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?

<p>Ionotropic receptors have a faster response time. (D)</p> Signup and view all the answers

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

<p>K+ and Cl- (A)</p> Signup and view all the answers

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

<p>The tendency of molecules to move from high concentration to low concentration (C)</p> Signup and view all the answers

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

<p>The charge inside the neuron becomes more positive (A)</p> Signup and view all the answers

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

<p>They restrict the flow of certain ions or molecules (D)</p> Signup and view all the answers

What occurs during the afterhyperpolarization phase?

<p>The membrane potential becomes less negative than the resting potential (D)</p> Signup and view all the answers

What happens to electrolytes like NaCl in a solution?

<p>They dissociate into cations and anions (B)</p> Signup and view all the answers

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

<p>The repulsion of like-charged ions from each other (D)</p> Signup and view all the answers

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

<p>Once the threshold is met, the neuron will fire fully or not at all (C)</p> Signup and view all the answers

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

<p>It affects the electrostatic potential within the neuron (C)</p> Signup and view all the answers

What is the typical resting potential of a prototypical neuron?

<p>-70 mV (C)</p> Signup and view all the answers

Which term describes a decrease in membrane potential toward neutrality?

<p>Depolarization (A)</p> Signup and view all the answers

At what threshold is an action potential typically initiated?

<p>-55 mV (D)</p> Signup and view all the answers

What kind of communication occurs specifically between neurons?

<p>Synaptic communication (C)</p> Signup and view all the answers

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

<p>Erythrocytes (D)</p> Signup and view all the answers

What does hyperpolarization refer to?

<p>An increase in membrane polarization (C)</p> Signup and view all the answers

How would you describe the action potential?

<p>Large depolarization followed by repolarization (B)</p> Signup and view all the answers

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

<p>Astroglia (C)</p> Signup and view all the answers

What allows for the integration of inputs in neuronal communication?

<p>Synaptic communication (A)</p> Signup and view all the answers

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

<p>Membrane potential (B)</p> Signup and view all the answers

What happens when neurotransmitters bind to autoreceptors?

<p>They inhibit further synthesis and release of neurotransmitters. (D)</p> Signup and view all the answers

Which pool of neurotransmitter vesicles is ready for immediate release?

<p>Readily releasable pool (D)</p> Signup and view all the answers

What is typically required for neurotransmitter binding to postsynaptic receptors?

<p>Two or more molecules of neurotransmitter. (C)</p> Signup and view all the answers

Which transporter proteins are involved in the reuptake of neurotransmitters?

<p>DAT, NET, SERT (B)</p> Signup and view all the answers

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

<p>It has a quantum effect, which is very small. (A)</p> Signup and view all the answers

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

<p>It is degraded and choline is reuptaken. (C)</p> Signup and view all the answers

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

<p>They are not reuptaken at all. (D)</p> Signup and view all the answers

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

<p>To degrade released neurotransmitters into waste products. (D)</p> Signup and view all the answers

What distinguishes metabotropic receptors from ionotropic receptors?

<p>Metabotropic receptors have slow onset and enduring actions. (A)</p> Signup and view all the answers

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

<p>Spatial summation (D)</p> Signup and view all the answers

What is the first step in neurotransmission?

<p>Neurotransmitter synthesis (B)</p> Signup and view all the answers

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

<p>Inhibitory and excitatory inputs together (D)</p> Signup and view all the answers

What happens during neurotransmitter release?

<p>Vesicles fuse with the presynaptic membrane. (A)</p> Signup and view all the answers

What is the role of enzymes in neurotransmitter storage?

<p>To catabolize leaked neurotransmitters. (C)</p> Signup and view all the answers

Which of the following best describes temporal summation?

<p>A single input providing repeated stimulation in quick succession. (D)</p> Signup and view all the answers

What role does convergence play in signaling between neurons?

<p>It facilitates the summation of inputs. (B)</p> Signup and view all the answers

How do neurotransmitters diffuse after being released?

<p>Across the synapse passively. (A)</p> Signup and view all the answers

What is the purpose of vesicular packaging in neurotransmitter storage?

<p>To protect neurotransmitters from enzymatic degradation. (C)</p> Signup and view all the answers

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

<p>To maintain the resting potential by actively transporting Na+ and K+ (B)</p> Signup and view all the answers

Why is the membrane almost impermeable to Na+ ions?

<p>There are few open channels specifically for Na+ transport (C)</p> Signup and view all the answers

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

<p>Electrical gradient inside the neuron that attracts K+ (C)</p> Signup and view all the answers

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

<p>-70mV (A)</p> Signup and view all the answers

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

<p>Cl- and Na+ (A)</p> 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?

<p>It is responsible for generating the membrane potential (A)</p> Signup and view all the answers

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

<p>40% (B)</p> Signup and view all the answers

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

<p>K+ is more concentrated inside, while Na+ and Cl- are more concentrated outside (B)</p> Signup and view all the answers

Flashcards

Resting Potential

The stable, negative electrical charge of a neuron when it is not transmitting information.

