chapter 18
Post on 26-May-2015
242 Views
Preview:
TRANSCRIPT
Copyright © John Wiley & Sons, Inc. All rights reserved.
CHAPTER 18The Endocrine System
Copyright © John Wiley & Sons, Inc. All rights reserved.
INTRODUCTION The nervous and endocrine systems
coordinate all of the body systems
The nervous system does so through the
action of neurons, and the
neurotransmitters they secrete
The endocrine
system uses
hormones produced
by endocrine structures
to produce their
effects
Copyright © John Wiley & Sons, Inc. All rights reserved.
Hormones are simply mediator
molecules that have effects on cells in the
local environment, or in a distant part of the
body
Some hormones, called autocrine
hormones are local hormones that are
secreted, and bind to the same cell.
TYPES OF HORMONES
Copyright © John Wiley & Sons, Inc. All rights reserved.
TYPES OF HORMONES Hormones as mediator molecules …
Paracrine hormones are local hormones
that are secreted into interstitial fluid and
act on nearby cells
Copyright © John Wiley & Sons, Inc. All rights reserved.
Hormones as mediator molecules …
Endocrine hormones are secreted into
interstitial fluid and then absorbed into the
bloodstream to be carried systemically
to any cell that
displays the
appropriate type
of receptor
TYPES OF HORMONES
Copyright © John Wiley & Sons, Inc. All rights reserved.
SOLUBILITY OF HORMONES Hormones can be divided into two broad
chemical classes. This chemical
classification is useful because the two
classes exert their effects differently
Lipid soluble hormones bind to receptors
in the cytoplasm or nucleus of the cell
Water soluble hormones bind to
receptors on the surface of the cell
Copyright © John Wiley & Sons, Inc. All rights reserved.
SOLUBILITY OF HORMONES Lipid soluble hormones consist of steroid
hormones, thyroid hormones, and the gas
nitric oxide
Steroid hormones are derived from
cholesterol
Thyroid hormones (T3 and T4) are
synthesized by attaching iodine to the
amino acid tyrosine
The gas nitric oxide (NO) is both a hormone
and a neurotransmitter. Its synthesis is
catalyzed by the enzyme nitric oxide
synthase
Copyright © John Wiley & Sons, Inc. All rights reserved.
SOLUBILITY OF HORMONES Lipid soluble hormones require a carrier
protein for transport in the watery
environment of the blood
Copyright © John Wiley & Sons, Inc. All rights reserved.
1 Lipid-solublehormonediffuses into cell
Blood capillary
Target cell
Transportprotein
Free hormone
1 Lipid-solublehormonediffuses into cell
Blood capillary
Activatedreceptor-hormonecomplex altersgene expression
NucleusReceptor
mRNA
DNA
Cytosol
Target cell
Transportprotein
Free hormone
2
1 Lipid-solublehormonediffuses into cell
Blood capillary
Activatedreceptor-hormonecomplex altersgene expression
NucleusReceptor
mRNANewly formedmRNA directssynthesis ofspecific proteinson ribosomes
DNA
Cytosol
Target cell
Transportprotein
Free hormone
Ribosome
2
3
1 Lipid-solublehormonediffuses into cell
Blood capillary
Activatedreceptor-hormonecomplex altersgene expression
NucleusReceptor
mRNANewly formedmRNA directssynthesis ofspecific proteinson ribosomes
DNA
Cytosol
Target cell
New proteins altercell's activity
Transportprotein
Free hormone
Ribosome
Newprotein
2
3
4
Lipid-SolubleHormone Action
Copyright © John Wiley & Sons, Inc. All rights reserved.
SOLUBILITY OF HORMONES Water soluble hormones include peptide
and protein hormones (and others with an
amine group), and a group of local hormones
derived from the arachidonic acid on our cell
membranes called eicosanoids
Peptide hormones and protein hormones are
amino acid polymers
The two major types of eicosanoids are
prostaglandins and leukotrienes – both play
a role in mediating the inflammatory
response
Copyright © John Wiley & Sons, Inc. All rights reserved.
SOLUBILITY OF HORMONES Water soluble hormones are easy to
transport in the watery blood. The plasma
membrane of target cells, however, is
impermeable to them
Water soluble hormones exert their effects
by binding to receptors exposed to the
interstitial fluid on the surface of target
cells
• the hormone binding to its receptor acts
as the first messenger in a cascade of
signal transduction
Copyright © John Wiley & Sons, Inc. All rights reserved.
