LETS FACE IT… If you don’t understand
diffusion and cell membranes you really don’t have
a chance at understanding cell to cell signaling.
LETS REVIEW A FEW THINGS
2 main types of transport…
 ACTIVE TRANSPORT- the movement of
molecules across membrane using ATP
 moves molecules from an area of low
concentration to an area of higher
concentration
EXAMPLE- endocytosis and exocytosis, sodium
potassium pumps voltage gated channels
 PASSIVE TRANSPORT- the movement of
molecules due to their own kinetic energy no
ATP
-moves molecules from an area of high
concentration to an area of lower
concentration down their concentration
gradient.
- EXAMPLE- oxygen moving from the
bloodstream through the cell membrane into
cells
Membranes are composed of a phospholipid
bilayer with specialized proteins9often called
receptors) to act as channels allowing specific
molecules to cross through into the cytoplasm.
Some examples we will look at our house so
diffuses across in membrane and help oxygen
escapes an Elodea leaf.
Before anyone can be expected to understand
hormones you need to understand “BASIC” gene
expression.
•Though all cells have a complete set of genes
they generally only use about 10% of their genes.
TRANSCRIPTION-
•many genes control it and how fast aging will be
transcribed into an mRNA
•transcription factors effect this is well by
binding to areas and encouraging or discouraging
RNA polymerase
ENDOCRINE SYSTEM-YOUR CONTROLLING
SYSTEM
 Hormones first discovered in early 1900s by
W Bayliss and E starling while studying the
regulation of pancreatic juices.
 This mode of signaling had been hypothesized
about centuries ago.
 The endocrine system includes a collection of
glands, the gonads, and the hypothalamus.
•
Specialized cells within organs may also
release hormones including cells of the small
intestine and.
•
Control and coordination of the vertebrate
body relies upon the neuroendocrine and system
which synthesizes how closely linked these two
systems are…
→ Hormones influence brain development
-effect sleep and wake cycles, mood,
memory, emotions
→ brain influences hormone secretion
-EXAMPLE: During stress sympathetic
nervous system increases some hormones while
suppressing others.
 ENDOCRINE DISRUPTORS-are molecules
that interfere with the action of hormones
 Two major endocrine disruptors are DDT and
PCBs - both were banned in the 1970s but due
to their high stability they still persist in the
environment.
 Atrazine a synthetic herbicide remains in
wide use it is another endocrine disruptor.
o Atrazine effects actual development
creating a feminizing effect on fish and
amphibians, the problem with this is many
vertebrates share endocrine signaling
molecules. DO YOU FIND THIS
FRIGHTENING?
TWO broad groups of hormones…
STEROID
membrane in
HORMONES
nuclear membrane
 cholesterol-based
 move easily
through cell
to hormone
receptor complex
 causes
transcription of a
specific gene
 protein made
 FASTER!
 amino acid-based
 must bind to
receptor protein in
membrane
 catalyzes a second
messenger
 second messenger
PEPTIDE & PROTEIN
HORMONES
activates another
enzyme
Hormone action is a three-step process…
SIGNAL RECEPTION→ SIGNAL
TRANSDUCTION→ CELLULAR RESPONSE
*transduction – [ a change into a form that
affects cell behavior]
The response summons up by a hormone declines
over time, as the body breaks down and
eliminates hormone molecules. Most often
hormone is taken up from the blood by the liver
and broken down by liver enzymes. Other
methods occur in the blood, inside target cells, or
in the kidneys.
Receptors may be intracellular or within the
plasma membrane. Steroid hormones may enter
the plasma membrane and bind to receptor in the
cytoplasm or the nucleus. Most often this
hormone receptor complex binds to a promoter
effecting the rate of transcription for a
particular protein or enzyme. Most amine
hormones and all peptide or protein hormones
cannot diffuse directly across the lipid bilayer
and must bind to receptors in the cell membrane.
This will activate a second messenger causing a
shift in the cells activity. A good example of this
is cyclic AMP. Some steroid hormones may bind to
receptors either inside the cytoplasm or within
the plasma membrane, initiating different
responses for each situation.
LETS SEE
http://www.cengage.com/biology/book_content/9
781111425692_starr_udl13e/animations/PowerPoi
nt_Lectures/chapter34/videos_animations/intrac
ellular_receptors_m.html
A cell can only respond to a hormone for which it
has appropriate and functional receptors.
Remember all receptors are proteins and gene
mutations may occur which deemed them
nonfunctional.
Good example is an XY embryo without
testosterone receptors without actual receptors
it is as if testosterone is not even present.
Testes form but do not descend individuals are
often raised as female.
Different tissues have receptor proteins that
respond in different ways when binding to the
same hormone.
→ Antidiuretic hormone [ADH] effects urine
formation within kidney cells but causes
vasoconstriction in blood vessels, maintaining
blood pressure, within the brain effects social
and sexual behavior. One chemical many uses!
HYPOTHALAMUS and PITUITARY GLAND
-The hypothalamus is the mail control center for
the internal envi, its inside the forebrain and
connects with pituitary gland by neuro secretory
neurons .
