Neuron Structure and Electrochemical Gradients

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Questions and Answers

What process occurs during Na+ influx in a neuron?

It makes the inside of the neuron more negative.

It moves the membrane potential towards zero. (correct)

It restores the resting potential by K+ efflux.

It causes hyperpolarization of the cell.

Which neurons are primarily involved in cognition and memory?

Granule Cells

Spiny Stellate Cells

Inhibitory Neurons

Pyramidal Neurons (correct)

What occurs during the absolute refractory period?

No stimulus can trigger another action potential. (correct)

A stronger-than-usual stimulus is needed to trigger an action potential.

The neuron can respond to any stimulus.

The membrane potential becomes hyperpolarized.

Which of the following steps is NOT part of the mechanism of action for excitatory neurons?

Glutamate binds to GABA_A receptors. Signup and view all the answers

What type of glutamate receptor mediates fast synaptic transmission?

AMPA Receptor Signup and view all the answers

What is the effect of GABA binding to GABA_A receptors?

It opens channels for chloride ions to enter the cell. Signup and view all the answers

Which periodic phase allows another action potential only with a stronger-than-usual stimulus?

Relative refractory period Signup and view all the answers

What is the primary role of granule cells in the hippocampus?

Memory formation Signup and view all the answers

What is the main function of the cell body in a neuron?

Processing incoming signals and maintaining the neuron's health Signup and view all the answers

Which ion is primarily associated with the intracellular fluid (ICF) in neurons?

Potassium (K+) Signup and view all the answers

What roles do the electrochemical gradient play in neuronal function?

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

What is the primary role of the Nodes of Ranvier in a neuron?

To increase the speed of action potential propagation Signup and view all the answers

What is the primary purpose of myelin sheath in neurons?

To insulate and speed up signal transmission Signup and view all the answers

What is the typical resting potential of a neuron?

-70 mV Signup and view all the answers

Which ion is found mainly in the extracellular fluid (ECF)?

Sodium (Na+) Signup and view all the answers

What initiates the action potential in a neuron?

The axon hillock where the axon joins the cell body Signup and view all the answers

Which neurotransmitter is primarily associated with excitatory neurons?

Glutamate Signup and view all the answers

How does diffusion relate to ion movement in neurons?

It describes the passive movement of ions from higher to lower concentration areas. Signup and view all the answers

What occurs during the depolarization phase of an action potential?

Na+ ions rush into the neuron, making it more positive Signup and view all the answers

Which of the following components is responsible for creating specific pathways for ion passage in neurons?

Ion channels Signup and view all the answers

What is the function of the Sodium-Potassium pump?

It maintains concentration gradients of Na+ and K+ ions Signup and view all the answers

What does the all-or-nothing principle state in the context of action potentials?

An action potential must fully occur once the threshold is met or not at all Signup and view all the answers

During the refractory period, what is the primary characteristic of a neuron's ability to fire another action potential?

It cannot fire an action potential until the period is over Signup and view all the answers

What defines the term 'permeability' in the context of cell membranes?

The ability of the membrane to allow certain substances to pass through Signup and view all the answers

What is the primary role of chandelier cells in the brain?

They inhibit action potential initiation in pyramidal neurons. Signup and view all the answers

Which type of synapse is most commonly excitatory?

Axodendritic Signup and view all the answers

What distinguishes electrical synapses from chemical synapses?

Electrical synapses allow fast, direct communication via gap junctions. Signup and view all the answers

What is the function of a neuromuscular junction?

To facilitate communication between a motor neuron and a muscle cell. Signup and view all the answers

Which type of synapse often serves to inhibit the activity of the postsynaptic cell?

Axosomatic Signup and view all the answers

What can result from issues with neurotransmitter release?

Reduced synaptic transmission efficiency. Signup and view all the answers

Which of the following describes the directionality of electrical synapses?

They permit bidirectional signal travel. Signup and view all the answers

What is the role of neurotransmitter systems in the brain?

They are important for brain function and signaling. Signup and view all the answers

What is the main purpose of neurotransmitter recycling?

To allow neurotransmitters to be reused Signup and view all the answers

Which method is commonly used to visualize specific proteins in cells?

Immunocytochemistry Signup and view all the answers

What effect do neurotransmitters have on the receiving neuron?

