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Chapter 13

PSYC 370 Chapter Notes - Chapter 13: Breastfeeding, Gonadotropin, Scrotum

Course Code
PSYC 370

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Psyc370 Chapter 13: Hormones and Sex
Men-Are-Men-And-Women-Are-Women Assumption
- Most people assume that men and women are opposites and have hormones that
make them look and act female/ male. This is wrong.
Developmental And Activational Effects of Sex Hormones
- Hormones influence sex in 2 fundamentally different ways:
o1. Developmental By influencing the development from conception to
sexual maturity of the anatomical, physiological, and behavioural
characteristics that distinguish one as female or male
o2. Activational By activating the reproduction-related behaviour of
sexually mature adults
13.1 Neuroendocrine System
Endocrine glands  only organs whose primary function is the release of
Other organs (stomach, liver, intestine) also release hormones and are thus part of
the endocrine system
oExocrine Glands: glands that release chemicals into ducts that carry them
to targets, mostly on the surface of the body
oEndocrine Glands: ductless glands that release chemicals called
hormones directly into the circulatory system
Once released, hormone travels via circulatory system until it
reaches its target on which it exerts its effect
oGonads: male testes (create sperm cells) & female ovaries (create ova).
Also release steroid hormones.
oZygote: a single cell formed by a sperm & an ovum, which contains all
info necessary for normal growth of a complete adult organism
oEach cell of human body has 23 pairs of chromosomes. Sex cells only
have half of each pair of chromosomes.
oSex Chromosomes: contain the genetic programs that direct sexual
development  XX & XY
Y chromosomes smaller than X. Encode about 27 proteins, while
X encode about 1,500
Classes of Hormones
o1. Amino Acid Derivative Hormones: hormones that are synthesized in a
few simple steps from amino acids
Ex. Epinephrine is synthesized from tyrosine
o2. Peptide Hormones: hormones that are short chains of amino acids
Protein Hormones: hormones that are long chains of amino acids
o3. Steroid Hormones: hormones that are synthesized from cholesterol

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Sex hormones are all steroid hormones
Bind to receptors to produce effect like other hormones, but since
they are fat-soluble, can produce a 2nd effect. Can enter cell and
bind to receptors in cytoplasm or nucleus to directly influence gene
Sex Steroids
o2 main classes of gonadal hormones:
Androgens: the class of steroid hormones that includes
Most common = testosterone:
Estrogens: the class of steroid hormones that are released in large
amounts by the ovaries; an example is estradiol
Most common = Estradiol
oProgestins : the class of steroid hormones that includes progesterone
Most common = Progesterone: a progestin that prepares the uterus
and breasts for pregnancy. Male function unclear.
oAdrenal Cortex: outer layer of the adrenal glands. Releases steroid
hormones but not considered a sex gland because primary function is
regulation of glucose & salt levels
Hormones of the Pituitary
oPituitary releases tropic hormones: hormones whose primary function is to
influence the release of hormones from other glands
oGonadotropin: tropic hormone that stimulates the release of hormones
from the gonads
oPosterior Pituitary: the part of the pituitary gland that contains the
terminals the hypothalamic neurons
oPituitary Stalk: the structure connecting the hypothalamus and the
posterior pituitary gland
oAnterior Pituitary: the part of the pituitary gland that releases tropic
hormones the ‘master gland’
oPosterior & anterior begin separately and attach during embryological
Female Gonadal Hormone Levels are Cyclic; Male Gonadal Hormone Levels are
oIn females, the levels of gonadal and gonadotropic hormones go through a
repeating cycle  menstrual cycle
oIn males, levels of gonadal and gonadotropic hormones stay steady
oTransplantation experiment: when anterior pituitary transplanted from
female to male, it became steady. When transplanted from male to female,
it began to cycle
Neural Control of the Pituitary
oHypothalamus controls anterior pituitary, although unclear how at first
because anterior receives no neural input from hypothalamus (only
posterior is connected)

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Control of the Anterior and Posterior Pituitary by the Hypothalamus
oHypothalamus controls pituitary by 2 different mechanisms:
1. For posterior:
Vasopressin & Oxytocin synthesized in paraventricular &
supraoptic nuclei. Transported along neural axons to
terminals in posterior pituitary. Stored there until action
potentials cause them to be released into blood.
Vasopressin: one of the two major peptide hormones of the
posterior pituitary; facilitates reabsorption of water by
kidneys and is thus also called antidiuretic hormone
Oxytocin: one of the two major peptide hormones of the
posterior pituitary, which in females stimulates contractions
of the uterus during labor and the ejection of milk during
2. For anterior:
Hypothalamopituitary System: the vascular network of
capillaries that carries hormones from the hypothalamus to
the anterior pituitary
Discovery of Hypothalamic Releasing Hormones
oDifferent hypothalamic hormones have either specific hormone releasing
or inhibiting effects:
Releasing Hormones: hypothalamic hormones that stimulate the
release of hormones from the anterior pituitary
All releasing hormones are peptides
Release-Inhibiting Factors: hypothalamic hormones that inhibit
the release of hormones from the anterior pituitary
oThyrotropin-Releasing Hormone: the hypothalamic hormone that
stimulates the release of thyrotropin from the anterior pituitary
oThyrotropin: the anterior pituitary hormone that stimulates the release of
hormones from the thyroid gland
oGonadotropin-Releasing Hormone: the hypothalamic releasing hormone
that controls the release of the two gonadotropic hormones from the
anterior pituitary
Follicle-Stimulating Hormone (FSH): gonadotropic hormone
that stimulates development of ovarian follicles
Luteinizing Hormone (LH): gonadotropic hormone that causes
the developing ovum to be released from its follicle
Regulation of Hormone Levels
oHormone release regulated by 3 kinds of signals: from nervous system,
from hormones, and from non-hormonal chemicals in blood
oRegulation by Neural Signals
All endocrine glands except anterior pituitary directly regulated by
signals from nervous system
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