HUMAN

ENDOCRINE SYSTEM

BY:M.SAIDI

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TOPIC COVARAGE
 Introduction
 endocrine and an exocrine gland
hormones
 Negative feedback mechanism

 Introduction: Homeostasis
 Homeostasis through negative
feedback
 Thermoregulation

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 INTRODUCTION
Ø endocrine system is the collection
of glands that produce hormones that
regulate metabolism, growth and
development, tissue function, sexual
function, reproduction, sleep, and
mood, among other things.

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 ENDOCRINE GLANDS
 (Ductless)
 release chemical
(hormones) substances
directly into the
bloodstream or tissues of
the body.
 EXOCRINE GLANDS
 release chemical
substances through ducts
to outside the body or onto
another surface within the
body
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 HORMONES:
 These are organic compounds proteins
in nature that act as messengers
needed in small amounts in the body.

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 (hypophysis)

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 Pituitary gland):
Hypothalamus: Ø GH -Controls growth
ØADH-Controls the ØTSH -Stimulates thyroid gland to secrete
concentration of water in thyroxin
the blood Ø FSH – stimulates the development of the
follicle in the ovaries
Ø LH – stimulates ovulation, and
stimulates development of the corpus
Adrenal gland: luteum
Ø Adrenalin -Increases, Ø Prolactin – stimulates the mammary
heartbeat, blood pressure glands to secrete milk
,conversion from glycogen
to glucose, skeletal muscle Thyroid gland:
tone, rate and depth of ØThyroxin: Controls basic
breathing , diameter of metabolic rate
pupils etc
ØAldosterone -Regulates
salt concentration in the
blood Pancreas:
ØGlucagon -Stimulates
conversion of glycogen to
Ovary: glucose
ØOestrogen– stimulates Ø Insulin- Stimulates
puberty in females, conversion of glucose to
promotes thickening of glycogen.
the endometrium
Ø Progesterone – Testes:
promotes thickening of Ø Testosterone-Stimulates the
the endometrium, maturation of sperm cells
maintains pregnancy ThunderEDUC Ø Stimulates puberty in males
 Questions
 Study the diagram below and answer the
questions that follow.
 A hormone secreted by one of the glands
labelled A to D has the following effects:
 Heartbeat increases
 Vasoconstriction of blood vessels to the
gut
 Dilation of pupils
 2.2.1 Give the letter and name of the
gland that secretes the hormone which
brings about the changes listed above. (2)
 2.2.2 Explain the significance of each of
the following changes:
 (a) Heartbeat increases (2)
 (b) Pupils dilate (2)
 2.2.3 Explain the relationship between
gland A and the kidney on a hot day.
(6)

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 MEMORANDUM ThunderEDUC

 2.2.1 C  adrenal gland  (2)

 2.2.2 (a) More blood can be pumped to
organs that need it to supply oxygen and glucose 
(2)
 (b) More light can be directed to the retina 
for better vision  (2)
 2.2.3 On a hot day, the body will produce sweat
for thermoregulation 
 So water that would be lost in urine needs to be
conserved 
 Gland A (pituitary) releases ADH / vasopressin 
when the water level of the blood passing through
the hypothalamus is detected to be lower 
 ADH travels via the blood to its target organ, the
kidney 
 ADH causes the collecting ducts to become more
permeable to water 
 So more water is thus re-absorbed from the urine
 / less is lost in urine  (any 6) (6)
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 NEGATIVE FEEDBACK MECHANISM
 Is a mechanisms operate in the human body to
detect changes or imbalances in the internal
environment and to restore the balance.
 general sequence of events in a negative
feedback mechanism
 an imbalance is detected by the receptor
 a control centre is stimulated
 the control centre responds
 a message sent to target organ/s (effectors)
 the effectors responds it opposes (reverses) the
imbalance
 balance is restored ThunderEDUC
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 Negative feed back
mechanism

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THYROXIN

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  DISORDERS OF THYROID GLAND
Ø1. Hyperthyroidism
Ø(overactive thyroid) occurs when thyroid gland produces
too much of the hormone thyroxine.
Ø Hyperthyroidism can accelerate the body's metabolism,
causing weight loss and a rapid or irregular heartbeat
ØExamples include Goitre, is a swelling in the neck
resulting from an enlarged thyroid gland caused by iodine
deficiency
Ø2. 1. Hypothyroidism
ØOccurs thyroid gland can't make enough thyroid
hormone to keep the body running normally eg
Myxoedema

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