Download Chapter 15

Chapter 15
Hormones
Objectives

Students should be able to:
– Define a hormone as a chemical substance,
produced by a gland, carried by the blood,
which alters the activity of one or more specific
target organs and is then destroyed by the
liver
– Explain what is meant by a endocrine gland,
with reference to the islets of Langerhans in
the pancreas
State the role of the hormone adrenaline in
boosting blood glucose levels and give
examples of situations in which this may
occur
 Explain how the glucose concentration is
regulated by insulin and glucagon as a
homeostatic mechanism
 Describe the signs such as an increased
blood glucose level and glucose in urine,
and the treatment of diabetes mellitus using
insulin

Living with stress
Butterflies in your stomach?
 Increase in pulse rate?
 Sweaty hands which feel cold and clammy?

– Why?
– Because we are nervous and our body is
preparing for action
Such symptoms are induced by the
hormone ADRENALINE
 Adrenaline:

– Increases the heart rate
– Increases the rate of breathing
– Causes vasoconstriction of the blood vessels
around the intestine (why?)
– Raises the metabolic rate?
– Dilates the pupils
15.1 Hormones

A hormone is a chemical substance
produced in minute quantities by an
endocrine gland. It is transported in the
bloodstream to target organ(s) where it
exerts its effects
Hormones influence the growth,
development and activity of an organism
 Some hormones also exercise control over
other glands or muscles

Where are hormones produced?

Hormones are produced by glands

Hormones are produced by ductless
glands. This means that the hormones
which the glands produce passes directly
into the bloodstream which then distributes
the hormones round the body

Some glands are purely endocrine glands
producing only hormones (e.g. adrenal
gland produces only adrenaline)

There are glands that produce both
hormones and other secretions. Can you
think of one?

Hormones production must be balanced to
ensure that body functions normally
 After hormones have performed their
functions, they are eventually destroyed by
the liver and excreted by the kidneys

Chapter 15 Hormones
Glands and Their Hormonal Secretions
24 May 2017
Glands and Their Hormonal Secretions
Hypothalamus
An endocrine gland that
regulates the secretion of some
pituitary hormones.
Glands and Their Hormonal Secretions
Hypothalamus
Pituitary gland
Plays an important
role as a ‘controller’. It
secretes a number of
hormones, which
control the functions
of several other
endocrine glands.
This is why the
pituitary gland is often
referred to as the
‘master gland’. The
pituitary gland also
secretes antidiuretic
hormone (ADH).
An endocrine gland that
regulates the secretion
of some pituitary
hormones.
Glands and Their Hormonal Secretions
Pituitary gland
Plays an important role as a
‘controller’. It secretes a
number of hormones,
which control the functions
of several other endocrine
glands. This is why the
pituitary gland is often
referred to as the ‘master
gland’. The pituitary gland
also secretes antidiuretic
hormone (ADH).
Hypothalamus
An endocrine gland that
regulates the secretion of some
pituitary hormones.
Thyroid gland
Secretes thyroxine.
Thyroxine controls the
rate of metabolism and
influences physical
development.
Glands and Their Hormonal Secretions
Pituitary gland
Plays an important role as a
‘controller’. It secretes a
number of hormones,
which control the functions
of several other endocrine
glands. This is why the
pituitary gland is often
referred to as the ‘master
gland’. The pituitary gland
also secretes antidiuretic
hormone (ADH).
kidney
Hypothalamus
An endocrine gland that
regulates the secretion of some
pituitary hormones.
Thyroid gland
Secretes thyroxine. Thyroxine
controls the rate of metabolism
and influences physical
development.
Adrenal gland (medulla)
Secretes adrenaline.
Adrenaline has wideranging effects that
prepare the body for
‘fight or flight’ situations.
Glands and Their Hormonal Secretions
Pituitary gland
Plays an important role as a
‘controller’. It secretes a
number of hormones,
which control the functions
of several other endocrine
glands. This is why the
pituitary gland is often
referred to as the ‘master
gland’. The pituitary gland
also secretes antidiuretic
hormone (ADH).
kidney
Hypothalamus
An endocrine gland that
regulates the secretion of some
pituitary hormones.
Thyroid gland
Secretes thyroxine. Thyroxine
controls the rate of metabolism
and influences physical
development.
Adrenal gland (medulla)
Secretes adrenaline. Adrenaline
has wide-ranging effects that
prepare the body for ‘fight or
flight’ situations.
Pancreas
Islets of Langerhans in
the pancreas secrete
insulin and glucagon that
regulate the blood
glucose concentration.
Glands and Their Hormonal Secretions
Pituitary gland
Plays an important role as a
‘controller’. It secretes a
number of hormones,
which control the functions
of several other endocrine
glands. This is why the
pituitary gland is often
referred to as the ‘master
gland’. The pituitary gland
also secretes antidiuretic
hormone (ADH).
kidney
Ovaries (in females)
Secretes oestrogen
and progesterone.
Hypothalamus
An endocrine gland that
regulates the secretion of some
pituitary hormones.
Thyroid gland
Secretes thyroxine. Thyroxine
controls the rate of metabolism
and influences physical
development.
Adrenal gland (medulla)
Secretes adrenaline. Adrenaline
has wide-ranging effects that
prepare the body for ‘fight or
flight’ situations.
Pancreas
Islets of Langerhans in the
pancreas secrete insulin and
glucagon that regulate the
blood glucose concentration.
Glands and Their Hormonal Secretions
Pituitary gland
Plays an important role as a
‘controller’. It secretes a
number of hormones,
which control the functions
of several other endocrine
glands. This is why the
pituitary gland is often
referred to as the ‘master
gland’. The pituitary gland
also secretes antidiuretic
hormone (ADH).
kidney
Ovaries (in females)
Secretes oestrogen and
progesterone.
Testes (in males)
Secretes testosterone.
Hypothalamus
An endocrine gland that
regulates the secretion of some
pituitary hormones.
Thyroid gland
Secretes thyroxine. Thyroxine
controls the rate of metabolism
and influences physical
development.
Adrenal gland (medulla)
Secretes adrenaline. Adrenaline
has wide-ranging effects that
prepare the body for ‘fight or
flight’ situations.
Pancreas
Islets of Langerhans in the
pancreas secrete insulin and
glucagon that regulate the
blood glucose concentration.
Chapter 15 Hormones
How Adrenal Medulla Responds to Stimuli
24 May 2017
How Adrenal Medulla Responds to Stimuli
1
Stimuli
Fear,
anger,
anxiety,
stress, etc
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24 May 2017
20
How Adrenal Medulla Responds to Stimuli
2
1
Stimuli
Receptor
Hypothalamus stimulated
Fear,
anger,
anxiety,
stress, etc
Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
24 May 2017
21
How Adrenal Medulla Responds to Stimuli
2
1
Stimuli
Receptor
Hypothalamus stimulated
Fear,
anger,
anxiety,
stress, etc
Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
3
sensory
neurone
Certain sensory
neurones in the
hypothalamus
are activated
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22
How Adrenal Medulla Responds to Stimuli
2
1
3
Receptor
Hypothalamus stimulated
Stimuli
sensory
neurone
4
Fear,
anger,
anxiety,
stress, etc
Nerve impulses
are transmitted
to the spinal
cord
spinal cord
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24 May 2017
23
How Adrenal Medulla Responds to Stimuli
2
1
Stimuli
Fear,
anger,
anxiety,
stress, etc
3
Receptor
Hypothalamus stimulated
sensory
neurone
4
5
Nerve
spinal cord impulses leave
the spinal cord
to adrenal
medulla
Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
adrenal
medulla
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24
How Adrenal Medulla Responds to Stimuli
2
1
Stimuli
3
Receptor
Hypothalamus stimulated
sensory
neurone
4
Fear,
anger,
anxiety,
stress, etc
5
spinal cord
Adrenal medulla is
stimulate, producing
adrenaline.
6
adrenal
medulla
Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
24 May 2017
25
How Adrenal Medulla Responds to Stimuli
2
1
3
Receptor
Hypothalamus stimulated
Stimuli
sensory
neurone
4
Fear,
anger,
anxiety,
stress, etc
5
6
spinal cord
adrenal
medulla
Adrenaline is
carried in
blood
Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
7
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26
How Adrenal Medulla Responds to Stimuli
2
1
Stimuli
3
Receptor
Hypothalamus stimulated
sensory
neurone
4
Fear,
anger,
anxiety,
stress, etc
5
6
spinal cord
adrenal
medulla
8 Adrenaline reaches target organs
in various parts of the body. It
brings about short-term
responses that prepare the body
for ‘fight or flight’.
Adrenaline is
carried in
blood
Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
7
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27
Effects of adrenaline secretion
Increases blood glucose levels by speeding
up the breakdown of glycogen to glucose in
the liver and muscles
 Increases metabolic rate (more energy
released)
 Increases rate of heartbeat
 Constricts arteries in skin
 Causes pupils to dilate to enhance vision
 Contracts hair muscles producing ‘goose
pimples’

