Transcript File - Science at St. Dominics

Responses in the Human –Endocrine
System
• -
 Define the term: hormone.
 Outline what the Endocrine System is
 Compare action, distinguishing between exocrine &
endocrine glands.
 Comparison endocrine action with nerve action
 Location of the main glands in the endocrine system
and know which hormones they release
Glands
Glands are parts of the body that secrete
substances.
• There are two types:
1. Exocrine glands
2. Endocrine glands
Exocrine glands
 Exocrine glands have ducts (tubes) to release their
products into e.g. salivary glands, tear glands, sweat
glands, mammary glands etc
Endocrine Glands
• The endocrine glands are ductless glands.
• They release their products (hormones)
straight into the tissue fluid, where they
pass into the blood.
Hormones
 Hormones are chemical ‘messengers’, produced
in specialised glands, and transported in the
blood to a particular area where they have their
specific effect.
 The endocrine glands interact with the
nervous system to provide the
communication, co-ordination and control
within the body.
 The action of hormones is slower and more general than
nerve action and they control mainly long-term changes
such as growth, metabolism and sexual maturity.
 On passing through the liver, the hormones are broken
down and excreted by the kidneys.
Endocrine
Cells where message
starts
Message
Carried by
Message sent from
Message received by
Transmission time
Effects
Duration
Nervous
Comparison of the endocrine and nervous systems - 1
Endocrine
Cells where
message starts
Gland
Message
Chemical
(Hormone)
Carried by
Blood
Message sent to
Cells throughout
the body
Received by
Target organ
Comparison of the endocrine and nervous systems - 1
Endocrine
Nervous
Cells where
message starts
Gland
Sense receptor
Message
Chemical
(Hormone)
Electrical(Impulse)
Carried by
Blood
Nerve cell
Message sent to
Cells throughout
the body
A specific cell or
tissue
Received by
Target organ
Effector (muscle or
gland)
Comparison of the endocrine and nervous systems -- 2
Endocrine
Speed of
transmission
Usually slow
Effects
Can be widespread
Duration
long-lasting
(hours)
Comparison of the endocrine and nervous systems -- 2
Endocrine
Nervous
Speed of
transmission
Usually slow
Rapid
Effects
Can be widespread Localised usually
Duration
long-lasting
(hours)
Usually brief
(seconds)
Which body system?
 Define the term: hormone.
 Outline what the Endocrine System is
 Compare action, distinguishing between exocrine &
endocrine glands.
 Tell the difference between nervous and endocrine
system
Today’s objectives
 State the location of the principal glands in the
human.
 Outline for each gland, one hormone & its function.
ENDOCRINE GLANDS
Hypothalamus
• It releases hormones to
control the pituitary gland
Example:
• Growth hormone releasing
factor – stimulates the
production of growth
hormone from the pituitary
gland.
 The pituitary is often called the ‘master gland’, as many of its
hormones trigger other glands to release theirs.
 Example of hormone released here:
Growth hormone – causes body to build proteins and so leads to
growth
Gigantism
Dwarfism
Thyroid gland
 The thyroid gland, in the neck,
produces thyroxine, which
controls the rate of reactions in
the body (our metabolism)
Parathyroid
 The parathyroid produces parathyroid
hormone, which increases blood calcium
levels.
The pancreas
 Is an endocrine and exocrine gland.
 The Islets of Langerhans is
the endocrine portion
 It produces the hormone
insulin, which stimulates cells
to absorb glucose from the
blood, and store it as
glycogen.
 The exocrine portion produces
enzymes for digestion.
Adrenal glands
 The adrenal gland produces adrenaline, which helps the body
cope with emergencies —the ‘flight or fight’ hormone.
The ovaries
 The ovary produces oestrogen to
prepare the female for pregnancy.
Testes
 The testes produce
testosterone which
triggers sperm
production and
secondary sexual
characterisitics in
the male.
Name that gland
Match hormones to glands
LEARNING CHECK
• Name the main endocrine glands in the
body.
• Name one hormone produced by each
gland.
• Give one function for each hormone.
• Why is the pituitary often called the “master
gland”?
• Where would you find the Islets of
Langerhans?
DISORDERS of the Endocrine System
Endocrine glands can sometimes malfunction
THYROID gland:
 Low levels of thyroxine reduce the rate of metabolism.
 Taking the hormone in tablet form once a day can solve the
problem – hormone supplement
 Excess thyroxine can greatly increase metabolic rate.
 Treatment is often by removal of part of the gland.
Cretinism
• Too little
thyroid
hormone
Graves disease – too much
thyroid hormone
Common hormone supplements examples
• In some people, the pancreas cannot
produce insulin, which results in
diabetes
• Regular daily injections of insulin are
required to treat diabetes– hormone
supplement.
Hormone supplements
 In oral contraceptives, oestrogen and progesterone are
taken to prevent ovulation and therefore pregnancy
HIGHER LEVEL ONLY
Feedback mechanism for
hormone control
• Often the level of a hormone in the blood
controls the production of another
Check your learning..
 Explain 1 Hormone giving a description of its
deficiency symptoms, excess symptoms & corrective
measures
 Name 2 examples of hormone supplements & their
use.
 Describe the feedback mechanism for a named
hormone