What are the functions of the nervous system's main divisions, and what are the three main types of neurons?

The three (3) main types of neurons are: 1) sensory - these relay information from receptors in the periphery into the Central Nervous System (CNS), which is comprised of the brain and spinal cord.

2) interneurons - these are actually CNS functional neurons, either in the brain or spinal cord, which make "decisions" to respond to a sensory message or not, and if so then in what manner.

3) motor - these neurons perform actions, under direct control of the CNS interneurons, often leading to effectors in the periphery (to glands for secretion, or to muscles for contraction).

The functional divisions of the nervous system are:

1) CNS - control centers composed of brain and spinal cord

2) Peripheral Nervous System (PNS)

*this is everything else in the nervous system besides the CNS, comprised of:

a) Somatic Nervous System (SNS) - [mostly] voluntary sensory and motor functions from and to, respectively, the periphery of the body (skin, skeletal muscles, tendons, and bones)

b) Autonomic Nervous System (ANS) - these are involuntary sensory and motor functions, both from and to, respectively, internal organs, e. g. blood vessels, digestive organs, heart and lungs, kidneys, glands (endocrine and exocrine), and reproductive organs.

i. Sympathetic subdivision: this is the "fight or flight" nervous system readying the body for action

ii. Parasympathetic subdivision: this is the "read, rest, and digest" nervous system maintaining normal bodily functions most of the time, since we are not regularly often in sympathetic mode.