The Endocrine System (Hormones)
By:William Collins,Hannah Legaspi, Alex Nguyen,
and Carrie Suen
Basic Definitions
● The Endocrine System- a collection of glands and the hormones that
they create that are in charge of regulating and creating long term changes
within your body.
● Glands-are groups of cells that produce and transmit chemicals
(hormones) to the body through the bloodstream (endocrine) or into
cavities inside the body or its surface (exocrine). Made from epithelial
cells.
● Epithelium- aka epithelial cells are cells that line the organs of your body
and help produce secretions that those organs use.
● Hormones- are the chemical messengers of your body that are created by
glands.Unlike neurotransmitters they work very slow and provide a long
term effect on your body.
Endocrine System
● Coordinates activities of organ systems
○ metabolism
○ growth and development
○ tissue function
○ sexual function
○ reproduction
○ sleep
● Helps maintain homeostasis
● Use of negative feedback mechanism
○ e.g. rise in blood glucose level causes pancreas to release
Exocrine Glands
● Is the most common type of gland in the body.
● In comparison to Endocrine Glands, Exocrine glands
have ducts. These ducts primary function are to collect
the secretions by the exocrine glands until they fill the
duct causing them to rise towards the surface they are in
contact with.
○ Skin (Sweat glands), Tongue (Salivary Glands),
Types of Exocrine Ducts
Exocrine Secretion
● In the exocrine glands there are three methods of exocrine secretion:
○ The Merocrine method involves vesicle transportation within the
gland. The product is produced within the glandular epithelial cell and
then the vesicle is used to collect and transport the product to the
surface of the cell. Most exocrine glands work in this way
○ The Apocrine method involves pinching a portion of the glandular
epithelial cell that contains the product off from the cell. This results
not only in the release of the product but also the other molecules that
made up the epithelial cell. The mammary glands work in this way
○ The last method of secretion, Holocrine involves the death of the
epithelial cell where typically the product is made. In this scenario, the
secretory cell breaks off from the gland and its contents become the
secretion. Present in some sweat glands located in the pubic regions.
Diagrams of Exocrine Secretion
Endocrine Glands
•
Secrete products into bloodstream, which
delivers them throughout the body
o
o
•
Only target cells can respond to certain hormones
Cell response to hormone
 Hormone and receptor proteins (key fits a lock)
Examples:
o
Adrenal, Hypothalamus, Ovaries, Parathyroid,
Pineal, Pituitary, Testes, Thyroid
Hormones
•
•
•
•
•
Communication
Act at a distance between body parts and travel in the bloodstream
from the gland to target cells
Secretions produced by neurosecretory cells (hypothalamus)
o Through capillary network between hypothalamus and
pituitary gland
o Some secretions stimulate or prevent pituitary secretion of
hormones
Not all hormones act between body parts
o e.g. prostaglandins and growth factors (local hormones)
Pheromones - affect chemical signals that influence the behavior of
Peptide Hormones
•
Peptide hormones - type of hormone that is a
protein, peptide, or derived from an amino
acid
o
•
•
e.g. growth hormone affect cell metabolism leading
to changes in the structure of bone
Most hormonal glands secrete peptide
hormones
Actions of peptide hormones can vary
Protein Hormones
These are protein hormones you need to know:
● ADH- signals to the kidney that it needs to reabsorb more water.Made by
the hypothalamus
● Angiotensin-makes the kidney reabsorb more NaCl (salt) and water
which helps it to lower your blood pressure.
● Aldosterone-absorbs the Na+ (sodium ion) and water. Its produced by
the adrenal glands and it helps to increase your blood pressure.
● Glucagon-it increases the glucose levels in the blood by hydrolyzing
glycogen in the liver. Its produced in the pancreas.
● Insulin-decreases glucose levels in the blood, by storing glucose as
glycogen in the liver. It is also produced by the pancreas
Protein Hormones
● Calcitonin- produced by the thyroid,it decreases the Ca+ levels in the
blood by storing Ca+ in bone and allowing the kidney to urinate more Ca+
out.
● PTH-parathyroid hormone, produced by the parathyroid. This increases
blood Ca+ levels by accessing stored Ca+ in bone and telling the kidney to
reabsorb (keep) more Ca+ ions.
● Adrenaline-produced by adrenal glands. Acts as the “fight or flight”
hormone.(epinephrine)
● Oxytocin-produced by the hypothalamus, released by the posterior
pituitary. It causes uterine contractions during labor.
*Muscle cells after the hormone epinephrine
binds to a receptor in the plasma membrane
● Breakdown of glycogen to glucose,
provides energy for ATP production
● Binding results in formation of cyclic
adenosine monophosphate (cAMP)
● cAMP activates a protein kinase enzyme,
and this enzyme in turn activates another
enzyme, and so on
○ i.e. enzyme cascade
● Many molecules of glycogen are broken
down to glucose, which enters the
bloodstream
*Epinephrine never enters the cell
Steroid Hormones
•
•
•
Steroid hormones - type of hormone that has
the same complex of four carbon rings, but
each one has different side chains; derived
from cholesterol
Only the adrenal cortex, the ovaries, and the
testes produce steroid hormones
Thyroid hormones act similarly to steroid
hormones, despite different structures
Steroid Hormones
Important hormones you need to know:
● GnRH-Produced by the hypothalamus. “Tells” the pituitary to make FSH
and LH
● FSH-Follicle stimulation hormone; aids in egg and sperm development.
Made by the pituitary and under the control of GnRH levels
● LH-luteinizing hormone. Tells the gonads to either release estrogen or
testosterone.
● Progesterone-It is secreted by the corpus luteum and by the placenta
and is responsible for preparing the body for pregnancy and, if pregnancy
occurs, maintaining it until birth (thickens the uterine lining)
● Estrogen-secreted by ovaries, develops eggs and is responsible for the
secondary sexual characteristics in females.
● Testosterone-helps sperm develop; responsible for the secondary sexual
● Steroid hormones are able to enter the cell
because they are lipids
● Once they have entered, the hormone
binds to a receptors
● In the nucleus, the hormone-receptor
complex binds with DNA and activates
certain genes.
● mRNA moves to the ribosomes in the
cytoplasm and protein synthesis follows
*Steroids act more slowly than peptides
because it takes more time to synthesize new
proteins than to activate enzymes already
present in cells. However, their actions are
longer lasting.
Break Time
Fun Video:
https://www.youtube.com/watch?v=uUr3j82
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Helpful Video:
https://www.youtube.com/watch?v=UqEgT
UlG8FU
Hypothalamus
● Hypothalamus - regulates the
internal environment through the
autonomic system (e.g. heartbeat,
body temperature, and water
balance)
○
It controls the glandular secretion of the
pituitary gland (connected)
Pituitary Gland
•
Posterior Pituitary
*Hormones ADH and oxytocin are produced by neurosecretory cells in hypothalamus
o
o
Antidiuretic hormones (ADH)

