Synapses and Action Potentials

An axon conducts nerve impulses _________ the cell body.

• away from

• toward

• both toward and away

• around, bypassing

Receive electrical impulses from the neighbouring neurons.

• Dendrites

• Axon

• Soma

• Nucleus

What is the change of a cell membrane from positive to negative called?

• Glycolysis

• Action Potential

•  Temporal Summation

• Electrolysis

Action potentials run along the ______ from ______ to ________.

• axon

• myelin

• dendrites

• axon terminals

The critical point at which a stimulus causes an action potential

• Synapse

•  Action potential

• Membrane potential

• Threshold

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.

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.

What is most likely to happen if a post-synaptic neuron is depolarized? Hyperolarized?

• Depolarized- becomes more positive, action pot more likely

  Hyperpolarized- becomes very negative, action pot less likely

• Depolarized- becomes more negative, action pot less likely

  Hyperpolarized- becomes very positive, action pot more likely

Answer explanation

When a post-synaptic neuron is depolarized, it becomes more positive, increasing the likelihood of an action potential. Conversely, if it is hyperpolarized, it becomes very negative, making an action potential less likely.

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.