Mastering Biology Chapter 46 – Flashcards
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When you touch a warm plate of food being handed around the dinner table, the first type of neuron to be activated is a(n) _____.
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Sensory Neuron. Sensory neurons transmit information about the environment to the brain.
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Which structure is not part of a neuron?
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Myelin Sheath. The myelin sheath is the layer of Schwann cells wrapped around a neuron.
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Action potentials in a given neuron are propogated _____
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They are propagated down the length of the axon.
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Action potentials travel in only one direction down an axon because sodium channels in the neuron are refractory.
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Action potentials travel in only one direction down an axon because sodium channels in the neuron are refractory.
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Which event triggers the creation of an action potential?
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The membrane depolarizes above a certain threshold potential. Influx of Na+ ions into the neuron can lead to membrane depolarization above the threshold potential; this event triggers the creation of an action potential.
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Which of the following terms describes how a neuronal membrane's potential is altered in the presence of inhibitory signals?
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Hyperpolarization. Inhibitory signals hyperpolarize the membrane and make the membrane potential even more negative than normal.
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Where in the neuron do action potentials begin?
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Axon hillock. The axon hillock is the region where voltage-gated channels begin in a neuron, near the cell body.
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How is an action potential propagated down an axon after voltage-gated sodium channels open in a region of the neuron's membrane?
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Sodium ions enter the neuron and diffuse to adjacent areas, resulting in the opening of voltage-gated sodium channels farther down the axon
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How is an action potential propagated down an axon after voltage-gated sodium channels open in a region of the neuron's membrane?
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The entry of sodium ions into the neuron and their diffusion to adjacent areas of the membrane causes those portions of the membrane to become depolarized and results in the opening of voltage-gated sodium channels farther down the axon, which release potassium ions to the outside, returning the charge to its previous state.
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What would occur if sodium channels remained open once membrane depolarization was complete?
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Repolarization would occur, but much more slowly. While sodium ions would continue to move into the cell, potassium moving out would counteract it.
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Sequence of initiation of action potential
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Membrane potential reaches threshold.
Many voltage-gated Na+ channels open.
Na+ ions rush into the cell.
Membrane potential rises (depolarizes) rapidly.
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How does myelination affect the propagation of an action potential?
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It speeds propagation because cations do not leak out of the membrane as they spread down the axon
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Which of these causes the release of neurotransmitter molecules?
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an action potential reaching the end of the axon. When an action potential reaches the end of an axon, vesicles fuse with the plasma membrane and release neurotransmitter into the synaptic cleft.
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The space between an axon of one neuron and the dendrite of another neuron is called a(n) _____.
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synaptic cleft
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Neurons store neurotransmitter molecules in vesicles located within
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Synaptic terminals. Vesicles within synaptic terminals contain neurotransmitter that may be released into the synaptic cleft.
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Neurotransmitters are released from neurons in response to the increase in intracellular concentration of what ion?
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Calcium
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Which of the following brain regions is responsible for formation of new memories?
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hippocampus
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What is a key mechanism behind learning and memory?
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Changes in the number, sensitivity, and placement of synapses
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What might occur to an animal with an untreated lesion on its brain stem?
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It would likely die. As the brain stem is responsible for most of the core bodily functions.
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Which of the following is most likely to result in an action potential at a postsynaptic neuron?
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many EPSPs and few IPSPs.
The summing of many EPSPs triggers the action potential and isn't inhibited by an abundance of IPSPs
