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PART I
The Endocrine Glands & their Hormones
The Endocrine Glands & their Hormones
Basic principles in hormone actions:
Many effects of one hormone are
antagonized by another hormone
This helps maintain HOMEOSTASIS
The Endocrine Glands & their Hormones
Pineal Gland
-Main hormone secreted
MELATONIN
-Role Melatonin
--Mammals : Regulate
reproductive activity in
response to environmental
light cycles
e.g. Some mammals mate in
summer (lot of light), while
others mate in winter (low
light).
The Endocrine Glands & their Hormones
Thyroid Gland
-Produces 3 main hormones
-Triiodothyronine (T3)
-Thyroxine (T4)
Regulate body metabolism and are
important in bone growth and maturation
of the brain
-Congenital lack of thyroid hormones:
Cretinism.
-Calcitonin
Acts by reducing calcium levels
The Endocrine Glands & their Hormones
Parathyroid Gland
-Parathyroid Hormone
Raises Blood Calcium
(antagonize Calcitonin)
This hormone acts on bone, kidney
and the gut
The Endocrine Glands & their Hormones
Thymus Gland
-Thymosin : Stimulates the
production of Lymphocytes
-Thymostatin : Inhibits the
production of Lymphocytes
Thymus : Important for the neonatal
production of antibodies
Thymus : Gland being at the center
of endocrine, neural, and immune
systems
The Endocrine Glands & their Hormones
Heart
-Granular cells in the heart muscle
secrete Atrial Natriuretic Factor (ANF)
..ANF : Regulates blood pressure,
blood volume, and excretion
of water, sodium and
potassium
..ANF : Also a neuropeptide in
the brain
The Endocrine Glands & their Hormones
Gastrointestinal Hormones
-The mucosa of the GI tract secretes a
dozen PEPTIDE hormones
3 most important:
1. Secretin : Secreted in the small intestine
Stimulates the secretion of
pancreatic bicarbonate and has
other functions on digestion
2. Gastrin: Secreted in the walls of stomach
Stimulate hydrochloric acid secretion
stimulate pancreatic enzyme secretion
3. Cholecystokinin : Secreted in the small intestine
Stimulate gall bladder contraction
Stimulate pancreatic enzyme secretion
The Endocrine Glands & their Hormones
Pancreas
Endocrine cells in the pancreas secrete
2 major types of hormones
1. Insulin : Secreted in response to
increase in blood glucose levels ;
So insulin LOWERS glucose levels by
INCREASING glucose UPTAKE in cells
where it is stored as glycogen.
2. Glucagon : Increases blood glucose
levels by stimulating the conversion
of glycogen to glucose in the liver.
A parte : Insulin & Diabetes
Insulin & Diabetes
Diabetes : Hyperglycemia, ie.
Elevated Blood Sugar
2 Types : The distinction is based upon
whether the blood sugar problem is
caused by insulin deficiency (Type 1)
or insulin resistance (Type 2)
Type 1- Insulin Deficiency : There is not
enough insulin produced by the pancreas
so the patient must inject insulin on a daily
basis
Type 2 - Insulin Resistance : There is plenty of
insulin but the cells of the body are resistant
to its action so, increase in blood sugar
This form is controlled by a strict diet
The Endocrine Glands & their Hormones
Adrenal Glands
2 parts : Medulla & Cortex
Adrenal Cortex : 3 categories of steroid
hormones
1. Mineralocorticoids
2. Glucocorticoids
3. Sex Steroids
Adrenal Medulla
1. Adrenaline
2. Noradrenaline
The Endocrine Glands & their Hormones
Adrenal Cortex
Androgen
Influence sexual differentiation
and bodily changes during puberty
Estrogen
Stress Hormone, converts stored
proteins to carbohydrate during stress.
Antiinflammatory and
Immunosuppressive functions.
If there is a sodium deprivation,
Aldosterone is secreted and acts
to increase reabsorption of
sodium ions (NA+) in the kidneys
salivary glands, and sweat glands.
