Synaptic Transmission, Neurotransmitters, Synaptic Plasticity

Electrical synapses involve ___ whereas chemical synapses involve ___.

• direct electrical connections; release and reception of neurotransmitters

• direct electrical connections; release and reception of hormones

• indirect electrical connections; release and reception of neurotransmitters

• direct chemical connections; release and reception of hormones

• indirect chemical connections; release of electrical signals

Answer explanation

Electrical synapses involve direct electrical connections between neurons, allowing for rapid signal transmission. In contrast, chemical synapses rely on the release and reception of neurotransmitters to communicate between neurons.

What is the action of the neurotransmitter at a chemical synapse?

• It acts on receptors in the postsynaptic membrane.

• It electrically activates the presynaptic neuron

• It crosses the postsynaptic membrane and then activates ion channels in the postsynaptic neuron.

• It depolarizes the postsynaptic membrane by delivering an electrical charge.

• It transfers an action potential from the presynaptic neuron to the postsynaptic neuron.

Answer explanation

The correct choice is that the neurotransmitter acts on receptors in the postsynaptic membrane, initiating a response in the postsynaptic neuron. This is the primary function of neurotransmitters at chemical synapses.

Which event is the first in the series of events that take place during chemical synaptic transmission?

• Neurotransmitter binds to its receptors.

• Influx of Ca²⁺ in the presynaptic terminal.

• Voltage-gated Ca²⁺ channels open.

• Neurotransmitter is released into the synaptic cleft.

• Synaptic vesicles fuse with the presynaptic membrane.

Answer explanation

The first event in chemical synaptic transmission is the opening of voltage-gated Ca2+ channels. This allows Ca2+ to enter the presynaptic terminal, triggering subsequent events like neurotransmitter release.

At which point during signal transmission at a chemical synapse is exocytosis occurring?

• As neurotransmitter binds to its receptors.

• While Ca²⁺ enters the presynaptic terminal.

• As voltage-gated Ca²⁺ channels are opening.

• During neurotransmitter release into the synaptic cleft.

• During reuptake, as synaptic vesicles are reformed from the plasma membrane.

Answer explanation

Exocytosis occurs during neurotransmitter release into the synaptic cleft, where neurotransmitters are expelled from synaptic vesicles into the space between neurons, facilitating communication.

The figure shows an electron micrograph of a chemical synapse in the cerebral cortex. Which statement about this synapse is accurate?

• Inside the postsynaptic neuron are synaptic vesicles, which fuse with the membrane in the postsynaptic density.

• Inside the presynaptic neuron are synaptic vesicles, which fuse with the membrane in the active zone.

• Inside the presynaptic neuron are synaptic vesicles, which fuse with the membrane in the postsynaptic density.

• A gap junction connects the two neurons via connexons that span the pre- and postsynaptic membranes.

Answer explanation

The correct statement is that inside the presynaptic neuron are synaptic vesicles, which fuse with the membrane in the active zone. This is where neurotransmitter release occurs, facilitating communication between neurons.

Small-molecule neurotransmitters are _______ for _______.

• taken back into the presynaptic terminal; degradation

• taken back into the presynaptic terminal; reuse

• taken up by the postsynaptic cell; degradation

• taken up by the postsynaptic cell; reuse

• scattered in the synaptic cleft; reuse

Answer explanation

Small-molecule neurotransmitters are taken back into the presynaptic terminal for reuse after they have transmitted signals. This process allows the neuron to recycle neurotransmitters efficiently.

How would application of a Ca²⁺ channel blocker affect the function of a synapse?

• It would increase the magnitude of postsynaptic potential.

• It would decrease the magnitude of postsynaptic potential.

• It would eliminate the postsynaptic potential but have no effect on presynaptic neuron.

• It would eliminate the postsynaptic potential and the presynaptic Ca²⁺ current.

• It would eliminate the presynaptic Ca²⁺ current but have no effect on the postsynaptic potential.

Answer explanation

A Ca2+ channel blocker prevents calcium influx in the presynaptic neuron, which is essential for neurotransmitter release. This results in no postsynaptic potential and eliminates the presynaptic Ca2+ current.

Tags

NGSS.HS-PS3-5

Which of these is a FALSE statement about neurotransmitters?

• They act as chemical messengers

• They can be inhibitory

• They can be excitatory

• Glucose is an example

Answer explanation

Glucose is not a neurotransmitter; it is a sugar that provides energy to cells. Neurotransmitters are specific chemical messengers that can be excitatory or inhibitory, such as dopamine or serotonin.

What type of ion causes an excitatory response?

• Calcium

• Chlorine

• Potassium

• Sodium

Answer explanation

Sodium ions (Na+) are crucial for generating excitatory responses in neurons. When sodium channels open, Na+ influx depolarizes the membrane, leading to action potentials, which are essential for nerve signal transmission.

What type of ion causes an inhibitory response?

• Calcium

• Chlorine

• Potassium

• Sodium

Answer explanation

Chlorine ions (Cl-) are associated with inhibitory responses in neurons. They help hyperpolarize the cell membrane, making it less likely to fire an action potential, thus causing inhibition.