Download Hormonal Regula on of Homeostasis

Chapter
13
Hormonal
Regula3on
of
Homeostasis
Chapter
13
Hormonal
Regula3on
of
Homeostasis
13.1
The
Glands
and
Hormones
of
the
Endocrine
System
13.2
Hormonal
Regula3on
of
Growth,
Development,
and
Metabolism
13.3
Hormonal
Regula3on
of
the
Stress
Response
13.4
Hormonal
Regula3on
of
Blood
Sugar
Chapter
13
Hormonal
Regula3on
of
Homeostasis
In
Sec3on
1,
you
will
learn
that:
• The
endocrine
system
func3ons
with
the
nervous
system
to
regulate
other
body
systems
and
maintain
homeostasis.
• The
endocrine
glands
secrete
hormones
directly
into
the
bloodstream.
• Hormone
secre3on
is
regulated
by
the
nervous
system,
other
hormones,
or
nega3ve
feedback
mechanisms.
The
Glands
and
Hormones
of
the
Endocrine
System
• The
nervous
and
endocrine
systems
are
self‐regula3ng,
and
help
regulate
other
body
systems,
thereby
maintaining
homeostasis.
The
Glands
and
Hormones
of
the
Endocrine
System
• The
nervous
system
rapidly
affects
specific
3ssues,
to
which
it
is
directly
connected
by
neurons.
The
endocrine
system
relies
on
chemical
messengers
called
hormones,
which
circulate
in
the
blood
and
have
broad,
long‐las3ng
effects.
Over
200
human
hormones
have
been
iden3fied!
The
Glands
and
Hormones
of
the
Endocrine
System
• The
endocrine
glands
have
no
ducts,
and
secrete
hormones
directly
into
the
bloodstream.
These
hormones
then
bind
to
receptor
proteins
on
their
target
cell
membranes.
The pancreas is
an endocrine
gland that
secretes the
hormone insulin
into the
bloodstream.
Pancreas tissue
The
Glands
and
Hormones
of
the
Endocrine
System
• Hormones
trigger
changes
in
their
target
cells
when
they
bind
to
receptor
proteins
on
or
within
the
cells.
A model of a hormone
(A) bound to its protein
receptor (B). Each
hormone of the
endocrine system has
a unique molecular
shape, which fits into a
specific receptor
protein on its target
cells.
LIPID‐SOLUBLE
AND
WATER‐SOLUBLE
HORMONES
• LIPID‐SOLUBLE
• WATER‐SOLUBLE
• Can
diffuse
easily
across
cell
membranes
• Cannot
diffuse
across
the
cell
membrane
• Bind
to
receptor
proteins
inside
the
cell
• Combine
with
receptor
proteins
on
the
surface
of
the
target
cell
• Ac3vate
specific
genes
which
cause
changes
in
the
cell
• Starts
a
series
of
reac3ons
inside
the
cell
• E.g.
testosterone,
estrogen,
cor3sol
• E.g.
epinephrine,
GH,
thyroxine,
insulin
The
Glands
and
Hormones
of
the
Endocrine
System
• Many
hormones
are
regulated
by
nega3ve
feedback
mechanisms
(the
response
acts
in
opposi3on
to
the
s3mulus).
For
example,
ADH
is
released
when
the
blood
plasma
concentra3on
is
high
(and
blood
pressure
is
low).
ADH
s3mulates
the
kidneys
to
absorb
more
water,
which
dilutes
the
blood
plasma
(and
increases
blood
pressure).
See
Fig.13.9
p.441
The
Glands
and
Hormones
of
the
Endocrine
System
• Many
hormones
from
the
hypothalamus
and
pituitary
are
called
tropic
hormones
(s3mulate
endocrine
glands
to
produce
other
hormones).
The generalized
regulatory pathway of
tropic hormones.
Chapter
13
Hormonal
Regula3on
of
Homeostasis
In
Sec3on
2,
you
will
learn
that:
• The
hypothalamus
regulates
the
pituitary
gland,
which
secretes
tropic
hormones
that
affect
various
endocrine
glands.
• Human
growth
hormone
mainly
affects
bone
and
muscle
growth.
The
thyroid
hormones
s3mulate
metabolism.
Hormonal
Regula3on
of
Growth,
Development,
and
Metabolism
• The
hypothalamus
controls
the
pituitary
gland.
The
pituitary
gland
has
two
lobes
(and
is
about
the
size
of
a
pea!)
that
store
and
release
tropic
hormones,
which
are
regulated
by
nega3ve
feedback
mechanisms.
