Neuroscience Chapter on Neuron Fluid Composition

Questions and Answers

What is the charge of a cation?

Positive charge (correct)

Negative charge

Variable charge

Neutral charge

Which ion is primarily responsible for the positive charge in a neuron?

Sodium (Na⁺) (correct)

Potassium (K⁺)

Chloride (Cl⁻)

Calcium (Ca²⁺)

What component of the neuron membrane allows specific ions to pass through?

Ion channels (correct)

Phospholipids

Receptors

Pumps

How does the sodium-potassium pump contribute to resting potential?

By removing three sodium ions for every two potassium ions exchanged Signup and view all the answers

What is the typical resting potential of a neuron in millivolts?

-70 mV Signup and view all the answers

What characteristic of the neuron membrane contributes to its selective permeability?

Lipid bilayer structure Signup and view all the answers

Which ion is trapped inside the neuron and contributes to resting potential?

Proteins (anions) Signup and view all the answers

What is the role of neurotransmitter receptors in the neuron membrane?

To bind neurotransmitters Signup and view all the answers

What is primarily responsible for maintaining the concentration gradients of sodium and potassium across the neuron's membrane?

Sodium-potassium pump Signup and view all the answers

What characteristic distinguishes leak channels from gated ion channels?

They are always open. Signup and view all the answers

What happens if depolarization does not reach the threshold in a neuron?

The neuron will stay in a resting state. Signup and view all the answers

In the context of resting potential, what do large negatively charged proteins contribute to?

Stability of the resting membrane potential Signup and view all the answers

Which of the following best describes the movement of ions during diffusion?

Ions move from higher concentration to lower concentration. Signup and view all the answers

What triggers voltage-gated channels to open?

Electrical changes in membrane potential Signup and view all the answers

What role does electrostatic pressure play in a neuron?

It drives the movement of ions across the membrane. Signup and view all the answers

What is the resting membrane potential approximate value for most neurons?

-70 mV Signup and view all the answers

What is the primary function of the absolute refractory period?

To prevent any new action potentials from occurring Signup and view all the answers

Which statement best describes the role of the sodium-potassium pump?

It maintains ion gradients for resting potential Signup and view all the answers

What distinguishes axosomatic synapses from axodendritic synapses?

Axosomatic synapses exert strong control over neuron firing Signup and view all the answers

How do electrical synapses differ from chemical synapses?

Electrical synapses transmit signals via gap junctions Signup and view all the answers

What does the key-and-lock analogy represent in terms of neurotransmitter-receptor interactions?

The specificity and functionality of neurotransmitter binding to receptors. Signup and view all the answers

What role does the presynaptic neuron play in neural communication?

It releases neurotransmitters into the synaptic cleft Signup and view all the answers

Which statement correctly describes ionotropic receptors?

They mediate rapid changes in ion flow. Signup and view all the answers

What is the first step in the process of exocytosis?

Formation of a vesicle containing neurotransmitters Signup and view all the answers

What primarily allows for increased neuronal excitability during the relative refractory period?

Lowered thresholds for action potentials Signup and view all the answers

What primarily causes an excitatory postsynaptic potential (EPSP)?

The influx of positive ions. Signup and view all the answers

What is the main effect of an inhibitory postsynaptic potential (IPSP) on a neuron?

Decreases the likelihood of firing an action potential. Signup and view all the answers

Which synaptic type is primarily involved in modulating neurotransmitter release?

Axoaxonic synapse Signup and view all the answers

How does hyperpolarization affect a postsynaptic neuron?

It decreases the neuron's overall excitability. Signup and view all the answers

What role do EPSPs play in neural circuits?

They enhance neuronal excitability and facilitate communication. Signup and view all the answers

What distinguishes an agonist from an antagonist in the context of neurotransmitter action?

An agonist enhances receptor activity, while an antagonist blocks it. Signup and view all the answers

What is the main action of agonists on receptors?

To activate receptors and mimic natural ligands Signup and view all the answers

What effect does an agonist have on an inhibitory receptor?

Increases inhibition of the postsynaptic neuron Signup and view all the answers

How do antagonists affect the excitatory action of neurotransmitters?

They block the action and increase inhibition Signup and view all the answers

What determines whether a neurotransmitter is classified as excitatory or inhibitory?

Its action on the postsynaptic neuron, either leading to depolarization or hyperpolarization Signup and view all the answers

What is the effect of naloxone as an antagonist in opioid receptors?

It prevents the action of opioids during overdose Signup and view all the answers

What happens when an antagonist interacts with an excitatory receptor?