Depolarization

The process of making the inside of a neuron more positive, moving it closer to the threshold for firing.

Threshold

The critical level of depolarization that must be reached for a neuron to fire an action potential.

Action Potential

A brief but large electrical signal that travels down the axon of a neuron.

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Repolarization

The process of restoring the neuron's negative charge after an action potential, returning it to its resting state.

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Concentration Gradient

The difference in concentration of a substance across a membrane.

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Electrostatic Potential

The electrical force that pulls ions towards or away from each other.

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Membrane Permeability

The extent to which a membrane allows molecules to pass through it.

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Membrane Potential

The difference in electrical charge across the cell membrane, creating a stored source of energy.

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Hyperpolarization

An increase in membrane potential, making the inside of the cell more negative.

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Propagation

The movement of the action potential along the axon, from the cell body to the synapses.

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Axon Terminal

The end of the axon where the action potential reaches and triggers the release of neurotransmitters.

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Synapse

The junction between two neurons where communication occurs through neurotransmitter release.

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Neurotransmitter

Chemical messengers released from the axon terminal that transmit signals across the synapse.

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Sodium-Potassium Pump

A protein active transport mechanism that pumps 3 sodium ions (Na+) out of the cell and 2 potassium ions (K+) into the cell. It maintains the concentration gradients and requires ATP for energy.

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Sodium Ion (Na+)

A positively charged ion more concentrated outside the neuron. It's crucial for action potential generation, but its movement across the membrane is tightly controlled.

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Potassium Ion (K+)

A positively charged ion more concentrated inside the neuron. It plays a key role in repolarization after an action potential.

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Equilibrium Potential

The membrane potential at which the electrical force driving an ion across the membrane is equal and opposite to the chemical force (concentration gradient).

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Electrostatic Attraction

The attraction between opposite charges, like the inner and outer surfaces of the neuron's membrane.

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Ionotropic Receptor

A type of receptor that directly opens an ion channel when a neurotransmitter binds to it, typically requiring two or more neurotransmitter molecules.

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Metabotropic Receptor

A type of receptor that, upon neurotransmitter binding, initiates a series of intracellular signaling events, ultimately leading to changes in ion channel activity or other cellular processes.

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EPSP (Excitatory Postsynaptic Potential)

A depolarizing potential that makes it more likely for a neuron to fire an action potential, often caused by the opening of sodium (Na+) channels.

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IPSP (Inhibitory Postsynaptic Potential)

A hyperpolarizing potential that makes it less likely for a neuron to fire an action potential, often caused by the opening of potassium (K+) or chloride (Cl-) channels.

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Calcium Channels (Ca2+)

Ion channels that, when opened, allow calcium ions to flow into the neuron, often leading to the release of neurotransmitters or other cellular processes.

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Spatial Summation

The combined effect of multiple excitatory or inhibitory inputs arriving at different locations on the postsynaptic neuron simultaneously.

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Temporal Summation

The combined effect of multiple excitatory or inhibitory inputs arriving at the same location on the postsynaptic neuron in quick succession.

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Convergence in Neural Signaling

The process where multiple neurons send signals to a single postsynaptic neuron.

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Divergence in Neural Signaling

The process where a single neuron sends signals to multiple postsynaptic neurons.

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Neurotransmitter Synthesis

The process of creating neurotransmitters within the neuron.

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Neurotransmitter Storage

The process of packaging and storing neurotransmitters within vesicles.

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Neurotransmitter Vesicle Pools

Neurons store neurotransmitters in three distinct pools: readily releasable, recycling, and reserve pools. Each pool serves a specific role in neurotransmitter release.

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Autoreceptors

Autoreceptors are specialized receptors located on the presynaptic membrane that detect the released neurotransmitter. They act as a feedback mechanism, inhibiting further synthesis and release.

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Neurotransmitter Binding

Neurotransmitters bind to receptors on the postsynaptic neuron, but usually require multiple molecules to initiate a response. There's some selectivity between neurotransmitters and their target receptors.

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Quantum Effect

The effect of releasing a single vesicle of neurotransmitters on the postsynaptic neuron is very small and is called a quantum effect. Many quanta are required to significantly alter postsynaptic activity.

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Neurotransmitter Reuptake

After release, most neurotransmitters are rapidly reuptaken back into the presynaptic neuron by specialized transporter proteins. This ensures efficient recycling and limits signaling.

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Acetylcholine Breakdown

Acetylcholine is a neurotransmitter that is broken down by enzymes in the synapse. The breakdown product, choline, is then reuptaken back into the presynaptic neuron for reuse.

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Glutamate Reuptake

Glutamate is mainly reuptaken by glial cells, modified, and returned to glutamatergic neurons. This process helps regulate glutamate levels in the synapse.

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Enzymatic Degradation

Some neurotransmitters are broken down by specific enzymes in the synapse. This is a major way to terminate neurotransmitter signaling. Most breakdown products are excreted as waste.

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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.

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