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
(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!