Animal Hormones And Behavior (Zoology)

1. Animal Behavior (Zoology) Assignment
Page 1 of 7
Name:
Program:
Subject:
Topic: H
University of Education, Division of Science and Technology
Assignment
Name: Abdullah Khan
Program: MSc Zoology
ubject: Zoology
H o r m o n e s A n d B e
Education, Division of Science and Technology, Township, Lahore
@Abdullah Khan
Abdullah Khan
Zoology
e h a v i o r
, Township, Lahore

2. Animal Behavior (Zoology) Assignment @Abdullah Khan
Page 2 of 7
Hormones And Behavior
Hormones:
Hormones are your body's chemical messengers. They travel in your bloodstream to tissues or organs. They
work slowly, over time, and affect many different processes, including: Growth and development. Metabolism
- how your body gets energy from the foods you eat.
Classification of hormones:
Hormones can be classified according to their chemical nature, mechanism of action, nature of action, their
effects, and stimulation of Endocrine glands.
1. Chemical nature of hormones:
This category of hormones are divided to six classes, they are hormones steroid; amines; peptide;
protein; glycoprotein and eicosanoid. They are further described in Table 13.3. Steroid hormones are
classified according to the organs that synthesize them therefore this hormone are classified as sex
hormones, adrenal cortex hormones and placenta hormones.
a. Sex hormones:
These are group of hormone that produced in the testes in males and ovaries in the female. The male
sex hormones are usually referred to as androgens and the principal androgen is known as
testosterone. These hormones are produced primarily by the testes and in discrete amounts by
the adrenal cortex. Androgens are primarily responsible for the proper development and maintenance
of male reproductive function and stimulation of the secondary sex characteristics. Androgens are
anabolic, and used in stimulating the production of skeletal muscles and bone as well as red blood
cells. In order to enhance the anabolic activity of androgens without increasing their masculinizing
ability, anabolic steroids were developed to combat diseases marked by wasting, these synthetic
hormones have been abused by individuals desiring to increase their muscle mass, such as athletes
seeking to gain a competitive advantage. Overdosing has been linked to serious side effects, including
infertility and coronary heart disease.
On the other hand, there are basically two female sex hormones which are estrogen and progestin’s.
Estrogens are secreted mainly by the ovaries and in smaller amounts by the adrenal glands and (in
men) by the testes. The most potent estrogen is estradiol. This hormone has a similar function similarly
to androgens in men, the estrogens promote the development and maintenance of the primary and
secondary female sexual characteristics; they also stimulate linear growth and skeletal maturation. In
some other mammals these hormones have been shown to precipitate estrus (heat). The ovarian
production of estrogen stops plummets during menopause.

3. Animal Behavior (Zoology) Assignment @Abdullah Khan
Page 3 of 7
b. The adrenal cortex hormones:
These hormones are produced in the adrenal cortex. They are mainly adrenocortical hormones, which
basically divided to two, i.e., glucocorticoids and the mineralocorticoids. Glucocorticoids consist of
hormones such as cortisol which mainly control and influence many metabolic processes like
deposition of glycogen in the liver and the formation of glucose from amino acids and fatty acids. It
also helps in the maintenance of normal blood pressure, and also possessed antiinflammatory and
immunosuppressive actions, which are useful in treating rheumatoid arthritis and prevents the
rejection of transplanted organs. Mineralocorticoids like aldosterone help maintain the balance
between salts and water in the body and the predominantly exerts their effects within the kidney.
2. Mechanism of action of hormones:
a. Group I hormones
These are group of lipophilic hormones that are usually derived from cholesterol (except T3 and T4).
These hormones usually bind to intracellular receptors thereby forming hormone-receptor
complex. They are mostly found in general circulation in association with transport
proteins however they have relatively longer half-lives in hours or days. Examples of these
hormones are T3, T4, estrogen, progesterone and testosterone.
b. Group II hormones
These are hormones that bind to cell surface (plasma membrane) receptor before they stimulate
the release of certain molecules known as second messenger which will then perform the
biochemical function of these hormones. These hormones are transported in free form and they
usually possess short half-lives in minutes. Group II are further subdivided into 3 categories based
on the chemical nature of the second messenger; (i) Camp—ACTH, FSH, LH; (ii)
phospholipid/inositol/Ca2 +
—TRH, GnRH, Gastrin; (iii) Unknown—insulin STH, LTH, oxytocin.
3. Nature of hormones action
a. Local hormones—These hormones have a specific local effect through paracrine secretion, for
example, hormone testosterone
b. General hormones—These are hormones transported through circulation to the distal target
tissue/organ examples are thyroid hormones and insulin
Types of Hormone Molecules:
Hormones are heterogeneous in their molecular size, chemical properties, and pathways of synthesis. Nitric
oxide is at one extreme of the size range; the pituitary gonadotropins consisting of two subunits are among
the largest of the protein hormones with molecular weights ranging between 25 and 36 kDa, depending on
the extent of added carbohydrates (glycosylation). Peptide or protein hormones range from three amino to
over 100 per subunit. Thyroid hormone and epinephrine are derived from the amino acid tyrosine. Steroid

