Question

use the following information to answer questions 29 and 30. measuring the membrane potential of a spinal nerve a microelectrode can be inserted into the axon of a neuron in order to measure the differences in charge between the outside and inside of the cell. a specialized, sensitive voltmeter is used to measure this difference. electrode 1 is placed on the outside of the cell membrane and electrode 2 is placed on the inside of the cell membrane. 29. the neuron in an experiment was taken from a spinal cord. the generation of an action potential in the neuron was slower than the 24 m/s that is typical with sensory neurons. why? a. axon length is much longer in sensory neurons. b. myelination was absent in this spinal neuron. c. the neurotransmitters were blocked in this spinal neuron. d. the nodes of ranvier were absent in sensory neurons. hint: the spinal cord has both grey matter (myelin lacking) and white matter (myelin present). 30. the voltmeter showed a negative reading and the sodium ion concentration remained constant outside the axon. this could best be explained by the fact that the a. sodium pump has exhausted atp reserves b. dendrites were stimulated by the release of acetylcholine (ach) c. threshold for the neuron was not reached d. action potential was established and sustained

Explanation:

For question 29, myelination speeds up action - potential conduction. Absence of myelination in the spinal neuron can slow it down. For question 30, if the threshold for the neuron is not reached, no action potential is generated, the sodium - ion concentration outside remains constant, and the voltmeter shows a negative (resting - potential) reading.

Answer:

1. B. Myelination was absent in this spinal neuron.
2. C. threshold for the neuron was not reached