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 small quantities in the brain, but they play a crucial role in communication between neurons. They are released by one neuron and bind to receptors on another neuron, initiating a response.

Option A is incorrect because neurotransmitters are not primarily secreted into the bloodstream by endocrine glands, although some hormones can act as neurotransmitters.

Option C is incorrect because while the brain can adapt to new experiences and form new neural connections, the basic molecular shape of neurotransmitters remains consistent.

Option D is incorrect because neurotransmitters do not compete with sodium and potassium ions for receptor sites, although these ions can play a role in maintaining the electrical charge across neurons.