Download the endocrine system

THE ENDOCRINE SYSTEM
Mrs. Woytowich
Regents Biology
OBJECTIVES
Upon completion of this unit students will be able to:
1. Compare the operations of the nervous and endocrine systems.
2. Differentiate exocrine, endocrine glands and hormones.
3. Explain the regulation of hormone secretion through negative
feedback.
4. Identify the two basic mechanisms of hormone action and
describe each.
5. Name the major endocrine glands of the body.
6. List the endocrine hormones and describe their functions.
7. Identify disorders caused by hyper/hypo-secretion of specific
hormones.
KEY WORDS
1.
2.
3.
4.
5.
diabetes mellitus
glands
glucagons
hormones
hypersecretion
6.
7.
8.
9.
10.
hyposecretion
insulin
negative feedback
positive feedback
thyroxin
I. INTRODUCTION
• The endocrine system is the system which
PRODUCES HORMONES FROM GLANDS
TO REGULATE METABOLISM,
HOMEOSTASIS, GROWTH AND
REPRODUCTION
• Endocrine glands DISCHARGE
SECRETIONS DIRECTLY INTO THE
BLOODSTREAM (DUCTLESS GLANDS) and
exocrine glands DISCHARGE SECRETIONS
INTO DUCTS (e.g., DIGESTIVE GLANDS)
• Hormones are SECRETIONS THAT COME
FROM GLANDS
II. REPRESENTATIVE ORGANISMS
A. Protozoans
• Ameoba and paramecium have no endocrine system, but they do
RESPOND TO STIMULI FROM THE ENVIRONMENT
B. Hydra
• Also do not have an endocrine system, but do respond to stimuli in
the environment.
C. Earthworm
• Also do not have an endocrine system, but do respond to stimuli in
the environment.
D. Grasshopper
• Hormones regulate METAMORPHOSIS, color changes, and
molting. Some insects have no metamorphosis, some have
incomplete metamorphosis (egg larvae [nymph] adult), and
some have complete metamorphosis (egg larva pupa adult).
• Insects that undergo incomplete metamorphosis include
grasshoppers, bugs and mantids. Insects that do not undergo
metamorphosis include the SILVERFISH
E. Humans
• Hormones are transported by the BLOODSTREAM
to target
organs.
• The endocrine glands may undersecrete (HYPOSECRETION) or
oversecrete (HYPERSECRETION)
• There
are 2 ways in which
hormones
may have an effectMODEL
on an
ONE-MESSENGER
MODEL
TWO-MESSENGER
organ:
• (STEROID HORMONES)
• HORMONE PASSES
THROUGH CELL
MEMBRANE AND ENTERS
TARGET CELL TO COMBINE
WITH RECEPTOR PROTEIN
• ALTERS THE RATE OF
REACTION
• (PROTEIN HORMONES)
• HORMONE CANNOT PASS
THROUGH CELL
MEMBRANE AND
COMBINES WITH
RECEPTOR MOLECULE ON
MEMBRANE SURFACE
• THIS CAUSES THE
PRODUCTION OF ENZYMES
(2ND MESSENGER)
• The major endocrine glands are as follows:
1. Thyroid Gland
o Located in the NECK and secretes
THYROXIN, the hormone which regulates
metabolic rate. Thyroxin contains IODINE.
o Undersecretion of thyroxin during
childhood results in a condition called
CRETINISM. The cretin dwarf is not only
small but has reduced mental ability.
2. Pituitary Gland
• The major link between the endocrine system and
the NERVOUS SYSTEM
• Called the “MASTER GLAND” because it releases
a variety of HORMONES which affect other glands;
however, we now know that the secretions of other
glands also influence the pituitary, thus, maintaining
HOMEOSTASIS in the body by the NEGATIVE
FEEDBACK MECHANISM
Example: Thyroid stimulating hormone (TSH)
released from the PITUITARY GLAND stimulates the
thyroid gland to release THROXIN. The thyroxin level
in the blood increases and this affects the pituitary so
that it decreases the release of TSH.
o Many other hormones are also released by the
pituitary, and are often named by the gland or part of
the body which the hormone affects. For example,
follicle stimulating hormone (FSH), parathyroid
stimulating hormone, adrenalcorticotropic hormone
(ACTH), human growth hormone (HGH) etc.
o Giantism: HYPERSECRETION OF HGH; RESULTS
IN VERY TALL HUMAN
Dwarfism: HYPOSECRETION OF HGH; RESULTS IN
VERY SHORT HUMAN
o The HYPOTHALAMUS of the brain appears to
produce hormones which influence the pituitary gland.
