Hormones, the Brain, and Behavior
Pituitary gland: master gland, controlled by hypothalamus
Hypothalamic hormone release is regulated by neurotransmitters released from nerve cells in the brain
Neurotransmitter release influences behavior and hormones, hormones influence release of neurotransmitters through chemical messengers

The Body’s Three Communication Systems
Nervous system, endocrine system, and immune system
Nerve cells communicate through release of neurotransmitters
Endocrine glands communicate through hormones
Immune system communicates through cytokines
Systems are not independent and interact
Non-cognitive stimuli (bacteria and viruses) influence systems through action on immune system
Common receptor mechanisms integrate the 3 systems

Endocrine Communication
Endocrine cells release hormones into bloodstream, travel through circulation to distant target cells
Thyroid Stimulating Hormone (TSH) released through pituitary gland and travels to stimulate its target in the thyroid gland

Paracrine Communication
Endocrine cells release hormones that act on adjacent cells, and may diffuse from one cell to the next, or travel a short distance in bloodstream
Paracrine secretion=localized hormone action
To produce sperm in the testes, the Sertoli cells must be stimulated by testosterone from adjacent interstitial cells
Important in the immune system

Autocrine Communication
A cell releases a hormone or neurotransmitter that has a direct feedback effect on the secretory cell
Neurotransmitters can act presynaptically to modify its own release

Neuroendocrine Communication
Modified neurons which release neurohormones into peripheral circulatory system to stimulate distant target cells (oxytocin from posterior pituitary to stimulate target cells in uterus), or into hypophyseal portal vessels to induce release of pituitary hormones

Neurocrine Communication
Neurons release discrete messengers that are active over short distances (release neurotransmitters into a synapse to stimulate a postsynaptic cell)
Neural cell releases neuropeptide which acts as a neuromodulator and stimulates a receptor on a nearby cell, and regulates activity

Phytohormones
Growth regulators produced by higher plants (auxins, kinins)
Used as drugs to influence neuroendocrine system (nicotine and morphine)

Hormones
Effective in minute qualities
Synthesized in a ductless or endocrine gland
Secreted into circulatory system and transported through body by blood
Acts on receptors of target cells located at a distance
Exerts regulatory action on target cell

Neurohormones
Produced and released from a neurosecretory cell
Releasing hormones of the hypothalamus are neurohormones

Neurotransmitters
Synthesized by nerve cells
Released into synapse between nerve cells
Ex. Dopamine, acetylcholine, noradrenaline

Pheromones
Chemical messengers produced in exocrine or ducted glands
Secreted into outside environment and act on others
Stimulate olfactory or gustatory receptors
Releaser effects: rapid behavioral changes
Primer effects: later behavioral changes

Parahormones
Not produced in endocrine gland, but has all same characteristics
Ex. Histamine
Affects the cells that produce them

Prohormones
Hormone precursors
Ex. Proopiomelanocortin

Growth Factors
Chemical messengers which are synthesized in various types of cell and act to stimulate tissue growth
Nerve growth factor, epidermal growth factor, fibroglast growth factor

Cytokines
Regulate activities of the immune system to defend body from bacteria and viruses, and produce inflammatory responses
Brain regulates nervous system through direct nerve pathways to the thymus gland, through release of neurotransmitters, or release of hormones

Vitamins
Vitamin B not hormone because not produced in body
Vitamins A,D, and K are formed in body and have hormone-like actions
Vitamin A=carotene
Vitamin D=skin by sunlight
Vitamin K=bacteria in intestines

Neuroregulators
Chemical messenger that regulates activity of a