Chapter 3

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Questions and Answers

What occurs when a neurotransmitter binds to an ionotropic receptor?

The receptor activates a G protein.

The receptor changes biochemical activity.

The receptor undergoes structural transformation.

The receptor opens an ion channel. (correct)

What type of receptor is responsible for opening Na+ channels to create an EPSP?

G protein-coupled receptors

Ionotropic receptors (correct)

Cl- channels

Metabotropic receptors

Which characteristic distinguishes metabotropic receptors from ionotropic receptors?

They open ion channels directly.

They activate chemical signaling mechanisms. (correct)

They only produce inhibitory effects.

They bind to fewer neurotransmitter molecules.

In terms of response time, how do ionotropic receptors compare to metabotropic receptors?

Ionotropic receptors have a faster response time. Signup and view all the answers

What ions can lead to an inhibitory postsynaptic potential (IPSP) when they pass through specific channels?

K+ and Cl- Signup and view all the answers

What does a concentration gradient refer to in the context of molecular movement?

The tendency of molecules to move from high concentration to low concentration Signup and view all the answers

What is a key characteristic of the membrane potential during depolarization?

The charge inside the neuron becomes more positive Signup and view all the answers

How do impermeable or semi-permeable membranes impact molecular distribution?

They restrict the flow of certain ions or molecules Signup and view all the answers

What occurs during the afterhyperpolarization phase?

The membrane potential becomes less negative than the resting potential Signup and view all the answers

What happens to electrolytes like NaCl in a solution?

They dissociate into cations and anions Signup and view all the answers

What drives the movement of ions across a neuron's membrane under a voltage gradient?

The repulsion of like-charged ions from each other Signup and view all the answers

What is meant by the term 'all-or-none' in relation to neuron firing?

Once the threshold is met, the neuron will fire fully or not at all Signup and view all the answers

What is the significance of the 'cloud' of charge created by ion distribution across the membrane?

It affects the electrostatic potential within the neuron Signup and view all the answers

What is the typical resting potential of a prototypical neuron?

-70 mV Signup and view all the answers

Which term describes a decrease in membrane potential toward neutrality?

Depolarization Signup and view all the answers

At what threshold is an action potential typically initiated?

-55 mV Signup and view all the answers

What kind of communication occurs specifically between neurons?

Synaptic communication Signup and view all the answers

Which cell type has the lowest resting potential among those listed?

Erythrocytes Signup and view all the answers

What does hyperpolarization refer to?

An increase in membrane polarization Signup and view all the answers

How would you describe the action potential?

Large depolarization followed by repolarization Signup and view all the answers

Which of the following cells has a resting potential close to -90 mV?

Astroglia Signup and view all the answers

What allows for the integration of inputs in neuronal communication?

Synaptic communication Signup and view all the answers

What is the difference in electrical charge across the membrane called?

Membrane potential Signup and view all the answers

What happens when neurotransmitters bind to autoreceptors?

They inhibit further synthesis and release of neurotransmitters. Signup and view all the answers

Which pool of neurotransmitter vesicles is ready for immediate release?

Readily releasable pool Signup and view all the answers

What is typically required for neurotransmitter binding to postsynaptic receptors?

Two or more molecules of neurotransmitter. Signup and view all the answers

Which transporter proteins are involved in the reuptake of neurotransmitters?

DAT, NET, SERT Signup and view all the answers

What is the effect of releasing one vesicle of neurotransmitter on a postsynaptic neuron?

It has a quantum effect, which is very small. Signup and view all the answers

What occurs to acetylcholine after it is released into the synaptic cleft?

It is degraded and choline is reuptaken. Signup and view all the answers

How are peptide neurotransmitters different in terms of reuptake compared to other neurotransmitters?

They are not reuptaken at all. Signup and view all the answers

What is the role of specialized extracellular enzymes in neurotransmitter activity?

To degrade released neurotransmitters into waste products. Signup and view all the answers

What distinguishes metabotropic receptors from ionotropic receptors?

Metabotropic receptors have slow onset and enduring actions. Signup and view all the answers

Which process allows simultaneous inputs to arrive at a postsynaptic neuron?

Spatial summation Signup and view all the answers

What is the first step in neurotransmission?

Neurotransmitter synthesis Signup and view all the answers

What type of inputs results in the cancellation of potential at the axon hillock?

Inhibitory and excitatory inputs together Signup and view all the answers

What happens during neurotransmitter release?

Vesicles fuse with the presynaptic membrane. Signup and view all the answers

What is the role of enzymes in neurotransmitter storage?

To catabolize leaked neurotransmitters. Signup and view all the answers

Which of the following best describes temporal summation?

A single input providing repeated stimulation in quick succession. Signup and view all the answers

What role does convergence play in signaling between neurons?

It facilitates the summation of inputs. Signup and view all the answers

How do neurotransmitters diffuse after being released?

Across the synapse passively. Signup and view all the answers

What is the purpose of vesicular packaging in neurotransmitter storage?