The first messenger (the hormone) then
causes production of a second messenger
inside the cell, where specific hormone-
stimulated responses take place
One common second messenger is
cyclic AMP (cAMP). Neuro-
transmitters, neuropeptides, and
several sensory transduction
mechanisms (vision) also act via
second-messenger systems
SOLUBILITY OF HORMONES
Copyright © John Wiley & Sons, Inc. All rights reserved.
Water-solublehormone
Receptor
G protein
Blood capillary
Binding of hormone (first messenger)to its receptor activates G protein,which activates adenylate cyclase
Adenylate cyclase
Target cell
1
Water-solublehormone
Receptor
G protein
cAMP
Second messenger
Activated adenylatecyclase convertsATP to cAMP
Blood capillary
Binding of hormone (first messenger)to its receptor activates G protein,which activates adenylate cyclase
Adenylate cyclase
Target cell
ATP
1
2
Water-solublehormone
Receptor
cAMP serves as asecond messengerto activate proteinkinases
G protein
Protein kinases
cAMP
Second messenger
Activated adenylatecyclase convertsATP to cAMP
Blood capillary
Binding of hormone (first messenger)to its receptor activates G protein,which activates adenylate cyclase
Adenylate cyclase
Target cell
ATP
1
2
3 Activatedproteinkinases
Water-solublehormone
Receptor
cAMP serves as asecond messengerto activate proteinkinases
G protein
Protein kinases
cAMP
Activatedproteinkinases
Second messenger
Activated adenylatecyclase convertsATP to cAMP
Activated proteinkinasesphosphorylatecellular proteins
Blood capillary
Binding of hormone (first messenger)to its receptor activates G protein,which activates adenylate cyclase
Adenylate cyclase
Target cell
ATP
1
2
4
3
Protein— P
ADP
Protein
ATP
Water-solublehormone
Receptor
cAMP serves as asecond messengerto activate proteinkinases
G protein
Protein kinases
cAMP
Activatedproteinkinases
Protein—
Second messenger
Activated adenylatecyclase convertsATP to cAMP
Activated proteinkinasesphosphorylatecellular proteins
Millions of phosphorylatedproteins cause reactions thatproduce physiological responses
Blood capillary
Binding of hormone (first messenger)to its receptor activates G protein,which activates adenylate cyclase
Adenylate cyclase
Target cell
P
ADP
Protein
ATP
ATP
1
2
4
3
5
Water-solublehormone
Receptor
cAMP serves as asecond messengerto activate proteinkinases
G protein
Protein kinases
cAMP
Activatedproteinkinases
Protein—
Second messenger
Phosphodiesteraseinactivates cAMP
Activated adenylatecyclase convertsATP to cAMP
Activated proteinkinasesphosphorylatecellular proteins
Millions of phosphorylatedproteins cause reactions thatproduce physiological responses
Blood capillary
Binding of hormone (first messenger)to its receptor activates G protein,which activates adenylate cyclase
Adenylate cyclase
Target cell
P
ADP
Protein
ATP
ATP
1
2
6
4
3
5
Water-Soluble Hormone Action
Copyright © John Wiley & Sons, Inc. All rights reserved.
EFFECTS OF HORMONES Prostaglandins (PGs) and leukotrienes are
eicosanoid hormones with local control. They
are synthesized from membrane lipids and
have widespread effects
PG’s mediate pain, platelet aggregation,
fever, and inflammation. They regulate
smooth muscle contraction, gastric acid
secretion, and airway size
• aspirin is a drug that works by inhibiting an
enzyme necessary for synthesis of certain
PGs: the ones that facilitate pain and the
inflammatory response
Copyright © John Wiley & Sons, Inc. All rights reserved.
EFFECTS OF HORMONES Endocrine hormones control a variety of
physiological processes. Among other
things, they:
Balance the composition and volume of
body fluids
Regulate metabolism and energy
production
Direct the rate and timing of growth and
development
Exert emergency control during physical
and mental stress (trauma, starvation,
hemorrhage)
Oversee reproductive mechanisms
Copyright © John Wiley & Sons, Inc. All rights reserved.
EFFECTS OF HORMONES(Interactions Animation)
o Introduction to endocrine hormones: Regulation, secretion and concentration
You must be connected to the internet to run this animation
Copyright © John Wiley & Sons, Inc. All rights reserved.