The Endocrine Glands & their Hormones
Adrenal Medulla
Adrenaline : Released following
stress due to environmental
extremes; Increases heart
rate and blood glucose levels
so, increases the amount of work
the muscles can do (FLIGHT)
Noradrenaline : As Adrenaline, act as a NT
in the brain
Periphery; increase blood pressure
and constrict blood vessels
(noradrenaline, stress, and heart disease…)
The Endocrine Glands & their Hormones
Gonads ; Testes
The male gonads : produces Androgens
Primary androgen = TESTOSTERONE
Other androgen : Dihydrotestosterone
Androstenedione
Testosterone : Important for masculinization
Control of sperm production
Development of male sexual
characteristics
Activation of sexual and
aggressive behaviors
The Endocrine Glands & their Hormones
Gonads ; Ovaries
2 major classes of hormones
ESTROGENS
PROGESTINS
Primary ESTROGEN : Estradiol
others :
Estriol
Estrone
Synthetic estrogens : Birth control pills
Estrogens : -Development of sexual
characteristics at puberty
-Influence metabolic rate
-Influence sexual and
maternal behavior
The Endocrine Glands & their Hormones
Gonads ; Ovaries
PROGESTIN : Progesterone
-Stimulates breast and uterine
enlargement at puberty & during
menstrual cycle
-Maintains pregnancy (inhibits menstrual
cycle during pregnancy)
Other hormone released at the end of
pregnancy : Relaxin
Acts to prepare the birth canal.
Estrogen and Progesterone act in synergy.
The Endocrine Glands & their Hormones
Placenta
-Hormones secreted by the fertilized egg
(Used in pregnancy tests)
Human Chorionic Gonadotropin (HCG)
Act by keeping progesterone high at the
beginning of a pregnancy
Human Placental Lactogen (HPL)
Stimulates the mammary glands to begin
to secrete milk
PART II
The Pituitary Gland & its Hormone
Also called
the HYPOPHYSIS
The Pituitary Gland & its Hormone
-Attached to the HYPOTHALAMUS
-Secretion of the pituitary hormones
is regulated by hypothalamus
-HYPOTHALAMIC-PITUITARY
connection
The Pituitary Gland & its Hormone
ANATOMY
--> Anterior Lobe
-pars distalis
--> Intermediate Lobe
-pars intermedia
--> Posterior Lobe
-pars nervosa
(“neural” cells)
direct extension
of the
hypothalamus
ADENOhypophysis NEUROhypophysis
-3 parts
The Pituitary Gland & its Hormone
PVN SON
-Neuroscretory Cells
-Paraventricular nucleus (PVN)
-Supraoptic nucleus (SON)
AXONS
-Hormones secreted
-OXYTOCIN
-VASOPRESSIN
Attaches the
hypothalamus to the
pituitary. Also called
the Infundibulum
Neurohypophysis
The Pituitary Gland & its Hormone
PVN SON
OXYTOCIN & VASOPRESSIN
-Are really HYPOTHALAMIC
hormones
AXONS
-OXYTOCIN :
2 main functions
Attaches the
hypothalamus to the
pituitary. Also called
the Infundibulum
Neurohypophysis
--> promotes uterine contractions
--> stimulates milk ejection from
mammary glands during
lactation
The Pituitary Gland & its Hormone
PVN SON
-VASOPRESIN :
AXONS
Attaches the
hypothalamus to the
pituitary. Also called
the Infundibulum
--> Antidiuretic hormone
--> Raises blood pressure
--> promotes water reabsorption
by kidneys
--> centrally : may promote
memory
- Binding proteins for both
oxytocin & vasopressin
--> Neurophysins
Neurohypophysis
The Pituitary Gland & its Hormone
ADENOHYPOPHYSIS (ANTERIOR)
AXONS
Attaches the
hypothalamus to the
pituitary. Also called
the Infundibulum
Adenohypophysis
Mechanism for release of hormones
True endocrine gland because
release hormone in the bloodstream
(hypophysal portal system)
The Pituitary Gland & its Hormone
1. Neurosecretory cells of the
hypothalamus release their hormones
at the median eminence
Median eminence
2. Hormones circulate in bloodstream
3. Carried to the adenohypophysis
4. Stimulates secretion of other
hormones from the adenophysis
5. These hormones are then released
in the bloodstream to reach
their target cells.
