Action Potential in Neurons

What is an action potential?

An all-or-nothing response where a neuron fires completely if a certain voltage threshold is reached.

What is the threshold potential for an action potential to occur?

-55mV.

What happens during depolarization?

Voltage-gated Na⁺ channels open and Na⁺ rushes into the cell, increasing the charge from -70mV to around +30mV.

What is the charge of a neuron at depolarization?

+30mV.

What happens during repolarization?

Na⁺ channels close and voltage-gated K⁺ channels open, allowing K⁺ to exit the neuron.

What is the resting potential of a neuron?

-70mV.

What occurs during hyperpolarization?

K⁺ channels stay open too long, causing the inside of the neuron to become even more negative than -70mV.

What is the typical charge during hyperpolarization?

Around -80mV or lower.

What is the function of the sodium-potassium pump during the refractory period?

It restores the resting potential by moving Na⁺ out and K⁺ back in.

What is saltatory conduction?

The process where action potentials jump from one node of Ranvier to the next in myelinated neurons.

How do unmyelinated neurons conduct action potentials?

The action potential moves continuously down the axon.

What is the role of dopamine in the reward pathway?

Dopamine is the main neurotransmitter responsible for sensations of pleasure and reward.

What is tetrodotoxin (TTX)?

A substance found in pufferfish that blocks voltage-gated sodium channels, preventing action potentials.

What effect does tetraethyl ammonium (TEA) have on neurons?

It blocks potassium channels, disrupting the repolarization phase of action potentials.

Which neurotransmitter is essential for muscle contraction?

Acetylcholine.

What roles does dopamine play in the brain?

Pleasure, motivation, mood, attention, memory, and movement.

What is gamma-aminobutyric acid (GABA)?

The primary inhibitory neurotransmitter in the central nervous system.

Which neurotransmitter is the primary excitatory neurotransmitter in the brain?

Glutamate.

What neurotransmitters are involved in the fight-or-flight response?

Epinephrine and norepinephrine.

What is the typical effect of serotonin in the body?

Regulation of mood and sleep.

What happens to neurotransmitters during the reuptake process?

They are reabsorbed back into the neurons.

What does it mean for a substance to be an agonist?

It mimics or enhances the action of a neurotransmitter.

What is the function of an antagonist in neuropharmacology?

It blocks or inhibits the action of a neurotransmitter.

What is a reuptake inhibitor?

A substance that prevents the reabsorption of neurotransmitters, increasing their availability.

What effect does caffeine have on adenosine receptors?

It acts as an antagonist, blocking adenosine and increasing alertness.

How does cocaine affect neurotransmitter levels?

It acts as a reuptake inhibitor for dopamine, serotonin, and norepinephrine.

What neurotransmitter is primarily involved in the sensation of euphoria?

Dopamine.

How does opioid use affect the dopamine system?

It leads to a massive release of dopamine, creating feelings of euphoria.

What occurs in the limbic system in relation to addiction?

It stores memories of pleasurable drug effects, leading to cravings.

What is drug tolerance?

The brain reduces the number of dopamine receptors, requiring higher doses for the same effect.

What are the key brain areas involved in the reward pathway?

Midbrain, amygdala, hippocampus, and prefrontal cortex.

What is substance use disorder?

A condition where a person is unable to control drug use despite negative consequences.

What role do mu opioid receptors play in addiction?

They trigger the release of dopamine when activated by opioids.

What is the initial effect of drug use on dopamine levels?

It triggers a massive release of dopamine, creating feelings of euphoria.

What happens when the brain becomes overstimulated by drug use?

The brain adjusts by reducing the number of dopamine receptors.

What factors contribute to the development of drug addiction?

Initial drug use, memory formation, tolerance development, and the inability to control use.

How does sharing a dessert affect serotonin and dopamine levels?

It increases both serotonin and dopamine levels significantly.

What happens during the refractory period in relation to action potentials?

The neuron cannot fire again until it resets to resting potential.

What role do sodium channels play during depolarization?

They open to allow Na⁺ ions to enter the cell, changing the charge.

What happens to K⁺ ions during repolarization?

They exit the neuron, making the inside more negative.

How does the action potential propagate in myelinated neurons?

Through saltatory conduction at nodes of Ranvier.

What leads to hyperpolarization in a neuron?

Excessive K⁺ exiting the cell.

What is the purpose of the sodium-potassium pump?

To maintain resting potential by moving Na⁺ out and K⁺ in.

How do action potentials move in unmyelinated neurons?

Continuously along the axon.

What are the implications of TTX use in research?

Helps study action potential propagation by blocking Na⁺ channels.

What are the effects of TEA on neuron functionality?

Disrupts the repolarization phase and hampers recovery.

What neurotransmitter regulates alertness?

Dopamine.

In what conditions is glutamate released in higher quantities?

During stress responses.

What is the significance of the sodium-potassium pump in action potentials?

Restores the neuron to its resting potential.

How does morphine affect pain perception?

It acts as an agonist at opioid receptors, mimicking natural pain-relievers.

What is the role of the prefrontal cortex in addiction?

