endocrine gland ICSE biology std 10

1. What is a hormone ?
A hormone is any member of a class of
signaling molecules, produced by glands
in multicellular organisms, that are
transported by the circulatory system to
target distant organs to regulate
physiology and behavior

2.  Although both the endocrine system and the nervous
system are both regulatory, there are a few fundamental
differences. For one, the endocrine system uses chemical
signaling (hormones, produced by glands) while the
system uses electrical signaling (neural impulses). The signal
transmission of the nervous system is fast because neurons
are interconnected, but the functions are more short-lived.
Signal transmission in the endocrine system is slow, since
hormones must travel through the bloodstream, but the
responses tend to last longer.

3.  Neurons generally use
neurotransmitters or neuropeptides
at synaptic gaps,
(ii) Whereas hormones travel
through the blood to various
locations within the body.

4. Endocrine glands
 Endocrine glands are ductless glands of the endocrine system that secrete their
products, hormones, directly into the blood. The major glands of
the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries,
testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands.

5. Endocrine System
 The endocrine system includes the endocrine glands and their hormones
 The function of the endocrine system is to secrete hormones into the
bloodstream.
 Hormone: A Chemical messenger which targets a specific group of cells, in
order to cause that group of cells do some activity or stop doing an activity.

7. Endocrine hormones
 Produced by endocrine (“ductless”) glands and secreted into the
bloodstream.
 Endocrine hormones may affect a wide array of target cells to produce
multiple effects.
 Two types: peptides (small proteins) and steroids (lipids).

8. Hormones and Receptors

10.  Where it comes from: thyroid gland
 Where it acts: most cells of the body
 What it does: controls the rate of
metabolic processes (how energy is
used) in the body and influences physical
development
 People may not produce enough of this
hormone and get a condition known as
hypothyroidism. They can take thyroxine
to treat this condition.
Return to hormones slide

11. Hypothyroidism-goiter, cretinism ,
myxoedema

12. Hyperthyroidism-exophthalmic
goitre,calcitonin

14. Adrenal Gland:

16.  Where it comes from: Adrenal Gland
 Where it acts: heart, blood vessels, eyes
 What it does: stimulates heart rate,
increases blood pressure, dilates pupils
 Causes "Adrenaline Rush”
 A 'fight and flight' hormone.
 It is released in high stress conditions or in
excitement or fear.
 Loud noise, high temperature etc. may also
trigger its release since these are also high
stress situations.

17.  Where it comes from: outer part of
adrenal gland
 Where it acts: multiple tissues
 What it does: mental stimulation,
breaks down fat and protein to
glucose, anti-inflammation
 It is usually referred to as the "stress
hormone" as it is involved in
response to stress and anxiety.
Return to hormones slide

19. pancreas

20. islets
 Beta -insulin
 Alpha -glucagon
 Delta- somatostatin

21.  Where it comes from: Insulin is
produced in the pancreas
 Where it acts: liver, muscle, and fat
tissue
 What it does: Insulin causes cells to
take up glucose (sugar) from the
blood, storing it in the liver and
muscle, and stopping use of fat as
an energy source.
 Problems with insulin production or
use in the body can lead to
diabetes.
Return to hormones slide

22.  Where it comes from: ovary
 Where it acts: breast tissue, reproductive
structures in female
 What it does: stimulates development of
female sexual characteristics
 Estrogen levels may be related somehow
to migraine headaches in women.

23.  Where it comes from: testicles
 Where it acts: body-hair cells, muscle,
reproductive structures
 What it does: stimulates development of
male sexual characteristics
 Testosterone is a steroid and has been
administered to athletes in order to
improve performance. This is considered
to be a form of doping in most sports
and is a very dangerous practice.
 Females also produce small amounts of
testosterone in their ovaries that affect
muscle development and other body
functions.

24. • Where it comes from:
ovary (where an egg
was released)
• Where it acts: uterus
• What it does: controls
menstruation in
women and plays a
role in pregnancy.
• One of the
components of birth
control pills

25. Anterior pituitary
 The anterior lobe of your pituitary gland is made up of several different types of cells that produce and release different types of
hormones, including:
 Growth hormone. Growth hormone regulates growth and physical development. It can stimulate growth in almost all of your
tissues. Its primary targets are bones and muscles.
 Thyroid-stimulating hormone. This hormone activates your thyroid to release thyroid hormones. Your thyroid gland and the
hormones it produces are crucial for metabolism.
 Adrenocorticotropic hormone. This hormone stimulates your adrenal glands to produce cortisol and other hormones.
 Follicle-stimulating hormone. Follicle-stimulating hormone is involved with estrogen secretion and the growth of egg cells in
women. It’s also important for sperm cell production in men.
 Luteinizing hormone. Luteinizing hormone is involved in the production of estrogen in women and testosterone in men.
 Prolactin. Prolactin helps women who are breastfeeding produce milk.
 Endorphins. Endorphins have pain-relieving properties and are thought to be connected to the “pleasure centers” of the brain.
 Enkephalins. Enkephalins are closely related to endorphins and have similar pain-relieving effects.
 Beta-melanocyte-stimulating hormone. This hormone helps to stimulate increased pigmentation of your skin in response to
exposure to ultraviolet radiation.

26. Endocrine System Control
 Regulated by feedback mechanisms
 2 types of feedback mechanisms
1. positive feedback
2. negative feedback

27. Feedback Mechanisms
 Negative Feedback mechanisms:
 Act like a thermostat in a home
 As the temperature cools, the thermostat detects the change and triggers the furnace to turn on
and warm the house
 Once the temperature reaches its thermostat setting, the furnace turns off
 Example: Body sugar increases after a meal, so the pancreas secretes insulin, which tells the body’s cells to
take in glucose. Once blood sugar levels reach normal, the pancreas stops making insulin.
 Often used to maintain homeostasis

28. Negative Feedback
 Homeostasis is often maintained by two hormones who have antagonistic
effects
 Each hormone does the opposite of the other.
For example, if the blood pressure drops too low, the pituitary releases
ADH, which causes the kidneys to reabsorb more water. If it the blood
pressure increases too much, then the heart will release ANH, which will
cause the kidneys to reabsorb less water.

29. Positive Feedback Mechanisms
 Positive Feedback mechanisms control events that can be out
of control and do not require continuous adjustment
 Rarely used to maintain homeostasis
 Example of positive feedback found in childbirth
 Oxytocin stimulates and enhances labor contractions
 As labor continues, more oxytocin is produced
 Intensifies contractions until the baby is outside birth canal
 Oxytocin production stops and labor contractions stop