ENDOCRINE SYSTEM GLANDS Glands that secrete endocrine hormones into
the bloodstream are called endocrine
glands
They are one of two major types of glands
in the body, the other being exocrine
glands (which
secrete their products into ducts )
In this chapter we will focus our
study on the endocrine glands
and the widespread effects of
endocrine hormones
Copyright © John Wiley & Sons, Inc. All rights reserved.
CONTROL OF HORMONES When stimulated, an endocrine gland will
release its hormone in frequent bursts,
increasing the concentration of the hormone
in the blood
Hormone secretion is regulated by signals
from the nervous system, chemical
changes in the blood, and other
hormones
• Most hormonal regulatory systems work
via negative feedback, but a few
operate via positive feedback
Copyright © John Wiley & Sons, Inc. All rights reserved.
CONTROL OF HORMONES This example shows how PTH and calcitonin
have negative feedback influence on one
another
Copyright © John Wiley & Sons, Inc. All rights reserved.
CONTROL OF HORMONES In a positive feedback
system the hormone
output reinforces and
encourages the stimulus.
For example, during
childbirth, the hormone
oxytocin stimulates
contractions of the uterus,
and uterine contractions in
turn stimulate more
oxytocin release, a positive
feedback effect
Copyright © John Wiley & Sons, Inc. All rights reserved.
CONTROL OF HORMONES(Interactions Animation)
o Hormones Summary
You must be connected to the internet to run this animation
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE ENDOCRINE SYSTEM The endocrine system consists of the
pituitary, thyroid, parathyroid, adrenal
and pineal glands
Some of the most important glands of the
endocrine system are not exclusively
endocrine glands: The hypothalamus,
thymus, pancreas, ovaries, and testes
are paramount;
the kidneys, stomach, liver,
small intestine, skin, heart,
and placenta also contribute
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE ENDOCRINE SYSTEM
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE HYPOTHALAMUS The hypothalamus is the major link
between the nervous and endocrine systems
It receives input from several regions in the
brain including the
thalamus, the
RAS, and
the limbic
system
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE PITUITARY GLAND The hypothalamus mainly controls the
pituitary gland, which is also called the
hypophysis
The pituitary hangs down from the
hypothalamus
on a stalk called the infundibulum
The gland is divided into an anterior
adenohypophysis and a posterior
neurohypophysis - the anterior pituitary
accounts
for about 75% of the total
weight of the gland
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE ADENOHYPOPHYSIS The anterior pituitary (adenohypophysis) is
anatomically and functionally connected
to the hypothalamus by blood vessels that
form a portal system called the
hypophyseal portal system
In a portal system, blood flows from one
capillary network into a portal vein, and
then into a second capillary network before
returning to the heart
• The name of the portal system indicates
the location of the second capillary
network
Copyright © John Wiley & Sons, Inc. All rights reserved.
Specialized neurosecretory cells in the
hypothalamus secrete releasing hormones
into the hypophyseal portal system
that supplies blood to the
anterior pituitary
gland
THE ADENOHYPOPHYSIS
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE ADENOHYPOPHYSIS The second capillary system of the
hypophyseal portal system delivers the
hypothalamic releasing hormones to the
anterior pituitary
5 types of anterior pituitary cells secrete
seven hormones
Copyright © John Wiley & Sons, Inc. All rights reserved.
ANTERIOR PITUITARY HORMONES
Hypothalamus Hormone
Hormone released from Adenohypoph
ysis
Major Function/ Target
Growth hormone releasing hormone (GHRH)
Human Growth Hormone (hGH)
Also called somatostatin, stimulates secretion of insulin-like growth factors (IGFs) that promote growth
Thyrotropin releasing hormone (TRH)
Thyroid Stimulating Hormone (TSH)
Stimulates synthesis and secretion of thyroid hormones by the thyroid gland
Prolactin releasing hormone (PRH)
Prolactin (PRL)
Stimulates breast growth, and development of the mammary glands
Copyright © John Wiley & Sons, Inc. All rights reserved.
ANTERIOR PITUITARY HORMONES
Hypothalamus Hormone
Hormone released
from Adenohypop
hysis
Major Function/ Target
Gonadotropic releasing hormone (GnRH)
Follicle Stimulating hormone (FSH)
Ovaries initiate development of oocytes; testes initiate development of spermatozoa
Gonadotropic releasing hormone (GnRH)
Luteinizing hormone (LH)
Ovaries stimulate ovulation; testes stimulate testosterone production
Copyright © John Wiley & Sons, Inc. All rights reserved.
