The Endocrine
System
CHAPTER 6
Learning Targets
At the end of this chapter, the students should be
able to:
● State the role or hormones in the body and
describe its effect in terms of maintaining the
balance in the body;
● Identify the glands of the endocrine system and
determine the hormones secretion to describe their
functions; and
● Cite diseases attributed to the overproduction and
less production of hormones in the human body.
6. 1
Secretion of
What are hormones?
hormones
● These are very potent substances which control activities in parts of
the body such as these chemical messengers influence growth,
development, and metabollic activities.
● Classified as proteins (react with receptor on the surface of the cell
which is relatively rapid) or steroids (react with receptor sites inside
a cell which is relatively slow.
Endocrine Glands
• There are eight (8) major glands in
the human body although these
glands are part of the same
system (Endocrine system) same
roles, similar mechanisms of
influence, and several significant
connections.
• It is composed of cells that
produce and secretes hormones
into the bloodstream, which
carries the secretions throughout
the body.
A particular hormone has distinct receptor sites in the
cells that respond to it. If the hormone binds to the
receptor location, it will affect that cell. Hormones, even
in very small amount, can have a significant impact on
metabolic processes. Therefore, to keep the body's
homeostasis, hormone secretion must be controlled
within very narrow limits. The endocrine system
communicates chemical information to itself in this way.
The target cell has
receptors that are unique to
a certain hormone, and
either a lipid-soluble
hormone (permeable to
plasma membrane) or a
water-soluble hormone
(binds to a cell-surface
receptor) will activate those
receptors.
• A particular gland is sensitive to
the concentration of a substance
that it regulates, and a negative
feedback mechanism regulates
the release of hormones to keep
the body's state of equilibrium.
• The gland that releases the
hormone will stop or slow down in
production when the target tissue
sends a chemical signal back to
Basic Pathway of Hormones. the gland if the target tissue
responds to its hormone.
• In the opposite direction, when
the hormone level falls, the tissue
signals the gland to begin
secreting the hormone. When the
blood hormone level is kept at the
appropriate level, the body's
equilibrium or homeostasis is
preserved.
Basic Pathway of Hormones.
Hormones are classified into two stimulus.
External stimuli Internal stimuli
● By way of nerves from the ● By way of nerves and
other sensory organs in other hormones from
your nervous system. inside the body.
The human brain….
● Reacts by way of secreting
hormones from neurons in
hypothalamus.
● Reacts by way of nerves from
hypothalamus and brainstem.
01 HYPOTHALAMUS 02 PINEAL GLAND
PITUITARY THYROID
03
GLAND
04 GLAND
6.2 The Glands
of Endocrine 05
PARATHYROID
06 OVARIES
GLAND
System
PANCREAS (ISLET
TESTES
07 08 OF LANGERHANS)
Hypothalamus Description: Hormones:
● Can be seen in cerebral ● thyrotropin-releasing
hemispheres, deep within hormone (TRH),
the brain. gonadotropin-releasing
● consists of several nuclei, hormone (GnRH), growth
which are clusters of hormone-releasing hormone
neurons with a variety of (GHRH), corticotropin-
functions, including releasing hormone (CRH),
hormone secretion. somatostatin, and dopamine.
Functions:
● regulates a variety of physiological functions, including thirst,
hunger, and food intake as well as the autonomic nervous
system, which is the portion of the peripheral nervous system
in charge of controlling organs and glands. It also controls
blood pressure, body temperature, breastfeeding, learning
and memory, sexual drive, and emotional expression.
Pituitary Gland
Description:
• also known as hypophysis
• about 1 cm in diameter surrounded
by bone
• consists of two regions: anterior lobe
(controlled by releasing hormones
from the hypothalamus) and posterior
lobe (controlled by nerve stimulation
• master gland that signals other
glands to release hormones when
needed
Pituitary Gland
Hormones:
• Follicle-Stimulating Hormone (FSH)
• Luteinizing Hormone (LH)
• Thyroid-Stimulating Hormone (TSH)
• Adrenocorticotrophic Hormone
(ACTH)
• Melanocyte- Stimulating Hormone
(MSH)
• Growth Hormone (GH)
• Antidiuretic Hormone (AH)
• Oxytocin
Pituitary Gland
Functions:
• Maturation of egg in the ovary and
release of sex hormones
• Maturation of egg and the corpus
luteum surrounding the egg which
affects female sex hormones and
menstrual cycle
• Release of thyroxine
Pituitary Gland
Functions:
• Causes the adrenal to release
cortisol
• Synthesis of skin pigments
• Stimulates growth during infancy
and puberty
• Signals the kidney to conserve
water
• Affects childbirth and lactation
(milk production)
Pineal gland
Description: Hormones:
● Also known as ● Melatonin
epiphysis cerebri
● Small cone-shaped
structure located in
the middle of the
brain
Functions:
● Regulates wake-sleep cycle of the body;
affects reproductive development
Thyroid gland
Description: Hormones:
● Vascular organ ● Thyroxine
located in the lower ● Triiodothyronine
front of the neck ● Calcitonin
Functions:
● Regulates metabolism
● Increases the metabolic rate
● Lowers the amount of calcium ions in the
blood
Parathyroid gland
Description:
● Small glands located in the neck
Hormones:
● Parathyroid hormone
● Glucocorticoids (Adrenal Cortex)
● Aldosterone or Mineralocorticoids
(Adrenal Cortex)
● Testosterone (Adrenal Cortex)
● Epinephrine (Adrenal Medulla)
Parathyroid gland
Description: Hormones:
● Small glands ● Parathyroid hormone
located in the neck ● Glucocorticoids (Adrenal
Cortex)
● Aldosterone or
Mineralocorticoids
Functions: (Adrenal Cortex)
● Regulates metabolism
● Increases the metabolic rate
● Lowers the amount of calcium ions in the
blood
Pancreas Description: Hormones:
(Islet of Langerhans) ● Small glands ● Parathyroid hormone
located in the neck ● Glucocorticoids (Adrenal
Cortex)
● Aldosterone or
Mineralocorticoids
(Adrenal Cortex)
Functions:
● Regulates metabolism
● Increases the metabolic rate
● Lowers the amount of calcium ions in the
blood
Pancreas
(Islet of Langerhans)
Description:
• Gland located near the
duodenum
Hormones:
• Insulin
• Glucagon
Pancreas
(Islet of Langerhans)
Functions:
• Lowers the blood sugar
level
• Increases the level of
glucose in blood
Ovaries Description: Hormones:
● Located in the ● Estrogen
abdominal cavity ● Progesterone
which is adjacent
to the uterus
Functions:
● Controls secondary sex characteristics in
female
● Prepares the uterus to receive a
fertilized egg
Testes Description: Hormones:
● Covered with a
● Testosterone
pouch of skin
known as scrotum.
Functions:
● Regulates secondary sex characteristics
in male; regulates production of sperm
cells.
Common diseases due to
overproduction or less
production of hormones.
If the hormones produced
aren’t enough, it can lead to
hypothyroidism or myxedema
Increased thyroid hormone
released can cause…
Long term increase of
hormones released by Adrenal
cortex might lead to..
Serious increase of sodium in
the kidney by hormones
released by Adrenal cortex can
cause….
Decreasing insulin secretion by
the pancreas might lead to…
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