It is involved in decision-making and controlling behavior.

How does repeated drug use impact the reward pathway?

It can lead to neuroadaptations that make it less responsive to natural rewards.

What characterizes an all-or-nothing response in neurons?

An action potential fires completely or not at all based on reaching the threshold.

What changes occur in the resting potential during hyperpolarization?

The inside of the neuron becomes more negative than -70mV.

What happens to the charge of the neuron during depolarization?

It rapidly increases from -70mV to +30mV.

What are the long-term effects of opioid use on the brain's reward system?

It can lead to addiction and a reduced ability to experience pleasure.

What is the role of neurotransmitters during synaptic transmission?

They relay signals between neurons, influencing their activity.

What does dopamine release coincide with?

Feelings of euphoria and reward.

What happens in the brain when an individual experiences a pleasurable event?

The reward pathway activates, leading to dopamine release.

What is an antagonist's effect on neurotransmission?

It prevents neurotransmitter action by blocking receptors.

In what way does caffeine impact neurotransmitter activity in the brain?

Increases alertness by blocking adenosine receptors.

What effect does drug tolerance have on the brain's reward system?

Users need higher doses to achieve the same euphoric effect.

What are common neurotransmitters released in response to stress?

Glutamate, epinephrine, and norepinephrine.

How does sharing enjoyable experiences impact neurotransmitter levels?

It significantly increases serotonin and dopamine.

Describe the significance of the refractory period in neuronal firing.

It ensures that action potentials move in one direction and provides time for the neuron to reset.

How are sodium ions involved in generating an action potential?

Their influx during depolarization raises the neuron's charge.

What is the importance of potassium in repolarization?

K⁺ exit helps restore the negative inside charge of the neuron.

Why do neurons have saltatory conduction?

To increase the speed of signal transmission along myelinated axons.

What is the role of the limbic system in addiction?

It processes emotions and memories related to drug use, reinforcing behavior.

What is the overall effect of drugs on the brain's neurotransmitter systems?

They can disrupt normal signaling and lead to addiction.

What does a reuptake inhibitor do at synapses?

It increases the levels of neurotransmitters in the synaptic cleft.

Define euphoria in the context of drug use.

A heightened state of pleasure resulting from dopamine release.

What physiological change occurs during hyperpolarization?

The neuron becomes less excitable, moving towards more negative voltages.

What does the term synaptic transmission refer to?

The process by which signaling molecules are transferred between neurons.

How does the brain compensate for drug-induced overstimulation of dopamine?

By reducing the number of dopamine receptors over time.

What drug class do substances like morphine belong to?

Opioids.

What physiological mechanism is involved in the reward pathway?

Dopamine transmission encourages behavior through positive reinforcement.

What mechanisms of action do agonists have on neurotransmitters?

They enhance or mimic the effects of natural neurotransmitters.

What is the function of the sodium-potassium pump in relation to ion balance?

To maintain the difference in ion concentration across the neuronal membrane.

How can TTX and TEA aid in research?

They provide insights into neuron function by blocking specific ion channels.

What neurotransmitters can increase during stressful situations?

Glutamate, epinephrine, norepinephrine.

Who identified the mechanisms for dopamine's role in the reward pathway?

Researchers in neuropharmacology.

What is the significance of 'jumping' in saltatory conduction?

It allows faster propagation of action potentials in myelinated neurons.

What brain structure often associates drug use with pleasure?

The limbic system.

What is neuropharmacology?

The study of how drugs affect neuronal communication.

Responding to different levels of stimulation is crucial for neurons. What is the threshold for action potential initiation?

-55mV.

What happens to neurotransmitter levels when an agonist is introduced?

Levels increase as the agonist mimics neurotransmitter action.

How does drug tolerance impact a user's experience?

Users require larger doses to achieve the same euphoric effects.

Define the term 'addiction' in relation to neurotransmitters.

A chronic condition characterized by compulsive drug use and changes in brain function.

What role does the prefrontal cortex have in addiction?

It is involved in controlling impulses and decision-making regarding drug use.

How is memory connected to the limbic system in the context of addiction?

The limbic system forms lasting memories associated with the pleasurable effects of drugs.

What physiological state indicates an overshoot in the repolarization phase?

Hyperpolarization.

What happens to the voltage during an action potential's propagation?

It moves rapidly from resting potential, through depolarization, repolarization, and recovery.

Why are neurotransmitters important for neuron communication?

They allow for signal transmission across synapses.

What neurotransmitter is commonly associated with muscle contractions and learning?

Acetylcholine.

How does the presence of myelin affect neuronal conduction speed?

It greatly increases the speed of signal propagation.

Why is sodium crucial for depolarization in neurons?

Its influx changes the neuron's charge, triggering an action potential.

In The context of addiction, how do memories of drug use affect behavior?

They create cravings and reinforce the desire to use drugs again.

What type of drug is caffeine classified as based on its action on adenosine?

Antagonist.

What is a potential effect of an antagonist drug on neurotransmitter release?

It may decrease the action of neurotransmitters by blocking their receptors.