ANTERIOR PITUITARY HORMONES
Hypothalamus
Hormone
Hormone released from Adenohypoph
ysis
Major Function/ Target
Corticotropin releasing hormone (CRH)
Adrenocorticotropic Hormone (ACTH)
Stimulates release of mineralocorticoid, glucocorticoid, and androgen hormones from the adrenal cortex
Corticotropin releasing hormone (CRH)
Melanocyte Stimulating hormone (MSH)
Stimulate the production and release of melanin by melanocytes in skin and hair. MSH signals to the brain have effects on appetite and sexual arousal
Copyright © John Wiley & Sons, Inc. All rights reserved.
ANTERIOR PITUITARY HORMONES(Interactions Animation)
hGH Stimulating Glyc
ogenolysis
hGH Growth and Dev
elopment
You must be connected to the internet to run this animation
Copyright © John Wiley & Sons, Inc. All rights reserved.
ANTERIOR PITUITARY HORMONES(Interactions Animation)
Cortisol
ACTH and Cortisol
You must be connected to the internet to run this animation
Copyright © John Wiley & Sons, Inc. All rights reserved.
ANTERIOR PITUITARY HORMONES(Interactions Animation)
TRH and TSH
You must be connected to the internet to run this animation
Copyright © John Wiley & Sons, Inc. All rights reserved.
ANTERIOR PITUITARY HORMONES
Tropic hormones are hormones produced
and secreted by the anterior pituitary that
target other endocrine glands
All hormones in the previous lists target
other endocrine glands (are trophic
hormones) except hGH, Prolactin, and
MSH, which directly target the end organs
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE NEUROHYPOPHYSIS The posterior pituitary (neurohypophysis)
is embryologically derived from and
anatomically connected to the hypothalamus
– it releases, but does not synthesize any
hormones
When stimulated, neurosecretory
cells in the hypothalamus
release oxytocin and
ADH from their axon
terminals located in
the posterior pituitary
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE NEUROHYPOPHYSIS Oxytocin targets smooth muscle in the
uterus and breasts. In the uterus, oxytocin
stimulates uterine contractions, and in
response to the sucking from an infant,
oxytocin stimulates “milk letdown” in the
breasts
ADH targets the collecting ducts in the
kidney and sweat glands in the skin to
minimize water loss. It also directly causes
arterioles to constrict thereby increasing
blood pressure
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE NEUROHYPOPHYSIS
This graphic
demonstrates the
regulation of ADH
secretion
Copyright © John Wiley & Sons, Inc. All rights reserved.
POSTERIOR PITUITARY HORMONES
Antidiuretic Hormone Animation
You must be connected to the internet to run this animation
Copyright © John Wiley & Sons, Inc. All rights reserved.
PITUITARY GLAND DISORDERS Acromegaly occurs as a result of excess HGH
during adulthood. This disease is marked by
enlargement and elongation of the bones of
the face, jaw, cheeks, and hands (the long
bones of
the extremities are
unaffected because the
growth plates have
already closed)
Copyright © John Wiley & Sons, Inc. All rights reserved.
PITUITARY GLAND DISORDERS Diabetes Insipidus (DI) is very different from
the disease called sugar diabetes (diabetes
mellitus)
DI is caused by the insufficient release of
ADH from the neurohypophysis. Without
ADH acting on the collecting ducts in the
kidneys, the normal urine output of 1–1.5
liters per day increases to over 2.5 liters
per day and dehydration and
hypernatremia results
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE THYROID GLAND The butterfly-shaped thyroid gland is
located inferior to the larynx and anterior to
the trachea. It has two laterally placed lobes
separated by a bridge-like isthmus
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE THYROID GLAND Most of the thyroid gland is composed of
spherical groups of follicular cells called
thyroid follicles
The follicles store
a 100-day supply
of its two hormones
in an inactive
gel-like substance
called TGB (for
thyroglobulin)
Copyright © John Wiley & Sons, Inc. All rights reserved.
Thyroid-stimulating hormone (TSH) is
released by the anterior pituitary gland in
response to TRH secreted into the portal
system
The hypothalamus
responds to higher
circulating levels of
T3 and T4 via negative
feedback to inhibit
TRH secretion
THYROID HORMONES
Copyright © John Wiley & Sons, Inc. All rights reserved.
