The
Endocrine
System
Nervous vs. Endocrine

Both systems oversee cell-to-cell
communication using chemical signals


Intro to
Endocrine
System
Animation
Chemical signals both bind to receptor molecules
Receptors are VERY specific to only respond to
certain signals
Nervous Sys
Endocrine Sys
Main cell/s
Neuron
Glandular epithelial
Chemical signal
Neurotransmitter
Hormone
Speed
Seconds
Seconds – hours
Duration of action
Brief
Brief – days
Exocrine vs Endocrine
Classified by location of secretion
 Exocrine:

 Through tube or duct to a surface (outside)
 Ex: skin, lining of digestive tract

Endocrine:
 Secrete into internal environment
 Help regulate metabolic processes
○ How? Controlling rate of chemical rxns, aiding in
transport of substances , regulating H2O and
electrolytes
 Ex: Thymus, hypothalamus, pineal, adrenal
Endocrine Glands
Can be cell, tissue, or organ (gland)
 Secrete hormones

 Hormones are chemical messengers
 Diffuse from interstitial fluid into the blood stream,
eventually acting on a target cell

Target cell
 Receives the message
 Receptor for hormone
 Hormone creates a response in target cell

Tropic hormones
 Hormone whose target cell is another endocrine
gland
Other Chemical Messengers

“Local Hormones”
 Never reach bloodstream
 2 types:
○ Paracrine - affect neighboring cells
○ Autocrine - affect only cell secreting them

Prostaglandins
 Lipids messenger usually affecting organ secreted
into
 Ex: inducing childbirth, treat glaucoma, treat erectile
dysfunction
Types of Hormones

Two types:
 1) Cholesterol Derivatives
○ Ex: Steroids (estrogen, testosterone, aldosterone,
cortisol)
 2) Amino Acid Derivatives
○ Ex: Amines (norepinephrine, epinephrine)
○ Ex: Peptides (ADH, oxytocin)
○ Ex: Proteins (Parathyroid hormones, growth hormones,
prolactin)
○ Ex: Glycoprotein (follicle-stimulating hormone,
luteinizing hormone, thyroid-stimulating hormone)
Hormone Action

Steroid Hormone
 Characteristics:
○ Must be carried by plasma proteins through blood
○ Insoluble in water
○ Made of rings of carbon and hydrogen atoms
 Action sequence of events for steroids:
1. Diffuse into any cell
2. Binds to receptor in cell , enters the cell
3. Activates specific area of DNA
4. Protein synthesis is end result
 Examples: Estrogen, testosterone, aldosterone, cortisol
Hormone Action (cont)

Nonsteriod hormone (amines, peptides, proteins)
 Characteristics:
○ Activate proteins which alter cellular processes
○ Ex: altering membrane permeabilities, activating enzymes,
stimulating metabolic processes, release of other hormones
 Ex: growth hormone, epinephrine, oxytocin
 Sequence of events in nonsteroids:
Hormone (primary messenger) binds to receptor on outside
of cell
2. Binding causes activity center inside cell to activate a
messenger (sometimes cAMP) – called second messenger
3. This messenger then causes change
1.
Hormonal Control
Controlled by increasing or decreasing
hormone secretion (VERY precise!)
 See Figure 11.5!!!!!!!
 Stimulation of hormone release:

 All use negative feedback mechanisms
 Hypothalamus and pituitary
 Nervous system
 Changing internal environment

Inhibition of hormone release:
 Negative feedback loop
Practice Quiz (take on notes)
1. The hormone _______________ helps to stimulate the
development of female secondary sex characteristics. This
hormone is produced by the ovaries in the female.
 2. The hormone _______________ is called the "fight or
flight" hormone.
 3. The hormone _______________ maintains the thickness
of the uterus lining in preparation for a possible pregnancy.
 4. The hormone _______________ stimulates the
conversion of excess sugar in the blood to glycogen which
is animal starch in the liver and assists in taking glucose
into the cells. This hormone is produced in the pancreas.

Answers
1.
2.
3.
4.
estrogen
adrenalin
progesterone
insulin
Practice Quiz Continued
 5. The major secretions of the endocrine glands are
called _______________.
 6. The hormone _______________ helps to
stimulate the development of secondary sex
characteristics in the male.
 7. The condition _______________ results usually
from an inability to regulate blood glucose levels
properly. (Usually the blood glucose tend to
become too high.)
 8. _______________ are all the ductless glands.
Answers
5.
6.
7.
8.
hormones
testosterone
diabetes
endocrine glands
Hypothalamus
•Located deep inside
the brain
•Releasing and
inhibiting hormone
secretion to anterior
pituitary
•Direct innervations
to posterior pituitary
Pituitary Gland
•Located deep within the
brain
•Divided into 2 sections:
1) Anterior Pituitary
• glandular
epithelium with
many blood
vessels
2) Posterior Pituitary
• nerve fibers and
neuroglial cells
Tropic Hormones of the
Anterior Pituitary
Thyroid-stimulating
hormone (TSH)
 Adrenocorticotropic
hormone (ACTH)
 Gonadotropins: 2 types

