Animal Behavi22 - by extreme duress Hormones as a Feedback...

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Animal Behavior: Instinct Hormones and their Functions There are three basic types of hormones: steroids, small peptides, and catecholamines. Steroids are large, 17 carbon, 4 ring molecules that bind to the nucleus after entering it. Examples of steroids are estrogens, which includes estradiol (commonly called estrogen) and progesterone; androgens, which include testosterone and dehydroxytestosterone (DHT); and corticosteroids, such as cortisone. Small peptides bind to the cell surface and include some hormones and neurotransmitters that perform analogous functions. Important peptide hormones are endorphines, which includes natural forms of morphine; oxytocin and prolactin which are involved in parental care, and vasopression, which is an antidiuretic that causes urination after you drink. Catecholamines also bind to the cell surface and include epinephrine (commonly called adrenaline) and noradrendaline, which are involved in the "fight or flight" response caused
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Unformatted text preview: by extreme duress. Hormones as a Feedback system One way in which such hormones can function as a feedback system is in reproduction. A good example of a reproductive feedback loop can be seen in ringdoves, studied by Daniel Lehrman. Gonadotropins stimulate the gonads of both males and females to produces steroids. Courtship and nest building follows this increase in gonadal steroids. Rising levels of female progesterone stimulate egg laying and incubation. At this stage, gonadotropins decrease, as do female courtship displays. Males, however, remain responsive to females at this point. After approximately one week of incubation, levels of prolactin increase in both sexes, allowing both males and females to produce a milk-like substance; gonadotropin and steroid levels decrease. When the eggs hatch and the chicks mature, prolactin levels decrease, gonadotropins increase, and the cycle begins again....
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