Effects of Insulin
Secreted by Islets of Langerhans in pancreas
 Secretion caused by an increase in
concentration of blood glucose above the
normal level


Effect(s):
– Decrease in blood glucose concentration by:



Increasing the permeability of cell membranes to
glucose thereby increasing the rate of glucose uptake
by cells
Causing the conversion of glucose to glycogen for
storage in liver and muscles
Causing an increased oxidation of glucose during
tissue respiration
– This leads to an overall increase in the
utilization of glucose by cells

Lack of secretion:
– Glucose cannot be utilized by cells, some lost in
urine => diabetes mellitus
– Muscle cells no reserves of glycogen, body
weakness flows and then loss of weight
– Body oxidizes fats instead of glucose to
produce energy resulting in poisonous
substances formed

Effects of Oversecretion
– Abnormal decrease in blood sugar
concentration
– Shock HAPPENS
– Coma and death may follow
Diabetes mellitus
A disease where the body is unable to
control its blood glucose concentration so
that it remains within normal limits.
 Kidneys unable to reabsorb all the glucose,
hence some gets excreted in the urine

2 Types of diabetes:

Type 1:
– Juvenile diabetes. Inability of the pancreas to
produce insulin

Type 2:
– Occurs later in life. Overweight people seem
more prone to it. May be due to a decrease in
the production of insulin by the pancreas or a
failure of the target cells to respond well to it.

Signs
– Persistently high blood glucose level
– Glucose in urine after a meal
– Healing of wounds is slow or difficult

Treatment
– Measure blood glucose concentrations and test
urine regularly
– Watch their diet, take less carbohydrates
– Inject insulin into veins (Type 1)
– Control intake of carbohydrate (Type 2)
Glucagon
Produced by islets of Langerhans when the
concentration of blood glucose decreases
below the normal levels
 Target organ of glucagon is Liver
 Glucagon increases the blood glucose
concentration by stimulating:

– The conversion of glycogen into glucose
– The conversion of fats and amino acids into
glucose
– The conversion of lactic acid into glucose
Hormonal & Nervous Control
Both serve as a means of co-ordination
within the body
 There are differences between the 2 systems
though:
