Download Hormones - Castle High School

30
Animal Hormones
Chapter 30 Animal Hormones
Key Concepts
• 30.1 Hormones Are Chemical Messengers
• 30.2 Hormones Act by Binding to
Receptors
• 30.3 The Pituitary Gland Links the
Nervous and Endocrine Systems
• 30.4 Hormones Regulate Mammalian
Physiological Systems
Chapter 30 Opening Question
How do the transformative effects of
testosterone exemplify the way many
hormones work?
Concept 30.1 Hormones Are Chemical Messengers
Endocrine secretion—cells secrete
substances into the extracellular fluid
Exocrine secretion—cells secrete
substances into a duct or a body cavity
that communicates to the external world
Concept 30.1 Hormones Are Chemical Messengers
Endocrine cells—cells that secrete
endocrine signals
Some endocrine cells exist as single cells
(e.g., in the digestive tract).
Endocrine glands—secretory organs
composed of aggregations of endocrine
cells
Concept 30.1 Hormones Are Chemical Messengers
Endocrine signaling molecules are paracrine
signals, autocrine signals, or hormones.
Hormones are “long-distance” endocrine
signals that are released into the
bloodstream and circulate throughout the
body.
Concept 30.1 Hormones Are Chemical Messengers
Target cells—cells that have receptors for
the chemical signals
The same hormone can have a variety of
different target cells, all distant from the
site of release.
Concept 30.1 Hormones Are Chemical Messengers
Hormones are in three chemical groups:
• Peptide and protein hormones—watersoluble, transported in blood with
receptors on exterior of target cells
• Steroid hormones—synthesized from
cholesterol; lipid-soluble; bound to carrier
proteins in blood; receptors inside target
cells
Concept 30.1 Hormones Are Chemical Messengers
• Amine hormones—synthesized from
single amino acids; may be lipid-soluble or
water-soluble, depending on the charge of
the amino acid
Figure 30.1 Three Classes of Hormones (Part 1)
Figure 30.1 Three Classes of Hormones (Part 2)
Figure 30.1 Three Classes of Hormones (Part 3)
Concept 30.1 Hormones Are Chemical Messengers
Chemical communication was critical for
evolution of multicellular organisms.
Plants, sponges, and protists all use
chemical signals.
Signaling molecules are highly conserved,
but their functions differ.
Concept 30.1 Hormones Are Chemical Messengers
In arthropods, hormones control molting and
metamorphosis
The rigid exoskeleton is shed during molts
to allow growth.
Growth stages between molts are called
instars.
Figure 30.2 A Diffusible Substance Triggers Molting (Part 1)
Figure 30.2 A Diffusible Substance Triggers Molting (Part 2)
Concept 30.1 Hormones Are Chemical Messengers
Two hormones regulate molting:
PTTH (prothoracicotropic hormone), from
cells in the brain, is stored in the corpora
cardiaca
PTTH stimulates the prothoracic gland to
secrete ecdysone.
Ecdysone diffuses to target tissues and
stimulates molting.
Concept 30.1 Hormones Are Chemical Messengers
A third hormone, juvenile hormone, is also
released from the brain—prevents
maturation to adult form.
Control of development by juvenile hormone
is important in insects with complete
metamorphosis.
Figure 30.3 Hormonal Control of Metamorphosis
Concept 30.2 Hormones Act by Binding to Receptors
Hormone receptors can be membranebound with three domains:
• Binding domain—projects outside plasma
membrane
• Transmembrane domain—anchors
receptor
• Cytoplasmic domain—extends into
cytoplasm, initiates target cell response
Concept 30.2 Hormones Act by Binding to Receptors
Hormone receptors can also be intracellular:
• Lipid soluble hormones—receptors are
inside the cell, usually in the cytoplasm
When hormone binds, the hormone–
receptor complex moves into the nucleus.
Concept 30.2 Hormones Act by Binding to Receptors
One hormone can trigger different
responses in different types of cells.
Epinephrine and norepinephrine are
secreted by adrenal glands in the fight-orflight response.
These hormones bind to adrenergic
receptors.
Figure 30.4 The Fight-or-Flight Response
Concept 30.2 Hormones Act by Binding to Receptors
Two categories: -adrenergic and adrenergic receptors
Stimulation of one receptor can cause
diverse effects, depending on its location.