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
HypothalamusTRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
Anteriorpituitary
TRH, carriedby hypophysealportal veins toanterior pituitary,stimulatesrelease of TSHby thyrotrophs
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
Hypothalamus
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
2
Anteriorpituitary
TRH, carriedby hypophysealportal veins toanterior pituitary,stimulatesrelease of TSHby thyrotrophs
TSH released intoblood stimulatesthyroid follicular cells
Thyroidfollicle
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
Hypothalamus
Anteriorpituitary
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
2
3
T3 and T4
released intoblood byfollicular cells
TRH, carriedby hypophysealportal veins toanterior pituitary,stimulatesrelease of TSHby thyrotrophs
TSH released intoblood stimulatesthyroid follicular cells
Thyroidfollicle
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
Hypothalamus
Anteriorpituitary
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
2
3
4 T3 and T4
released intoblood byfollicular cells
ElevatedT3inhibitsrelease ofTRH andTSH(negativefeedback)
TRH, carriedby hypophysealportal veins toanterior pituitary,stimulatesrelease of TSHby thyrotrophs
TSH released intoblood stimulatesthyroid follicular cells
Thyroidfollicle
Low blood levels of T3
and T3 or low metabolicrate stimulate release of
Hypothalamus
Anteriorpituitary
TSH
TRH
Actions of Thyroid Hormones:
Increase basal metabolic rate
Stimulate synthesis of Na+/K+ ATPase
Increase body temperature (calorigenic effect)
Stimulate protein synthesis
Increase the use of glucose and fatty acids for ATP production
Stimulate lipolysis
Enhance some actions of catecholamines
Regulate development and growth of nervous tissue and bones
1
2
3
5
4
Thyroid HormoneRegulation
Copyright © John Wiley & Sons, Inc. All rights reserved.
A goiter is an enlargement of the thyroid
gland and may be associated with
hyperthyroidism, hypothyroidism, or
euthyroidism
In many third-word countries
dietary iodine intake is inadequate;
the resultant low level of thyroid
hormone in the blood stimulates
secretion of TSH, which causes
thyroid gland enlargement
THYROID HORMONES
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE PARATHYROID GLANDS The parathyroid glands are small, round
masses of tissue attached to the posterior
surface of the lateral lobes of the thyroid
gland
There are usually two
parathyroid glands
attached to each
lobe of the thyroid,
one superior and one inferior
Copyright © John Wiley & Sons, Inc. All rights reserved.
PARATHYROID HORMONES Calcitonin (Thyrocalcitonin) is made by the
parafollicular (C-cells) of the thyroid gland
and
when secreted lowers the blood calcium
level
An increase in blood calcium will stimulate
the C-cells of the thyroid to secrete calcitonin
Increased calcitonin will cause a negative
feedback inhibition of parathyroid hormone
(PTH) which
causes a decrease in blood calcium and an
increase in blood phosphate levels
Copyright © John Wiley & Sons, Inc. All rights reserved.
PARATHYROID HORMONES(Interactions Animation)
Calcitonin
You must be connected to the internet to run this animation
Copyright © John Wiley & Sons, Inc. All rights reserved.
Parathyroid hormone (PTH) is made by the
more numerous chief (principal) cells of the
gland
PTH increases absorption
of Ca2+ from the GI tract
and stimulates osteoclastic
activity so that Ca2+ is
released from bone into
the blood
PARATHYROID HORMONES
Copyright © John Wiley & Sons, Inc. All rights reserved.
PARATHYROID HORMONES(Interactions Animation)
Parathyroid Hormone
You must be connected to the internet to run this animation
Copyright © John Wiley & Sons, Inc. All rights reserved.
1 High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
1 High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
2
1 High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
Low level of Ca2+ in bloodstimulates parathyroid gland chief cells to release more PTH.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
3
2
1 High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
Low level of Ca2+ in bloodstimulates parathyroid gland chief cells to release more PTH.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
PARATHYROID HORMONE (PTH)promotes release of Ca2+ frombone extracellular matrix intoblood and slows loss of Ca2+ in urine, thus increasing bloodCa2+ level.
3
4 2
1
PTH also stimulatesthe kidneys to releaseCALCITRIOL.
High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
Low level of Ca2+ in bloodstimulates parathyroid gland chief cells to release more PTH.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
PARATHYROID HORMONE (PTH)promotes release of Ca2+ frombone extracellular matrix intoblood and slows loss of Ca2+ in urine, thus increasing bloodCa2+ level.
3
4 25
1
CALCITRIOL stimulatesincreased absorption ofCa2+ from foods, whichincreases blood Ca2+ level.
PTH also stimulatesthe kidneys to releaseCALCITRIOL.
