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The Endocrine System
By Evil Mr. Bleecker
Endocrine vs Nervous System
NERVOUS
• Uses impulses sent along
axons and chemical
neurotransmitters at
synapses
ENDOCRINE
• Uses chemical hormones
released from glands into the
blood
• Receptors are on postsynaptic membrane
• Receptors are on the plasma
membranes of target cells or
intercellular
• Signals are very fast
(milliseconds)
• Signals are slower
(seconds to days)
• Response is immediate
but short-lived
• Response is delayed but
more sustained
Characteristics of Hormones

Hormones:

exert their effects some distance from where
they are produced

are active under very low (nanogram 10-9)
concentrations in the blood

usually have a short half-life in the body several seconds to 60 mins. They are
degraded by enzymes in their target cells or
in the kidney or liver.
Characteristics of Hormones

Hormones bring about their effects by altering cell activity.
The precise response depends on the target cell type.

Typical cellular effects include:
 Altering membrane permeability
 Stimulating protein synthesis
 Activating enzymes
 Inducing cells to secrete materials
 Stimulating mitosis
Control of Hormone Release

Synthesis and release of most hormones are
regulated by a Negative Feedback System. As
hormone levels rise, they cause target organ
effects which inhibit further hormone release.
Hormone - Target Cell Specificity

Hormones circulate to virtually all tissues but
influence the activity of only certain tissue cells,
known as its target cells.
The Hypothalamus Contros the
Anterior Pituitary
Hypothalamus “tastes blood” for
hormone levels. It sends orders to
the anterior/posterior pituitary to
regulate the release of hormones.

Hormonal control rather than by
nerves

Hypothalamus neurons
synthesize releasing and
inhibiting hormones.

Hormones secreted regulate the
secretions of the anterior pituitary

HORMONE
GLAND
NORMAL EFFECTS
OF HORMONE
CONTROL OF
RELEASE
TARGET
ORGAN
EFFECTS OF
HYPER- AND
HYPOSECRETION
pituitary gland

Pituitary gland is
located in the
diencephalon below
the hypothalamus

Structurally and
functionally divided
into:


Anterior lobe
Posterior lobe
Anterior Pituitary – Master Gland

growth hormone - GH

prolactin- PRL
adrenocorticotropic
hormone - ACTH
thyroid stimulating
hormone - TSH
lutenizing hormone - LH
follicle-stimulating
hormone - FSH




posterior pituitary

antidiuretic
hormone – ADH

oxytocin - OT
pituitary gland
growth hormone

Direct effects are the result
of GH binding its receptor
on target cells.

Target cells then believe
they should take in more
nutrients and grow, then
divide
GROWTH HORMONE DISORDERS

12 year-old with mother
Gigantism (Acromegaly)
refers to a condition
characterized by extreme
physical size and stature
due to a hyper-secretion
of growth hormone during
infancy, childhood or
adolescence
Remember Andre the Giant? (WWF)
At the Start of his Career
By the End of his Career  Topping out at 625 lbs!
Click for the action------>
GROWTH HORMONE DISORDER #2

Dwarfed brothers with
researcher in India
Dwarfism results from a
GH deficiency in childhood,
leading to a maximum
height of 4 feet typically
with normal body
proportions. If diagnosed
before puberty, hormone
replacement therapy can
promote nearly normal
growth.
THE THYROID GLAND

Thyroid gland is a large gland located in the neck, just
below the larynx. Needs IODINE to work properly.

Thyroid follicle cells stimulated by the anterior pituitary
gland hormone TSH = Thyroid-stimulating Hormone

Secretes THRYOXIN = adjusts metabolism for all body
cells – ie. Burning more glucose
Goiter - Due to iodine
deficiency
Hypothyroid in Infants



Cretinism:
Hypothyroid from end of 1st
trimester to 6 months after birth.
Severe mental retardation

Short disproportionately sized body
with a thick neck and tongue
Hypothyroid in Adults

In adults, it is called
Myxedema:


Accumulation of proteins
and fluid in subcutaneous
tissue.
Symptoms:
Decreased metabolic rate.
 Weight gain.
 Decreased ability to adapt
to cold.
 Lethargy (= fatigue)

Hyperthyroid in Adults

Grave’s disease

Elevated metabolic rate
(rapid heartbeat, sweating,
nervousness) and bulging
eyeballs (expophthalmia)
HORMONES OF CALCIUM BALANCE


Calcitonin - protein
Produced by thyroid

Reduces blood serum calcium
levels by stimulating calcium
uptake in bone

Important only in childhood
when bones are quickly
growing
Parathyroid Glands – Calcium II

Parathyroid Hormone (PTH)
 Produced by parathyroid glands

Opposite effect to Calcitonin 
Increases blood calcium levels by
enhancing absorption of calcium
in the small intestine, bone and
promoting Ca2+ reabsorption in
the kidney
Adrenal Gland


Paired organs that cap the kidneys.
Each gland consists of an outer cortex
and inner medulla.
Adrenal Cortex

Adrenal cortex

Stimulated hormonally (ACTH = Adrenal
CorticoTropic Hormone)

