Title: Thursday Oct 14
1Thursday Oct 14
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3- Roles of Hormones
- Influence all basic drive states eating,
drinking, sexual activity - Help maintain homeostasis relatively constant
internal environment - Influence mood and behavior
- Influence brain development and development of
other organ systems - Influence bodily (incl. brain) changes in puberty
- Influence aging
- Thus, hormones influence anatomy, physiology, and
behavior.
4- Principles of Hormone Action
- Gradual and slow responses may come minutes,
hours, or weeks after hormones are released - Hormones act on probabilities of behaviors
occurring making you more or less likely to
take some action depending on hormonal state
(hunger thirst sexual activity) - Hormones and behavior act reciprocally hormones
alter behavior, behavior alters hormones - A single hormone effects multiple tissues and
behaviors - Hormones are secreted in small amounts and often
in bursts (pulsatile secretion)
5- Principles of Hormone Action
- Hormones are secreted in small amounts and often
in bursts (pulsatile secretion) - Hormone levels may vary rhythmically throughout
the day with levels controlled by circadian
clocks within the brain - The effects of hormones are highly interactive
action may depend on the ratios of what is
present - The same sets of chemicals are used as hormones
across all vertebrate species, but the responses
to the hormones may vary across species - Hormones act via binding with receptors
- Hormonal secretions are monitored and regulated
by feedback control systems
6- Principles of Hormone Action
- Hormonal secretions are monitored and regulated
by feedback control systems - Glands manufacture, detect, evaluate effects and
participate in regulation of hormones - Regulation may be within the gland or based on
the glands response to products released from
other cells or under neural control by actions of
hypothalamus alone or plus pituitary gland
7- Types of Hormones
- Reproductive hormones control the menstrual
cycle, child birth, breast feeding (activational
effects). Also organizational effects instruct
the body to develop as male or female. - Homeostatic hormones maintain internal bodily
environment relevant to life itself the balance
of sugars, proteins, carbohydrates, salt and
water in the bloodstream and all body cells
(activational effects that cells can respond to
from early life) - Stress Hormones control behavioral and
physiological responses to stress (best
understood re. activational effects)
8Hormones act by 1. Promoting the proliferation,
growth and differentiation of cells In early
development, this applies to brain tissue as
well as the reproductive tissues. At puberty,
hormones trigger physical changes. (Development
al roles) 2. Modulating the rate of cell
function may promote metabolic activity may
promote hormone release (Homeostatic and
rhythmic/cyclical controls)
9Developmental role of hormones Organizational
effects - permanent effects on tissue
differentiation of body and brain Activational
effects - effects that occur later in life
mostly beginning at puberty
10Pituitary is master controller of the rest of the
bodys endocrine system. Hypothalamus - area of
brain that controls the pituitary. Certain
neurons in the hypothalamus respond to neural and
hormonal signals by secreting hormones (releasing
hormones and inhibiting hormones).
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13 Hormones from the Hypothalamus Releasing
hormones influence the pituitary to release
hormones that act on other glands in body (tropic
hormones). Inhibiting hormones influence the
pituitary to inhibit release of certain hormones.
