Biology 2
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Nervous system regulates many body
activities.
Endocrine system regulates life functions.
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The study of the endocrine system.
Changes effected by the endocrine system are
more gradual than the changes made by the
nervous system.
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Endocrine glands secrete chemicals directly
into the bloodstream.
Exocrine glands release the chemicals they
produce through a duct (Example: tear gland)
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Thyroid
Parathyroid
Adrenal
Pituitary
Thymus
Pancreas
Gonads
Pineal
Hypothalamus
These glands send out chemical messengers to all
parts of the body.
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Chemical messangers = hormones
Hormones travel through the blood; therefore,
travel much more slowly than nerve impulses,
but their effects are much longer.
Hormones influence the action of target cells.
Target cells contain receptors for specific
hormones.
Target cells are often located at a distance in
the body from the endocrine glands that
produce the hormones.
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Endocrine glands regulate themselves with a
type of feedback mechanism.
2 types:
Negative feedback
 Positive feedback
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If the end product stops the first stem, then it is
negative feedback.
The end product stops the production of a
particular hormone.
MOST ENDOCRINE GLANDS USE
NEGATIVE FEEDBACK!
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If the end product is needed in order for the
first step to begin, then it’s positive feedback.
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A two-lobed gland located in the neck.
It produces the hormone thyroxin.
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Helps regulate the body’s growth and
metabolism (the rate at which the body
oxidizes its food).
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When the thyroid gland produces too much
thyroxin leading to a condition.
People with this condition usually have high
blood pressure and an overactive metabolism.
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When the thyroid gland produces too little
thyroxin leading to a condition.
People with this condition tire easily and are
often overweight.
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When a baby has an underactive thyroid gland.
This condition stunts the growth and can cause
mental retardation.
This condition can be corrected if diagnosed
early.
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Causes problems with the thyroid gland.
The thyroid needs iodine to produce thyroxin
and without it abnormal growth of thyroid
tissue can occur producing an enlarged thyroid
called a goiter.
Goiters are rare today largely due to the
addition of iodine to table salt.
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There are 4 located in the back of the thyroid
gland.
Parathyroid glands secrete the parathyroid
hormone called parathormone.
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Parathormone helps control the levels of calcium in
the blood.
It is very important in the formation of bones and
controlling proper functioning of nerves and
muscles.
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Located at the top of each kidney.
Each adrenal gland has an inner layer
(medulla) and an outer layer (cortex).
Medulla - Produces the hormones adrenaline
and noradrenaline.
Cortex – Produces the hormones
corticosteroids & aldosterone
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Adrenaline
helps the body respond to stressful situations.
 Increases the level of blood sugar
 Increases the heart rate and blood pressure
 Enlarges blood vessels
 Increases the flow of blood to muscles that are
attached to skeleton.
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Noradrenaline
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Produces the same effects on the body as adrenaline
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Corticosteroids
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Also called corticoids
Influence the metabolism of carbohydrates, proteins,
& fats.
Aldosterone
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Helps control the balance of water and salts in the
body.
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Also called the “Master Gland” because it
controls the actions of many other endocrine
glands.
Small structure located at the base of the brain.
Divided into 2 lobes:
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Anterior (Front) Lobe
Posterior (Rear) Lobe
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Secretes 3 major hormones:
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GH (Growth Hormone) – stimulates growth of bones
in body.
LH (Luteinizing Hormone) – Causes secretions of
sex hormones by the testes & ovaries.
FSH (Follicle Stimulating Hormone) – Influences the
maturing of eggs and the production of sperm.
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Secretes 2 major hormones:
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Oxytocin – Begins uterine contractions in a woman
when her child is about to be born & controls the
production of milk after the child is born.
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Vasopressin - Regulates water absorption by the
kidneys.
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Located in the chest below Thyroid gland.
It is large in small children, but becomes
smaller in adults.
Produces the hormone Thymosin.
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Helps children develop their immune systems.
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Found in the abdomen near the stomach.
Produces digestive enzymes.
Contains area of cells called Islets of
Langerhans.
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Produce hormones that enter the bloodstream
directly: Insulin & Glucagon
Insulin – Decreases blood sugar level
Glucagon – Increases blood sugar level
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When a person lacks the correct amount of
insulin.
Condition where there is a high level of sugar
in the blood, and the cells of the body are being
denied the sugar they need to produce energy.
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When a person has too low a level of sugar in
the blood.
Caused when too much insulin is produced.
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Responsible for producing gametes &
hormones.
2 types of gametes:
Sperm (produced by testes in males)
 Eggs (produced by ovaries in females)
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Also produces hormones. 3 types:
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Testosterone - Male
Estrogens
Progesterone
Female
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Made in the testes located in the scrotal sac.
Produces male secondary sex characteristics:
Facial hair
 Broadening of the chest
 Deep voice
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Both are made in the ovaries located in the
female’s internal pelvic region.
Estrogen
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Regulate the development of the female secondary
sex characteristics.
Progesterone
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Helps control the female’s monthly reproduction
cycle.
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Located deep inside the brain.
Produces melatonin.
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Helps regulate the onset of puberty and sexual
maturity.