Neuroscience Quiz on Ion Channels

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Questions and Answers

Why do Na+ ions prefer to stay outside of potassium ion channels?

They cannot fit unhydrated in the channel's pore (correct)

They are larger than K+ ions

They lack a hydration shell

They have a higher charge than K+ ions

What is the primary function of a gene promoter in DNA?

To enhance structural stability

To initiate gene transcription (correct)

To encode proteins directly

To protect DNA from degradation

How many distinct genes for the voltage-gated potassium channel are found in the human genome?

40 (correct)

What happens to ions when they are dissolved in water?

They become hydrated Signup and view all the answers

What is true about the evolution of voltage-gated potassium channels?

There is no perfect version of this channel Signup and view all the answers

What role does the selectivity filter of ion channels play?

It replaces the ion's hydration shell Signup and view all the answers

Which statement accurately describes gene variants of voltage-gated potassium channels?

Most have been conserved for millions of years Signup and view all the answers

What effect does attaching a gene promoter region to foreign DNA have?

It instructs the cell to read and express the gene Signup and view all the answers

Which type of ion channel is responsible for initiating and propagating the action potential?

Voltage-gated sodium channel Signup and view all the answers

What is the role of the voltage-gated potassium channel?

To restore the resting membrane potential Signup and view all the answers

Which ion is specifically blocked by potassium ion channels despite both having a +1 charge?

Sodium ion (Na+) Signup and view all the answers

Which type of receptor opens in response to ligand binding?

Ionotropic receptor Signup and view all the answers

What is the primary function of neurotransmitters?

To bind with receptors and facilitate signaling Signup and view all the answers

In the context of the ion channels, what significance does the sequence 'TCAGGCCCG' have?

It encodes the amino acid glycine Signup and view all the answers

What is the purpose of altering the DNA sequence in the study of ion channel selectivity?

To test the role of specific amino acids in ion selectivity Signup and view all the answers

What is the typical time frame for effects to become evident after neurotransmitter signaling begins?

100ms Signup and view all the answers

Which method is used to determine the three-dimensional shape of ion channel proteins?

X-ray crystallography Signup and view all the answers

What distinguishes metabotropic receptors from ionotropic receptors?

Metabotropic receptors are primarily involved in G protein signaling Signup and view all the answers

What technique do researchers use to test the function of modified proteins in neurons?

DNA injection Signup and view all the answers

What characteristic allows potassium channels to selectively permit K+ ions over Na+ ions?

Specific amino acid interactions in the channel Signup and view all the answers

What is the diameter of a typical small synaptic vesicle?

30 nm Signup and view all the answers

Where would you find a postsynaptic receptor?

On the membrane of a muscle cell Signup and view all the answers

How long does the peak effect of ionotropic receptors last after ligand binding?

A few milliseconds Signup and view all the answers

What term is used to describe a signaling molecule that binds to a receptor?

Ligand Signup and view all the answers

What is the primary mechanism by which neurotransmitter signaling is kept brief in the synapse?

Reuptake Signup and view all the answers

Which type of receptor produces rapid postsynaptic potentials?

Ionotropic receptors Signup and view all the answers

Which type of receptor is NOT found on the presynaptic membrane?

Postsynaptic receptor Signup and view all the answers

What kind of postsynaptic potential results from the entry of positive sodium ions?

Excitatory postsynaptic potential (EPSP) Signup and view all the answers

Which ion movement is primarily responsible for hyperpolarization of a neuron?

Inflow of chloride ions Signup and view all the answers

In a scenario where a neuron in the cortex sends an action potential to the spinal cord, what is the potential outcome?

Hyperpolarization of motor neurons and inhibition of a reflex Signup and view all the answers

In terms of postsynaptic potency, which receptor type might not produce a postsynaptic potential?

Metabotropic receptors Signup and view all the answers

What best describes the effect of opening Na+ ion channels in a neuron?

Leads to depolarization and increased likelihood of spiking Signup and view all the answers

What primarily determines whether a neurotransmitter will have an excitatory or inhibitory effect?