They may either excite or calm the receiving neuron. Signup and view all the answers

Which technique involves using light to activate specific synapses?

Optogenetics Signup and view all the answers

What is the role of nitric oxide (NO) in the brain?

It regulates blood flow and acts as a retrograde messenger. Signup and view all the answers

Which process strengthens synapses through repeated use?

Synaptic plasticity Signup and view all the answers

What does In Situ Hybridization detect?

Specific mRNA related to neurotransmitter synthesis Signup and view all the answers

Which method tests whether a neurotransmitter candidate evokes a postsynaptic response?

Microiontophoresis Signup and view all the answers

Study Notes

Neuron Structure and Function

Neurons are specialized cells responsible for communication in the body.
The cell body acts as the control center, processing signals and maintaining cell health.
Major components of the cell body include:
- Nucleus: Contains DNA.
- Cytoplasm: Houses organelles like mitochondria and ribosomes.
- Dendrites: Receive signals from other neurons.
- Axon: Transmits electrical impulses away from the cell body.

Intracellular and Extracellular Fluids

Intracellular Fluid (ICF) major ions: Potassium (K+), Phosphate (HPO4^2-), Proteins, Sodium (Na+).
Extracellular Fluid (ECF) major ions: Sodium (Na+), Chloride (Cl-), Calcium (Ca2+), Potassium (K+).

Electrochemical Gradients

Chemical Gradient: Concentration differences of ions drive movement from high to low concentration.
Electrical Gradient: Charge differences across the membrane attract ions to oppositely charged areas.

Action Potentials

Action potentials are rapid, transient changes in membrane potential.
Threshold for firing an action potential is around -55 mV.
Depolarization: Membrane potential becomes less negative as Na+ ions enter.
Repolarization: K+ ions exit to restore negative resting potential (-70 mV).
Hyperpolarization: Membrane potential becomes more negative than resting potential.
The all-or-nothing principle indicates that action potentials either occur fully or not at all.

Components of Axons

Axon Hillock: Initiates action potentials, cone-shaped region.
Myelin Sheath: Insulates the axon, increasing signal transmission speed.
Nodes of Ranvier: Gaps in myelin sheath where action potentials jump.
Axon Terminals: Release neurotransmitters to communicate with other cells.

Synaptic Transmission

Synapse: Junction between two cells (e.g., neuron and muscle) for communication.
Types of Synapses include:
- Electrical Synapses: Fast communication via gap junctions.
- Chemical Synapses: Slower, using neurotransmitters to relay signals.

Neurotransmitter Systems

Neurotransmitters play a crucial role in communication between neurons.
Two main types:
- Excitatory Neurons: Promote action potentials (e.g., Glutamate).
- Inhibitory Neurons: Decrease likelihood of action potentials (e.g., GABA).

Excitatory and Inhibitory Mechanisms

Excitatory Mechanism:
- Glutamate binds to AMPA and NMDA receptors, facilitating Na+ and Ca2+ influx leading to depolarization.
Inhibitory Mechanism:
- GABA binds to GABA_A receptors, allowing Cl⁻ influx and generating rapid inhibitory signals.

Neurotransmitter Release and Recycling

Neurotransmitter release is triggered by action potentials at synapses.
Neurotransmitter recycling: Breakdown and reuptake of neurotransmitters for reuse.

Studying Synaptic Function

Techniques for studying neurotransmitters and receptors:
- Immunocytochemistry: Visualizes specific proteins in cells.
- In Situ Hybridization: Detects mRNA related to neurotransmitter synthesis.
- Optogenetics: Activates specific synapses with light.
- Microiontophoresis: Tests neurotransmitter effects on postsynaptic responses.

Neurotransmitter Types

Glutamate: Main excitatory neurotransmitter in the CNS.
GABA: Main inhibitory neurotransmitter in the brain.
Endocannabinoids: Retrograde signaling molecules for modulating synaptic transmission.
Gaseous Neurotransmitters: Nitric Oxide (NO), a retrograde messenger regulating blood flow.

Synaptic Plasticity

The process by which frequent use of synapses increases their strength, essential for memory and learning.

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Description

Explore the intricate structure and function of neurons, including their cellular components and the roles of intracellular and extracellular fluids. This quiz also delves into electrochemical gradients and their significance in neuron signaling. Test your knowledge on how these elements contribute to the nervous system's communication processes.