It leads to hyperpolarization and reduces likelihood of action potential Signup and view all the answers

Which scenario describes the effect of an agonist interacting with an excitatory receptor?

Leads to more excitation, possibly resulting in an action potential Signup and view all the answers

The influx of which ions typically indicates an excitatory effect of a neurotransmitter?

Positive ions Signup and view all the answers

Study Notes

Neuronal Fluid Composition

Intracellular fluid has high concentrations of potassium (K⁺) and large negatively charged proteins.
Extracellular fluid has high concentrations of sodium (Na⁺) and chloride (Cl⁻).

Sodium-Potassium Pump

Pumps 3 Na⁺ out of and 2 K⁺ into the neuron, using ATP to maintain ion gradients essential for resting potential.

Ion Channels

Leak channels are protein structures that allow specific ions to passively flow in or out of the neuron.
These channels are selective and always open, facilitating continuous ion movement.

Diffusion and Electrostatic Pressure

Diffusion refers to movement from higher to lower particle concentration.
Electrostatic pressure arises from the electric charge difference across the membrane.

Voltage-Gated vs. Chemically-Gated Channels

Voltage-gated channels respond to changes in membrane potential.
Chemically-gated channels respond to specific chemical signals or neurotransmitters.

Ionic Basis of Resting Potential

Resting potential, around -70 mV, is determined by the distribution of Na⁺, K⁺, Cl⁻, and negatively charged proteins.
Maintained by the sodium-potassium pump, selective permeability of the membrane, and trapped anions inside.

Action Potentials and Threshold

Depolarization must reach a specific threshold to trigger an action potential; otherwise, the neuron will not fire.

Ions in Neuron Communication

Sodium (Na⁺), Potassium (K⁺), and Calcium (Ca²⁺) are cations (positively charged).
Chloride (Cl⁻) is an anion (negatively charged).

Neuron Membrane Structure

Composed of a lipid bilayer with hydrophilic heads facing outward and hydrophobic tails inward.
Embedded proteins serve as ion channels, neurotransmitter receptors, and pumps.

Resting Potential Maintenance

Sodium-Potassium Pump actively moves Na⁺ and K⁺ to maintain ion gradients.
Selective permeability allows more K⁺ to leak out, enhancing negativity inside the neuron.
Trapped negatively charged molecules contribute to the overall negative charge.

Refractory Periods

Absolute refractory period prevents any new action potentials.
Relative refractory period allows possible firing with a stronger stimulus.

Synapses

Axodendritic synapses connect axons to dendrites; facilitate excitatory/inhibitory transmission.
Axosomatic synapses connect axons to cell bodies; exert strong control over firing.
Axoaxonic synapses connect axons to other axons; modulate neurotransmitter release.

Electrical vs. Chemical Synapses

Electrical synapses enable rapid, direct signal transmission through gap junctions.
Chemical synapses use neurotransmitter release, allowing for complex signaling.

Presynaptic and Postsynaptic Neurons

Presynaptic neurons send signals and release neurotransmitters.
Postsynaptic neurons receive signals and respond via receptors.

Exocytosis

Process that releases neurotransmitters from vesicles into the extracellular space, crucial for communication between neurons.

Neurotransmitter Interaction

Key-and-lock analogy: neurotransmitter specificity for binding to receptors reflects precision in neuronal communication.

Ionotropic vs. Metabotropic Receptors

Ionotropic receptors mediate rapid ion flow changes; immediate effects on membrane potential.
Metabotropic receptors induce slower, prolonged signaling cascades affecting cellular functions.

Excitatory and Inhibitory Postsynaptic Potentials (EPSPs and IPSPs)

EPSPs lead to depolarization from positive ion influx, increasing firing likelihood.
IPSPs lead to hyperpolarization from negative ion influx or positive ion efflux, decreasing firing likelihood.

Impact of EPSPs and IPSPs

EPSPs enhance neuronal excitability, potentially leading to action potentials.
IPSPs reduce excitability, making it less likely for the neuron to fire.

Agonists and Antagonists

Agonists activate receptors and mimic natural ligand effects (e.g., morphine).
Antagonists block receptor activation, inhibiting natural ligand effects (e.g., naloxone).

Effects of Drugs on Receptors

Agonists enhance the effects of neurotransmitters at their respective receptors, while antagonists interfere with neurotransmitter actions to either increase excitation or inhibition.

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Description

This quiz explores the differences in ionic composition between the intracellular and extracellular fluids of a resting neuron. It highlights the significance of sodium, potassium, chloride, and negatively charged proteins in neuronal function and their role in maintaining resting membrane potential.