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Chapter 41
Lecture 14
Animal Hormones
Dr. Chris Faulkes
Animal Hormones
Aims:
•  To appreciate the variety and roles of hormones in
the body
•  To understand the basic types of hormones
•  To understand how hormones work
•  To introduce the study of mechanisms of hormone
action
•  To examine the roles of hormones in maintaining
blood glucose levels
Animal Hormones
Aims:
•  To appreciate the variety and roles of hormones in the body
•  To understand the basic types of hormones
•  To understand how hormones work
•  To introduce the study of mechanisms of hormone action
•  To examine the roles of hormones in maintaining blood glucose levels
These lecture aims form part of the knowledge
required for learning outcome 4:
Appreciate how the physiology of an organism fits
it for its environment (LOC4).
Animal Hormones
Essential reading
•  Pages 874-876
•  Pages 878-881
•  Page 883
•  Page 887
•  Pages 890-893
All of the chapter is worth reading.
41 Animal Hormones
• 41.1 What Are Hormones and How Do
They Work?
• 41.2 How Do the Nervous and
Endocrine Systems Interact?
• 41.3 What Are the Major Mammalian
Endocrine Glands and Hormones?
• 41.4 How Do We Study Mechanisms of
Hormone Action?
41.1 What Are Hormones and How Do They Work?
Hormones are chemical signals secreted
by cells of the endocrine system.
Endocrine cells: cells that secrete
hormones
Target cells: cells that have receptors for
the hormones
41.1 What Are Hormones and How Do They Work?
Circulating hormones diffuse into the
blood and can activate target cells far
from the site of release.
Paracrine hormones: affect only target
cells near the site of release.
Autocrine hormones: affect the cells
that released the hormones.
Figure 41.1 Chemical Signaling Systems
41.1 What Are Hormones and How Do They Work?
Some endocrine cells are single cells
(e.g., in the digestive tract.)
Endocrine glands: aggregations of
secretory cells. Hormones are secreted
to the extracellular space.
Exocrine glands: ducts carry products to
the outside of the body.
41.1 What Are Hormones and How Do They Work?
Chemical communication arose early in
evolution.
Plants, sponges, protists all use chemical
signals.
In arthropods, hormones control molting
and metamorphosis.
41.1 What Are Hormones and How Do They Work?
Three types of hormones:
• Peptides or polypeptides: water-soluble,
transported in blood but not across
membranes.
• Steroid hormones: lipid-soluble; must be
bound to carrier proteins to be carried in
blood.
• Amine hormones: derivatives of tyrosine
41.1 What Are Hormones and How Do They Work?
Hormone receptors:
• Lipid soluble hormones: receptors are
inside the cell
• Water-soluble hormones cannot readily
pass cell membrane—receptors are on
the outside
41.1 What Are Hormones and How Do They Work?
Receptors are glycoproteins with three
domains:
• Binding domain: projects outside plasma
membrane
• Transmembrane domain
• Cytoplasmic domain: extends into
cytoplasm—initiates target cell response
41.1 What Are Hormones and How Do They Work?
One hormone can trigger different
responses in different types of cells.
Example: epinephrine (amine), fight-orflight response
Figure 41.4 Epinephrine Stimulates Fight or Flight Responses
Epinephrine Stimulates Fight or Flight Responses
Human physiological response to adrenaline
Figure 41.5 The Endocrine System of Humans
41.2 How Do the Nervous and Endocrine Systems Interact?
The pituitary gland is attached to the
hypothalamus of the brain.
Posterior pituitary secretes
neurohormones (synthesized by
neurons in the hypothalmus): oxytocin
and ADH.
Figure 41.6 The Posterior Pituitary Releases Neurohormones
Neurobiology of sociality
(extra reading)
41.2 How Do the Nervous and Endocrine Systems Interact?
The anterior pituitary secretes:
• Tropic hormones: control other endocrine
glands
• Growth hormone: promotes growth
• Prolactin: breast development and milk
production
• Enkephalins and endorphins: natural
opiates
Figure 41.7 The Anterior Pituitary Produces Many Hormones
41.3 What Are the Major Mammalian Endocrine Glands and
Hormones?
