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Questions and Answers
What is the resting membrane potential of a typical neuron?
What is the resting membrane potential of a typical neuron?
- -70 mV (correct)
- +70 mV
- -40 mV
- 0 mV
Action potentials can vary in strength depending on the stimulus.
Action potentials can vary in strength depending on the stimulus.
False (B)
Which two ions are most important in generating and maintaining the resting potential in neurons?
Which two ions are most important in generating and maintaining the resting potential in neurons?
potassium (K+) and sodium (Na+)
The movement of __________ ions is primarily responsible for the cell's resting membrane potential.
The movement of __________ ions is primarily responsible for the cell's resting membrane potential.
Match the following terms with their descriptions.
Match the following terms with their descriptions.
What happens to potassium ions as negative charge builds up inside the neuron?
What happens to potassium ions as negative charge builds up inside the neuron?
The outside of a resting neuron is slightly positively charged compared to the inside.
The outside of a resting neuron is slightly positively charged compared to the inside.
What is the process called when the nerve signal 'hops' from node to node?
What is the process called when the nerve signal 'hops' from node to node?
All action potentials within the same type of neuron have different potential differences during depolarization.
All action potentials within the same type of neuron have different potential differences during depolarization.
What are the two types of neurons based on the effect of neurotransmitters?
What are the two types of neurons based on the effect of neurotransmitters?
The small space between neurons is called the ______.
The small space between neurons is called the ______.
Match the following neurotransmitter mechanisms with their descriptions:
Match the following neurotransmitter mechanisms with their descriptions:
Which neurotransmitter is broken down by acetylcholinesterase?
Which neurotransmitter is broken down by acetylcholinesterase?
Neurotransmitters can only be removed from the synaptic cleft by enzymatic reactions.
Neurotransmitters can only be removed from the synaptic cleft by enzymatic reactions.
What triggers the release of neurotransmitters from synaptic vesicles?
What triggers the release of neurotransmitters from synaptic vesicles?
Neurons communicating with glands or muscles are called ______ cells.
Neurons communicating with glands or muscles are called ______ cells.
What triggers the opening of voltage-gated sodium channels?
What triggers the opening of voltage-gated sodium channels?
During depolarization, the inside of the cell becomes more negative.
During depolarization, the inside of the cell becomes more negative.
What are the three states of sodium channels?
What are the three states of sodium channels?
The ______ pump helps restore the resting potential after an action potential.
The ______ pump helps restore the resting potential after an action potential.
What happens during the absolute refractory period?
What happens during the absolute refractory period?
Match the terms with their definitions:
Match the terms with their definitions:
Potassium ions efflux contributes to depolarization of the neuron.
Potassium ions efflux contributes to depolarization of the neuron.
What effect does tetrodotoxin have on neuronal transmission?
What effect does tetrodotoxin have on neuronal transmission?
Which factor more significantly affects the speed of action potential propagation?
Which factor more significantly affects the speed of action potential propagation?
Local anesthetics enhance pain perception by blocking sodium channels.
Local anesthetics enhance pain perception by blocking sodium channels.
What causes hyperpolarization of the neuron?
What causes hyperpolarization of the neuron?
Match the effects to their causes:
Match the effects to their causes:
What is the resting potential of a neuron?
What is the resting potential of a neuron?
What is the equilibrium potential of potassium?
What is the equilibrium potential of potassium?
What effect does sodium have on the resting membrane potential?
What effect does sodium have on the resting membrane potential?
Potassium's equilibrium potential is positive.
Potassium's equilibrium potential is positive.
What is the typical resting membrane potential of an average nerve cell?
What is the typical resting membrane potential of an average nerve cell?
The process of Na+/K+ ATPase pumps sodium ______ the cell and potassium ______ the cell.
The process of Na+/K+ ATPase pumps sodium ______ the cell and potassium ______ the cell.
What is the equilibrium potential of potassium?
What is the equilibrium potential of potassium?
The equilibrium potential of sodium is negative.
The equilibrium potential of sodium is negative.
What is the term for the additive effect of multiple signals received by a postsynaptic neuron?
What is the term for the additive effect of multiple signals received by a postsynaptic neuron?
The resting membrane potential of a typical nerve cell is around __________ mV.
The resting membrane potential of a typical nerve cell is around __________ mV.
