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Questions and Answers
What are action potentials?
What are action potentials?
- Chemical signals released at synapses
- Information in the form of electrochemical impulses (correct)
- Neurons with multiple dendrites
- The central body of a neuron
What happens during synaptic transmission?
What happens during synaptic transmission?
The signal is transformed into a chemical signal with the release of neurotransmitter into the synaptic cleft.
What is a soma?
What is a soma?
The central body of a neuron containing the nucleus.
What type of neurons have one dendrite?
What type of neurons have one dendrite?
What type of neurons have multiple dendrites?
What type of neurons have multiple dendrites?
What are synaptic knobs?
What are synaptic knobs?
What is the synaptic cleft?
What is the synaptic cleft?
In which direction does an action potential travel?
In which direction does an action potential travel?
What is the difference between a neuron and a nerve?
What is the difference between a neuron and a nerve?
What is the resting membrane potential (RMP)?
What is the resting membrane potential (RMP)?
What are the two primary membrane proteins necessary to establish RMP?
What are the two primary membrane proteins necessary to establish RMP?
What does the Na/K ATPase do?
What does the Na/K ATPase do?
What are leak channels?
What are leak channels?
What is the ratio of Na to K leak channels?
What is the ratio of Na to K leak channels?
Are neurons the only cells with a resting membrane potential?
Are neurons the only cells with a resting membrane potential?
What happens if potassium leak channels are blocked?
What happens if potassium leak channels are blocked?
What will happen if Na is allowed to leak down its gradient?
What will happen if Na is allowed to leak down its gradient?
What is polarization?
What is polarization?
What is depolarization?
What is depolarization?
What is repolarization?
What is repolarization?
What are the key proteins for depolarization?
What are the key proteins for depolarization?
What causes the voltage-gated channels to open?
What causes the voltage-gated channels to open?
What is -50mV called?
What is -50mV called?
If an action potential starts at one end of an axon, will it ever run out of energy?
If an action potential starts at one end of an axon, will it ever run out of energy?
What happens after depolarization?
What happens after depolarization?
What happens after voltage-gated Na channels become inactivated?
What happens after voltage-gated Na channels become inactivated?
What happens after the cell is hyperpolarized to -90mV?
What happens after the cell is hyperpolarized to -90mV?
Can the Na/K ATPase repolarize the cell alone?
Can the Na/K ATPase repolarize the cell alone?
What happens if a toxin prevents voltage-gated Na channels from closing?
What happens if a toxin prevents voltage-gated Na channels from closing?
What is myelin?
What is myelin?
Where is myelin created?
Where is myelin created?
What is the effect of myelin sheath on action potentials?
What is the effect of myelin sheath on action potentials?
What are the nodes of Ranvier?
What are the nodes of Ranvier?
What is the advantage of myelin sheath?
What is the advantage of myelin sheath?
Is the amount of energy consumed by Na/K ATPase more in myelinated axons?
Is the amount of energy consumed by Na/K ATPase more in myelinated axons?
What is the equilibrium potential for Na+?
What is the equilibrium potential for Na+?
What is the equilibrium potential for K+?
What is the equilibrium potential for K+?
What does it indicate if the equilibrium potential for K+ is very close to the resting membrane potential?
What does it indicate if the equilibrium potential for K+ is very close to the resting membrane potential?
What is the refractory period?
What is the refractory period?
What is the absolute refractory period?
What is the absolute refractory period?
What happens to the voltage-gated Na channels during the absolute refractory period?
What happens to the voltage-gated Na channels during the absolute refractory period?
What is the relative refractory period?
What is the relative refractory period?
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Study Notes
Action Potentials
- Electrochemical impulses that transmit information between neurons.
- Initiates synaptic transmission at axon terminals.
Synaptic Transmission
- Occurs when an action potential reaches a synapse, converting electrical signals into chemical signals.
- Neurotransmitters are released into the synaptic cleft.
Neuronal Structure
- Soma: Central part containing the nucleus; involved in cell's biosynthetic activities.
- Synaptic Knobs: Terminal ends of axons that connect with target cells.
- Synaptic Cleft: Small gap between neurons for neurotransmitter diffusion.
Neuron Classifications
- Bipolar Neurons: Feature a single dendrite.
- Multipolar Neurons: Contain multiple dendrites.
Action Potential Direction
- Travels from the cell body down the axon.
Neuron vs Nerve
- Neuron: Single nerve cell.
- Nerve: Bundle of multiple axons from various neurons.
Resting Membrane Potential (RMP)
- Approximately -70mV; interior of the cell is negatively charged.
- Maintained by two primary proteins: Na/K ATPase and potassium leak channels.
Na/K ATPase Function
- Pumps three Na+ ions out and two K+ ions into the cell, resulting in a net charge of -1 inside.
- Establishes sodium and potassium gradients across the membrane.
Ion Leak Channels
- Always open; allow ions to passively move according to concentration gradients.
- Primarily permits K+ to exit, influencing membrane potential.
Effects of Ion Leak Channel Blockade
- Blocking potassium channels reduces RMP, making the interior less negative.
Polarization Effects
- Polarization: Negative inside, positive outside.
- Depolarization: Reduction in negativity or potential shift to positive.
- Repolarization: Return to resting membrane potential.
Key Proteins in Depolarization
- Voltage-gated Na+ channels enable Na+ influx, leading to cell positivity.
Threshold Potential
- At -50mV, triggers action potential initiation.
Action Potential Propagation
- Once initiated, the action potential is self-propagating and maintains amplitude.
After Depolarization Mechanism
- Voltage-gated Na+ channels inactivate around +35mV; followed by voltage-gated K+ channels opening to repolarize the cell.
Hyperpolarization
- Voltage drops to -90mV post-action potential due to K+ efflux.
Role of Na/K ATPase in Repolarization
- While Na/K ATPase can eventually restore RMP, rapid repolarization is primarily due to voltage-gated K+ channels.
Effects of Toxins on Voltage-Gated Channels
- If toxins prevent Na+ channel closure, hyperpolarization persists, causing excessive cell positivity.
Myelin Sheath
- Insulating covering around axons created by Schwann cells.
- Prevents ion flow in myelinated regions, enhancing signal transmission efficiency.
Nodes of Ranvier
- Gaps in myelin where voltage-gated channels are concentrated.
- Facilitate saltatory conduction, speeding action potential propagation.
Energy Consumption in Myelinated Axons
- Energy use by Na/K ATPase is lower in myelinated axons due to restricted activity to nodes.
Equilibrium Potentials
- Na+ Equilibrium Potential: +50mV, inhibiting further Na+ influx.
- K+ Equilibrium Potential: -90mV, preventing further K+ efflux.
Refractory Periods
- Absolute Refractory Period: No new action potential regardless of stimulus strength due to inactivated Na+ channels.
- Relative Refractory Period: Action potential can be induced but requires a stronger stimulus due to hyperpolarization.
Summary of Refractory Period Behavior
- Voltage-gated Na+ channels remain inactive during the absolute refractory period, only recovering as the membrane potential normalizes.
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