Download The Living World - Chapter 29 - McGraw Hill Higher Education

Essentials of
The Living World
First Edition
GEORGE B. JOHNSON
24
Chemical Signaling
Within the
Animal Body
PowerPoint® Lectures prepared by Johnny El-Rady
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
24.1 Hormones
A hormone is a chemical signal that is produced in
one part of the body and that acts at a distant site
Three advantages to using chemical signals
1. Can spread to all tissues via the blood
2. Can persist much longer than electric signals
3. Many can act as hormones
Different hormones can target different tissues
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Hormones are produced by endocrine glands
These glands do not have ducts
Hormones are secreted directly into the blood
Hormones are under the control of the
neuroendocrine system
The hypothalamus is the main switchboard
Issues commands to the nearby pituitary gland
Pituitary sends chemical signals to the
various hormone-producing glands in body
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Fig. 24.1
Major glands
of the human
endocrine
system
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Hormones are effective because they are
recognized by specific receptors
These are on or in target cells
The path of communication of a hormone signal
1. Issuing the command
By the hypothalamus
2. Transporting the signal
By the blood
3. Hitting the target
Binding to the receptor
4. Having an effect
A change in cell activity
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Fig. 24.2 How hormonal communication works
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
24.2 How Hormones Target Cells
Steroid hormones
Manufactured from cholesterol
Lipid-soluble and thus can across the lipid bilayer
of the cell membrane
Bind to receptors within the nucleus usually
The hormone-receptor complex binds to
DNA causing changes in gene activity
Anabolic steroids
Synthetic compounds resembling testosterone
Cause muscle cells to produce more protein
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Fig. 24.3 How steroid hormones work
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Peptide hormones
Short peptides or
full-sized proteins
Bind to receptors
embedded in the
cell membrane
Induce a change
in cytoplasmic
end of the
receptor protein
Triggers
events within
the cytoplasm
Fig. 24.4
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
The change in cellular activity is facilitated by
second messengers such as cAMP
Trigger a cascade of enzymic activation within cell
Fig. 24.5
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
24.3 The Hypothalamus
and the Pituitary
The pituitary gland is located in a bony recess in the
brain below the hypothalamus
It produces nine major hormones
It is actually two glands
Posterior lobe
Anterior lobe
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
The Posterior Pituitary
Stores and releases two short peptide hormones
Vasopressin (antidiuretic hormone, ADH)
Regulates water conservation by the kidney
Oxytocin
Initiates uterine contractions during childbirth
Causes milk letdown
Both synthesized within hypothalamus neurons
Transported down nerve axons to the
posterior lobe
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Fig. 24.6 Posterior pituitary
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
The Anterior Pituitary
A complete gland that produces seven major
hormones
1.
2.
3.
4.
5.
6.
7.
Thyroid-stimulating hormone (TSH)
Luteinizing hormone (LH)
Follicle-stimulating hormone (FSH)
Adrenocorticotropic hormone (ACTH)
Growth hormone (GH)
Prolactin
Melanocyte-stimulating hormone (MSH)
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Fig. 24.7 The role of the pituitary
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
The hypothalamus controls the anterior pituitary
Secretes
releasing and
inhibiting
hormones into
capillaries
Hypothalamohypophyseal
portal system
carries the
hormones to
the pituitary
Fig. 24.8
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Hypothalamus and anterior pituitary are themselves
controlled by negative feedback inhibition
Regulated by the hormones whose secretion they stimulate!
Fig. 24.9
Thyrotropinreleasing hormone
Gonadotropinreleasing hormone
Corticotropinreleasing hormone
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
24.4 The Pancreas
The pancreas gland is located behind the stomach
Secretes a number of digestive enzymes into the small
intestine through a narrow tube
Islets of Langerhans govern blood glucose levels
Insulin
Secreted by beta cells
Storage hormone that promotes accumulation of
glycogen in liver and triglycerides in fat cells
Glucagon
Secreted by alpha cells
Cause release of stored glucose and fat breakdown
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Fig. 24.10
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Diabetes mellitus
Affected individuals cannot take up glucose from the blood
Type I
~ 5-10% of diabetics
Autoimmune disorder in which immune systems attacks
the Islets of Langerhans
Develops before age 20 (juvenile-onset diabetes)
Treated by daily injections of insulin
Type II
~ 90-95% of diabetics
Caused by abnormally low number of insulin receptors
Develops after age 40 (adult-onset diabetes)
Typically in obese individuals
Treated by diet and exercise
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
24.5 The Thyroid, Parathyroid
and Adrenal Glands
The thyroid gland lies just below the Adam’s apple in
front of the neck
Its two most important hormones are
Thyroxine
Increases metabolic rate and promotes growth
Contains iodine
Lack of iodine in diet causes goiters
Calcitonin
Stimulates calcium deposition in the bone
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Fig. 24.11 The thyroid gland secretes thyroxine
Goiter
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
The parathyroid glands are four small glands
attached to the thyroid
Produce parathyroid hormone (PTH)
One of only two hormones essential for survival
Acts as a fail-safe mechanism ensuring that calcium
levels never fall too low
Calcium ions are key to muscle contractions
When levels are low, PTH stimulates osteoclast
cells to break down bone matrix
This raises calcium levels in the blood
PTH also acts on kidneys to reabsorb calcium ions from
the urine
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Fig. 24.12 Maintenance of proper calcium levels in the blood
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
The adrenal glands are two glands, one located just
above each kidney
Each composed of two parts
Medulla – Inner core
Adrenaline and norepinephrine
Released in times of stress to stimulate rapid
deployment of body fuel
Cortex – Outer shell
Cortisol – Stimulates carbohydrate metabolism and
reduces inflammation
Aldosterone – Stimulates the kidney to uptake
sodium and other ions from the urine
This is the other hormone that is absolutely
essential for survival
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
24.6 A Host of Other Hormones
Steroid sex hormones
Estrogen, progesterone and testosterone
Produced by gonads to regulate sexual development
Atrial natriuretic hormone
Secreted by the right atrium of the heart
Stimulate kidneys to excrete salts and water in the urine
Erythropoietin
Secreted by the kidney
Stimulates the bone marrow to produce RBC
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Molting and Metamorphosis in Insects
Molting is triggered by the molting hormone, also
called ecdysone
The production of ecdysone is itself controlled by
the brain hormone
These two hormones are balanced by a third
hormone, the juvenile hormone
If present in high levels, it inhibits the formation
of the pupa and adult forms
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Fig. 24.13 The hormonal control of metamorphosis in the silkworm moth, Bombyx mori
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display