4. Animal Behavior (Zoology) Assignment @Abdullah Khan
Page 4 of 7
hormones and vitamin D and its metabolites are derived from cholesterol or 7-dehydrocholesterol,
respectively. Arachidonic acid, cleaved from membrane phospholipids, is the main precursor of
the prostaglandins and other eicosanoids .
The initial step in the action of a hormone, the interaction with its receptor, depends to some extent on its
chemical nature. Peptide and protein hormones have receptors that are membrane-spanning proteins so that
the molecule does not have to enter the cell, but can deliver its message on the outside where it will be
conveyed to the interior of the cell by structural changes in the receptor protein. Steroid hormones,
considered to be soluble in the phospholipid bilayer, can enter the cell so that the receptors for these
hormones are located either in the cytoplasm or the nucleus of the cell. The actions of these hormones are
propagated by interaction of the receptor with nuclear proteins and DNA. The amino acid-derived hormones
differ from one another: thyroid hormone has an intracellular receptor similar to those for the steroid
hormones and epinephrine interacts with its membrane receptor.
Anterior pituitary hormones
The hormones of the anterior lobe of the pituitary gland regulate hormone released by the peripheral
hormone glands. The release of anterior pituitary hormones is controlled by the hypothalamic releasing
hormones. Because of their high molecular weight, pituitary hormones do not cross the placenta. Therefore, a
direct effect on the fetus is not to be expected. The following hormones are released from the anterior
pituitary gland.
Growth hormone
This has effects on somatic growth and on metabolism. A hormone similar structurally and functionally to GH
is produced in increasing quantities by the placenta in advanced pregnancy. It is referred to as human
placental lactogen (HPL) or, less often, as human chorionic somatomammotropin (HCS). Functionally, this
hormone is similar to prolactin.
Follicle stimulating hormone (FSH)
This stimulates growth and maturation of the ovarian follicle, and granulosa cell release of
estrogen. Luteinizing hormone (LH) stimulates ovulation. During pregnancy, human chorionic
gonadotrophin (hCG), which is analogous to LH, is synthesized in the placenta, and is responsible for
maintaining the corpus luteum of pregnancy. FSH and a mixture of FSH and LH have been used
therapeutically. Human menopause gonadotrophins (hMG) and hCG are two of these mixtures (analogs
are menotropin and urogonadotropin). These hormones are used for ovulation induction and for additional
support of the corpus luteum. Inducing ovulation with gonadotrophins can lead to multiple pregnancies; of
these, 5–6% involve triplets (Scialli 1986). Two publications report on a rare complex of multiple
malformations and four cases of neuroblastoma in infants below 1 year, born of pregnancies involving
exposure to gonadotrophins. These findings were not confirmed in other studies, nor were other pregnancy
risks or abnormalities in early childhood and pubertal development associated with use of these agents for
ovulation induction.