Example: -adrenergic stimulation causes
sweating in skin and shutdown of digestive
enzymes and decreased blood flow in gut.
Figure 30.5 Adrenergic Receptors (Part 1)
Figure 30.5 Adrenergic Receptors (Part 2)
Concept 30.2 Hormones Act by Binding to Receptors
Abundance of hormone receptors can be
regulated by negative feedback.
Downregulation—continuous high level of
hormone decreases number of receptors.
Upregulation—when hormone secretion is
suppressed, receptors increase.
Figure 30.6 The Human Endocrine System
Concept 30.3 The Pituitary Gland Links the Nervous and
Endocrine Systems
The nervous system communicates via
molecules—neurotransmitters.
The endocrine system communicates via
molecules released into the blood.
The systems are complementary—nervous
system is rapid and specific, endocrine
system is broader and longer-term.
Concept 30.3 The Pituitary Gland Links the Nervous and
Endocrine Systems
The nervous and endocrine systems also
interact.
Nervous system controls activity of many
endocrine glands.
Some neurons secrete hormones directly—
neurohormones.
Endocrine system can also influence the
nervous system—steroids promote sexual
behavior.
Concept 30.3 The Pituitary Gland Links the Nervous and
Endocrine Systems
The pituitary gland connects the nervous
and endocrine systems.
The pituitary gland is attached to the
hypothalamus of the brain.
Two parts—the anterior pituitary and
posterior pituitary
Figure 30.7 The Posterior Pituitary (Part 1)
Concept 30.3 The Pituitary Gland Links the Nervous and
Endocrine Systems
The hypothalamus secretes two
neurohormones into the posterior pituitary:
antidiuretic hormone (vasopressin) and
oxytocin.
Antidiuretic hormone (ADH) serves to
increase the water retained by the kidneys
when necessary.
Oxytocin stimulates contractions, milk flow,
promotes bonding—the “cuddle chemical”
Figure 30.7 The Posterior Pituitary (Part 2)
Concept 30.3 The Pituitary Gland Links the Nervous and
Endocrine Systems
The anterior pituitary secretes four tropic
hormones that control other endocrine
glands:
• Thyroid-stimulating hormone (TSH)
• Luteinizing hormone (LH)
• Follicle-stimulating hormone (FSH)
• Adrenocorticotropin hormone (ACTH)
Figure 30.8 The Anterior Pituitary
Concept 30.3 The Pituitary Gland Links the Nervous and
Endocrine Systems
The anterior pituitary also secretes other
peptide hormones including prolactin and
growth hormone.
Growth hormone (GH) stimulates cells to
take up amino acids.
GH stimulates the liver to produce
somatomedins or insulin-like growth
factors (IGFs).
Overproduction of GH causes gigantism;
underproduction causes pituitary dwarfism.
Concept 30.3 The Pituitary Gland Links the Nervous and
Endocrine Systems
Neurohormones from the hypothalamus
control subsequent hormone production in
the anterior pituitary.
The hypothalamus sends secretions to the
anterior pituitary via the portal blood
vessels.
Concept 30.3 The Pituitary Gland Links the Nervous and
Endocrine Systems
Hypothalamic neurohormones are released
in minute quantities measurable by
immunoassay.
The first releasing hormone to be purified
was thyrotropin-releasing hormone
(TRH).
TRH causes anterior pituitary cells to
release thyroid-stimulating hormone
(TSH).
TSH causes the thyroid gland to release
thyroxine.
Concept 30.3 The Pituitary Gland Links the Nervous and
Endocrine Systems
Negative feedback loops control hormone
secretion from the anterior pituitary.
Corticotropin is released by pituitary—
adrenal produces cortisol in response.
Circulating cortisol in bloodstream reaches
pituitary and inhibits production.
Hypothalamus slows release of
corticotropin-releasing hormone.
Figure 30.9 Multiple Feedback Loops Control Hormone Secretion
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
The thyroid gland contains two cell types
that produce two different hormones,
thyroxine and calcitonin.
In or near the thyroid gland are the
parathyroid glands, which produce
parathyroid hormone.
Thyroxine (T4) is synthesized from the
amino acid tyrosine and iodine.
T3 is a similar hormone that is more active.
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
In birds and mammals, thyroxine raises
metabolic rate.
Thyroxine regulates cell metabolism by
acting as a transcription factor for many
genes and is crucial during development.