 Follicle-stimulating
hormone (FSH)
 Lutenizing hormone (LH)
Thyroid-stimulating hormone
(TSH)

Stimulation:
 Thyrotropin-releasing hormone (TRH) from
hypothalamus

Inhibition:
 Circulating thyroid hormones decrease TSH and
TRH secretion

Target Cell:
 Thyroid gland/cells

Action:
 Increase thyroid secretions
Adrenocorticotropic hormone
(ACTH)

Stimulation:
 Corticotropin-releasing hormone (CRH) from
hypothalamus

Target Cell:
 Adrenal cortex

Action:
 Increase adrenal cortex
secretions
Follicle-stimulating hormone
(FSH)

Stimulation:
 Gonadotropin-releasing hormone from
hypothalamus

Target Cell:
 Gonads (testes in males and ovaries in females)

Action:
 Female- maturation of egg; secretion of estrogen
 Male- development of sperm
Lutenizing hormone (LH)
 Also called Interstitial cell stimulating
hormone (ICSH)
 Stimulation:
 Gonadotropin-releasing hormone from
hypothalamus
 Target Cell:
 Gonads (testes in males and ovaries in females)
 Action:
 Female- release of mature egg from ovary
(ovulation)
 Male- development of interstitial cell; secretion of
male sex hormones
Other hormones of the
Anterior Pituitary
 Growth Hormone (GH)
 Stimulation:
○ GH-releasing hormone from hypothalamus
 Inhibition:
○ GH release-inhibiting hormone
 Target Cell: Somatic cells (non-sex cells)
 Action:
○ Enhances movement of amino acids across cell
membrane; speeds up rate of carbohydrate
utilization
Other hormones of the
Anterior Pituitary

Prolactin (PRL)
 Stimulates breast development necessary for
lactation
 Stimulates breast to secrete milk after birth
Posterior Pituitary
 Antidiuretic hormone (ADH)
 Stimulation:
○ Nerve Impulse from hypothalamus when
osmoreceptors sense dehydration
 Target Cell: kidneys
 Action:
○ Kidneys produce less urine to conserve water
 Oxytocin (OT)
 Stimulates contraction of the pregnant uterus
 Stimulates “let-down” of milk
Thumbs Up, Thumbs Down





TSH is released by thyroid gland
 DOWN!
Most pituitary-released hormones are
controlled/stimulated by hypothalamus
 UP!
Prolactin stimulates gonad development
 DOWN!
Oxytocin helps uterus to contract during labor
 UP!
ADH prevents you from becoming dehydrated by
preventing your kidneys from making urine
 UP!
Thyroid
•Location: attached to
front of trachea
•Contains follicles
•Follicles have hollow
center cavity filled with
colloid
Quick Review of Pituitary
control
Thyroid (cont)

Follicular cells of thyroid secrete two
hormones:
 1) Thyroxine (tetraiodothyronine) - T4
 2) Triiodothyronine - T3 (much more potent)
 Increases metabolism of carbohydrates, lipids, and
proteins

Extrafollicular cells of thyroid secrete
calcitonin
 Lowers blood calcium level by inhibiting
osteoclasts (bone cells)
 Makes kidney secrete more calcium in urine
Parathyroid glands
Located on the thyroid in four patches
 Highly dense, secretory cells
 Secrete Parathyroid hormone (PTH)

 Raises blood calcium levels
 Inhibits osteoblasts
 Stimulates osteoclasts
 Makes kidneys conserve calcium
 Increase absorption of calcium in intestine
 Opposite of calcitonin
Adrenal glands
Very closely related to
kidneys
 Located/Sit on top of
kidneys
 Consists of two parts:

1. Adrenal cortex
2. Adrenal medulla
Adrenal Cortex

Three layers:
 Outer, middle, and inner
Closely packed masses
of epithelial tissue
 Makes up bulk of
adrenal glands
 Well-supplied with
blood

Outer Layer of Cortex
 Outer (glomerulosa)
 Mineralocorticoid (MC)- regulate mineral
electrolytes
○ Ex: Aldosterone hormone
 Stimulated by decrease in blood levels of sodium,
increase in potassium in blood levels, or decrease
in blood pressure
 Cause kidneys to retain sodium and secrete
potassium into urine
 Indirectly, water is retained – IMPORTANT!
Adrenal Cortex (cont)
 Middle (fasciculata)
 Glucocorticoids- affects glucose metabolism
○ Ex: Cortisol or hydrocortisone hormones
 Increase gluconeogenisis (glucose synthesis)
 Inhibition of protein synthesis
 Promotion of fatty acid release from adipose
tissue
 Produce state of stress
Adrenal Cortex (cont)

Inner (reticularis)
 Secretes sex
hormones
○ Produces androgen
hormones
○ Can be used to
synthesize female
sex hormones like
estrogens
Adrenal Medulla
Irregularly shaped cells
 Well supplied with blood
 Composed of modified neurons
 Secrete epinephrine (adrenaline) and
norepinephrine (noradrenaline)

 Important in “Fight or Flight” response

Directly innervated by sympathetic nervous
system
Pancreas

Structure and Location:
 Elongated, somewhat flattened
 Posterior to stomach
 Duct joins pancreas to intestine