5. Animal Behavior (Zoology) Assignment
Page 5 of 7
HORMONES AND BEHAVIOR
1. The Neuroendocrine System:
Sum of the glands, hormones, and target tissues/organs involved in the control of bodily functions (including behavior)
2. Glands:
Specific cell masses in various parts of the body which produce and secrete a variety of chemicals.
Types
Exocrine glands: secrete their chemicals into “ducts”,
sweat and tear glands)
Endocrine glands: ductless glands that secrete “hormones” into the general circulation (ex., pituitary
and gonadal glands)
Hierarchical control of hormones:
The brain (hypothalamus) ultimately controls many of the hormones found in the body.
This is usually regulated through “multi-
glands in the body that synthesize hormones.
In turn, many hormones reach back to the brain and influence various cognitive and behavioral functions.
Assignment
The Neuroendocrine System:
target tissues/organs involved in the control of bodily functions (including behavior)
Specific cell masses in various parts of the body which produce and secrete a variety of chemicals.
secrete their chemicals into “ducts”, which are carried to the surface of the body (ex.,
ductless glands that secrete “hormones” into the general circulation (ex., pituitary
:
(hypothalamus) ultimately controls many of the hormones found in the body.
-step” signaling mechanisms (pituitary gland) all the way to the various
glands in the body that synthesize hormones.
reach back to the brain and influence various cognitive and behavioral functions.
@Abdullah Khan
target tissues/organs involved in the control of bodily functions (including behavior)
Specific cell masses in various parts of the body which produce and secrete a variety of chemicals.
which are carried to the surface of the body (ex.,
ductless glands that secrete “hormones” into the general circulation (ex., pituitary
(hypothalamus) ultimately controls many of the hormones found in the body.
(pituitary gland) all the way to the various
reach back to the brain and influence various cognitive and behavioral functions.

6. Animal Behavior (Zoology) Assignment @Abdullah Khan
Page 6 of 7
MOTIVATED BEHAVIORS:
There are 2 general classes of motivated behaviors:
Regulatory Behaviors: behaviors controlled by a homeostatic mechanism.
Examples: temperature regulation, eating (energy) and drinking, salt appetite, waste elimination.
Non-regulatory Behaviors: behaviors that are not controlled by homeostatic mechanisms - all behaviors
excluding those regulated by homeostatic processes Examples: sexual behavior, parental behavior, aggression,
playing sports, watching TV, etc.
Example of Non-regulatory behavior: Sexual Behavior:
Gonadal (sex) hormones have various actions on the brain and behavior; these actions are both
developmental (organizational effects) and in adulthood (activation effects).
1. Organizational effects of sex steroids on the brain and body:
Process whereby gonadal hormones act on the brain to produce distinctly female or male brains;
--Some brain areas are referred to as sexually dimorphic;
--the suprachiasmatic and parts of the preoptic nuclei are generally larger in males; additional
differences in spinal cord, amygdala, and frontal cortex.
2. Activational effects of gonadal hormones:
Female reproductive cycle: While males have daily fluctuations in sex steroid levels, females display
“cycling” gonadal steroid levels, called the menstrual cycle in primates (including humans) and estrous
cycle in other mammals;
The levels of the different sex steroid hormones change significantly over the cycle period in women
(on average, 28 days).
In animals, adult female behavior varies across estrous cycle;
- high estrogen levels are associated with sexual receptivity;
- high estrogen levels are also associated with increased numbers of dendritic spines in the
hippocampus (next page).
In adult males, high testosterone levels are associated with increased motivation to seek sexual and
copulatory behaviors.

7. Animal Behavior (Zoology) Assignment @Abdullah Khan
Page 7 of 7
Pheromones:
Pheromones are similar to hormones but work outside of the body. They induce activity in other individuals,
such as sexual arousal. Most insects use pheromones to communicate. Some chemicals have been
investigated for pheromone actions in humans but evidence is weak.
*****************************************************
Abdullah Khan