The endocrine system regulates metabolic processes, reproduction, growth and development through the secretion of hormones directly into the body's fluids. The pituitary gland is called the "master gland" as it controls other endocrine glands. Hormones can be steroid or nonsteroid and act through feedback loops to maintain homeostasis. Stress triggers the hypothalamus and adrenal glands, releasing hormones that increase blood pressure, breathing and glucose levels in the short term. Long term stress suppresses the immune system.

1. The Endocrine System
THE SECRETION OF HORMONES
DIRECTLY INTO BODY FLUIDS.
BY GALCHU TENO

2. General Characteristics
Endocrine glands and their hormones help to
◦ Regulate metabolic processes,
◦ Play a vital role in reproduction, growth, and development,
◦ Control the rates of certain chemical reactions,
◦ Aid in the transport of substances across membranes, and
◦ Regulate water and electrolyte balances.

3. Hormone Action
Hormone – a biochemical that a cell secretes
that affects the functions of another cell.
Target cells – cells with specific receptors for
the hormone molecules. They contain
proteins or glycoproteins with binding sites
for a specific hormone.

4. Types of Hormones
Steroid Hormones
◦ Molecules contain complex rings of C and H
◦ Soluble in lipids and therefore can easily diffuse
into cells
◦ May combine with specific protein molecules –
the receptors in the nucleus

5. Types of Hormones
Nonsteroid Hormones
◦ Amines, peptides, and proteins
◦ Combine with receptors in the target cell
membranes to create the change

6. Types of Hormones
Prostaglandins
◦ Lipids synthesized from a fatty acid in cell membranes
◦ Cells that produce prostaglandins: liver, kidneys, heart,
lungs, thymus gland, pancreas, brain, and reproductive
organs
◦ Stimulate hormone secretion from the adrenal cortex,
inhibit secretion of HCl from the stomach, influence the
movement of sodium ions and water molecules in the
kidneys, regulate blood pressure, and have powerful
effects on male and female reproduction

7. Control of Hormonal
Secretions
The pituitary is often
called the “master
gland”
Its actions are controlled
by the hypothalamus in
the brain.

8. Control of Hormonal
Secretions
Negative feedback
system
When the hormone
levels rise, the organ
that secretes the
hormone is switched off

9. Maintaining homeostasis
high
low
hormone 1
lowers
body condition
hormone 2
gland
specific body condition
raises
body condition
gland
Negative Feedback
Model

10. Controlling Body Temperature
high
low
nerve signals
sweat
nerve signals
body temperature
(37°C)
shiver
dilates surface
blood vessels
constricts surface
blood vessels
Nervous System Control Feedback
hypothalamus
hypothalamus

11. liver
pancreas
liver
Regulation of Blood Sugar
blood sugar level
(90mg/100ml)
insulin
body
cells take
up sugar
from blood
liver stores
glycogen
reduces
appetite
glucagon
pancreas
liver
releases
glucose
triggers
hunger
high
low
Feedback
Endocrine System Control
islets of Langerhans
beta islet cells
islets of Langerhans
alpha islet cells

12. osmoreceptors in
hypothalamus
nephron
nephron
Blood Osmolarity
blood osmolarity
blood pressure
ADH
increased
water
reabsorption
increase
thirst
renin
increased
water & salt
reabsorption
high
Feedback
Endocrine System Control
pituitary
angiotensinogen
angiotensin
adrenal
gland
aldosterone
JuxtaGlomerular
Apparatus
nephron
(JGA)
low

13. Regulation of Blood Calcium
blood calcium level
(10 mg/100mL)
calcitonin
parathyroid hormone (PTH)
 Ca++ uptake
in intestines
high
low
Feedback
Endocrine System Control
 kidney
reabsorption
of Ca++
bones
release Ca++
 kidney
reabsorption
of Ca++
Ca++ deposited
in bones
activated Vitamin D
thyroid
parathyroid

14. Control Sources
Hypothalamus controls the anterior pituitary
Nervous system stimulates some glands directly
◦ Adrenal medulla secretes hormones in response to the
sympathetic nerve impulses (“fight or flight”)
Some group of glands respond directly to changes
in the composition of the internal environment
◦ Blood glucose increases, insulin is secreted; blood glucose
decreases, glucagon is secreted

15. Pituitary Gland – Other Endocrine
Glands

16. Problems with the pituitary gland
can result in Dwarfism

17. Or a person
can grow too
much. These
are pictures of
the man
known as
“The Alton
Giant”, Robert
Wadlow.

18. Problems with the Thyroid
Thyroid hormone is partly made of
iodine. Iodine is essential for the
formation of thyroxin. If a person
doesn’t eat enough iodine, they
can’t make thyroid hormone.
so it the size of the follicle grows •
gland grows • GOITER.
Iodine is only found in seafood, so
if salt wasn’t iodized, a lot of
people wouldn’t get enough
iodine, and there would be a lot of
goiters.

19. Stress and Health
Types
◦ Physical - Extreme heat or cold, decreased O2
concentration, infections, injuries, prolonged
heavy exercise, loud sounds
◦ Psychological – real or imagined danger, personal
losses, feelings of grief, anger, fear, anxiety,
depression or guilt
◦ Joy, happiness, or sexual arousal

20. Stress and Health
Responses
◦ Hypothalamus triggers
sympathetic impulses
to various organs. It
also stimulates
epinephrine release,
intensifying the
sympathetic
responses.
Stress
Changes in internal environment
Sensory receptors stimulated
Hypothalamus

21. Effects of stress on a body
Spinal cord
(cross section)
Nerve
signals
Nerve
cell
Releasing
hormone
Stress
Hypothalamus
Anterior pituitary
Blood vessel
ACTH
Adrenal
gland
Kidney
adrenal medulla
secretes epinephrine
& norepinephrine
Adrenal cortex
secretes
mineralocorticoids
& glucocorticoids
(B) LONG-TERM STRESS RESPONSE
(A) SHORT-TERM STRESS RESPONSE
Nerve cell
Effects of epinephrine and norepinephrine:
1. Glycogen broken down to glucose;
increased blood glucose
2. Increased blood pressure
3. Increased breathing rate
4. Increased metabolic rate
5. Change in blood flow patterns, leading
to increased alertness & decreased
digestive & kidney activity
Effects of
mineralocorticoids:
1. Retention of
sodium ions &
water by kidneys
2. Increased blood
volume & blood
pressure
Effects of
glucocorticoids:
1. Proteins & fats broken
down & converted to
glucose, leading to
increased blood
glucose
2. Immune system
suppressed