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First formal experiment in endocrinology:

Arnold Adolph Berthold, 1849—Studied roosters

Effects of prepubertal castration of male chick(used to make capons—more tender meat):

reduces secondary male appearance—

also affects behavior—

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Berthold wanted to know if these extensive effectswere dependent on neural connection to the testes.

[There was a general appreciation of the role ofnerves in functionally connecting different parts ofthe body, even though neurons had not yet beenidentified]

Note: A single testis was implanted

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Additional results:1) on autopsy the transplanted testis had re-established a blood supply, but not a neuralsupply

implication—

2) reimplanted or transplanted testis was alsoapproximately 2 times larger than normal:

implication—

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Puzzle:

What is the mechanism of compensatoryhypertrophy?

Question:

So, hormones affect behavior (the Mind); Canbehavior (the Mind) affect hormones?

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Bea

rd g

row

th (

mg)

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Is this study valid?

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Bioassay — using a physiological measure to indirectlyassess hormone activity/levels

Organizational effects of hormones: relativelypermanent effects of hormones on structure andfunction of the body.

Often there is a critical period of developmentduring which these organizational effects can takeplace. The most important critical periods areduring fetal development and puberty.

Activational effects of hormones: immediate(temporary) effects of hormones that "comeand go" with the presence and absence of thehormone.

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What is a hormone?

Partial Definition: An example of an intercellularchemical signal—a chemical substance, a molecule,that is secreted by one cell of the body and modifiesthe function of another cell of the body.

Neurotransmitter Hormone

Chemical Structure

Source (cell type)

Target

Mode of delivery totarget

Distinction between a hormone and a neurotransmitter:

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Most hormones are systemic:

they circulate throughout the entire body (“system”)

Q. What determines which cells are a target for asystemic hormone?

A. Whether or not a particular cell “expresses”(contains within the cell or displays on its surface)receptors specific for the hormone.

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Puzzle:

Why have hormones for intercellular signalinginstead of neurotransmitters?