Match the following ions with their equilibrium potentials:
Match the following ions with their equilibrium potentials:
Which of the following is a reason why potassium has a stronger influence on the resting potential?
Which of the following is a reason why potassium has a stronger influence on the resting potential?
Both sodium and potassium ions are continuously leaking across the cell membrane.
Both sodium and potassium ions are continuously leaking across the cell membrane.
What process do neurons use to maintain ion concentration gradients against their natural tendency?
What process do neurons use to maintain ion concentration gradients against their natural tendency?
In spatial summation, the additive effects depend on the __________ and location of incoming signals.
In spatial summation, the additive effects depend on the __________ and location of incoming signals.
What role does the axon hillock play in action potential generation?
What role does the axon hillock play in action potential generation?
The influx of sodium ions tends to hyperpolarize the neuron.
The influx of sodium ions tends to hyperpolarize the neuron.
What is the typical concentration of sodium inside the cell in mM?
What is the typical concentration of sodium inside the cell in mM?
Match the following terms with their descriptions:
Match the following terms with their descriptions:
The electric potential due to a small amount of potassium exiting is called the __________ potential.
The electric potential due to a small amount of potassium exiting is called the __________ potential.
What is the primary function of Na+/K+ ATPase beyond maintaining resting potential?
What is the primary function of Na+/K+ ATPase beyond maintaining resting potential?
Study Notes
Action Potentials
- Action potentials are all-or-nothing electrical messages used by neurons to relay impulses down the axon.
- Trigger the release of neurotransmitters into the synaptic cleft.
Resting Potential
- Resting membrane potential averages around -70 mV, with the inside of the neuron being negative compared to the outside.
- Key ions: potassium (K+) is about 140 mM inside the cell and 4 mM outside; sodium (Na+) is about 12 mM inside and 145 mM outside.
- Potassium's equilibrium potential is around -90 mV; sodium's equilibrium potential is around +60 mV.
- The resting potential results from the opposing movements of sodium and potassium, maintaining a balance around -70 mV.
Mechanisms Maintaining Resting Potential
- Na+/K+ ATPase continuously pumps Na+ out of the cell and K+ into the cell, consuming more ATP than any other cellular activity.
- Ion leakage is facilitated by specific ion channels for both sodium and potassium.
Axon Hillock
- The axon hillock integrates excitatory and inhibitory inputs, determining whether an action potential is fired.
- Action potentials are triggered if the membrane potential reaches a threshold of about -55 to -40 mV due to excitatory input.
- Summation of signals occurs through temporal (timing) and spatial (location and number) summation.
Ion Channels and Action Potential Phases
- Upon reaching threshold, voltage-gated sodium channels open, allowing Na+ to flood into the cell (depolarization).
- Sodium channels become inactive at +35 mV; potassium channels then open, allowing K+ to exit (repolarization), leading to a temporary hyperpolarization.
- Absolute refractory period: no action potential can occur; relative refractory period: requires stronger stimulation for action potential.
Impulse Propagation
- Action potentials propagate along the axon via depolarization of adjacent sections, allowing only unidirectional signal flow due to refractory periods.
- Myelin insulation allows for faster conduction through saltatory conduction, as action potentials jump between nodes of Ranvier.
Synaptic Transmission
- The synapse is the gap between neurons where neurotransmitters are released from the presynaptic neuron to affect the postsynaptic neuron.
- Neurotransmitters are stored in vesicles and released upon action potential-induced calcium influx, leading to exocytosis.
Regulation of Neurotransmission
- Neurotransmission is terminated through enzymatic breakdown, reuptake by presynaptic neurons, or diffusion away from the synaptic cleft.
- Acetylcholine (ACh) is broken down by acetylcholinesterase; serotonin (5-HT) is reabsorbed via reuptake carriers.
Key Concepts
- The distinction between electrical (within the neuron) and chemical (between neurons) transmission of signals is crucial for understanding neurobiology.
- Increased stimulus intensity results in a greater frequency of action potentials rather than higher voltage of individual action potentials.
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Description
Explore the fundamental concepts of action potentials and resting potentials in neurons. This quiz delves into how electrical impulses are generated and transmitted, as well as the implications for neurotransmitter release. Understand the key mechanisms that underlie neuronal communication.