To protect neurotransmitters from enzymatic degradation. Signup and view all the answers

What is the primary role of the sodium-potassium pump in a neuron?

To maintain the resting potential by actively transporting Na+ and K+ Signup and view all the answers

Why is the membrane almost impermeable to Na+ ions?

There are few open channels specifically for Na+ transport Signup and view all the answers

What primarily keeps K+ ions within the cell despite their concentration gradient pushing them outward?

Electrical gradient inside the neuron that attracts K+ Signup and view all the answers

What is the resting potential of a neuron typically measured at?

-70mV Signup and view all the answers

Which ions are more concentrated in the extracellular fluid compared to inside the neuron?

Cl- and Na+ Signup and view all the answers

What is the significance of the 'cloud' of charge that forms over the inner and outer surfaces of the membrane?

It is responsible for generating the membrane potential Signup and view all the answers

What percentage of a neuron's energy resources is used by the sodium-potassium pump?

40% Signup and view all the answers

Which of the following describes the gradients present at resting potential accurately?

K+ is more concentrated inside, while Na+ and Cl- are more concentrated outside Signup and view all the answers

Study Notes

Neurophysiology

Communication within a neuron involves local changes in membrane potential, action potentials, synaptic communication, and integration of inputs.

Communication Within a Neuron

Membrane potential: A stored source of electrical energy that represents the difference in charge across the cell membrane (inside vs. outside). Typical resting neuron potential is approximately -70mV. Values can differ slightly between cell types.
Resting potential: A polarized state of the neuron's membrane.
Depolarization: A decrease in membrane potential toward a neutral state.
Hyperpolarization: An increase in membrane polarization.
Action potential: A large depolarization and reverse polarization, propagated down the axon to the terminal region. Triggered when a stimulus exceeds a specific threshold. Crucially, its magnitude remains consistent regardless of the size of the original stimulus. This is an "all-or-none" response.
Concentration gradient: Molecules move to minimize concentration differences across a membrane; diffusion is the process.
Electrostatic potential: Ions in solution (e.g. Na+, K+, Cl-) create an electrical gradient. Opposites attract; like charges repel. Membranes influence ion distributions.
Equilibrium potential: For an ion, the membrane potential where there's no net movement of the ion across the membrane (diffusion and electrostatic forces balance). This is calculated using the Nernst equation, which takes into account factors such as ion concentration both inside and outside of the cell. Values for various ions are often given.
Sodium-Potassium Pump: Actively transports 3 Na+ ions out of the cell and 2 K+ ions into the cell to maintain resting membrane potential. This is a highly energy-consuming process.
Voltage-gated ion channels: Specific ion channels that open or close in response to changes in membrane potential.
Action potential propagation: Conduction along unmyelinated axons is slow; myelinated axons use saltatory conduction (action potentials jump between Nodes of Ranvier) for much faster transmission. Speeds (m/s) of conduction in different axon types are given.

Communication Between Neurons

Synapses: Junctions between neurons where communication transmits information.
Synaptic types: Axodendritic, axosomatic, axoaxonic, and dendrodendritic synapses.
Synaptic transmission: The process by which neurotransmitters carry the signal across synaptic gaps; a "chemical messenger" system.
Synaptic structure: The structure of the synapse includes a presynaptic terminal with vesicles storing neurotransmitter and postsynaptic receptors receiving the neurotransmitter. The synapse cleft separates the pre and post-synaptic cells.
Neurotransmitter release: Action potential triggers vesicles to release neurotransmitters into the synaptic cleft. Types of release include "kiss and run" and "merge and recycle."
Neurotransmitter receptors: Specificity exists, and effects (excitatory/inhibitory PSPs, or excitatory/inhibitory postsynaptic potentials), can vary with different neurotransmitters. The postsynaptic response is determined by the receptor type.
Neurotransmitter reuptake/degradation: Specialized proteins reabsorb/recycle neurotransmitters; enzymes degrade others to prevent continual stimulation.
Saltatory conduction: Faster transmission of signals within myelinated neurons.
Summation: Temporal (same presynaptic neuron firing repeatedly) and spatial (multiple presynaptic neurons firing at once) summation of signals at the postsynaptic cell. A combination of these factors (timing and strength input) will determine if the neuron "fires."
Communication types: Gap junctions (direct electrical, rare in vertebrates) vs. synaptic (indirect chemical communication). Neuromuscular junctions are examples of highly specialized and efficient synapses. Nonsynaptic communication also exists using hormones, neuromodulators and neurotransmitters to influence targets other than traditional synapses. Varicosities and en passant synapses represent forms of non-traditional synapse-like communication.

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Description

This quiz explores the essential aspects of communication within a neuron, including membrane potential, action potentials, and synaptic communication. Understand concepts like resting potential, depolarization, and hyperpolarization, critical for grasping neuronal functions. Test your knowledge on the electrical properties and responses of neurons.