PSYC 2240 Study Guide - Midterm Guide: Paramesonephric Duct, Posterior Pituitary, Anterior Pituitary

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Published on 14 Apr 2013
School
York University
Department
Psychology
Course
PSYC 2240
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Bio Basis Exam 3 Notes
Hormones (page 62)
A hormone is a chemical that is secreted in most cases by a gland but also by
other kinds of cells, and conveyed by the blood to other organs
A neurotransmitter is like a signal on a telephone line, it conveys a message
directly and exclusively from the sender to the receiver
Hormones function more like a radio stations, they convey a message to any
receiver that happens to be tuned in to the right station
Hormones are useful for long lasting changes in multiple parts of the body
Protein hormones and peptide hormones, composed of chains of amino acids
Attach to membrane receptors, where they activate a second messenger within the
cell
Hormones secreted by the brain control the secretion of many other hormones
The pituitary gland, attached to the hypothalamus, consists of two distinct glands
Anterior pituitary and the posterior pituitary, release different sets of hormones
Posterior pituitary, composed of neural tissue, can be considered an extension of
the hypothalamus
Neurons in the hypothalamus synthesize the hormones oxytocin and vasopression,
which migrate down axons to the posterior pituitary. Later the posterior pituitary
releases these hormones into the blood
The anterior pituitary, composed of glandular tissues, synthesizes six hormones,
although the hypothalamus controls their release
The hypothalamus secretes releasing hormones, which flow through the blood to
the anterior pituitary. There they stimulate or inhibit the release of ACTH, TSH,
Prolactin, Somatoropin (also known as Growth Hormone), Gonadotropin
Negative feedback system
Pituitary hormones
The hypothalamus produces vasopressin and oxytocin, which travel to the posterior
pituitary (really an extension of the hypothalamus
The posterior pituitary releases those hormones in response to neural signals
The hypothalamus also produces releasing hormones and inhibiting hormones, which
travel to the anterior pituitary, where they control the release of six hormones synthesized
there
Chapter 11 – Reproductive Behaviors
Sex and Hormones
Steroid hormones
oContain four carbon rings
oDerived from cholesterol
oBind to membrane receptors, like neurotransmitters, exerting rapid effects
oEnter cells and activate certain kinds of proteins in the cytoplasm
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oBind to receptors that bind to chromosomes, where they activate or
inactivate specific genes
Sex hormones, a special category of steroids released mostly by the gonads and to
a lesser extent the adrenal gland
Androgens – male hormones (ex. Testosterone)
Estrogens – female hormones (ex. Estradiol)
Both sexes have both types
Sex hormones affect the brain, the genitals, and other organs
Male and female bodies differ due to sex limited genes, which are activated by
androgens and estrogens
Organizing Effects of Sex Hormones
Organizing effects of sex hormones occur mostly at a sensitive stage of
development, before birth
Determine whether the brain and body will develop female or male characteristics
Activating effects can occur at any time in life, when a hormone temporarily
activates a particular response
Sex Differences in the Gonads
Sexual differentiation begins with the chromosomes
Female has two X, male has an X and a Y
During early stage of prenatal development in mammals, both male and female
have a set of Mullerian ducts and a set of Wolffian ducts
The male’s Y chromosome includes the SRY (sex determining region on the Y
chromosome) gene, which causes the primitive gonads to develop into testes,
which produce the hormone testosterone, causing more growth, and more
production of testosterone
Positive feedback cycle, last for a period of early development
Wolffian ducts, precursors for other male reproductive structures
Testosterone causes the primitive Wolffian ducts to develop into structures that
store semen (seminal vesicles) and the vas deferens (a duct from the testis into the
penis)
A Mullerian inhibiting hormone (a peptide) causes degeneration of the Mullerian
ducts, which are precursors to the female’s reproductive organs
Testosterone induced changes all lead to production of penis and scrotum
Because females do not have the SRY gene, their gonads develop into ovaries
The Wolffian ducts degenerate and the primitive Mullerian ducts develop and
mature
Differentiation of the external genitals and some aspects of brain development
depend mainly on the level of testosterone during a sensitive period, an early
period when hormones have long-lasting effects
High level of testosterone causes the external genitals to develop the male pattern,
and a low level leads to the female pattern
2
Estrogens produce important effects on the internal organs, but they have little
effect on the external
Sensitive period 3rd and 4th months of pregnancy
Genetic male develops the female-typical pattern of anatomy and behavior if he
lacks androgen receptors, if he is castrated, or if he is exposed to substances that
block testosterone effects
Male development is a fragile, vulnerable process, can easily be altered
Nature’s “default setting” is to make every mammal a female
Add early testosterone and it becomes males, without testosterone, it develops as
female regardless of the amount of estradiol or other estrogens
However, females lacking estradiol in prenatal environment may not develop
normal sexual behaviour
Shows little sexual response to male or female
Estradiol contributes to female development in terms of brain differentiation, but
not for external anatomy
Sex Differences in the Hypothalamus
Sex hormones early in life bind to receptors in specific areas of the hypothalamus,
amygdale, and other brain areas
Thereby induce anatomical and physiological differences between the sexes
Area in the anterior hypothalamus, known as the sexually dimorphic nucleus, is
larger in the male than in the female and contributes to control of male sexual
behaviour
Parts of the female hypothalamus can generate a cyclic pattern of hormone
release, as in the human menstrual cycle
The male hypothalamus cannot
Testosterone produces its organizing effects on the hypothalamus by itself
Large amounts of estradiol can masculinize female rodents
Activating Effects of Sex Hormones
At any time in life, current levels of testosterone or estradiol exert activating
effects, temporarily modifying behaviour
Changes in hormonal secretions influence sexual behaviour within 15 minutes
Behaviours can also influence hormonal secretions
Hormones do not cause sexual behaviour, they alter the activity in various brain
areas to change the way the brain responds to various stimuli
They also change sensitivity in the penis, vagina, and cervix
Rodents
Arousal can depend on previous experience, sexually experienced rats are aroused
more easily because the effects of previous experience sensitize the response to
future stimuli
Removal of testes or ovaries results in decline in sexual activity
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Document Summary

There they stimulate or inhibit the release of acth, tsh, Prolactin, somatoropin (also known as growth hormone), gonadotropin: negative feedback system. The hypothalamus produces vasopressin and oxytocin, which travel to the posterior pituitary (really an extension of the hypothalamus. The posterior pituitary releases those hormones in response to neural signals. The hypothalamus also produces releasing hormones and inhibiting hormones, which travel to the anterior pituitary, where they control the release of six hormones synthesized there. Sex and hormones: steroid hormones, contain four carbon rings, derived from cholesterol, bind to membrane receptors, like neurotransmitters, exerting rapid effects, enter cells and activate certain kinds of proteins in the cytoplasm. Estradiol: both sexes have both types, sex hormones affect the brain, the genitals, and other organs, male and female bodies differ due to sex limited genes, which are activated by androgens and estrogens.