Hormonal
Regula3on
of
Growth,
Development,
and
Metabolism
• The
anterior
pituitary
gland
releases
human
growth
hormone
(hGH),
which
s3mulates
fat
metabolism,
and
targets
the
liver
to
release
hormones
that
s3mulate
protein
synthesis,
and
muscle
and
bone
growth.
HUMAN
GROWTH
HORMONE
• Too
much
hGH
during
childhood
can
result
in
gigan3sm
• Too
li\le
hGH
during
childhood
can
result
in
pituitary
dwarfsim
• Too
much
hGH
in
adulthood
can
result
in
acromegaly
• Advances
in
gene3c
engineering
have
allowed
for
produc3on
of
synthe3c
hGH
using
bacteria
THE
ANTERIOR
PITUITARY
• Other
hormones
released
by
the
anterior
pituitary
include:
1)
Prolac3n
(PRL)
‐
s3mulates
milk
produc3on
in
the
breast
3ssue
a^er
birth
2)
Thyroid‐s3mula3ng
hormone
(TSH)
–
s3mulates
the
thyroid
to
produce
its
hormes
‐
thyroxine
(T4)
and
calcitonin
3)
Adrenocor3cotropic
hormone
(ACTH)
–
s3mulates
the
adrenal
cortex
to
produce
cor3sol
4)
Follicle
s3mula3ng
hormone
(FSH)
–
s3mulates
follicle
development
in
the
ovaries
and
sperm
development
in
the
testes
5)
Leutenizing
hormone
(LH)
–
plays
a
role
in
the
male
and
female
reproduc3ve
systems
THE
POSTERIOR
PITUITARY
• Stores
hormones
released
by
the
hypothalamus:
1)
Oxytocin
–
s3mulates
uterine
contrac3ons
and
contrac3ons
in
the
breast
3ssue
to
help
release
milk
from
the
milk
ducts
2)
Ani3diure3c
hormone
(ADH)
–
makes
the
distal
tubules
of
the
kidneys
more
permeable
to
water
(more
water
retained
by
the
body)
THE
THYROID
GLAND
• secretes
hormones
that
regulate
cell
metabolism,
growth,
and
development
• controls
the
rate
at
which
the
body
metabolizes
fats,
proteins
and
carbohydrates
DISORDERS
OF
THE
THYROID
GLAND
• Cre3nism
can
occur
if
the
thyroid
doesn’t
develop
properly
during
childhood
• This
can
cause
hypothyroidism
• Adults
with
hypothyroidism
tend
to
feel
3red,
have
a
slow
heart
rate,
have
puffy
skin,
and
experience
hair
loss
and
weight
gain
• Overproduc3on
of
thyroxine
is
called
hyperthyroidism
• Symptoms
include
anxiety,
insomnia,
heat
intolerance,
irregular
heartbeat
and
weight
loss
• A
condi3on
called
Graves’
disease
occurs
when
the
body’s
own
immune
system
a\acks
the
thyroid
–
it
is
an
extreme
form
of
hyperthyroidism
• Symptoms
include
swelling
around
the
eyes
that
makes
them
appear
to
protrude
(and
interferes
with
vision)
Hormonal
Regula3on
of
Growth,
Development,
and
Metabolism
• Thyroxine
(T4)
is
required
for
healthy
mental
and
physical
development
during
childhood,
and
an
ac3ve
metabolism
throughout
life.
Thyroxine
contains
iodine,
and
thus
people
require
iodine
in
the
diet.
Iodine is added to
table salt to
prevent
hypothyroidism, a
condition in which
the thyroid gland
does not produce
enough
thyroxine.
Hormonal
Regula3on
of
Growth,
Development,
and
Metabolism
• Thyroxine
secre3on
is
regulated
by
the
release
of
thyroid‐s3mula3ng
hormone
(TSH)
from
the
anterior
pituitary.
TSH
is
regulated
by
nega3ve
feedback
by
thyroxine
on
the
hypothalamus
and
pituitary.
1. Releasing hormone from
hypothalamus stimulates
anterior pituitary
2. Anterior pituitary releases
TSH into bloodstream
3. TSH targets thyroid
4. Thyroid secretes thyroxine
into bloodstream
5. High levels of thyroxine
cause negative feedback,
shutting down production
of TSH
Hormonal
Regula3on
of
Growth,
Development,
and
Metabolism
• The
thyroid
gland
also
produces
calcitonin,
which
helps
lower
blood
calcium
levels
(by
s3mula3ng
uptake
of
calcium
by
the
bones)
• The
parathyroid
glands
secrete
parathyroid
hormone
(PTH),
which
raises
blood
calcium
levels
(by
s3mula3ng
bone
cells
to
release
calcium)
Chapter
13
Hormonal
Regula3on
of
Homeostasis
In
Sec3on
3,
you
will
learn
that:
• The
hormones
of
the
adrenal
glands
regulate
the
short‐term
and
long‐term
stress
responses.
