Hormones, the Brain, and Behavior

Types of Chemical Communication

Synaptic (neurotransmitters)

ENDOCRINE (hormones)

- Released in bloodstream - act at distance (target

organs)- Slow action

Other types of communication: Exocrine, Pheromone

Some substances (e.g., adrenaline) act both as NT and hormone

Glands of the Endocrine System

(CRH)

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The HPA Axis – the key system controlling stress response

Target organs Glucocorticoidsi.e. cortisol

Glucocorticoids (stress)

Short term effect;– Mobilize energy stores

Long term effectHippocampal cell death

How are hormones controlled?

• The hypothalamus controls the pituitary gland• The pituitary has two major divisions

– Anterior: (aka hypophysis). It’s connected to the hypothalamus via blood vessels and is controlled by hormones released from the hypothalamus.

– Posterior. Hypothalamic neurons project axons that secrete oxytocin (and vasopressin) into capillaries of the posterior pituitary.

Hormone release affects behavior…•Estrogens (ovaries) female sexual behavior.

•Androgens (testes) male sexual behavior.

•Insulin (pancreas) food intake.

•Epinephrine (adrenal) arousal and alertness.

•Oxytocin (posterior pituitary) parental behavior.

…and behavior can affect hormone release•Fear or surprise epinephrine

•Smell of food insulin secretion

•Nipple stimulation or crying baby oxytocin release and milk letdown.

•Sexual intimacy oxytocin, among others

Endocrine manipulations are quite common in our society and have a long history.

Castration of male animals: Why do it?

• It’s easy!

• Positive effects on behavior

• May improve physical properties• Population control

• We don’t need a whole bunch of males anyway!!

Actually, there’s a long history of castrating men –eunuchs

•Punishment

•“Testosterone-sensitive” jobs –guarding the harem

•Castrati –male sopranos –until late 1700’s

• Over a million eunuchs in contemporary India – mostly by choice.

The first experimental endocrinology was done by

A.A. Berthoud – 1840s

• Caponization of roosters• Normal males: red comb, colorful plumage, struts,

fights, mates, and crows• Castrated before maturity: no comb, no strut, no fight, no

crow, no mates

• Castrated before maturity and testes implanted into

abdomen: just like normals!