Endocrine System
“Chapter 15”
Erythropoietin (EPO)
y Olga Yegorova upset reigning 5000m champion
Gabriel Szabo at 2001 World Track and Field
Championships held in Edmonton. She was booed
running across the finish line for what was seen as
an unfair advantage --- taking the banned chemical
hormone erythropoietin (EPO). She had tested
positive after the Paris competition but was
reinstated on a technicality. Her Urine had tested
positive, however the Paris Track meet organizers
had failed to do another follow – up blood test.
When she was tested again the abnormally high
levels were gone.
y Erythropoietin is a naturally occurring hormone produced by the
kidneys . It boosts red blood cell production, increasing oxygen
transport to the tissues. More oxygen means greater energy for
athletes. Tests have shown that athlete enhancement gained by using
EPO for four weeks matches that of several years of training.
y EPO is dangerous, increased red blood cell production makes blood
thicker and more difficult to pump. It can increase clotting and over
work the heart.
y According to doping experts the death of 20 European cyclists
between 1988 – 1998 have been linked to EPO
y Since the body produces EPO it is difficult to detect.
y Athletes can avoid being caught by stopping EPO treatments a few
weeks before the tests.
Activity
Homeostasis
y Human body works best at:
- Temperature 37 degrees Celsius
- Blood glucose level 0.1 %
- Blood pH of 7.35
y However the environment does not always provide the ideal
conditions for life.
y air temps in Canada fluctuates between -40 and +40
y rarely do foods consist of 0.1 % glucose and have pH of 7.35
y you place different demands on your body during different activities
y
Homeostasis - refers to the bodies attempt to adjust to a
fluctuating environment. The body maintains a constant
balance or steady state. This system of balance requires
constant monitoring and feedback of the bodies condition.
y
Examples: Sweating – evaporation of water helps to
regulate body temperature.
Hypothalamus – regulates temperature
and changes in osmotic
pressure
Pancreas – regulates blood sugar
Kidneys – maintain water balance
Blood – distributes heat throughout the body
Skeletal muscles – contract and release heat.
y All homeostatic control system have three
functional components:
1) receptor
2) coordinating centre
3) effector
y Dynamic equilibrium – a state of stability
within fluctuating limits.
Homeostatsis
Feedback Systems
y
Negative feedback systems - Mechanisms that make
adjustments to bring the body back within an acceptable
range. House hold thermostat is an example. Receptor
(thermometer), when room temp falls below a set point,
the thermostat switches on the effector (furnace). – to +
y
Example: Testosterone, the male sex hormone, which is
responsible for the development of secondary male
characteristics. Facial hair, sex drive, lowering of the
voice are all associated with the production of the
hormone. The hormone itself is regulated from the
pituitary gland, called the male lutenizing hormone (LH)
which activates testosterone producing cells of the male
testes. Once LH is produced, testosterone secretion
begin. Once testosterone reaches acceptable levels it must
be turned off.
y Positive feedback in the body are less common.
Positive feedbacks reinforce change, where as
negative feedbacks resist change.
y Positive feedback – the process by which a small
effect is amplified.
Hormones
y Trillions of cells in the body interact with each other. No cell operates
in isolation.
y The integration of body functions depends on chemical controls.
y Hormones – are chemical regulators produced by cells in one part
of the body that affect cells in another part.
y The word hormone comes from the Greek hormone, meaning “to
excite or to set in motion”.
y Hormones serve as regulators, speeding up or slowing down certain
bodily processes.
y
Only a small amount is needed.
y Endocrine Hormones – are chemical which are produced by
glands and secreted directly into the blood. The circulatory system
carries these hormones to various organs of the body.
y Target Tissues – Hormones that are classified according to their
activation site.
y target and nontarget hormones.
y Nontarget hormones affect many cells or tissues throughout the
body. For example, Insulin (produced when sugar levels are high)
makes practically every cell in the body permeable to glucose and
makes liver cells to convert glucose to glycogen. Human Growth
hormone (long bones) and epinephrine (during stress) are also
nontarget hormones.
y Target hormones affect specific cells or target tissues. For example,
gastrin stimulates only certain stomach cells, which then produce
digestive enzymes.