3. Parathyroid Glands
o Four glands which are embedded in
the THYROID gland
o They secrete parathormone which
regulates the amount of the element
Ca++ in the blood. It, therefore, affects
nerve transmission, bone and teeth
formation, and muscle contraction.
4. Islets of Langerhans (in the Pancreas)
o The Islets of Langerhans are groups of cells
embedded in the PANCREAS and secrete the
hormones INSULIN and GLUCAGON
o Insulin helps sugar get INTO the body cells as
well as stimulating the conversion of excess
sugars into animal starch called GLYCOGEN
o Glycogen is stored in the muscles and LIVER
o GLUCAGON acts antagonistically to insulin in
that it RAISES BLOOD GLUCOSE LEVEL
5. Adrenal Glands
o Located at the top of each KIDNEY
o Each has an outer region called the CORTEX (for
long-term stress) and the MEDULLA (for sudden
stress).
o The cortex releases STEROID hormones which
influence the conversion of fat and protein to glucose
as well as regulating water balance and salts in the
blood.
oThe medulla releases the hormone ADRENALINE
during times of emergency. This hormone stimulates
the release of glucose into the blood and faster
breathing rate and heartbeat. It is often referred to as
the “FIGHT OR FLIGHT“ hormone.
6. Thymus Gland
oReleases THYMOSIN which is thought to stimulate
development of T-LYMPHOCYTES during childhood.
T-lymphocytes are important in immunity.
7. Gonads (ORGANS)
o In addition to producing GAMETES, these organs also
release hormones which influence the development of the male
and female secondary sexual characteristics.
o At puberty, in the male, release of TESTOSTERONE
promotes development of a deeper VOICE, greater growth of
body hair, and muscle development.
o For the female, ESTROGEN is the main hormone. The
menstrual cycle begins at PUBERTY and the female is now
releasing EGGS and therefore capable of becoming pregnant.
Breast development and rounding out of the female contours
(shape) takes place.
8. Stomach and Small Intestine
(ORGANS)
o These organs also release hormones
which cause them to release digestive
juices.
oThe stomach releases GASTRIN which
stimulates the release of juices from the
walls of the STOMACH, and the small
intestine releases several hormones, one
of which is SECRETIN which stimulates
the flow of PANCREATRIC JUICE
GLAND
PITUITARY
THYROID
HORMONE
·
·
·
·
·
·
·
·
TSH
ACTH
HGH
FSH
LH
PROLACTIN
OXYTOCIN
VASOPRESSIN
PANCREAS
(ISLETS OF
LANGERHANS)
GONADS
THYMUS
THYROID STIMULATING HORMONE
ADRENAL STIMULATING HORMONE
STIMULATES GROWTH IN BONES
FOLLICLE STIMULATING HORMONE
LUTEINIZING HORMONE
SECRETION OF BREAST MILK
UTERINE CONTRACTION DURING LABOR
ANTIDIURETIC
 THYROXIN
· REGULATES RATE OF
METABOLISM
· PARATHORMONE
· REGULATES CALCIUM AND
PHOSPHATE METABOLISM
· ADRENALINE
FIGHT OR FLIGHT
AFFECT METABOLISM OF CARBS,
PROTEINS AND FATS
PUTS GLUCOSE IN CELLS
PUTS GLUCOSE IN BLOOD
PARATHYROID
ADRENAL
FUNCTIONS
·
·
·
·
·
·
·
·
·
CORTICOSTERIODS
·
·
·
·
INSULIN
GLUCAGON
·
·
·
·
·
ESTROGEN
PROGESTERONE
TESTSOSTERONE
· THYMOSIN
·
·
·
SECONDARY SEX CHARACTERISTICS; EGGS
MENSTRUATION
SECONDARY SEX CHARACTERISTICS AND
SPERM PRODUCTION
· DEVELOPMENT OF TLYMPHOCYTES