released when blood is too concentrated

in kidneys, it causes water to be reabsorbed

no longer released when blood is too dilute
negative feedback
o maintaining stable conditions and homeostasis

inability to produce ADH causes diabetes insipidus (watery
urine)

release of ADH is inhibited by the consumption of alcohol
•
Oxytocin

causes uterine contractions (childbirth) and milk decrease
(nursing)
Pituitary Gland cont.
•
Anterior Pituitary
o controlled by hypothalamus by producing
hypothalamic-releasing and -inhibiting
hormones
o hormones produced affect other glands
 Gonadotropic hormones
 Adrenocorticotropic hormone (ACTH)
 Thyroid-stimulating hormone (TSH)
o hormones under hypothalamic control and
do not affect other glands
 Prolactin (PRL)
 Growth Hormone (GH)
Thyroid Gland
•
•
•
•
Triiodothyronine (T3) and thyroxine (T4)
o gland actively acquires iodine
Thyroid Hormones increase metabolic rate
o stimulate all body cells
o more glucose broken down, more used energy
Thyroid Problems
o simple goiter
o congenital hypothyroidism (cretinism), myxedema
o exophthalmic goiter
Calcitonin (antagonistic)
Parathyroid Gland
•
Parathyroid Hormones (PTH, antagonistic)
o blood phosphate (HPO42-) level decrease
o blood calcium level to
 promote osteoclasts’ activity and release of calcium bones in
bones
 promotes reabsorption of calcium by the kidneys so it is not
excreted
 In kidneys, brings activation of vitamin D, which stimulates the
absorption of calcium from the intestine
o insufficient PTH production (hypoparathyroidism) results in tetany
Adrenal Glands
•
Hypothalamus exerts control over the
activity of the adrenal glands
o
initiates nerve impulses
● Stress prompts hypothalamus to
stimulate the adrenal glands
o
o
short-term stress: epinephrine (adrenaline),
norepinephrine (noradrenaline)
long-term stress: mineralocorticoids,
Adrenal Glands cont.
•
•
•
Glucocorticoids
o cortisol
 (produced by adrenal cortex) raises blood glucose
 counteracts the inflammatory response
Mineralocorticoids
o aldosterone
 primarily targets the kidney, where it promotes renal absorption
of sodium and renal excretion of potassium
 renin-angiotensin-aldosterone system
 atrial natriuretic hormone (ANH) is the antagonistic hormone
Addison disease
o low level of adrenal cortex hormones
Testes
•
Produce androgens (e.g. testosterone)
stimulates male characteristics such as large vocal
cords, pubic hair, etc.
o responsible for sex drive
o anabolic steroids (supplemental) - similar chemicals
with serious side effects
o affect sweat glands, expression of baldness in genes,
and etc.
o
Ovaries
•
Produce estrogen and progesterone
o
o
estrogen
 at puberty stimulate the maturation of ovaries
and other sexual organs
 necessary for oocyte development
 responsible for the development of female
secondary characteristics (e.g. layer of fat
beneath the skin, larger pelvic girdle, etc.)
both are required for breast development and the
•
•
•
•
Pineal Gland
Produces melatonin
o
circadian rhythms - 24-hour physiological cycle
Human sexual development
Young children who have a brain tumor that
has destroyed their pineal gland experience
puberty at an early age.
Thymus Gland
•
•
•
Reaches its maximum size and is
most active during childhood
o as age increases, it shrinks and
becomes fatty
Some lymphocytes that originate in
the bone marrow pass through the
thymus and change into T
lymphocytes
Produces thymosins
o aid in differentiation of T cells