The receptor expressed by the postsynaptic cell Signup and view all the answers

What happens when a sensory neuron spikes and releases neurotransmitters?

It depolarizes an excitatory interneuron and activates a motor neuron Signup and view all the answers

What is the role of acetylcholinesterase in neurotransmitter clearance?

It facilitates the breakdown of neurotransmitters. Signup and view all the answers

What characterizes an inhibitory neuron?

It reliably causes IPSCs in downstream neurons Signup and view all the answers

How can an inhibitory neuron influence the behavior of other neurons?

By inhibiting the firing of other inhibitory neurons Signup and view all the answers

What is the overall effect of competing neurons in behavior modulation?

They create a balance between excitatory and inhibitory signals. Signup and view all the answers

What can occur when an inhibitory neuron is activated?

It can also enable movement by inhibiting another inhibitory neuron. Signup and view all the answers

What is a significant role of inhibitory neurons in neural circuits?

To regulate the balance between excitation and inhibition. Signup and view all the answers

Study Notes

Membrane of a Neuron

Neurons have specific ion channels crucial for signaling and communication.

Ion Channel Selectivity

Voltage-gated sodium channels initiate action potentials.
Voltage-gated potassium channels restore resting membrane potential.
Voltage-gated calcium channels release neurotransmitters.
Each channel is selective for specific ions (Na+, K+, Ca+).

Modern Molecular Biology

DNA sequences dictate the structure of ion channel proteins.
The amino acid sequence, determined by DNA, influences ion channel selectivity.
Researchers can modify DNA to test the function of specific amino acids.

Hydrated Ions

Ions are encased in hydration shells in aqueous environments.
Ion channel selectivity filters replace hydration shells for specific ions, allowing selective passage.

Voltage-Gated Potassium Channel

Human genome contains 40 distinct genes for voltage-gated potassium channels.
These channels have been conserved through evolution for optimal cell function.

Electron Microscopy

Electron microscopy reveals synaptic structures like vesicles.
Diameter of small synaptic vesicles is approximately 30 nm, capable of holding over 5,000 neurotransmitter molecules.

Neurotransmitters

Neurotransmitters bind to receptors, acting as signaling molecules (ligands).
Two types of neurotransmitter receptors:
- Ionotropic receptors: ion channels that respond rapidly to ligand binding.
- Metabotropic receptors: non-ion channels that trigger slower intracellular signaling.

Neurotransmitter Clearance

Neurotransmitter signaling is terminated through:
- Diffusion: movement from high to low concentration.
- Enzymatic deactivation: enzymes break down neurotransmitters (e.g., acetylcholine).
- Reuptake: transporters recycle neurotransmitters back into the releasing cell.

Postsynaptic Receptor Activation

Neurotransmitter binding changes postsynaptic membrane potential.
Ionotropic receptors generate fast postsynaptic potentials (1-5 ms).
Metabotropic receptors generate slower postsynaptic potentials (100 ms to seconds).
Postsynaptic potentials can be excitatory (EPSPs) or inhibitory (IPSPs), depending on ion flow (e.g., Na+ for EPSPs, Cl- for IPSPs).

Changes in Membrane Potential

Depolarization: occurs when membrane potential becomes less negative.
Hyperpolarization: occurs when membrane potential becomes more negative.
Postsynaptic cell receptor determines whether neurotransmitter actions are excitatory or inhibitory.

Neural Circuits

Sensory neurons communicate with interneurons to elicit reflex responses (e.g., withdrawal reflex).
Cerebral cortex neurons can modulate other neural circuits, either facilitating or inhibiting reflex actions.

Neural Excitation Versus Behavioral Excitation

Inhibitory neurons can cause IPSCs, reducing downstream neuron's activity.
Inhibition of inhibitory neurons can lead to behavioral outcomes, illustrating complex neural interactions.
A balance between excitatory and inhibitory signals shapes behavioral responses.

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Description

Test your knowledge on the ion channels of neurons, including their mechanisms and significance in signaling. Explore the roles of different voltage-gated channels and how their selectivity impacts neuronal function. This quiz covers molecular biology aspects related to ion channel proteins and their genetic encoding.