High level of Ca2+ in bloodstimulates thyroid glandparafollicular cells to release more CT.
Low level of Ca2+ in bloodstimulates parathyroid gland chief cells to release more PTH.
CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.
PARATHYROID HORMONE (PTH)promotes release of Ca2+ frombone extracellular matrix intoblood and slows loss of Ca2+ in urine, thus increasing bloodCa2+ level.
3
4 25
6
Calcium Regulation
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE ADRENAL GLANDS There are two adrenal glands, one superior
to each kidney (also called the suprarenal
glands). During embryonic development,
the adrenal glands differentiate into two
structurally and functionally distinct regions
• the adrenal cortex
• the adrenal medulla Catecholamines like norepinephrine
Steroid hormones like cortisol
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE ADRENAL GLANDS
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE ADRENAL CORTEX The adrenal cortex is peripherally located
and makes up 80-90% of the total weight of
the gland
The cortex is subdivided into three zones,
each of which secretes a different group of
steroid hormones, all formed
from the cholesterol
molecule
Copyright © John Wiley & Sons, Inc. All rights reserved.
Just deep to the CT capsule, the cells of the
zona glomerulosa synthesize
mineralocorticoid hormones
The middle zone, or zona fasciculata,
secrete mainly glucocorticoid hormones,
primarily cortisol
The inner zona reticularis
is the site of synthesis
of weak androgens
(masculinizing hormones)
ADRENOCORTICAL HORMONES
Copyright © John Wiley & Sons, Inc. All rights reserved.
Mineralocorticoids regulate the
concentrations of Na+ and K+ in the blood
(affects blood volume/pressure)
Aldosterone is the major hormone in this
group
Glucocorticoids influence glucose
metabolism and the ability to resists the
effects of stress
Cortisol is the major hormone in this group
Weak androgens (masculinizing sex
hormones) have little effect in men, but play
an important role in promoting libido in
women
ADRENOCORTICAL HORMONES
Copyright © John Wiley & Sons, Inc. All rights reserved.
The most important effects of aldosterone is
seen in the renin-angiotensin-aldosterone
system (RAAS)
The RAAS is stimulated by a decrease in
blood volume and/or blood pressure – as in
cases of dehydration or hemorrhage. Low
BP stimulates juxtaglomerular cells
in the kidney to
secrete the
enzyme renin
RAAS
Copyright © John Wiley & Sons, Inc. All rights reserved.
RAAS Renin converts the plasma protein
angiotensinogen (produced in the liver) into
angiotensin I. As angiotensin I circulates to the
lungs, an enzyme called angiotensin converting
enzyme (ACE) converts angiotensin I to
angiotensin II
Angiotensin II stimulates the adrenal cortex to
secrete aldosterone (salt and H20 resorption
indirectly increases BP), and it is a
potent vasoconstrictor (which
directly increases BP)
Copyright © John Wiley & Sons, Inc. All rights reserved.
RAAS
Copyright © John Wiley & Sons, Inc. All rights reserved.
GLUCOCORTICOIDS Glucocorticoids (mainly cortisol) regulate
metabolism by promoting the breakdown of
proteins and fats to form glucose
(gluconeogenesis). Increased blood sugar
levels assist the body to cope with stress Their inflammatory effects result from
inhibiting white blood cells. Unfortunately
they also retard tissue repair and slow
wound healing • glucocorticoids are very useful in the
treatment of chronic inflammatory
disorders such as Lupus, though long
term side-effects are severe
Copyright © John Wiley & Sons, Inc. All rights reserved.
GLUCOCORTICOIDS High levels of circulating cortisol, as
seen with corticosteroid drugs (prednisone),
or tumors (adrenal cortex, pituitary gland) is
called Cushing’s syndrome
Manifestations include hyper-
glycemia, poor wound healing,
osteoporosis, dermatitis, fat
redistribution (spindly arms and
legs, moon face, buffalo hump at
the neck), and truncal obesity
Copyright © John Wiley & Sons, Inc. All rights reserved.
GLUCOCORTICOIDS In adults, hyposecretion of
glucocorticoids and aldosterone, usually as
a result of an autoimmune disorder, is called
Addison’s disease
The physiologic effects include
hypoglycemia, Na+ loss, low BP,
dehydration, and muscle weakness
• only after his death did the world
learn that President Kennedy
suffered from Addison’s disease
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE ADRENAL MEDULLA The inner region of the adrenal gland, the
adrenal medulla, is a modified sympathetic
ganglion that develops from the same
embryonic tissue as all other sympathetic
ganglia of the ANS and is innervated by
sympathetic preganglionic neurons
The catecholamines epinephrine (80%),
and norepinephrine (20%), are secreted
at the adrenal medulla and serve to
prolong the sympathetic response
Copyright © John Wiley & Sons, Inc. All rights reserved.
