Download The Endocrine System - Valhalla High School

The Endocrine
System
Endocrine System
• A set of glands that produce
hormones-- chemical messengers
that circulate in the blood
Hormone
• Chemical messengers produced by
the endocrine glands and circulated
in the blood
• Similar to neurotransmitters in that
they are also messengers
• Slower communication system, but
with longer lasting effects
Endocrine System
Hypothalamus
• Brain region that controls the
pituitary gland
• Controls homeostasis – the
bodies ability to remain at a status
quo level
Pituitary Gland
• The endocrine system’s gland that controls the other
endocrine glands
• Called the “master gland”
• Located at the base of the brain and connects to the
hypothalamus
• Controls thirst by controlling the amount of water in
the body’s cells
• Controls female contractions, and tells the mammary
glands to produce milk for newborns
• May control grooming habits, companionship, and
sexual behavior
• Controls the flow of the human growth hormones –
dwarfism and gigantism
Thyroid Gland
• Endocrine gland that helps regulate the
energy level in the body
• Located in the neck
• Controls body temperature
• Controls metabolism – our body’s ability to
transform the food we eat into usable energy
Adrenal Gland
• Endocrine glands that help to arouse
the body in times of stress
• Located just above the kidneys
• Release epinephrine (adrenaline)
and norepinephrine (noradrenaline)
• Increase heart rate, blood pressure,
and blood sugar
Pancreatic Gland
• Regulates the level of blood sugar in
the blood by insulin
• Insulin is needed in the body to break
down sugars in the body
Sex Glands
• Ovaries (females) and testes (males) are
the glands that influence emotion and
physical development.
• Testosterone – primary male hormone
• Estrogen – primary female hormone
• Males and females have both estrogen
and testosterone in their systems.
Gonads (sex organs)
• Testicles – release androgens (male
hormones)
• Ovaries – release estrogens (female
hormones)
• The presence of these chemicals
influence male and female
reproductive characteristics.
Maintaining Homeostasis
• Homeostasis is the maintenance of a
stable internal state within an organism.
• Organisms detect changes in their
environment and respond to these
changes in a variety of ways.
• A feedback mechanism occurs when the
level of one substance influences the level
of another substance or activity of another
organ.
Feedback Mechanisms
Three parts of the mechanism
– Sensor – something that can detect a change
• Ex. Structures in the brain detect changes in CO2 levels
– Control Unit – something that knows what the correct
level should be
• Ex. Information in the brain is preset for the correct CO2 level
– Effector – something to take the instructions and
make changes
• Ex. Muscles in the chest used for breathing
Feedback Mechanisms
• Positive feedback - designed to accelerate or enhance
the output created by a stimulus that has already been
activated.
• Designed to push levels out of normal ranges.
• Example is the release of oxytocin to intensify the
contractions that take place during childbirth.
– The more oxytocin, the greater and more frequent the
contractions, which in turn produces more oxytocin
Feedback Mechanisms
• Negative feedback – process in which a stimulus produces a
response that opposes the original stimulus.
• Ex. Blood sugar regulation
– An increase in blood sugar level triggers the release of the hormone
insulin by the pancreas
– the hormone insulin lowers blood sugar level restoring the body to its
original blood glucose level in two major ways:
• it increases the ability of body cells to take in glucose from the blood
• it converts blood glucose to the compound glycogen -- this compound is
also called animal starch and is stored in our liver and muscles
– A decrease in blood sugar levels triggers the release of the hormone
glucagon by the pancreas
• It causes the liver to release glucose into the blood to regulate blood sugar
levels
Endocrine Disorders
Diabetes
• interruption of the feedback system that controls
blood sugar.
• Too little insulin = buildup of sugar in the blood
• the kidneys use a lot more water to flush it out of the
body.
• extra water comes from surrounding cells, which in
turn dehydrates them
– leaves the cells vulnerable to infection and poisons.
• Type I – born with it
– Controlled by insulin injections
• Type II – acquired
– Usually occurs in older people
– May be controlled with diet
Endocrine Disorders
– Hyperactive thyroid- Behaviors may include
excitability, insomnia, ADD, agitation, difficulty
focusing
– Hypoactive thyroid - Behaviors may include
sleepiness, reduced muscle tone, overweight
– Hypoglycemia - Too much insulin in the body
devours all of the sugar in the blood. May
appear sluggish and inattentive.