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HOMEOSTASIS, FEEDBACK, AND
REGULATION
Pg. 468 – Read about EPO.
Starting Points; Read and Notes on pages
470-474
HOMEOSTASIS
How do these chemicals called
hormones help to maintain a
steady state in our bodies?
And what happens if they
don’t??
Negative Feedback
The mechanism by which homeostasis
works is negative feedback…..when a
deviation is offset by a corrective action in
the opposite direction.
Negative Feedback
-substances produced by a response to changes will go back
and turn off the system when HOMEOSTASIS is achieved.
NEGATIVE = OPPOSITE
Hormone produced
by Pituitary
Activates target to produce
hormone
Response by target
organ
Feedback to
TURN OFF
production of
the pituitary
hormone
if negative
feedback does not
function properly,
disorders can
result (ie.
gigantism - growth
hormone
production not
turned off
Endocrine glands
 An endocrine gland is a
ductless gland whose secretions (hormones) are released
directly into the blood stream
where the hormone will travel to its target tissue or
organ…….
 this contrasts exocrine glands whose secretions
(e.g.enzymes)are released via ducts to their
required location.
Comparing the Nervous System
and Endocrine system
Nervous
Characteristic
Endocrine
electrical
and
2
chemical
very5 fast
Type
of
1
message
Speed
of
4
message
Duration
of
7
message
Target of the
10
effect
chemical
3
short
8
muscles/glands
11
slower
and
6
variable
long
9
many tissues
12
and variable
Chemical Signals
2 Types of Hormones:
1) Steroid hormones: made from cholesterol (lipid)
and are fat soluble
eg. sex hormones, cortisol
- these leave the blood, ENTER the target cell,
bind to receptors, go to nucleus and cause
specific proteins to be produced
Chemical Signals
2 Types of Hormones:
2) Protein hormones: are chains of amino acids
and are water soluble eg. insulin, growth
hormone, epinepherine
- do NOT enter target cells but “land” on
receptors on the cell surface
- this causes chemical changes that
activates other enzymes in the cell to carry
out their functions
Actions of Steroid vs. Peptide Hormones
What are the common
endocrine glands??
GLANDS
There are many
glands that regulate
the body through
production and
release of hormones.
Most of these glands
are under control of
hormones from the
pituitary.
PITUITARY
-located close to the hypothalamus in the brain
2 Lobes:
Anterior Lobe
Posterior Lobe
Hypothalamus/Pituitary Complex
 ANTERIOR LOBE
 hypothalamus sends
releasing or
inhibiting factors
that regulate the
anterior pituitary
 these factors travel
via the bloodstream
to the anterior
lobe of the pituitary
 POSTERIOR LOBE
 hypothalamus makes
ADH and oxytocin
which are stored in
the posterior pituitary
 these 2 hormones
travel via nerve fibers
to the posterior lobe
of the pituitary
Pituitary hormones
of the posterior lobe
Hormone
Target
Primary
Function
Oxytocin
-Uterus,
-mammary
glands
-uterine
contractions
-milk letdown
ADH
Kidney
Increases water
reabsorption
from kidney
ADH feedback loop
Pituitary hormones
of the anterior lobe
HORMONE
TARGET
PRIMARY FUNCTION
TSH
Thyroid gland
Stimulates thyroxin release
ACTH
Adrenal Cortex
Stimulates release of “stress
hormones”
hGH (Somatotropin )
All body cells; long bones
Promotes growth of bones and
other tissue
LH
Ovaries
Testes
Stimulates ovulation & corpus luteum
Stimulates testosterone prod.
FSH
Ovaries
Testes
Promotes follicle development
Promotes sperm development
Prolactin
Mammary glands
Stimulates milk production in
females
ANTERIOR PITUITARY
Growth Hormone (somatotropin)
-affects most cells of the body but
mostly the cartilage and bone cells.
HYPERPRODUCTION: gigantism and
acromegaly
HYPOPRODUCTION: dwarfism
Acromegaly
CUTTHROAT:
- ONE “Asker”
- TWO “Answerers”
- Asker gives a hormone action; First
Answerer to give the correct hormone
gets a point and remains an Answerer.
- Loser becomes Asker; Asker
becomes Answerer.
- Keep score.
THYROID
Located at the base of the neck in front of the
trachea.
Produce THYROXINE and triiodothyronine used in metabolism.
People who produce a lot of THYROXINE
have high metabolic rates - they oxidize food
(glucose) faster, produce more heat, and
have low weight. People with hypothyroidism
will be subject to cold and may gain weight as
glucose is first stored as glycogen then as fat.
Thyroid animation
THYROID
THYROID
Disorders: Thyroid hormones require iodine. Without iodine the
thyroid enlarges and GOITER results. (negative feedback is
displayed here in that low thyroxine causes TSH to continue to
stimulate the thyroid causing swelling.