ADRENAL MEDULLA HORMONES(Interactions Animation)
Epinephrine/Norepinephrine
You must be connected to the internet to run this animation
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE PANCREAS The pancreas is both an endocrine and an
exocrine gland. It is located posterior and
inferior to the stomach. We will discuss its
endocrine functions here and its exocrine
functions
in detail in chapter 24
Copyright © John Wiley & Sons, Inc. All rights reserved.
Most of the exocrine cells of the pancreas
are arranged in clusters called acini and
produce digestive enzymes which flow
through ducts into the GI tract
Distributed among the acini are clusters of
endocrine tissue
called pancreatic
islets (islets of
Langerhans)
THE PANCREAS
Copyright © John Wiley & Sons, Inc. All rights reserved.
Each pancreatic islet contains four types of
hormone-secreting cells: alpha (A), beta (B),
delta (D), and F cells
Alpha cells secrete glucagon which
increases blood glucose levels by acting
on hepatocytes to
convert glycogen
to glucose
Beta cells secrete
insulin
PANCREATIC HORMONES
Copyright © John Wiley & Sons, Inc. All rights reserved.
PANCREATIC HORMONES Insulin is an anabolic hormone - it decreases
blood glucose levels by acting on
hepatocytes to convert glucose
to glycogen and then facilitating
diffusion of glucose into the cells
Insulin and glucagon are counter-
regulatory hormones in that
their actions act to balance one
another in terms of blood glucose
Copyright © John Wiley & Sons, Inc. All rights reserved.
Somatostatin acts in a paracrine manner to
inhibit both insulin and glucagon release
from neighboring beta and alpha cells. It
also inhibits the secretion
of hGH
The interactions of the
four pancreatic hormones
are complex and not
completely understood
PANCREATIC HORMONES
Copyright © John Wiley & Sons, Inc. All rights reserved.
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
1
GLUCAGON
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
GLUCAGON
1
2 Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
GLUCAGON
1
2
3
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
GLUCAGON
1
2
3
4
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
High blood glucose(hyperglycemia)stimulates beta cellsto secrete
GLUCAGON
1 5
2
3
4
INSULIN
Insulin acts on variousbody cells to:
• accelerate facilitated diffusion of glucose into cells• speed conversion of glucose into glycogen (glycogenesis)• increase uptake of amino acids and increase protein synthesis• speed synthesis of fatty acids (lipogenesis)• slow glycogenolysis• slow gluconeogenesis
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
High blood glucose(hyperglycemia)stimulates beta cellsto secrete
INSULINGLUCAGON
1 5
2
3
4
6 Insulin acts on variousbody cells to:
• accelerate facilitated diffusion of glucose into cells• speed conversion of glucose into glycogen (glycogenesis)• increase uptake of amino acids and increase protein synthesis• speed synthesis of fatty acids (lipogenesis)• slow glycogenolysis• slow gluconeogenesis
Blood glucose level falls
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
High blood glucose(hyperglycemia)stimulates beta cellsto secrete
INSULINGLUCAGON
1 5
2
3
4
6
7
Insulin acts on variousbody cells to:
• accelerate facilitated diffusion of glucose into cells• speed conversion of glucose into glycogen (glycogenesis)• increase uptake of amino acids and increase protein synthesis• speed synthesis of fatty acids (lipogenesis)• slow glycogenolysis• slow gluconeogenesis
If blood glucose continuesto fall, hypoglycemiainhibits release ofinsulin
Blood glucose level falls
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
High blood glucose(hyperglycemia)stimulates beta cellsto secrete
INSULINGLUCAGON
1 5
2
3
4
6
7
8
Glucose/InsulinRegulation
Copyright © John Wiley & Sons, Inc. All rights reserved.
PANCREATIC HORMONES(Interactions Animation)
Insulin
You must be connected to the internet to run this animation
Copyright © John Wiley & Sons, Inc. All rights reserved.
GONADAL HORMONES The ovaries are paired oval bodies located
in the female pelvic cavity. They produce
several steroid hormones including two
estrogens (estradiol and estrone),
progesterone, relaxin, and inhibin
Estrogens, along with FSH and
LH from the anterior pituitary,
regulate the menstrual cycle,
maintain pregnancy, and prepare
the mammary glands for lactation
Copyright © John Wiley & Sons, Inc. All rights reserved.