Thyroxine regulates cell metabolism.
Anterior pituitary secretes thyrotropin
(TSH), which activates the follicles to
produce thyroxine.
41.3 What Are the Major Mammalian Endocrine Glands and
Hormones?
The thyroid gland produces thyroxine (T4)
and triiodothyronine (T3)
Figure 41.9 The Thyroid Gland Consists of Many Follicles (A)
Thyroxine is produced
by the follicles
41.3 What Are the Major Mammalian Endocrine Glands and
Hormones?
Adrenal gland: two glands
Adrenal medulla: epinephrine and
norepinephrine
On target cells: α-adrenergic and βadrenergic receptors.
β-blockers block β-adrenergic receptors.
Figure 41.11 The Adrenal Gland Has an Outer and an Inner Portion
41.3 What Are the Major Mammalian Endocrine Glands and
Hormones?
Adrenal cortex produces corticosteroids
from cholesterol:
• Glucocorticoids: cortisol
• Mineralocorticoids: aldosterone
• Sex steroids
Figure 41.12 The Corticosteroid Hormones are Built from Cholesterol
41.4 How Do We Study Mechanisms of Hormone Action?
To study hormone action:
• Identify and measure the hormone
• Identify the receptors
• Determine the signal transduction
pathways in different tissues.
41.4 How Do We Study Mechanisms of Hormone Action?
Hormones occur in extremely small
concentrations.
Immunoassay techniques are used to
measure concentration in the blood.
Half-life: time required for one half of the
hormone molecules to be depleted.
Figure 41.15 An Immunoassay Measures Hormone Concentration
Reproduc)ve+suppression+in+female+naked+mole4rats+
41.4 How Do We Study Mechanisms of Hormone Action?
One hormone may bind to different
receptors.
Drugs can be created to block specific
responses.
Receptors can be identified by affinity
chromatography.
Receptors can also be identified by
genomic analyses.
41.4 How Do We Study Mechanisms of Hormone Action?
Abundance of hormone receptors can be
regulated by negative feedback.
Downregulation: continuous high levels of
hormone decreases number of receptors.
Upregulation: when hormone secretion is
suppressed, receptors increase.
41.4 How Do We Study Mechanisms of Hormone Action?
Type II diabetes mellitus results from downregulation
of insulin receptors.
Possibly due to overstimulation of pancreatic release
of insulin by excessive carbohydrate intake.
Beta blockers can result in upregulation—if beta
receptors are blocked over time, more receptors
are produced.
41.4 How Do We Study Mechanisms of Hormone Action?
Receptors can be linked to different signal
transduction pathways.
Example: epinephrine and norepinephrine
connect with different pathways—can
have different effects even in the same
cell.
Figure 41.17 Some Hormones Can Activate a Variety of Signal Transduction Pathways
41.4 How Do We Study Mechanisms of Hormone Action?
Signal transduction pathways can be
cascades, in which each step amplifies
the response.
One hormone molecule binding to a
receptor might result in millions of
molecules of final product.
Example: response of liver cells to
epinephrine.
Animal Hormones
Check out
•  41.1 RECAP, page 879, questions 2 and 3
•  41.1 CHAPTER SUMMARY, page 893, see Web/CD activity 41.1
•  41.3 RECAP, page 890, question 3 only
•  41.4 RECAP, page 893
•  41.4 CHAPTER SUMMARY, page 894, See WEB/CD Activity 41.2
Self Quiz
page 894: Chapter 41, questions 5, 9 and 10
For Discussion
•  page 895: Chapter 41, question 4
Animal Hormones
Key terms:
affinity chromatography, amine hormone, autocrine,
chemical messenger, diabetes, downregulation,
endocrine, epinephrine, exocrine, feedback,
glucagon, hormone, hypothalamus, immunoassay,
insulin, neurohormone, pancreas, paracrine, peptide
hormone, pituitary gland, receptor, signal
transduction pathway, steroid hormone,
stomatostatin, target cell, upregulation