-The posterior pituitary gland secretes hormones
that are made in the hypothalamus. While the
anterior lobe makes its own hormones.
-ADH (antidiuretic hormone) and OT (oxytocin)
hormones produce in the hypothalamus travel
through the neurons to the pituitary glands where
they are stored.
-When an action potential reaches the pituitary
these hormones can be released into the blood
stream.
-ADH is involved in kidney function.
-OT is involved with labor and milk production
-Anterior Pituitary Gland- Produces its own
hormones but the rate/control involves releasing
and inhabiting hormones from the hypothalamus.
-Very involved in Growth, thyroid, sex hormones,
and adrenal hormones.
GH-Growth Hormone
-Increases production of cartilage and bone and
increases muscle mass.
-Most active during teen years.
-Tumors on pituitary gland can increase or
decrease the production of extremes.
-In adulthood its important for maintaining
healthy muscle mass.
-As we learn about effects of specific hormones
keep in mind that cells in most tissues have
receptors for more than one hormone.
-Thyroid and parathyroid Glandsj
-Lies at the base of the neck.
-Thyroid hormone increases metabolic activity in
cells throughout the body.
-Thyroid hormone synthesis requires iodine so
iodine is essential for normal function
-Parathyroid gland, releases PTH parathyroid
hormone
PANCREATIC HORMONES- regulate the level of
sugar in the blood.
-pancrease lies behind the stomach and has both
an endocrine and exocrine function.
-Exocrine-secretes digestive enzymes into
small intestines.
-Endocrine- grouped in clusters called islets.
Each islet has 3 types of cells.
1. Alpha cells- secretes (Glucagon) causes
glycogen to be broken into glucose.
2. Beta Cells- secretes (Insulin) causing
the uptake of glucose by target cells, mostly
skeletal muscle, fat and liver cells.
3. Delta Cells- secretes (Somatostatin)
aids in digestion and nutrient absorbtion.
DIABETES MELLITUS- a metabolic disorder
where cells are NOT stimulated to take in glucose
(blood sugar) and store it.
-When cells do not take up glucose from the
blood they end up breaking down protein and fats
from your body which yield harmful waste
products!
Two Types
-Type 1 – develops after an autoimmune response
where white blood cells wrongly indentify Beta
cells as foreign and destroy them.
-Type 2 – insulin levels are normal or even high
BUT target cells do not respond to the hormone
so blood glucose levels remain high.
Adrenal Glands -Located above each kidney-the
outer layer is the adrenal cortex- inner layer
adrenal medulla
-Adrenal cortex releases steroid hormones
-Aldosterone: controls Na and H2O balance in
kidneys (Urine concentration)
-Cortisol: ensures glucose availability to the
brain inducing liver cells to break down glycogen.
Also it causes adipose tissue to release fatty
acids and Muscle to release proteins to be used
as an energy source.
*Cortisol levels affect health too much = bad
health too little can be fatal..
-Adrenal Medulla contains specializes neuron for
the sympathetic division. They release
norepinephrine and epinephrine into the
bloodstream where they act as hormones to cause
sympathetic (fight of flight) reactions on target
organs –dialate pupils, increase breathing, and
heart rate.
Gonads-Primary reproductive organ responsible for the
production o gametes and the production of sex
hormones
Testes: produce mainly testosterone
Ovaries: produce mainly estrogen and
progesterone
-Hypothalamus and Anterior Pituitary gland
control sex hormone secretion
-Hypothalamus Produces gonadotropin –
releasing hormone (GnRH) this causes anterior
pituitary to secrete follicle stimulating hormone
(FSH) and leutenizing hormone (LH) which target
the gonads and initiates the production of sex
hormones
-LH and FSH often called “gonadotropins”
-Sex Hormones increase during puberty maturing
reproductive organs and causing secondary sexual
trains to occur.
Pineal Gland: secrets the hormone melatonin
which is (in mammals) secreted in low light or
darkness
-melatonin secretion follows a circadian rhythm
(24 hourish cycle)
-At night, causes body temp decreases
-After sunrise, melatonin decreases, body
temp increases and we wake up
-Working Night Shifts all the time or having poor
sleep habits disrupt melatonin AND raises the
risk of CANCER!!
-Melatonin directly inhibits the division of cancer
cells in animals
-WOW! Notice sleep at NIGHT is much
better for you.
-SAD: seasonal affective disorder “winter blues”
arises in some where seasonal changes cause long
periods of low/ no light.
-Melatonin regulates seasonal behaviors in many
animals
THYMUS
-The thymus lies behind the sternum and releases
a complex mix of polypeptides (called Thymosins)
which enhance wound healing and immune
function.
-Thymulin encourages maturation of white blood
cells called T cells.
Additional Hormone Info
- Several receptors for hormones are common
among invertebrates as well as vertebrates
insinuating common evolutionary ancestry
- Some hormones are unique to invertebrates
Molting is an example controlled by the hormone
ecdyso