PART 1 TOPIC 8 INTRODUCTION TO HORMONES.pptx

1. TOPIC 8 INTRODUCTION TO
HORMONES
BIOCHEMISTRY
AF 1032

2. LEARNING
OUTCOMES
At the end of this lecture, students will be able to:
 State the definition and characteristics of hormones.
 Explain intracellular and cell membrane hormone
receptor
 Discuss the role of feedback loops and humoral,
hormonal and neural stimuli in hormone control.
 Identify different types of hormones and its functions

3. WHATISA
HORMONE?
 Definition: hormones are
chemical that act as
messengers that
coordinate different
functions in the body.
 Hormones are generally
made up of amino acids,
proteins, fatty acids or can
be classified as steroids.

5. CHARACTERISTICS
OFHORMONES
 They act on target organs that may be distally located
 Hormones show high degree of specificity
 They are secreted in response to specific stimuli
 They are non-antigenic
 Most of the hormones have low molecular weight and
therefore they can easily pass out through blood
capillaries
 They act in very low concentration but their effect is long
lasting
 Once their function is over, hormones are readily
destroyed by enzymatic action or are inactivated or
excreted.
 Hormones are not species-specific because hormones
extracted form animals are found to be effective in man.

6. CELL
SIGNALING
 The effects of hormones depends on how
they are released.
 Signalling effects can be classified into
the following:
 Autocrine: hormone act on cell that secreted
it
 Paracrine: hormone act on nearby cell
without having to enter the blood circulation
 Intracrine: hormone is produced in the cell
and acts intracellularly means inside the cell.
 Endocrine: hormone act on target cells once it
is released from the perspective glands into
the bloodstream.

7. PATHWAYSOF
HORMONE
ACTION
 Hormones have defined molecular shape and
only bind specific receptor on their target cells.
 Cells are therefore only affected by a hormone
if they have right receptor for it. But an
individual cell may be a target for more than
one type of hormone
 When hormone bind to its receptor, this
triggers a chain of events that result in
changes in the cell.
 Mechanism of hormonal action is categorized
into two:
1. Intracellular hormone receptor
2. Cell membrane hormone receptors

8. 1. Intracellular
Hormone
Receptor
 Intracellular hormone receptor located inside the cell
 Steroid hormones and thyroid hormones are lipid soluble
are able to pass trough the lipid bilayer of cell membrane
 Steroid hormone: bind to receptors within cytosol or
within nucleus. Binding generates hormone-receptor
complex that moves towards the chromatin in cell
nucleus. Then bind to particular segment of cell’s DNA
 Thyroid hormone: bind to receptors already bound to
DNA.
 Binding of hormone-receptor complex with DNA triggers
transcription of target gene to mRNA for protein
synthesis.

9. Stepsfor
Intracellular
Hormone
Receptor

10. 2.CellMembrane
Hormone
Receptor
 Water soluble (hydrophilic) hormones unable to pass
through the cell membrane.
 They must pass their message to the receptor on the
extracellular surface of the cell membrane.
 Therefore, they initiate a signalling cascade to second
messenger for transcription of target genes to happen.
 In this case, hormone is the first messenger.
 Second messenger: cyclic adenosine monophosphate
(cAMP).

11. StepsforCell
Membrane
Hormone
Receptor

12. REGULATION
OFHORMONE
SECRETION
 There are two types of feedback loops for hormone
regulations: positive feedback and negative feedback
Positive feedback:
Characterized by release of additional hormone in
response to an original hormone release.
Example: Oxytocin
1. Oxytocin initially release to signal uterine muscles to
contract, which pushes the fetus toward the cervix,
causing it to stretch.
2. This, in turns, signal pituitary gland to release more
oxytocin, causing labour contraction to intensify
3. The release of oxytocin decreases after the birth of the
child.

13. REGULATION
OFHORMONE
SECRETION
Negative Feedback
Characterized by inhibition of further secretion of a
hormone in response to adequate level of that hormone.
More common method of hormone regulation
Example: Glucocorticoid Hormones.
1. Adrenal gland release glucocorticoid hormone, as
directed by hypothalamus and pituitary gland.
2. Glucocorticoid concentration in blood rise,
hypothalamus and pituitary gland reduce their signal
to adrenal glands to prevent additional glucocorticoid
secretion.

15. ENDOCRINE
SYSTEM
 There are two major categories of glands in
the body - exocrine and endocrine.
 Exocrine Glands: have ducts that carry their
secretory product to a surface. These glands
include the sweat, sebaceous, and mammary
glands and, the glands that secrete digestive
enzymes.
 Endocrine Glands: The endocrine glands do not
have ducts to carry their product to a surface.
The secretory products of endocrine glands are
called hormones
 Pancreas can be both exocrine and endocrine
glands
 Exocrine function: produces enzymes that help
with digestion
 Endocrine function: sends out hormones

16. Major
Endocrine
Glands
1. Pituitary gland
2. Pineal gland
3. Thyroid
4. Thymus
5. Adrenal glands
6. Pancreas
7. Testes
8. Ovaries

17. ASSIGNMENT
Each topic must have:
 Hormone secreted and hormone function.
 Position/diagram of the glands.
 Categorize whether they are peptide hormones or
steroid hormone (water soluble or Lipid soluble)
Presentation will be on 20/9/2022