Chemical Control Systems
y
Nervous system and endocrine system work together to
control organs and tissues.
y
Nervous system enables the body to adjust quickly to
changes in the environment. The endocrine system is
designed to maintain control over a longer duration. Ex:
Growth hormone and various sex hormones regulate and
sustain development for several years.
y
The division of the nervous and endocrine systems is
most subtle in the hypothalamus. The hypothalamus
regulates the pituitary gland (master gland of the body)
through nerve stimulation. Endocrine glands are
stimulated by the pituitary gland. They secrete chemicals
that affect nerve activity of the hypothalamus.
y Example: Long before scientist studies hormones,
farmers knew that castrated bulls (steers) produce
better meat. Today we know that chemicals within
the testes of the bull are associated with the animals
aggressive nature and with tougher meat.
y
Example: In 1899 Joseph Von Merring and Oscar
Minkowski showed that chemical messenger produced in
the pancreas was responsible for the regulation of blood
sugar. After removing the pancreas from a number of dogs,
the two scientists noticed that the animals began to lose
weight very quickly. Within a few hours the dogs became
fatigued and displayed some symptoms that are now
associated with diabetes. They also found that ants
gathered in the kennels of the sick dogs. After testing the
urine they noticed that it contained glucose (a sugar). This
chemical messenger became known as Insulin.
Chemical Signals
y How do hormones signal cells?
y Important to note that hormones do not affect all
cells. Cells may have one receptors for one
hormone but not others. The number of receptors
on a cell may very also. Example: liver cells and
muscle cells have many receptor sites for the
hormone insulin. Fewer receptor sites are found in
less active cells such as bone cells and cartilage
cells.
Two Types of Hormones
y There are two different types of hormones that differ in chemical
structure and action.
y 1) Steroid hormones- which include both male and female sex
hormones and cortisol, are made from cholesterol, a lipid compound.
Are not soluble in water, but are soluble in fat.
y They act from the inside of the cell by diffusing into a specific cell and
binding with receptor molecules in the cytoplasm, which signals the cell
to produce a specific protein.
y 2) Protein, or protein related hormones. These include insulin, growth
hormone, and epinephrine. They contain chains of amino acids and
vary in length and are soluble in water.
y They act from outside the cell by binding to receptor sites on the cell
membrane, which activates enzymes in the cytoplasm to carry out
specific functions.
Hormones in Action
The Pituitary Gland: The Master
Gland
y It exercises control over the endocrine glands. The
small sac like structure is connected by a stalk to the
hypothalamus, the area of the brain associated with
homeostasis. The pituitary gland is composed of two
separate lobes: posterior and anterior.
y
The posterior stores and releases hormones such as
antidiuretic hormone (ADH) and oxytocin, which have been
produced by the hypothalamus. They act on the kidneys
and helps regulate water. Oxytocin initiates strong uterine
contractions during labour.
y
They travel by way of special cells from hypothalamus to
pituitary. The Pituitary stores the hormones releasing them
into the blood when needed.
y
The anterior produces its own hormones, but is richly
supplied with nerves like the posterior from the
hypothalamus. The hypothalamus regulates the release of
hormones.
Pituitary Hormones
Pituitary Gland
Summary
Homework
y Questions 1-6
y Review Questions page 468
y Questions 1-2
y Questions 1-3 page 472
y Questions 4-6 page 475
Using Recombinant DNA
Technology to Produce Hormones
y Genetic engineering involves extracting genes from
human chromosomes and inserting them into
bacteria. The human growth hormone can be
produced using this technology. Normally produced
in the pituitary , hGh promotes growth of bone and
muscle. Lower than normal concentrations cause
dewarfism.
Hormones that affect Blood Sugar
y Specific cells in Pancreas and adrenal glands.
y Pancreas produce two types of cells 1) digestive enzymes
2) hormones
y The hormone producing cells are in structures called isletsof
langerhans (named after discoverer) More that 200 000 tiny islets
each containing thousands of cells are scattered throughout the
pancreas. They are responsible for producing two hormones called
insulin and glucagon. Insulin – produced in the beta cells of the
islets and is released when blood sugar level increases (decreases
sugar level). Insulin causes cells to become permeable to glucose. In
the liver glucose is converted to glucagon,(storage for glucose
increases sugar level) This enables blood sugar level to return to
normal.