THYROID
Also makes CALCITONIN which helps regulate calcium in the
blood. Causes blood calcium to DROP by ADDING calcium to
bone and by causing urination of Ca2+.
Parathyroid glands - behind the thyroid. Produce PTH
(ParaThyroid Hormone) also used in calcium regulation (with
calcitonin from thyroid). Causes blood calcium to RISE by
LEACHING calcium from bone, INCREASING absorption of
calcium from small intestine, and DECREASING loss of Ca2+ in the
urine.
THYROID REGULATION
PANCREAS
The pancreas produces digestive enzymes AND hormones.
Hormones are produced in structures called the ISLETS OF
LANGERHANS. These have TWO types of cells: alpha and
beta cells.
ISLETS OF LANGERHANS - Produce two hormones:
1) INSULIN - produced by beta cells of IOL. Released when
blood sugar is high. Makes many cells of the body (especially
liver and muscles) permeable to glucose. Muscles use the
glucose for energy and liver cells store the glucose as
glycogen.
PANCREAS
PANCREAS
The pancreas produces digestive enzymes AND hormones.
Hormones are produced in structures called the ISLETS OF
LANGERHANS.
ISLETS OF LANGERHANS - Produce two hormones:
2) GLUCAGON - produced by alpha cells of IOL. Released
when blood sugar is low. Converts glycogen to glucose.
PANCREAS
PANCREAS
Diabetes Mellitus: inefficient insulin
production (perhaps due to destruction
of beta Islet cells) or inefficient use of
insulin in system (cells don’t respond to
it).
Leads to high blood glucose which can
be excreted in the urine along with large
volumes of water.
Diabetes Mellitus
Symptoms:
Body cells have low energy. Lipids and
Proteins may be metabolized leading to
acetone build up and lower blood pH.
If untreated, it may lead to blindness, kidney
failure, nerve damage and limb amputation.
Much research being done on cures including
Islet cell transplants.
Blood Glucose Levels After Ingestion of
100g of Glucose
500
450
400
350
300
Blood Glucose
250
(mg/100mL)
200
150
100
50
0
0
1
2
3
4
5
Time (h)
Plasma Insulin Levels After Ingestion of
100g of Glucose
60
50
40
Plasma Insulin
30
(mU/mL)
20
10
0
0
1
2
3
Time (h)
4
5
6
Diabetes mellitus (3 types)
Type I (juvenile onset)
Diagnosed in childhood
10% of people with diabetes have this
form
Beta cells are unable to produce insulin
Lots of glucose in blood, but body cells
can’t access it for cellular respiration.
Must take insulin injections to survive.
Diabetes mellitus (3 types)
Type II (adult onset)
90% of people with diabetes have this
form
Due to decreased production of insulin
OR ineffective use of the insulin that is
produced
Control with diet, exercise and oral
drugs
Diabetes mellitus (3 types)
Gestational Diabetes
Temporary condition that occurs in
2% to 4% of pregnancies
Increases the risk of type 2
diabetes in mother and child
Lab Ex 15A p. 483 (due)
ADRENAL GLAND
-located above each kidney.
- is two glands in one. The adrenal medulla (inside) is
regulated by nervous control. The adrenal cortex
(outside) is regulated by hormonal control.
ADRENAL GLAND
1) Adrenal Medulla - makes two hormones:
a) epinephrine and b) norepinephrine which are stimulated
by the sympathetic nervous system in times of stress.
Both cause glycogen----> glucose, increase heart rate and
breathing rate, dilate blood vessels (more O2), dilate iris of
eye to allow more light in.
ADRENAL GLAND
2) Adrenal Cortex makes three different
hormones:
a) GLUCOCORTICOIDS
- regulate blood glucose
levels. ex) CORTISOL increase blood amino
acids. AA’s are
converted to glucose in
liver. Excess aa’s can be
used to synthesize
proteins needed for cell
repair.
FEEDBACK:
ADRENAL GLAND
2) Adrenal Cortex makes three different
hormones:
b) MINERALOCORTICOIDS
- regulate mineral
absorption.
ex. ALDOSTERONE increase sodium retention
and water reabsorption
from the kidneys.
c) some SEX HORMONES very small amounts .
QUESTION
QUESTION
Use the following information to answer the next question.
Q. A logical interpretation of the graph is that the
A. secretion of cortisol is inhibited by increased ACTH
B. secretion of cortisol is doubled if the secretion of ACTH is
doubled
C. adrenal glands respond more quickly to small amounts of
ACTH than to large amounts of ACTH
D. adrenal glands respond to large amounts of ACTH by
having a maximum cortisol secretion rate
CH 15 REVIEW: PG 501-503
- #1-11 – MULT CH & NUM RESP
- GOOD TO READ AND REFLECT ON
#12-30
HOMEOSTASIS REVIEW: P. 504-505
-#1-9 – MC &NR
- READ AND REFLECT ON #10-38