o may stimulate immune cells
Pancreas
Blood Glucose Concentration
Regulation
•
Blood glucose concentration refers to the amount of
glucose/sugar (primarily glucose) in the blood.
o The optimal level is around 4 to 8 millimoles per
dm3 of blood.
Glucose concentration is maintained through a
positive/negative feedback system.
Overabundance causes a halt in production, and a lack
causes a jumpstart. The pancreas is connected to the
bloodstream through chemical signals.
•
Regulation
Cont.
Pancreas: Regulation Summary *IB
Glucagon (alpha cells)- secreted while the body is passive (not eating)
with low levels of glucose. Targets liver and adipose tissue. 1. Stimulates the
liver to break down glycogen into glucose/use fat and protein instead of
glucose for energy. Glucose conservation. 2. Adipose tissue cells form
glycerol and fatty acids from the breakdown of fat. Liver uses this to form
more glucose. Glucose production.
Insulin (beta cells)- After eating. Stimulates the uptake of glucose by cellsliver, muscle, and adipose tissue cells. Formed into glycogen in liver and
muscle cells- fat in adipose tissue. Muscles Cells build protein, while adipose
tissue keeps fat (glucose reserve)
Diabetes
Medical condition where your blood glucose levels are too
high.
Results when a hormone produced by the pancreas, called
insulin, is not being produced enough or is not
functioning as intended.
Insulin is responsible for carrying glucose to the cells in
your body. Glycogen, protein, and fat are the end
products.
Type 1 Diabetes (Juvenile onset) *IB
Occurs when the body fails to produce insulin. Typically thought to be caused
by an outside agent.
The body’s immune system attacks the pancreatic cells that produce insulin.
Once the body turns to the metabolism of fat, ketones start to build up,
leading to acid blood and serious harm.
A lack of insulin prevents cells from absorbing glucose which hinders them
from producing energy.
Possible results: hypoglycemia- symptoms.
Solutions: Pancreas transplant or insulin capsules.
Type 2 Diabetes (Adult-onset) *IB
Occurs when the body develops insulin resistance through
receptor impairment.
This is when the body is unable to use insulin the right
way.
Insulin deficiency occurs as Type 2 Diabetes gets worse.
This is when the pancreas produces less and less insulin
and a lack of glucose transporters.
Solutions: Healthy Diet/Exercise and drugs to 1. stimulate
increase in insulin 2. enhance glucose metabolism.
Summarizing Chart
Type 1 Diabetes
Type 2 Diabetes
The onset is usually early, sometime during
childhood.
The onset is usually late, sometime after
childhood.
Beta cells do not produce enough insulin.
Target cells become insensitive to insulin.
Diet by itself cannot be used to control the
condition. Insulin injections are needed to
control glucose levels.
Insulin injections are not usually needed.
Low carbohydrate diet can control the
condition.
Works Cited
Bernd, Karen. "Glandular Epithelium." Epithelial Cells. Davidson.edu, 2010. Web. 19 Mar. 2014.
"Biology (Mader), 10th Edition." Image PowerPoints. McGraw Hill, n.d. Web. 19 Mar. 2014.
"Endocrine System." KidsHealth - the Web's Most Visited Site about Children's Health. Ed. Steven Dowshen. The Nemours
Foundation, 01 Mar. 2012. Web. 19 Mar. 2014.
"Glands." Glands. McGraw Hill, 1999. Web. 19 Mar. 2014.
"Hormones: MedlinePlus." U.S National Library of Medicine. U.S. National Library of Medicine, n.d. Web. 18 Mar. 2014.