Insulin Release
Diabetes
y A chronic disease with no cure that affects two million Canadians.
Cause by and insufficient production or use of insulin.
y Left untreated can cause: Bindness, Kidney failure, nerve damage,
nontramatic limb amputation.
y Without insulin blood sugar levels rise sharply after a meal.
(Hyperglycemia)
y The kidneys are unable to reabsorb all blood glucose that is filtered
through them.
y Glucose appears in urine.
y People with diabetes pee a lot.
y They feel tired. (little sugar able to move into cells)
Insulin Injections
Types of Diabetes
y
Many types of diabetes mellitus:
y
type 1 (juvenile onset, pancreas unable to produce insulin
because of degeneration of the beta cells, must take insulin
to live, 10% have type 1)
y
type 2 (adult onset, decrease in insulin production, can be
controlled with diet and exercise, 90%)
y
type 3 (gestational, is temporary that occurs in 2% of
pregnancy, increased type 2 in mother and child later)
Islet Cell Transplants
y Type 1 second leading cause of blindness in
Canada.
y Islet transplants hold the potential to reverse the
effects of diabetes.
y One barrier is immune rejection.
y Researchers around the world are searching for
answers.
Homework
y Questions 1-3 page 479
y What is hyperglycemia?
Adrenal Glands
y Located above each kidney.
y Each gland is made up of two glands enclosed in a
shell.
y The inner gland, the adrenal medulla is
surrounded by an outer casing called the adrenal
cortex.
y The medulla is regulated by the nervous system,
while hormones regulate the adrenal cortex.
y Adrenal medulla produces two hormones:
epinephrine (adrenaline) norepinephrine
(nonadrenaline). Stimulated during times of
stress and both are released into the blood. Heart
rate increases, breathing, blood sugar rises. Blood
cells dialate. This allows more oxygen and nutrients
to reach cells
y
Adrenal cortex produces three types of hormones:
glucocorticoids, mineralocorticoids, and small
amounts of sex hormones. The gluco, are associated
with blood glucose levels. One of the most important are
cortisol, increases the level of amino acids in the blood in
attempt to help the body recover from stress. Increases
levels of glucose in cells.
y
Alderstone is the most important of the mineralocorticoids.
Increases sodium retention and water reabsorption by the
kidney and thereby helping maintaining body fluid levels.
Growth Hormone
y
The effects of the growth hormone, or somatotropin, are
most evident when the body produces too much or too little
of it.
y
Low secretion of growth hormone during childhood can
result in dwarfism.
y
High secretions during childhood can result in gigantism.
y
Although the growth hormone affects most cells of the
body, it affects cartilage cells and bones the most.
Dwarfism and Gigantism
Homework
y Lab 15A
y Page 341 Questions 7-13
y Review and Draw a diagram of Figure 5 page 482.
y Questions 4-6 page 483
Adrenal Glands
y Located above each kidney.
y Each gland is made up of two glands enclosed in a
shell.
y The inner gland, the adrenal medulla is
surrounded by an outer casing called the adrenal
cortex.
y The medulla is regulated by the nervous system,
while hormones regulate the adrenal cortex.
y
Adrenal medulla produces two hormones: epinephrine
(adrenaline) norepinephrine (nonadrenaline).
Stimulated during times of stress and both are released
into the blood. Heart rate increases, breathing, blood
sugar rises. Blood cells dialate. This allows more oxygen
and nutrients to reach cells
y
Adrenal cortex produces three types of hormones:
glucocorticoids, mineralocorticoids, and small
amounts of sex hormones. The gluco, are associated
with blood glucose levels. One of the most important are
cortisol, increases the level of amino acids in the blood
in attempt to help the body recover from stress. Increases
levels of glucose in cells.
y
Alderstone is the most important of the
mineralocorticoids. Increases sodium retention ans water
reabsorption by the kidney and thereby helping
maintaining body fluid levels
Summary
Review questions 1-7 page 484.
Thyroid Gland
y
Have you ever wondered why some people can eat lots
with our gaining any weight? While others gain weight at
the sight of food?
y
60% of glucose oxidized in the body is released as heat.
