Sec 4 Hormones

1. CHAPTER 15
Hormones
In this chapter, you need to learn
•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 an
endocrine gland, with reference to
the islets of Langerhans in the
pancreas.

2. Lesson recap :
• Animal possess 2 coordinated systems to
response to external stimuli and internal changes.
Nervous SystemNervous System Endocrine (Hormone)
System
Endocrine (Hormone)
System

3. 2 Types of Glands
(a) Exocrine glands
(b) Endocrine glands.
• Both glands secrete chemical substances.
However the secretions of exocrine glands are
carried away in a duct.
(e.g sweat glands, salivary glands)
• Endocrine glands have no ducts. The
secretions are released directly into the
bloodstream & carried throughout the body.
15.1

4. Types of glands
• Ductless glands that
transport their secretions via
the bloodstream
• Examples: adrenal glands,
pituitary gland, and pancreas
• Ducts present to transport
secretions to target organs
• Examples: sweat glands,
salivary glands and
pancreas
Endocrine glands Exocrine glands
Two Types of glands

5. Glands and the hormones they secrete
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.
kidney
Hypothalamus
An endocrine gland that
regulates the secretion of
some pituitary hormones.
Ovaries (in females)
Secretes oestrogen and
progesterone.
Testes (in males)
Secretes testosterone.
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’.

6. What is a hormone?
• A hormone is a chemical substance that is
produced in minute quantities by an
endocrine gland.
• It is carried by the blood and it changes
the activity of one or more specific target
organs.
• A hormone is then destroyed by the liver.
15.1

7. Hormone Insulin & Glucagon
• Insulin and glucagon are hormones that regulate the
concentration of glucose in the blood.
• Both are produced by the islets of Langerhans in the
pancreas.
• Insulin is released when blood glucose conc. is high.
• It causes the liver to convert excess glucose to
glycogen, hence reducing the blood glucose
concentration.
• Glucagon is released when blood glucose conc. is low.
It causes the liver to breakdown glycogen to glucose
hence increasing the blood glucose conc.
15.2

8. Effects:
INSULIN
GLUCAGON
Effect:
15.2

9. Diabetes Mellitus
• There are two types of diabetes : Type 1 & Type 2
15.3

10. Diabetes Mellitus
• In both cases, body is unable to control blood
glucose concentration .
• As a result, blood glucose becomes too high for
kidney to completely reabsorb all the glucose.
• Glucose is not absorbed but excreted in urine.
• Diabetics are at risk developing infections at face
and feet, may affect eyes leading to blindness.
15.3

12. Animation: Release of insulin after meal

13. Diabetes Mellitus
Sign of diabetic patients:
• High concentration of glucose in
blood and urine.
• Body become weak because no
reserve of glycogen.
• Persistently high blood glucose level
• Healing of wounds is slow or
difficult
15.3

14. Treatment
• Diet
• Exercise
• Insulin injection
15.3

15. Effects of insulin secreted
Amount of
insulin
secreted
Effects on the body
Normal Decreases blood glucose concentration by :
(a)Increasing the permeability of cell
membranes to glucose, thereby increasing rate of
glucose uptake by cells.
(b)Stimulating the liver and muscle cells to
convert excess glucose into glycogen for storage.
(c)Increasing oxidation of glucose during tissue
respiration.

16. Effects of insulin secreted
Amount of
insulin
secreted
Effects on the body
Lack of
secretion
Glucose cannot be stored or utilized by cells, so
blood glucose concentration rises. Some glucose
is subsequently lost in the urine. This leads to a
disease known as ‘diabetes mellitus’.
Since muscle cells have no reserve of glycogen,
the body grows weak and continuously loses
weight.
The body oxidizes fats increase of glucose to
release energy.

17. Effects of insulin secreted
Amount of
insulin
secreted
Effects on the body
Over-secretion
of insulin
• Abnormal decrease in blood glucose
concentration.
• Low blood glucose concentration results in a
condition known as ‘shock’.
• Coma and death may follow.

18. A diabetic mum gave birth to the heaviest baby (8.7
kg) in world record in Indonesia.
According to the doctor,
the baby's extreme weight was the result of
excessive glucose from his mother during pregnancy.

20. 1. What is an effect of insulin?
A decreased cell respiration
B decreased absorption of glucose by cells
C increased absorption of glucose
D increased synthesis of glycogen
Answer : D

21. 2. The graphs show the concentrations of glucose and insulin in
the blood of a healthy person. Which graph shows the changes
expected after a meal containing starch?
Answer : A

22. 3. What of the effects below is not due to insulin
secretion on the body?
A. Conversion of glucose to glycogen for storage.
B.Oxidation of glucose during tissue respiration
increases.
C. Oxidation of fats to produce energy.
D. Permeability of cell membranes to glucose increases.
Answer : C

23. Assignment:
• Using your science knowledge, create a
comic strip to educate the public about
diabetes mellitus.

24. When will it be secreted?
15.4 Pure Biology
Hormone Adrenaline
• Adrenaline is released during
anxious, stressed, angry or
excited.
• Adrenaline reaches target
organs in various parts of the
body and prepares your body
for “fight and flight” or for
states of emergency.
URL
adrenal gland
kidney

26. 15.4 Pure Biology
Effects of Adrenaline
• Liver and muscle cells – increase blood glucose
levels by speeding up the breakdown of glycogen to
glucose. The glucose produced is carried by the
blood to all the vital organs, especially the heart and
skeletal muscles.
• Heart - it quickens the respiration of the heart cells.
This makes the heart beat faster and supplies the
extra strength that the muscles need.
• Pupil - to dilate to enhance vision.
Increases blood
glucose level
Increases blood
pressure and rate
of heart beat
Increases
dilation of pupil

27. Increases
metabolic rate
Constricts
arterioles in skin
Increases the rate of
blood coagulation
Contracts hair muscles,
producing ‘goose pimples’
Increases rate and
depth of ventilation
Other effects of adrenaline

28. Nervous
System
Nervous
System
Endocrine
System
Endocrine
System

29. Comparing
Hormonal & Nervous System
• Both required stimulus and serve as means
of coordination and response.
• What are the differences between how they
work in the aspects of:
a. Form of messages
b. Response time
c. Effectors
15.5

30. Hormone System Nervous System
Involves chemical
substances (hormones)
Involves electrical signals
(nerve impulses)
Hormones carried by
blood
Impulses carried by
neurones
Usually slow responses Fast responses
Responses can be short-
lived or long-lived
Responses are short-lived
Involuntary May be voluntary or
involuntary
Can affect more than one
organ.
Effects are usually localised
Differences
15.5