Neural Communication and Receptor Signaling in the Nervous System

What are the two main types of signals used by neurons?

Electrical signals within a neuron and chemical signals between neurons.

What is the resting membrane potential of a neuron?

Approximately -70 millivolts (mV).

What ions contribute to the resting membrane potential?

Anions (like proteins and chloride) and cations (like potassium, sodium, and calcium).

What is the role of Na+/K+ pumps in neurons?

They help maintain the resting membrane potential by pumping sodium out and potassium into the cell.

What is the effect of an Inhibitory Post-Synaptic Potential (IPSP)?

Hyperpolarization, making the inside of the neuron more negative.

What triggers an Action Potential in a neuron?

If depolarization reaches a threshold of about -40 mV.

What is the ionic basis of an Action Potential?

A sudden influx of Na+ ions into the axon, causing a brief reversal of the membrane potential.

What are the three types of synapses based on their locations?

Axodendritic, axosomatic, and axoaxonic.

What neurotransmitter is primarily used at the Neuromuscular Junction (NMJ)?

Acetylcholine.

What are classical neurotransmitters?

Amino acids, monoamines, acetylcholine, and purines.

How are classical neurotransmitters synthesized?

From dietary precursors in the axon terminals by enzymes.

What is the function of vesicular transporters?

They actively transport neurotransmitters into vesicles using an electrochemical gradient.

What happens during neurotransmitter release?

An action potential triggers voltage-gated Ca2+ channels, leading to Ca2+ influx and vesicle fusion with the presynaptic membrane.

What is the role of autoreceptors?

They are receptors on the same neuron that released the neurotransmitter, providing feedback.

What is the difference between local potentials and action potentials?

Local potentials are graded and can be excitatory or inhibitory, while action potentials are all-or-nothing events.

What is the significance of ligand-gated ion channels?

They open in response to ligand binding, allowing ions to flow and change the membrane potential.

What are neuropeptides?

A type of non-classical neurotransmitter synthesized in the cell body and packaged into large vesicles.

What is the process of vesicle recycling?

The vesicle membrane is retrieved through endocytosis and refilled with neurotransmitter.

What is the effect of excitatory post-synaptic potentials (EPSPs)?

Depolarization, making the inside of the neuron less negative.

How fast can action potentials conduct?

Very rapidly, up to 1200 Hz.

What is the role of SNARE proteins in neurotransmitter release?

They mediate the fusion of vesicles with the presynaptic membrane during exocytosis.

What are autoreceptors?

Receptors on the same neuron releasing the neurotransmitter (NT) that provide negative feedback to modulate cell activity.

What are the two types of autoreceptors?

Terminal autoreceptors, which modulate NT release, and somatodendritic autoreceptors, which modulate NT synthesis or firing.

What is one method of neurotransmitter inactivation?

Enzymatic degradation, such as the rapid metabolism of acetylcholine by acetylcholine esterase (AChE).

What is reuptake in neurotransmitter inactivation?

The process where plasma membrane transporters remove neurotransmitters from the synaptic cleft, located in the nerve terminal or glia.

What are retrograde messengers?

Signaling molecules that travel from the postsynaptic cell to the presynaptic cell, including gases like nitric oxide and lipids like anandamide.

What defines receptors in the nervous system?

Proteins activated by the binding of a ligand (neurotransmitter or drug) that do not transport the ligand into the cell.

What are the two main categories of receptors?

Ionotropic receptors (ligand-gated ion channels) and metabotropic receptors (G protein-coupled receptors, GPCRs).

What is the structure of ionotropic receptors?

Comprised of 4-5 subunits that form an ion channel.

What are the properties of ionotropic receptors?

They have fast and rapidly reversible effects, with ligand binding directly opening the ion channel.

What is an example of an ionotropic receptor?

Nicotinic acetylcholine receptor (nAChR), which is a cation channel that allows Na+ in.

What is the structure of metabotropic receptors?

A single subunit with 7 transmembrane domains, coupled to an intracellular G protein.

How do metabotropic receptors differ from ionotropic receptors?

They have slower and longer-lasting effects, with ligand binding activating a G protein that causes changes via effectors and second messengers.

What are the two basic signaling mechanisms of G proteins?

G protein-gated ion channels and second messenger systems.

What is the sequence of events in second messenger systems?

Activation of G protein, change in effector enzyme activity, change in second messenger levels, activation of a protein kinase, and phosphorylation of a substrate protein.

What are the three types of G proteins based on the α subunit?

Gs (stimulatory), Gi (inhibitory), and Gq (increases IP3, DAG, and intracellular Ca++).

What role do protein kinases play in cellular signaling?

They modify other proteins by adding phosphate groups (phosphorylation), regulating neuronal excitability and synaptic plasticity.

What are immediate early genes (IEGs)?

Transcription factors that are rapidly transcribed/translated after neuronal activation, such as c-Fos, Jun, and CREB.

What is the significance of c-Fos in neuronal activation?

It is a common IEG and transcription factor used as a marker of neuronal activation.

What is epigenetics?

Heritable changes in gene expression without altering the underlying DNA sequence, potentially lasting a lifetime or passed to future generations.

What is a connectome?

A comprehensive map of all neural connections within the nervous system.