Chapter 2 Self-test questions

. Which of the following statements cannot be used as evidence in support of the theory that the nervous system is composed of individual cells?

Existence of free nerve endings in histological material stained with the Golgi method.

Existence of synaptic clefts.

Absence of synaptic delay at electric synapses.

Presence of synaptic delay at chemical synapses.

. The membrane potential can be measured by placing a microelectrode inside the cell membrane.

True

False

. Which of the following statements about the resting potential of nerve cells is correct?

The resting potential is 0V.

The resting potential is the result of thermodynamic forces causing a given ion to move down the concentration gradient until equal concentrations are reached inside and outside the cell.

The resting potential is the membrane potential at which equilibrium is reached between thermodynamic forces and electrostatic forces acting on ions differentially distributed across the cell membrane.

The resting potential is the result of electrostatic forces acting on ions until the overall electric charges inside and outside the cell are equal.

. Which of the following statements related to action potentials are true? Please select all that apply.

Action potentials are graded potentials.

The refractory period following each action potentials is a key factor in determining an upper limit of the number of spikes that can be generated within a given time.

Action potentials are caused by transient alterations in the permeability of specific ion channels, particularly Na⁺ channels and K⁺ channels.

The high concentration of voltage-gated Na⁺ channels at the nodes-of-Ranvier plays a critical role in the phenomenon of saltatory conduction.

. Which of the following statements does not describe correctly the difference between chemical and electrical synapses?

Transmission at chemical synapses is typically unidirectional, whereas transmission at electrical synapses is typically bidirectional.

The latency between the arrival of an action potential at the presynaptic side and the generation of a new action potential at the postsynaptic side is shorter at electrical synapses than at chemical synapses.

Communication between the presynaptic neuron and the postsynaptic neuron is mediated by direct ion flow at electrical synapses but neurotransmitters at chemical synapses.

At chemical synapses the postsynaptic potential is always excitatory, whereas at electrical synapses the postsynaptic potential is always inhibitory.

. When the channel associated with the nicotinic acetylcholine receptor is open, Na⁺ and K⁺ ions can pass through, whereas anions are repelled. This selectivity is mediated by which of the following molecular filter mechanism?

Three rings of negatively charged amino acids that line the channel pore.

Three rings of positively charged amino acids that line the channel pore.

Six amino acids in the alpha-subunit of the receptor protein that mediate the binding of acetylcholine.

Six amino acids in the alpha-subunit of the receptor protein that mediate the binding of nicotine.

. Which of the following statements correctly characterize a retrograde tracer substance? Please select all that apply.

Employed in neuronal tract tracing experiments to reveal structural connections between brain nuclei.

Transported in the axon of a neuron preferentially from the soma to the terminal region.

Transported in the axon of a neuron preferentially towards the cell body.

Experiments in which a retrograde tracer is used must be complemented by anterograde tracing experiments to correctly identify the neural connections between two brain nuclei.

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