Chapter 41: Animal Hormones
CHAPTER 41
Animal Hormones
Chapter 41: Animal Hormones
Chapter 41: Animal
Hormones
Hormones and Their Actions
Hormonal Control of Molting and Development
in Insects
Vertebrate Endocrine Systems
Mechanisms of Hormone Action
Chapter 41: Animal Hormones
Hormones and Their Actions
• Endocrine cells secrete chemical messages
called hormones, which bind to receptors on
or in target cells. See Figure 1
3
Chapter 41: Animal Hormones
Hormones and Their Actions
• Most hormones diffuse through extracellular
fluids, are picked up by the blood, and
distributed throughout the body.
• Some diffuse to targets near the secretion
site.
• Autocrine hormones influence the cell that
secretes them
• Paracrine hormones influence nearby cells.
Review Figure 41.1
4
Chapter 41: Animal Hormones
figure 41-01.jpg
Figure
41.1
Figure 41.1
Chapter 41: Animal Hormones
Hormones and Their Actions
• Hormones cause different responses in
different target cells.
6
Chapter 41: Animal Hormones
Hormones and Their Actions
• The chemical structures of hormones have
changed little through evolution, but their
functions have changed dramatically.
7
Chapter 41: Animal Hormones
Hormones and Their Actions
• Hormones may be secreted by single cells
or by cells organized into discrete endocrine
glands. Review Figure 41.2
8
Chapter 41: Animal Hormones
figure 41-02.jpg
Figure 41.2
Figure 41.2
Chapter 41: Animal Hormones
Hormonal Control of Molting
and Development in Insects
• Insects molt their exoskeletons to grow.
• Two diffusible substances, brain hormone
and ecdysone, control molting.
Review Figure 41.3
10
Chapter 41: Animal Hormones
figure 41-03a.jpg
Figure 41.3
– Part 1
Figure 41.3 – Part 1
Chapter 41: Animal Hormones
figure 41-03b.jpg
Figure 41.3
– Part 2
Figure 41.3 – Part 2
Chapter 41: Animal Hormones
Hormonal Control of Molting
and Development in Insects
• Juvenile hormone, another diffusible
substance, prevents maturation so that
juvenile instars molt into bigger juvenile
instars.
• When juvenile hormone level falls low
enough, the juvenile molts into the adult
form.
13
Chapter 41: Animal Hormones
Hormonal Control of Molting
and Development in Insects
• Some insects go through complete
metamorphosis.
• When juvenile hormone drops to a low
level, the larval form becomes a pupa.
• Because no juvenile hormone is secreted
during pupation, the pupa molts into an
adult.
Review Figure 41.4
14
Chapter 41: Animal Hormones
figure 41-04.jpg
Figure 41.4
Figure 41.4
Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• Vertebrates have nine endocrine glands that
secrete many hormones.
Review Figure 41.2, Table 41.1
16
Chapter 41: Animal Hormones
table 41-01a.jpg
Table 41.1
– Part 1
Table 41.1 – Part 1
Chapter 41: Animal Hormones
table 41-01b.jpg
Table 41.1
– Part 2
Table 41.1 – Part 2
Chapter 41: Animal Hormones
table 41-01c.jpg
Table 41.1
– Part 3
Table 41.1 – Part 3
Chapter 41: Animal Hormones
table 41-01d.jpg
Table 41.1 –
Part 4
Table 41.1 – Part 4
Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• The pituitary gland is divided into two parts.
• The anterior pituitary develops from
embryonic mouth tissue
• The posterior pituitary develops from the
brain.
21
Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• The posterior pituitary secretes the
neurohormones vasopressin and oxytocin.
Review Figure 41.5
22
Chapter 41: Animal Hormones
figure 41-05.jpg
Figure 41.5
Figure 41.5
Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• The anterior pituitary secretes:
• Tropic hormones (thyrotropin,
adrenocorticotropin, and two
gonadotropins), and
• Growth hormone, prolactin, melanocytestimulating hormone, endorphins, and
enkephalins.