14- I. Role of Hypothalamus-Posterior Pituitary
- Axons from hypothalamus travel to Posterior
Pituitary (PP) where their axon terminals
terminate and release Oxytocin and Vasopressin
into the capillaries inside the PP - from here, the hormones enter the general blood
stream - Examples
- Oxytocin acts on receptors (when present) in
breasts and uterus --- milk ejection uterine
contractions at end of pregnancy - Vasopressin acts to constrict blood vessels in
kidney, influences resorption of water and
minerals
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16Feedback system Levels of hormones in blood are
detected by cells in hypothalamus. Result is to
release releasing or inhibiting hormones to
pituitary This keeps hormonal levels at proper
balance like a thermostat
17- II. Role of Hypothalamus - Anterior Pituitary
- Hormones from hypothalamus travel in special
blood system (portal system) to Anterior
Pituitary - Bind with receptors in Anterior Pituitary gland
- Release of AP hormones is increased or decreased
(examples reproductive hormones stress
hormones) - AP hormones then travel in blood and find
receptors on major organs (gonads, adrenals, etc)
- tropic actions
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19Hormones from the Hypothalamus ----- Bind
receptors in AP ----- in response, AP
releases hormones ----- Hormones travel in
blood to receptors on target organs----- Target
organs respond in multiple ways that effect
release of hormones----- Hormones travel to
brain where the hypothalamus reads levels
----- Then, Hypothalamus secretes releasing or
inhibiting factors -----
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21- Example 1 - Reproductive Hormones in Females
- Hypothalamus releases Gonadotropin releasing
hormone (GRH). - Anterior Pituitary releases Follicle Stimulating
Hormone and Luteinizing Hormone. - FSH acts on receptors in ovaries to stimulate
development of egg LH causes rupture of egg. -
22- Example 1 - Reproductive Hormones in Females
- FSH acts on receptors in ovaries to stimulate
development of egg LH causes rupture of egg. - Rupture of egg triggers production of estrogens
and progestogens (from remaining tissues of
follicle) - These hormones travel in blood to the brain
- Hypothalamus senses levels - may then decrease
release of GRH
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24- Drugs can alter hypothalamic-pituitary control
systems ex Birth Control Pills - Mature egg and its rupture trigger release of
estrogens and progestogens. - Result is that hypothalamus detects high levels
and shuts down secretion of FSH releasing hormone
and LH releasing hormone. - BCP contain estrogens and progestogens - fool
brain into thinking levels are high due to egg
production
25Developmental role of hormones Organizational
effects - permanent effects on tissue
differentiation of body and brain Activational
effects - effects that occur later in life
mostly beginning at puberty
26- Development of Reproductive Systems
- Chromosomal sex is determined at fertilization
- XX - defines female
- XY - defines male
- Phenotype is determined by gene-environment
- interactions
- Phenotype depends on hormones present at
- specific points in time
27Reproductive systems are made up of 3 categories
of sex organs I. Gonads - testes or
ovaries II. Internal sex organs Female -
uterus, fallopian tubes, vagina Male -
epididymis, vas deferens, seminal vesicles,
prostate III. External sex organs Female
- labia, clitoris, outer vagina Male - penis,
scrotum
28- I. Development of Gonads
- A. Males and females have identical immature
gonads during first month of gestation - B. During 2nd month, differentiation of immature
gonads is controlled by presence/absence of
hormones. - MALES
- a gene on the Y chromosome causes production of
testis-determining factor (tdf) - early 2nd month - testis-determining factor tells the immature
gonad to become testes (male) - in absence of gene and tdf, immature gonads
become ovaries - in presence, gonads become testes
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30 II. Development of Internal Sex Organs A.
1st and part of 2nd month - embryo has bisexual
internal organs In same person (male or female),
the precursors for both male and female internal
organs are present. Tissues that can become
female internal organs - Mullerian system
Tissues that can become male internal organs -
Wolffian system B. Whether male or female
internal parts development depends on the
hormonal environment ! At end of 2nd month, this
is set.
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32 C. 3rd month (fetal period) MALE - To develop
male internal organs, testes (male gonads) must
begin to produce hormones and receptors must
respond! 1. Anti-mullerian hormone - tells the
Mullerian (potentially female) system not to
develop Mullerian tissues have receptors for
anti-Mullerian hormone - when bound, tissues do
not develop into female internal sex organs 2.
Androgens - tell the Wolffian system to
develop into internal male sex organs Wolffian
tissues have receptors for androgens when bound
by androgens, male internal organs develop
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34 C. 3rd month (fetal period) - continued FEMALE
To develop female internal organs, hormones must
be absent. In absence of hormones, Mullerian
system develops into female internal sex organs.
Wolffian tissues disappear. No hormonal
stimulation is required (default
setting). Mullerian system develops into
fallopian tubes, uterus, internal vagina
35- III. Development of External Sex Organs
- A. In first 2 months of gestation, males and
females have the same external appearance. - B. During the 3rd month, male or female
external sex organs develop. - 1. MALES
- testes (gonads) produce dihydrotestosterone
- this triggers development of external sex organs
- the penis and scrotum
36- III. Development of External Sex Organs
- A. In first 8 weeks of gestation, males and
females have the same external appearance. - B. During the 3rd month, male or female
external sex organs develop. - 2. FEMALES
- in absence of hormones, female external parts
develop - the labia, clitoris and outer vagina
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