The Pituitary Gland & its Hormone
Adenohypophysis : 6 hormones
1. Growth Hormone (GH)
(also called ‘somatotropin’)
…’tropic’=stimulating effect
AXONS
GH = promotes growth in almost
all body cells
Attaches the
hypothalamus to the
pituitary. Also called
the Infundibulum
Adenohypophysis
A lot of attention for degenerative
disease…..
-Alzheimer
-Parkinson
-Anti-Aging
etc.
The Pituitary Gland & its Hormone
Adenohypophysis : 6 hormones
2. Adrenocorticotropic Hormone
ACTH
AXONS
Attaches the
hypothalamus to the
pituitary. Also called
the Infundibulum
Adenohypophysis
Role : Stimulates synthesis and
release of glucocorticoid
hormones
‘Hypothalamic-pituitary-adrenal
axis’
1970’s : Role of memory
….little problems…..
The Pituitary Gland & its Hormone
Adenohypophysis : 6 hormones
3. Thyroid Stimulating Hormone
TSH
AXONS
Attaches the
hypothalamus to the
pituitary. Also called
the Infundibulum
Adenohypophysis
Role : Stimulates the synthesis and
release of thyroxine (T4)
and triiodochyronine (T3)
from the thyroid.
The Pituitary Gland & its Hormone
Adenohypophysis : 6 hormones
3 last hormones=
….gonadotropic hormones
4. Follicle stimulating hormone (FSH)
AXONS
Attaches the
hypothalamus to the
pituitary. Also called
the Infundibulum
Adenohypophysis
Role : In both sexes, promotes the
development of reproductive
cells (gametes) and
promotes secretion of
gonadal hormones
Males : stimulates sperm production
Females : stimulates growth of
primary follicle of ovary
The Pituitary Gland & its Hormone
Adenohypophysis : 6 hormones
3 last hormones=
….gonadotropic hormones
5. Luteinizing hormone (LH)
AXONS
Role :
Attaches the
hypothalamus to the
pituitary. Also called
the Infundibulum
Adenohypophysis
Female : Stimulates ovulation and
formation of progesteronesecreting cells
Males : Stimulates cells that secrete
androgens (e.g. testosterone)
The Pituitary Gland & its Hormone
Adenohypophysis : 6 hormones
3 last hormones=
….gonadotropic hormones
6. Prolactin (PRL)
AXONS
Role : Initiates milk synthesis in
mammary glands
Attaches the
hypothalamus to the
pituitary. Also called
the Infundibulum
Adenohypophysis
Other functions related to
growth & parental behavior
Interaction with serotonin also
(important in depression)
The Pituitary Gland & its Hormone
Non traditional hormone from the
adenohypophysis
--> beta-endorphin
AXONS
Attaches the
hypothalamus to the
pituitary. Also called
the Infundibulum
Adenohypophysis
Derivative from POMC
POMC : synthesized in the pars
distalis and pars intermedia
Broken down into ACTH, MSH &
beta-endorphins by enzymes
The Pituitary Gland & its Hormone
Beta-Endorphin : Role to play in --> Analgesia
--> Learning and Memory
--> Psychiatric diseases
--> Feeding, Thermoregulation,
--> Blood pressure
--> also called the ‘drug of the jogger’…..
The Pituitary Gland & its Hormone
Pars Intermedia :
Not present in adult humans but
present in fetal humans and mammals
AXONS
Attaches the
hypothalamus to the
pituitary. Also called
the Infundibulum
Pars Intermedia
Synthesize the hormone called
Melanocyte stimulating hormones
which acts in amphibian to change
skin color….
Our friend Watson :
Sex & Sunshine
MSH…..
http://www.psych.mcgill.ca/courses/342/h&
b.htm