Dual function:
 1) Exocrine gland: secretes digestive juices
 2) Endocrine gland: releases hormones
○ Contains groups of cells closely related to blood vessels
○ Called islets
Pancreatic Islets (Islets of
Langerhans)

Made of two types of secretory tissues/cells:
1. Alpha cells
○ Secrete hormone: glucagon
 Accelerates process of gylcogenolysis
2. Beta cells
○ Secrete hormone: Insulin
 Increases movement of glucose inside of cells for
metabolism
 Stimulates liver to produce glycogen
Exit Slip
 1) T3 is released by what gland?
 2) Which hormone (cortisol or T4) produces a
state of stress?
 3) The pancreas has a duct/tube which connects
it directly to what digestive system organ?
 GRADING TIME!!!!
 1) Thyroid
 2) Cortisol
 3) Intestines
Thymus
•Located in
mediastinum cavity
•Secretes hormones
called thymosins
•Important function
in development of
immune system
Pineal gland

Releases hormone
melatonin
 Regulates body clock and
sleep cycle
Female Sex Glands
Ovaries
 Ovarian follicles
 Corpus luteum
 We will discuss
these (and their
hormones) in the
reproductive
chapter!

Male sex glands
 Testes
 Interstitial cells produce testosterone
 Testosterone stimulates sperm production
Placenta
•Provides nutrients to
embryo/fetus while
developing
•Secretes chorionic
gonadotropins
•Pregnancy tests test for
the presence of this
hormone
•Prevents dissolution of
corpus luteum (prevents
menstrual cycle)
Other hormones

Heart
Hormone Review:
http://www.wisconline.com/
•Type in “hormones”
in search bar!
 Wall of Atrium:
○ Secretes Atrial Natriuretic hormone
○ Regulates fluid and electrolyte balance
○ How? By increasing removal of sodium and water
Various Digestive Glands (will discuss in
Digestive chapter)
 Kidneys

 Erythropoietin- red blood cell growth hormone
Stress and the Endocrine Sys.

Stress: A factor that can stimulate an increase
in the sympathetic division of your PNS
 Causes increase in secretion of adrenal gland (and
other) hormones
 Homeostatic mechanisms become threatened
○ Due to change in internal/external environmental
factors
○ Ex: Lack of sleep, death of family member,
depression, danger
Yes/No/Maybe So

Your thymus gland is connected to your
immune system.
 YES!

The placenta provides nutrients to embryo
and also can start a menstrual cycle.
 NO! – prevents menstrual cycles

Your heart can release hormones!
 YES!!
Types of Stress

Physical factors:
 Ex: exposure to extreme heat/cold, decreased
oxygen concentration, infections, injuries,
prolonged heavy exercise, loud sounds

Physiological factors:
 Ex (unpleasant): thoughts about real/imagined
danger, personal loss, unpleasant social
interactions, anxiety, depression, guilt
 Ex (pleasant): feelings of joy/happiness, sexual
arousal, friendly social contact
Stress response
 Physiological factors
affect hypothalamus
 Occurs in two stages:
○ 1) Immediate “alarm”
stage
 Hypothalamus prepares
for “fight or flight”
 Include: raise in blood
glucose; increase heart
rate/blood pressure;
increase epinephrine
secretion from adrenal
Stress response (cont)
 Physiological factors affect hypothalamus
 Occurs in two stages:
○ 2) Longer “resistance” stage
 Hypothalamus release CRH (stimulates anterior
pituitary to secrete ACTH)
 Increases cortisol secretion (cortisol supplies cells with
biochemicals required to deal with stress)
Endocrine System Disorders
 Hyperthyroidism
 Over-activity of thyroid cells
 Causes elevated metabolic rate, restlessness,
overeating, eye protrusion, goiter (enlarged thyroid
gland)
 Hypothyroidism
 Cretinism: stunted growth, abnormal bone
formation, mental handicaps, sluggishness
 Often, weight gain/puffiness in face, hands and feet
is associated with hypothyroidism
Hypothyroidism
treatment:
Before and After
photos
Endocrine System Disorders
 Diabetes Mellitus
 Metabolic issue caused by lack of insulin (or inability
for cells to recognize insulin)
 Reminder: Insulin helps glucose cross cell membranes
○ In diabetics, glucose doesn’t move into fat and skeletal
muscle tissue
 Results:
○ Glucose in urine increases, causing excessive urine output
○ Dehydration and extreme thirst
○ Muscles use proteins (instead of glucose) for energy
 Stunted growth, wounds don’t heal properly, exhaustion
Endocrine System Disorders
 Diabetes Mellitus, cont.
Blood sugar
animation
 Two types:
○ Type 1:
 Insulin-dependent (juvenile diabetes)
 Usually appears before age 20
 Auto-immune disease (destroys beta cells of pancreas)
 Treatment: Give insulin (inject several times day/week)
○ Type 2:
 Non-insulin dependent (maturity-onset)
 85-90% of people with diabetes have Type 2
 Beta cells produce insulin but body cells don’t recognize it
 Develops gradually after age 40
 Milder symptoms, controlled by diet (usually)