Hypothalamus releases thyrotropinreleasing hormone (TRH), which causes
anterior pituitary to secrete thyroidstimulating hormone (TSH).
TSH causes the thyroid to produce
thyroxine.
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
Goiter is an enlarged thyroid gland.
Hyperthyroidism (thyroxine excess) is often
caused by an autoimmune disease.
Antibody-binding activates TSH receptors
on follicle cells and increases thyroxine.
Thyroid remains stimulated and grows
bigger.
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
Hypothyroidism (thyroxine deficiency) is the
result of low circulating thyroxine.
The most common cause is iodine
deficiency—thyroid cannot produce
thyroxine.
TSH levels remain high and stimulate the
thyroid to grow bigger.
Figure 30.10 Goiter
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
Blood calcium concentration is controlled by
calcitonin, calcitriol (from vitamin D), and
parathyroid hormone (PTH).
Mechanisms for changing calcium levels:
• Deposition or absorption by bone
• Excretion or retention by kidneys
• Absorption of calcium from digestive tract
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
Calcitonin, released by thyroid, lowers blood
calcium (Ca2+) by regulating bone
turnover.
Osteoclasts break down bone, increasing
blood Ca2+.
Ca2+ is deposited into bone by osteoblasts;
levels of Ca2+ in blood decrease.
Calcitonin decreases osteoclast activity and
favors adding calcium to bones.
Figure 30.11 Hormonal Regulation of Calcium
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
Vitamin D (calciferol) is synthesized
from cholesterol in skin cells by UV
light.
Once synthesized it is converted to
calcitriol, a hormone that stimulates
calcium absorption from food.
If light is insufficient, vitamin D must be
obtained from diet or supplements.
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
The parathyroid glands secrete
parathyroid hormone (PTH).
PTH raises blood calcium levels:
• Stimulates osteoclasts and
osteoblasts
• Stimulates kidneys to reabsorb
calcium
• Activates synthesis of calcitriol from
vitamin D
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
Each of the two adrenal glands is a gland
within a gland.
The core, or adrenal medulla, produces
epinephrine and norepinephrine.
Release of these neurohormones is under
control of the nervous system and is very
rapid in the stress response.
Figure 30.12 The Adrenal Is a Gland within a Gland
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
The outer adrenal cortex produces two
types of corticosteroid hormones:
• Mineralocorticoids influence salt and
water balance
Aldosterone, the main mineralocorticoid,
stimulates kidneys to conserve sodium
and excrete potassium.
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
• Glucocorticoids influence blood glucose
concentration
Cortisol, the main glucocorticoid in
humans and mammals, mediates
metabolic stress response.
After a stressful stimulus, blood cortisol
rises.
Cells not critical for action decrease their
use of blood glucose—immune system
reactions are also blocked.
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
Gonads produce sex steroids.
Androgens—male steroids, testosterone
Estrogens and progesterone—female
steroids
Both sexes use both types, in varying levels.
In embryos, sex hormones determine sex of
fetus; at puberty, they stimulate maturation
and secondary sex characteristics.
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
Sex hormones exert their effects by the
seventh week of human development.
If a Y chromosome is present, gonads begin
producing testosterone and MIS
(Müllerian-inhibiting substance)—these
produce male reproductive organs and
inhibit female reproductive structures.
Without androgens, female reproductive
structures develop.
Figure 30.13 Sex Steroids Direct the Development of Human Sex Organs (Part 1)
Figure 30.13 Sex Steroids Direct the Development of Human Sex Organs (Part 2)
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
At puberty, production of sex hormones
increases.
Controlled by tropic hormones called
gonadotropins from the anterior pituitary:
• Luteinizing hormone (LH)
• Follicle-stimulating hormone (FSH)
Concept 30.4 Hormones Regulate Mammalian Physiological
Systems
Gonadotropins are controlled by
hypothalamic gonadotropin-releasing
hormone (GnrH)—its release increases at
puberty.
Increase in gonadotropins leads to increase
in sex steroids and development of
secondary sex characteristics.
Answer to Opening Question
Hormones and their receptor complexes can
have varying effects depending on the
type of target cells.
The receptors are essential because without
them the circulating hormones are unable
to have the desired effect.
Hormones may also be modified during
development, with different effects at
different stages.
Figure 30.14 Real People, Real Lives