen.
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What are the only cells that don't have electrical potential differences across their membranes?
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Dead cells -- all living cells do have a difference.
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What are the two key features of postsynaptic potentials?
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-Graded, meaning its amplitude varies with the strength of the stimulus
-Local, meaning the signal is biggest right where it's generated |
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What are the two key features of action potentials?
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-All-or-nothing signals
-Propagate long distances regeneratively |
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Compare concentrations of K+ and Cl- inside and outside of a nerve cell and explain how this works.
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Higher K+ outside and higher Cl- inside. This works because KCl ions are pumped into the cell while only K+ diffuse out of the cell through the potassium ion channel, leaving a buildup of Cl- inside.
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Compare the rate of potassium entering and exiting a nerve cell.
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They're the same -- there's equilibrium that means no net movement of potassium.
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What's the concentration of KCl inside a neuron? Outside?
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Inside it's 150 milli-molars, and outside it's 5 milli-molars.
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What's the resting potential of a neuron? How about outside?
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-70mV inside and 0 outside.
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What direction does K go, in or out of a cell? How about Na?
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The Na/K pump is always moving K+ into the cell and Na out of the cell.
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When will neurons be positive? Negative?
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Positive when the potassium channel is closed and the sodium channel is open, and negative when the opposite happens.
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What is it called when a stimulus causes a neuron to go from -70mV to -50mV? What are the characteristics of this?
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Depolarization. It's local and graded.
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What is it called when a stimulus causes a neuron to go from -70mV to +50mV? What are the characteristics of this?
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Action potential. It's all-or-nothing and regenerates over distances.
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What is it called when a stimulus causes a neuron to go from -70mV to -80mV?
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Hyperpolarization.
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What is it called when a stimulus causes a neuron to stay at -70mv?
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Resting potential.
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What determines whether ion gates are open or closed?
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Voltage differences across the membrane.
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What's the relationship between depolarization and ion channel gates? What's the name of this process? What kind of feedback is this and why?
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Depolarization increases the probability that ion channel gates open right away. It's called the Hodgkin cycle and it's positive feedback because it continues to open more channels for more depolarization.
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What happens to Na+ during depolarization?
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Na+ floods the inside of the neuron.
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What ion gate is most affected by voltage differences?
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Sodium channels.
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Why do cells become positive during an action potential?
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Because so many sodium ions flood in so fast that the charge becomes positive.
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Is potassium in equilibrium during an action potential? Why or why not?
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No, because both the electrical gradient and concentration gradient push potassium out of the cell.
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Why can't a nerve cell fire again immediately after it fires? What's this called?
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Because the inactivation gate (on the inside) stays closed for a bit of time after the action potential occurs. This is called the absolute refractory period.
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Compare open/close time and location of ion channel gates
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Inactivation gates are on the inside of the cell, whereas activation gates are outside. Inactivation gates take longer to open/close compared to activation gates.
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Under what circumstances do inactivation gates open? When do they close?
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Opens in negative potentials, closes with depolarization.
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What happens when there's a buildup of internal Na+ or depletion of internal K+ in a nerve?
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The Na/K pump reverses these problems.
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What defines the direction of current movement in a cell? What specific ion does this in nerves?
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Inward movement of cations -- sodium ions.
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Does current movement always = the movement of mass? Give an example of why or why not.
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No -- anions like chloride have movements that move in the opposite direction of their current.
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What effect does an action potential have on downstream membranes? Why's this significant?
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An action potential depolarizes downstream membranes. This is the mechanism of action potential regeneration.
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What kind of cells are myelin sheaths made from? What is the area in between myelin sheaths called, and is it made of?
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Glial cells. Node of Ranvier, made of voltage-gated Na+ channels.
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What feature is right next to Nodes of Ranvier? What's it made of?
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Paranodes, and they're made of voltage-gated K+ channels.
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Beginning with one myelin sheath and moving to the next, describe the features you'd encounter.
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Myelin sheath > voltage-gated K+ channel (paranode) > v-gated Na+ channel (Node of Ranvier) > v-gated K+ channel (paranode) > myelin sheath
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What are the benefits of having myelin sheaths? What's another name for them?
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They're faster and use less ATP. Saltatory conduction.
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Define gap junction.
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An intercellular junction with a water-filled pore that allows cell-signaling molecules to pass through.
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What's the main advantage of gap junctions? Disadvantage?
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Rapid transmission of action potential from pre- to post-synaptic neurons. Disadvantage is that they only coordinate adjacent cells.
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What are the advantages of chemical synapses? Disadvantage?
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-Signal amplification
-Diversity of postsynaptic responses -Plasticity Disadvantage is that it's slower compared to electrical synapses. |
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What important channels are at the axon terminals of neurons? What opens them?
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Calcium-ion selective channels that are opened by depolarization from the action potential.
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How do neurotransmitters travel?
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Diffusion.
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What are the different ways that neurotransmitters can be turned off?
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-They can diffuse away from the synapse.
-They can be degraded by enzymes in the synapse. -Either the presynaptic terminal or adjacent glial cells can take up the neurotransmitters |