24
Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• The anterior pituitary is controlled by
neurohormones produced by cells in the
hypothalamus and transported through
portal blood vessels to the anterior pituitary.
Review Figure 41.7, Table 41.2
25
Chapter 41: Animal Hormones
figure 41-07.jpg
Figure
41.7
Figure 41.7
Chapter 41: Animal Hormones
table 41-02.jpg
Table 41.2
Table 41.2
Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• Hormone release in the
hypothalamus/pituitary/endocrine gland axis
is controlled by many feedback loops.
Review Figure 41.8
28
Chapter 41: Animal Hormones
figure 41-08.jpg
Figure
41.8
Figure 41.8
Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• The thyroid gland is controlled by
thyrotropin and secretes thyroxine, which
controls cell metabolism.
Review Figure 41.9
30
Chapter 41: Animal Hormones
figure 41-09.jpg
Figure
41.9
Figure 41.9
Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• Calcium levels in the blood are regulated by
two hormones.
• Calcitonin, produced by the thyroid, lowers
blood calcium.
• Parathormone, produced by the parathyroid
glands, raises it.
Review Figure 41.10
32
Chapter 41: Animal Hormones
figure 41-10.jpg
Figure 41.10
Figure 41.10
Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• The pancreas secretes three hormones.
• Insulin stimulates glucose uptake by cells
and lowers blood glucose
• Glucagon raises blood glucose
• Somatostatin slows nutrient absorption rate
from the gut.
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Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• The adrenal gland has two portions.
• The hormones of the adrenal medulla,
epinephrine and norepinephrine, stimulate
the liver to supply glucose to the blood, as
well as other fight-or-flight reactions.
Review Figure 41.11
35
Chapter 41: Animal Hormones
figure 41-11.jpg
Figure
41.11
Figure 41.11
Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• The adrenal cortex produces three classes
of corticosteroids:
glucocorticoids
 mineralocorticoids
 small amounts of sex steroids.
Review Figure 41.12

37
Chapter 41: Animal Hormones
figure 41-12.jpg
Figure 41.12
Figure 41.12
Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• Aldosterone is a mineralocorticoid that
stimulates the kidney to conserve sodium
and to excrete potassium.
39
Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• Cortisol is a glucocorticoid that decreases
glucose utilization by most cells.
40
Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• Sex hormones are produced by the gonads
in response to tropic hormones.
• Sex hormones control sexual development,
secondary sexual characteristics, and
reproductive functions.
Review Figure 41.13
41
Chapter 41: Animal Hormones
figure 41-13.jpg
Figure
41.13
Figure 41.13
Chapter 41: Animal Hormones
Vertebrate Endocrine
Systems
• The pineal hormone melatonin is involved in
controlling biological rhythms and
photoperiodism.
Review Figure 41.14
43
Chapter 41: Animal Hormones
figure 41-14.jpg
Figure
41.14
Figure 41.14
Chapter 41: Animal Hormones
Mechanisms of Hormone
Action
• The responses of a cell to a hormone
depend on what receptors it has and what
signal transduction pathways those
receptors activate.
Review Table 41.3
45
Chapter 41: Animal Hormones
table 41-03.jpg
Table 41.3
Table 41.3
Chapter 41: Animal Hormones
Mechanisms of Hormone
Action
• Receptors for water-soluble hormones are
on the cell surface, and receptors for lipidsoluble hormones are inside the cell.
47
Chapter 41: Animal Hormones
Mechanisms of Hormone
Action
• Cell sensitivity to hormones can be altered
by up- or downregulation of the receptors in
that cell.
48
Chapter 41: Animal Hormones
Mechanisms of Hormone
Action
• Sensitivity and time course of hormone response
depend on many factors
receptor numbers
 properties of signal transduction
pathways
 other hormones
 binding of the hormone to carrier proteins
 elimination of the hormone through
degradation and excretion.

49
Chapter 41: Animal Hormones
Mechanisms of Hormone
Action
• Important tools for characterizing hormone
action are dose–response curves and
measurements of half-life.
Review Figure 41.15
50
Chapter 41: Animal Hormones
figure 41-15.jpg
Figure 41.15
Figure 41.15