Secretes corticosteroids
1.
Glucocorticoids – raises blood glucose,
increases protein breakdown. Another is
cortisone = anti-inflammatory
2.
3.
Aldosterone (Mineralcorticosteroid)
– sodium reabsorption in kidneys
Sex Hormones – stimulates sex organs,
development of reproductive organs
Negative Feedback Loop
Low blood sodium sensed by
kidneys  enzyme Angiotensin
secreted which turns on
secretion of aldosterone by
kidney
Increased H20 absorbed to
raise pressure
GLUCOCORTICOIDS

At high concentrations, cortisol has pronounced antiinflammatory and anti-immune effects including:

Depressing cartilage and bone formation

Inhibiting inflammation
GLUCOCORTICOIDS in Excess

Cushing’s disease = glucorticoid
excess

Symptoms include hyperglycemia
(high blood sugar), loss of muscle
and bone protein, moon face, and
a redistribution of fat to the
abdomen and posterior neck
(causing a “buffalo hump”)

Excess of aldosterone causes
excessive Na reabsorption,
flooding tissues with water =
edema
GLUCOCORTICOIDS – Insufficiencies

JFK had Addison’s, which he
kept from public knowledge
Addison’s disease is the major
hypo-secretory disorder of the
adrenal cortex, usually involving
of both glucocorticoids and
mineralcorticoids. Victims lose
weight, demonstrate
hypoglycemia and reduced
levels of sodium, and show an
increase in skin pigmentation
(bronzing)
Adrenal Medulla
Synthesizes and secretes

Epinepherine and some
NorEpinepherine

Sympathetic Nervous System
hormones made here!!!

Fight or Flight!!!
ANTIDIURETIC HORMONE

Antidiuretic Hormone (ADH; vasopressin) The main
regulator of body’s water (osmotic)balance

ADH increases the reabsorption rate of water in kidney

Secretion is regulated in the hypothalamus by
osmoreceptors, which sense water concentration
Pancreas



Islets of Langerhans
secrete insulin into
the bloodstream
Insulin tells cells to
absorb sugar and
store it
Huge storage in liver
as GLYCOGEN and
in muscles!!!
Homeostatis & Regulating Blood
Sugar Levels



Negative feedback loops
If blood sugar rises, insulin is secreted to bring
it down
If blood sugar lowers, glucagon is secreted to
place sugar into the blood
INSULIN

Diabetes mellitus results
from hypo-secretion of insulin
or hypo-activity of insulin.
When insulin is absent or
deficient, blood sugar levels
remain high after a meal
because glucose is unable to
enter most tissue cells.
DIABETES

Type I diabetes mellitis (insulindependent) afflicts 750, 000
Americans.
Autoimmune disease (the insulin
secreting beta cells of the Islets of
Langerhans are attacked by
immune cells)
 Insulin is not produced or secreted,
requiring regular insulin
injections.

DIABETES

Type II diabetes mellitis (non-insulin-dependent)
afflicts 7.5 million Americans

Insulin resistance - Insulin is usually produced but the
receptors do not respond. Loss of receptors possible – can
have all the insulin there, but can’t absorb it.
DIABETES & HEREDITY

Heredity plays a role - an estimated 30% of
Americans carry a gene that predisposes them to
Type II diabetes.

Lifestyle play a role - Type II diabetics are almost
always obese and sedentary. Adipose tissue
produces a hormone-like chemical that may prevent
uptake of insulin
PINEAL GLAND

Secretes melatonin:

Production stimulated by
the hypothalamus
 Sets daily = circadian
rhythms.
 Melatonin secretion
increases with
darkness and peaks
in middle of night.
MELATONIN

The Midnight
Sun
Melatonin secretion has been
linked to seasonal affective
disorder (SAD) in people
living in northern latitudes like
Alaska. Melatonin is elevated
in the winter months, and it
may lead to depression, long
bouts of sleeping, and eating
binges. Sun lamps with a full
spectrum of light are helpful
therapy for some people.
Thymus Gland & Hormones of
the Immune System

Secretes thymosins that
aid in the maturity of
lymphocytes inside the
lobules of the thymus.
Hormones of Digestion & Sex

Digestion - gut hormones – ex Gastrin & fullness

Sex hormones . . . .
1.
Testes


2.
produce androgens (testosterone)
Puberty - secondary sexual characteristics such as
 Pubic hair, Muscular strength, Deepening of voice
Ovaries


produce estrogens and progesterone.
Puberty - secondary sexual characteristics such as
 Pubic hair, Breast development, Widening of hips,
onset of menstrual cycle
Effects of Anabolic Steroids
1995
1997
2002
2005
Gynecomastia
Severe Acne
Accelerated Balding
Homeostasis – the Balance

Hypothalamus produces ADH and thus regulates blood
osmolarity (osmotic balance)

Endocrine system controls secretion of epinephrine and
norepinephrine and thus controls fight or flight responses.

Controls blood calcium levels.
 Muscle contraction.

Insulin encourages uptake of glucose by cells and storage of
glucose as glycogen in the liver and muscles.