13.3
Hormonal
Regula3on
of
the
Stress
Response
• The
adrenal
glands
release
several
hormones
involved
in
the
body’s
response
to
stress.
13.3
Hormonal
Regula3on
of
the
Stress
Response
• Each
adrenal
gland
is
composed
of
an
outer
layer
called
the
adrenal
cortex,
and
an
inner
part
called
the
adrenal
medulla.
The
adrenal
medulla
is
s3mulated
by
neurons
from
the
hypothalamus.
13.3
Hormonal
Regula3on
of
the
Stress
Response
• In
the
short‐term
stress
response,
also
called
the
fight‐or‐flight
response,
the
adrenal
medulla
is
s3mulated
to
release
epinephrine
and
norepinephrine.
These
hormones
increase
the
body’s
metabolism,
breathing
rate,
and
heart
rate.
This
provides
more
energy
for
the
body
to
respond
to
danger.
13.3
Hormonal
Regula3on
of
the
Stress
Response
• When
the
body
is
under
stress,
the
hypothalamus
secretes
a
releasing
hormone.
The
releasing
hormone
s3mulates
the
anterior
pituitary
to
release
adrenocor3cotropic
hormone
(ACTH),
which
s3mulates
the
adrenal
cortex
to
release
cor3sol,
a
steroid
hormone.
13.3
Hormonal
Regula3on
of
the
Stress
Response
• Cor3sol
triggers
the
metabolism
of
proteins
and
fats
to
produce
glucose.
Cor3sol
also
suppresses
the
immune
system,
which
is
probably
one
reason
that
chronic
stress
is
unhealthy.
• Cor3sol
secre3on
is
suppressed
by
nega3ve
feedback
to
the
hypothalamus
and
anterior
pituitary.
13.3
Hormonal
Regula3on
of
the
Stress
Response
• The
adrenal
cortex
also
secretes
aldosterone,
which
s3mulates
the
kidneys
to
absorb
sodium
and
thus
water.
This
increases
the
blood
pressure.
When
homeostasis
is
reached,
nega3ve
feedback
shuts
off
the
secre3on
of
aldosterone.
• Low
aldosterone
causes
low
blood
pressure,
an
imbalance
of
electrolytes
(sodium
and
potassium
ions)
in
the
blood,
and
unhealthy
weight
loss,
which
are
symptoms
of
Addison’s
disease.
Chapter
13
Hormonal
Regula3on
of
Homeostasis
In
Sec3on
4,
you
will
learn
that:
• The
hormones
of
the
pancreas
act
antagonis3cally
to
maintain
blood
glucose
levels
within
a
narrow
range.
Diabetes
results
from
improper
regula3on
of
blood
glucose.
13.4
Hormonal
Regula3on
of
Blood
Sugar
• Blood
glucose
levels
must
stay
within
a
narrow
range
for
the
body
to
maintain
homeostasis.
13.4
Hormonal
Regula3on
of
Blood
Sugar
• The
islets
of
Langerhans
in
the
pancreas
contain
beta
cells,
which
secrete
insulin
in
response
to
high
levels
of
blood
glucose.
• The
islets
of
Langerhans
also
contain
alpha
cells,
which
secrete
glucagon
in
response
to
low
levels
of
blood
glucose.
13.4
Hormonal
Regula3on
of
Blood
Sugar
• Insulin
s3mulates
the
cells
of
the
liver
to
take
up
and
store
glucose.
• Other
cells
respond
to
insulin
by
taking
up
more
glucose
for
cellular
respira3on.
13.4
Hormonal
Regula3on
of
Blood
Sugar
• Glucagon
s3mulates
the
liver
cells
to
break
down
glycogen,
which
releases
glucose.
13.4
Hormonal
Regula3on
of
Blood
Sugar
• If
the
beta
cells
are
destroyed,
Type
1
diabetes
results.
Type
2
diabetes
develops
when
the
insulin
receptors
on
the
cells
do
not
respond
properly
to
insulin.
Pancreatic cells from
someone with type 1
diabetes