GONADAL HORMONES Ovarian hormones also promote
enlargement of the breasts and widening of
the hips at puberty, and help maintain these
female secondary sex characteristics
Progesterone prepares the uterus lining for
implantation of a fertilized ovum
Copyright © John Wiley & Sons, Inc. All rights reserved.
OVARIAN HORMONES(Interactions Animation)
Hormonal Regulation of Female Reproductive System
You must be connected to the internet to run this animation
Copyright © John Wiley & Sons, Inc. All rights reserved.
GONADAL HORMONES The male gonads, the testes, are oval
glands that lie in the scrotum. The main
hormone produced and secreted by the
testes is testosterone, an androgen (male
sex hormone)
Testosterone is needed for
production of sperm and
maintenance of male
secondary sex characteristics
Copyright © John Wiley & Sons, Inc. All rights reserved.
TESTICULAR HORMONES(Interactions Animation)
Hormonal Regulation of Male Reproductive Function
You must be connected to the internet to run this animation
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE PINEAL GLAND The pineal gland is a small
endocrine gland
attached to the roof of the
third ventricle – it is part of
the epithalamus
The pineal gland secretes the hormone
melatonin, which contributes to
maintaining the biological clock (seasonal
and daily cycles)
• more melatonin is secreted in darkness;
the pineal gland is very developed in
nocturnal animals
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE THYMUS GLAND The thymus gland secretes thymosin, which
promotes the proliferation and maturation of
T cells
T cells are a type of white blood cell
(lymphocyte) that destroys microorganisms
and foreign substances
through direct
cellular contact
Copyright © John Wiley & Sons, Inc. All rights reserved.
GENERAL ADAPTATION SYNDROME
The general adaptation syndrome (GAS)
or stress response refers to the
consequences of failure to respond
appropriately to emotional or physical
threats, whether actual or imagined
Interestingly, stressful situations can be
events normally considered to be “good”,
as well as bad
• for instance, a marriage can be as
stressful as a divorce, a birth as stressful
as a death, etc.
Copyright © John Wiley & Sons, Inc. All rights reserved.
GENERAL ADAPTATION SYNDROME
It is impossible to remove all of the stress from
our everyday lives, and some levels of stress
actually help us perform well and be productive.
Regardless, the body’s homeostatic mechanisms
attempt to counteract stress, and maintain a
constant internal environment whenever
possible
If stress is extreme, unusual, or long lasting,
the normal mechanisms may not be enough,
and they may elicit a series of changes called
the stress response or GAS
Copyright © John Wiley & Sons, Inc. All rights reserved.
GENERAL ADAPTATION SYNDROME
There are three stages to a prolonged
stress response: alarm reaction, resistance
reaction, and exhaustion
The alarm reaction is the short-lived
fight-or-flight response initiated by the
hypothalamus and mediated by the
sympathetic division of the ANS
• it brings huge amounts of glucose and
oxygen to the brain, the lungs, and
skeletal muscles
• the RAAS is also activated to maintain
blood volume and BP
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE ALARM REACTION(Interactions Animation)
The Alarm Reaction
You must be connected to the internet to run this animation
Copyright © John Wiley & Sons, Inc. All rights reserved.
GENERAL ADAPTATION SYNDROME
The three stages to the GAS continued…
The resistance reaction is initiated in
large part by hypothalamic releasing
hormones and is a longer-lasting response.
The release of high levels of cortisol and
thyroid hormones assures that the tissues
of the body can sustain necessary
metabolic needs
Copyright © John Wiley & Sons, Inc. All rights reserved.
GENERAL ADAPTATION SYNDROME
The alarm reaction leads to a resistance response.
Copyright © John Wiley & Sons, Inc. All rights reserved.
GENERAL ADAPTATION SYNDROME
The three stages to the GAS continued… Exhaustion occurs when the body’s
reserves become so depleted that they
cannot sustain the resistance stage
• Prolonged exposure to high levels of
cortisol and other hormones causes
wasting of muscle, suppression of the
immune system, ulceration of the GI tract,
and failure of pancreatic beta cells…
disease often ensues
Copyright © John Wiley & Sons, Inc. All rights reserved.
THE GAS(Interactions Animation)
General Adaptation Syndrome
You must be connected to the internet to run this animation
top related