Transcript Endocrine System & Homeostasis

Homeostasis
Miller/Levine Textbook – Chapter 39
Modified September 2013
Content Standard 4.7

Recognize that communication between cells
is required for coordination of body
functions. The nerves communicate with
electrochemical signals, hormones circulate
through the blood, and some cells produce
signals to communicate only with nearby cells.
Content Standard 4.8

Recognize that the body’s systems
interact to maintain homeostasis.
Describe the basic function of a
physiological feedback loop.
Homeostasis
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The internal stability or “steady state”
maintained by your body
Your body buffers itself from changes
in the external environment, by
providing a relatively stable internal
environment.
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Stability is important because your
tissues can only survive within a narrow
range of conditions.
This range of operating conditions is
defined by set points.
Average set point for internal body
temperature is 98.6°F
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Homeostasis is regulated by
1.
Nerve impulses (Nervous System)
2. Hormones (Endocrine System)
Compare & contrast the messengers that
regulate homeostasis
Messenger
Produced by
Nerve Impulse
Nervous
System
Hormone
Endocrine
System
Nature
Electrochemical
Chemical
Body’s
Response Time
Immediate
(fraction of
second)
Varies (several
minutes to
days)
Physiological Feedback Loop
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Negative feedback - a change in
conditions causes a response that
counteracts or negates that change.
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Sometimes referred to as “feedback inhibition”
or “physiological feedback loop”
Example: if oxygen levels in your blood fall,
the body reacts to raise the level to normal
Thermoregulation
(Temperature Control)
Homeostasis controlled by the
nervous system
Body temperature rises above 98.6°F
(set point)
Thermoregulation portion of brain:
 Causes blood vessels in skin to dilate
and rise to surface (releasing heat)
 Activates sweat glands (water absorbs
heat)
 Result: Body returns to normal
temperature
Body temperature drops below
98.6°F (set point)
Thermoregulation portion of brain:
 Causes blood vessels in skin to constrict
(conserving heat)
 Stimulates rapids contraction of skeletal
muscles (causing shivering which generates
heat)
 Causes hairs on skin to stand on end – the air
that becomes trapped is another layer of
insulation.
 Result: Body returns to normal temperature
Endocrine System and
Homeostasis
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Gland – cell or group of cells that releases a
substance called secretions
Endocrine glands – release their secretions
directly into the blood
The chemical secretions of endocrine glands
are called hormones.
These substances are manufactured by the
Golgi complex in the cells that make up these
glands.
The cells of glands can be identified by the
large number of Golgi complexes inside them.
Other Glands
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Exocrine glands - release their
secretions through tube-like structures
called ducts directly into the organs
that use them.
Examples of such secretions: sweat,
tears, digestive juices
Classification of Hormones
1.
2.
Steroids – lipids
Nonsteroids – proteins & modified
amino acids
Hormone Facts
1.
2.
3.
4.
They are chemical messengers.
They are produced by endocrine
system
They travel from one place to another
in the blood (circulatory system).
They can only influence target cells.

Target cell – cell that has a specific
receptor site to which a
chemical messenger can
attach.
Where are the receptor sites on target
cells located?
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For nonsteroid hormones – cell
membranes
For steroid hormones – inside the cell
5.
There are more than 40 different
hormones released by the nine major
endocrine glands that make up the
endocrine system.
6.
They regulate:
growth
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cellular metabolism
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blood pressure
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heart rate
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muscle tone
calcium and glucose levels in blood
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salt and water balance in body
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Pancreas
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1.
2.
It is both an exocrine & an endocrine
gland
As an exocrine gland
It is attached to the small intestine by
a tube or duct.
It secretes digestive enzymes.
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As an endocrine gland it releases two
hormones
1.
Insulin
2. Glucagon
Working together they regulate the
amount of glucose in the blood
Target organ - liver
Blood Glucose Regulation
What happens when your blood glucose
level RISES?
1.
Pancreas produces insulin
2. Insulin enters the bloodstream.
3.
4.
When insulin reaches the liver, it leaves the
blood and attaches to receptor sites on the
cell membrane of liver cells.
This causes the liver cells to remove excess
glucose from the blood and store it as
glycogen.
What happens when your blood glucose
level DROPS?
1.
2.
Pancreas produces glucagon
Glucagon enters the bloodstream.
3.
4.
When glucagon reaches the liver, it leaves
the blood and attaches to receptor sites on
the cell membrane of liver cells.
This causes the liver cells to breakdown
stored glycogen into glucose which is
released into the bloodstream.
Homeostasis and the Kidneys
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Urea (nitrogen waste from the breakdown of
proteins and nucleic acids) is filtered out of
the blood by the kidneys
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Normal metabolism produces waste which is
anything that the cells produce that is harmful,
not needed, or already in abundance
Urea is combined with water and excreted as
urine
Kidneys also reabsorb or eliminate excess
water and salt
Homeostasis and the Lungs
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Carbon dioxide is produced by
breakdown of carbohydrates and lipids
for energy
Transported from cells to lungs by
circulatory system (blood vessels)
Removed from the body by exhalation
Homeostasis and the Skin
1.
2.
3.
4.
Provides a physical barrier against dirt
and microorganisms
Helps insulate body from cold and
contains sweat glands
Cushions internal organs from physical
injury
Senses changes in environment (nerve
receptors for pain and touch)
Video – Thermoregulation
 http://www.teachersdomain.org/resourc
e/tdc02.sci.life.reg.fevervid/
Biosnippet – Homeostasis
 http://www.phys.unsw.edu.au/biosnippet
s/