Questions and Answers
Ion ______ are essential for regulating the flow of ions across the cell membrane.
channels
An ______ potential is a rapid rise and fall in the membrane potential of a neuron.
action
If a stimulus causes gated sodium channels to open, the membrane's permeability to ______ increases.
Na+
In ______ transmission, neurotransmitters are released from one neuron and bind to receptors on another.
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The ______ membrane potential refers to the voltage difference across the membrane when a neuron is at rest.
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An action potential is an all-or-none event that requires the change in voltage to reach ______.
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Myelination increases the speed of ______ by insulating the axon with a fatty layer.
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During the refractory period, a second action potential cannot be initiated due to the inactivation of ______ channels.
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Myelinated axons conduct action potentials more rapidly because ion channel activities are limited to a ______ number of positions along the axon.
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The synaptic cleft is the gap that separates the presynaptic neuron from the ______ cell.
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Study Notes
Action Potentials and Graded Potentials
- Gated sodium channels open in response to a stimulus, increasing Na+ permeability.
- Graded potentials generate small electrical currents that dissipate over distance along the membrane.
- An action potential involves a significant voltage change, characterized by depolarization that hits a threshold.
- Refractory period occurs when sodium channels are inactivated, preventing the initiation of a second action potential.
Conduction of Action Potentials
- At the axon hillock, Na+ influx during the rising phase creates an electrical current, depolarizing adjacent axon regions.
- Action potentials are all-or-none; their magnitude and duration remain consistent along the axon.
- Myelin sheath, formed by oligodendrocytes in the CNS and Schwann cells in the PNS, insulates axons and facilitates faster action potential propagation.
Electrical Synapses and Neuronal Communication
- Electrical synapses have gap junctions allowing direct electrical current flow between neurons.
- The insulating lipid layers of myelin act as poor electrical conductors.
- Synaptic vesicles hold neurotransmitters, while the synaptic cleft is the gap between pre- and postsynaptic neurons.
Postsynaptic Potential
- Postsynaptic potentials occur when receptor proteins bind to neurotransmitters, triggering responses in the postsynaptic cell.
Cell Membrane and Potential
- The membrane potential is the voltage difference between the intracellular and extracellular environments, typically around -60 mV.
- Gated ion channels respond to voltage shifts across the plasma membrane, contributing to resting potential.
Resting Potential and Ion Transport
- Resting potential represents the voltage in an unstimulated neuron.
- The sodium-potassium pump uses ATP to transport Na+ out and K+ into the cell, maintaining concentration gradients: higher Na+ outside and higher K+ inside.
- Resting neurons have more open potassium channels, leading to a more negative interior compared to the outside.
Membrane Permeability and Transport
- The selectively permeable membrane regulates the transport of materials in and out of the cell.
- Diffusion processes can be passive or active, influenced by concentration gradients and temperature.
- Electric charge can impact diffusion rates and patterns.
Cell Surface Markers
- Glycoproteins are involved in self-recognition, creating unique protein/carbohydrate chain shapes per individual.
- Glycolipids contribute to tissue recognition through characteristic lipid/carbohydrate chain shapes.
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Description
This quiz focuses on the effects of stimuli on gated sodium channels and their role in altering membrane permeability to sodium ions (Na+). Test your understanding of the mechanisms involved in neuronal excitability and signal transmission. Perfect for students studying neuroscience or physiology!