The remaining 40% is transferred into ATP. Storage form
of cell energy. This energy storage is often consumed
during activity. Those who secrete higher levels of thyroid
hormones oxidize sugars and other nutrients faster.
y
Individuals with lower levels do not oxidize nutrient
quickly. Excess blood sugar is eventually converted into
liver and muscle glycogen. Once glycogen stores are
filled, excess sugar is converted into fat.
y Thyroid gland is located at the base of the neck,
immediately in front of the trachea or windpipe.
y The gland produces two hormones: 1) thyroxin
(T4) and Triiodthyronine (T3) that regulate the
body metabolism and growth of tissues. Although
bith appear to have the same function 65% of
thyroid secretions are thyroxin. Inaddition, the
thyroid gland produces calcitonin, a hormone that
acts on the bone cells to lower the level of calcium
found in the blood.
y
Control of thyroid hormones is accomplishes through
negative feedback. Should metabolic rate decrease,
receptors in the hypothalamus are activated. Nerve cells
secrete thyroid releasing hormone (TRH) which stimulates
the pituitary to release thyroid stimulating hormone (TSH)
The thyroid hormone is carried by the blood to the thyroid
gland which then releases T3 and T4. They raise
metabolism by stimulating increased use of sugar by body
cells.
y
Iodine is an important component of both thyroid
hormones. Problem arise when iodine levels fall. The
thyroid enlarges producing a goiter.
Thyroid Gland
Goiter
Parathyroid glands
y Four small glands are hidden in the thyroid gland.
y Respond directly to chemical changes. They keep
calcium level in homeostasis.
y Low levels of calcium stimulate the release of PTH
Homework
y Page 346 Questions 14-18
y Questions 1-2 page 486
y Review figure 4 page 487
y Review Questions 1-10 page 489
Hormones Affecting Water and Ion
Balance
y The body adjusts for increased water intake by
increasing urine output.
y These adjustments involve the nervous system and
two different hormones of the endocrine system
antidiuretic (ADH) and aldosterone.
ADH and water balance
y Main function of ADH is to conserve body water by
reducing urine output
y How does the body know when to conserve water?
There are sensory receptors in the hypothalamus
called osmoreceptors, which detect changes in
osmotic pressure in the bodies fluids.
y When you decrease water intake or increase water
loss (sweating) blood solutes become more
concentrated.
y This increases bloods osmotic pressure
y When this happens, the osmoreceptors stimulates
the posterior pituitary gland to release ADH, which
is carried by the blood stream to the kidneys.
y ADH causes the kidneys to reabsorb more water
y Figure 1 page 490
ADH and the Nephron
y 85% of water filtered through the nephron is
reabsorbed in the proximal tubule
y The remaining 15% of the water is filtered in to the
nephron will be lost if no ADH is present
y ADH makes the upper tubule permeable to water
Alderstone, Blood Pressure and Blood
Volume
y
Increased fluid loss can mean decreased blood pressure,
reducing delivery of oxygen to tissues.
y
Near the glomerlus is a complex of cell called
juxtaglomerular apparatus (JGA).
y
Blood pressure receptors in the apparatus detect changes in
blood pressure.
y
When blood pressure is low, specialized cell within the
structure release renin, an enzyme that converts
angiotensinogen, a plasma protein produced by liver into
angiotensin.
Diabetes Insipidus
y Most common disease associated with ADH.
y Production of excessive amounts of urine (as much
as 16L a day)
y Caused by the failure of the posterior pituitary to
secrete enough ADH or by failure of the kidney to
respond to ADH.
y Not life threatening as long as the person has
enough water.
y Angiotensin has two functions: causes constrition
of blood vessels, so blood pressure increases.
y Stimulates the release of the hormone aldosterone
from the adrenal cortex. Where it is carried to
kidneys where it acts on the cells of the distal
tubule and collecting duct to increase Na
reabsorption.
y Figure 2 page 492
y Questions 1-7 page 493
Adjustments to Stress
y When stress occurs both the nervous and
endocrine systems make adjustments.
y Nervous system increases heart rate and diverting
blood to muscles.
y Table 1 page 494
y Stress hormones provide more glucose to increase
energy
Protaglandins
y local responses to changes in the immediate
environment of cells are detected by mediator cells.
More than 16 types. Generally secreted in low
concentrations
Questions 1-10 page 497
Review question page 501 - 505