Chapter 9 Lecture Outline

Direct receptor activation (ionotropic) involves the direct opening of ion channels upon binding of a ligand to the receptor, leading to rapid signaling. Option 1 describes intracellular receptors, which are not involved in direct receptor activation. Option 2 refers to metabotropic receptors that result in slow signaling. Option 3 mentions indirect mechanisms involving secondary messengers, which are not part of direct ionotropic receptor activation.

Metabotropic or indirect receptor activation involves the binding of a ligand to the receptor, which then activates a G-protein leading to intracellular signaling. This process is slower compared to ionotropic receptors and involves biochemical reactions.

The correct answer clarifies that chemicals are involved in mediating synaptic transmission, which is a key process in communication between neurons. The incorrect answers are unrelated or false statements that do not align with the topic of the question.

The correct answer describes the process of electrical communication between cells involving direct current flow and the activation of cells through proteins forming gap junctions or connexus.

The correct answer describes the specific process by which junctions are formed in cells. Incorrect answers do not accurately portray this process.

In a rectified synapse, the postsynaptic axon activation does not lead to transmission, distinguishing it from a typical synaptic response.

The correct answer states that electrical synapses being rectified are determined by factors such as second messenger properties, voltage properties, and other relevant factors. The incorrect answers provided do not accurately reflect the factors determining rectification of electrical synapses.

In a chick ganglion cell, the dual electrical/chemical synapse involves stimulation of the presynaptic fiber, leading to the release of transmitter and the creation of a blip in the postsynaptic recording. This process includes both electrical and chemical components for signal transmission.

Injecting negative current into a postsynaptic neuron results in hyperpolarization of the cell, making it less likely to reach the threshold for firing an action potential. The mention of shocking the nerve is likely an oversimplification or misrepresentation of the consequences of hyperpolarization.

When a negative current is injected into the postsynaptic cell, it inhibits the response. However, shocking the nerve can still result in a two-fold response involving an instantaneous electrical component followed by a chemical EPSP later.

Injecting more negative current into the AP increases its negativity beyond a certain threshold, causing it to fail.

In chemical synaptic transmission, the process involves the action potential (AP) invading the terminal, leading to the docking of vesicles, which then merge their membrane with the plasma membrane to release neurotransmitters into the synaptic cleft.

The correct answer explains the specific mechanism involving voltage gated CA2+ channels and depolarization, which triggers the fusion process.

CA2+ facilitates membrane fusion by interacting with specific binding proteins that help mediate the fusion process, which is known to be a high energy process. The incorrect answers provided do not accurately describe the role of CA2+ in membrane fusion.

Exocytosis is a process by which cells release molecules by the fusion of vesicles with the plasma membrane. In neurons, docking proteins play a key role in enabling the fusion of vesicles containing neurotransmitters with the presynaptic membrane. The influx of calcium ions (CA2+) triggers this process and allows for the release of neurotransmitters into the synaptic cleft.

Endocytosis is the process by which cells absorb molecules by engulfing them. This process can involve clathrin proteins to form vesicles that are then reloaded with transmitters.

The endplate potential at the neuromuscular junction occurs when a motor nerve is shocked, leading to a postsynaptic response. This is known as an EPP at the neuromuscular junction or EPSP in the central nervous system.

When a muscle cell reaches its threshold, an action potential fires, leading to the activation of NA+ channels in that muscle cell. This is a critical step in muscle contraction.

Curare is a toxin that specifically blocks the postsynaptic receptor at the neuromuscular junction. It competes with acetylcholine for binding to the receptor, thus suppressing end-plate potentials (EPP). Muscarine, α-bungarotoxin, and botulinum toxin act through different mechanisms at the neuromuscular junction.

Curare is a neurotoxin that blocks nicotinic acetylcholine receptors on muscle cells, leading to paralysis. Without the ability to fire action potentials (APs), the muscle fibers decay and fail to function properly.

The correct answer explains how the current decays with distance in EPP systems, which is a common phenomenon due to loss of current. The incorrect answers provide alternative misconceptions that do not align with the principles of EPP.

Ionophoresis is a laboratory technique used to introduce ions into a cell by inserting a recording pipette filled with a specific solution. It is commonly used in neuroscience research to study ion channels and synaptic transmission.

Iontophoresis involves the introduction of ions into the skin through the use of a small electrical current. Since like charges repel each other, a net positive charge is used to drive positively charged ions into the skin, which increases with increased current.

The larger depolarizations are primarily seen near the end plate, known as ionophoretic EPP, as it is weaker when measured further away from the edge due to the distribution of ions and neurotransmitters.

The correct answer describes the actual purpose of soaking the snake NMJ in an enzyme in the experiment, which was to digest extracellular proteins and allow for the measurement of Ach sensitivity.

Alpha-BTX prevents ACh binding by blocking the binding site, which can then be visualized using fluorescent tagging to reveal the location of dense ACh receptors on the cell.

HRP stands for Horseradish Peroxidase, which is an enzyme commonly used in biological research for various purposes such as visualizing specific proteins and enzymes in cells and tissues under a microscope. The correct answer details its specific property in turning substrates black in an electromicroscope.

I-125 is revealed by applying it to BTX, placing a film over it, and examining it under an electromicroscope to observe the dense binding of BTX at the active zone in the synapse.