Neurotransmitters:
A) are chemical messengers that are secreted into the bloodstream primarily by endocrine glands.
B) are present in extremely small quantities in the brain.
C) are constantly changing their basic molecular shape as the human brain adapts to new experiences.
D) compete with sodium and potassium ions for the receptor sites on the surrounding neurons.

Question

Quizplus · Accepted Answer

Neurotransmitters are chemical messengers that are present in the brain and transmit signals between neurons. They are not secreted into the bloodstream by endocrine glands.

Answer: C
 Neurotransmitters can adapt to new experiences by changing their molecular shape and altering their effects on the neurons they transmit signals to.

Answer: D
 Neurotransmitters do not compete with sodium and potassium ions for receptor sites on neurons. Rather, they bind to specific receptor sites on the target neuron to transmit their signals.