Download The Endocrine System Recall What are hormones? The endocrine s

Recall
 Maintaining homeostasis requires the concerted actions
The Endocrine System
off both
b th communication
i ti systems
t
in
i th
the b
body:
d
 nervous and endocrine
Section 9.1
What are hormones?
 chemical messengers
 can be
lipids (steroids) or proteins
 produced by cells or glands in one part of the body,
The endocrine system
s stem
 a system
y
of g
glands,,
which secrete
hormones directly into
the bloodstream
and relay messages to other parts of the body
 these hormones
regulate processes
within the body
Target vs.
s Non
Non-Target
Target Hormones
 target hormones act on specific cells, or target tissues

e.g., gastrin acts on the epithelial cells of the stomach to stimulate
them to produce HCl
 non-target hormones
Types
yp of Hormones
 protein hormones are water-soluble
 e.g., Insulin; Growth hormone
 steroids are lipids; they are fat-soluble
 e.g., cortisol; Male and female sex hormones
affect many cells
th
throughout
h t the
th body
b d
 e.g., insulin
Differences in membrane solubility mean that protein
and steroid hormones act on cells in different ways
y
Protein hormones
 hormone interacts with a receptor
on the
th target
t
t cellll membrane
b
 hormone-receptor
hormone receptor complex
activates enzymes within the cell
 leads to further activation
cascades
d within
ithi cellll
Steroid hormones
 can diffuse into target
g cell
 inside cell, hormone combines with
receptor in the cytoplasm or nucleus
 hormone-receptor
hormone receptor complex triggers
The pit
pituitary
itar gland
 produces and stores hormones
 located in the brain; connected
to the hypothalamus
 bridge between nervous and endocrine systems
 receives nerve signals from the hypothalamus, to secrete
h
hormones
iinto
t bl
bloodstream
d t
changes in gene activity
 response takes longer
 the "master
master gland
gland“:: controls other endocrine glands
 two lobes: anterior and posterior
p
Both lobes release hormones after receiving signals
from the hypothalamus.
posterior lobe stores and
releases hormones produced
by the hypothalamus
 ADH and oxytocin only
Hormone regulation
 Tropic hormones – Hormones that act on other
anterior lobe produces its
own hormones
 list on pg. 392
endocrine glands, to stimulate the release of other
hormones
 releasing hormones (from hypothalamus)
 stimulating hormones (from pituitary)
 Hormone
H
release
l
iis regulated
l t d
by a negative feedback loop.
Hormonal control of growth,
development and metabolism
development,
Section 9.2
specific example: negative feedback system that
controls thyroid-stimulating hormone (TSH)
H
Hormones
affecting
ff ti growth
th & metabolism
t b li
Gland
Hormone produced
Anterior pituitary growth hormone
Thyroid
thyroxine
calcitonin
Parathyroid
parathyroid hormone
H man Gro
Human
Growth
th Hormone (hGH)
 produced and secreted by anterior pituitary
 effects:
 promotes
t protein
t i synthesis
th i (b
(builds
ild muscle)
l )
 promotes elongation of long bones
 metabolic breakdown of fat stores for energy
 continued overproduction can lead to acromegaly –
broadening of facial features and other bones
hGH abnormalities
 insufficient production in
childhood can lead to dwarfism
 overproduction in childhood can
lead to gigantism
The Thyroid & Parathyroid Glands
 thyroid: one of the largest endocrine glands in the body
 located in the neck
 attached to four small parathyroid glands
Major thyroid hormones
1. thyroxine
y
((aka T4)
2. calcitonin
Th ro ine (T4)
Thyroxine
 function:
f
ti
 increases cellular rate of metabolism
 no specific target
 secretion is controlled by
y negative
g
feedback
Hyperthyroidism:
Excessive secretion
of thyroid
y
hormones
1.
hypothalamus releases thyroid-releasing hormone (TRH)
2.
TRH signals anterior pituitary to release thyroid-stimulating
hormone (TSH)
3.
TSH acts on thyroid
4.
thyroid releases thyroxine
4.
Negative
N
ti ffeedback:
db k high
hi h llevels
l off thyroxine
th
i inhibit
i hibit the
th hypothalamus
h
th l
from releasing further TRH
Hypothyroidism:
Low secretion
of thyroid
y
hormones
 elevated metabolism
 muscle weakness
 high body temperature
 cold intolerance
 high heart rate, blood pressure
 dry skin and hair
 weight
g loss
 weight
g g
gain
 irritability
 low blood pressure and heart rate
Iodine and Thyroxine
 iodine is required for thyroxine production
 without adequate iodine, thyroxine is not produced
 TRH and TSH are not inhibited
 TSH continues to stimulate the thyroid's follicular cells
 thyroid enlarges → goitre forms
this iis why
thi
h iiodine
di iis
added to table salt
Calcitonin
 thyroid
y
gland
g
 lowers Ca2+ levels in the blood
 acts on bone cells to stimulate
uptake of calcium
 also acts on intestines to limit
absorption of calcium
Parathyroid Hormone (PTH)
 parathyroid glands
 raises Ca2+ levels in the blood
(works antagonistically with calcitonin)
 kidneys: Ca2+ reabsorption
 intestines:  Ca2+ absorption
 bones: Release Ca2+
Home ork
Homework
 Pg. 395 #1, 2, 4-8, 10, 11
 Pg. 403 #2, 7-10