Download Intro to Endocrine - Valdosta State University

CHAPTER 18
The Endocrine System
Endocrine is NOT Exocrine
• Exocrine glands secrete their products into
ducts.
– Sudoriferous (sweat) glands
– Sebaceous (oil) glands
– Mucous glands
– Digestive glands
None of these are hormones!
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
A Little Endocrine FYI:
• Endocrinology is the study of ductless glands or
tissues and their hormonal products
• Endocrine gland – composed of a prominent
parenchyma of secretory cells, connective tissue,
blood vessels and nerves.
• Endocrine glands are ductless and secrete their
products directly into the blood.
– Can include any group of cells that secrete a hormone.
Endocrine Glands
• Endocrine glands secrete hormones.
– Do not have ducts
– Secrete their hormones directly into the
interstitial fluid that surrounds them.
– The hormones then diffuse into the blood stream
through capillaries and are carried to target cells
throughout the body.
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Endocrine Glands/Organs
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Endocrine Glands & Organs
• Classic Glands
– Pituitary
– Thyroid
– Parathyroid
– Islets of Langerhans
– Adrenal Glands
– Gonads
– Placenta
• Organs w/ Endocrine
Functions
– Brain
– Heart
– Liver
– GI Tract
– Kidneys
– Adipose (fat)
Chemical Messenger Classifications
• Chemical messenger is any substance
produced by a cell that plays a physiological
role in the control of the activity of a another
cell.
• Hormone is any substance elaborated by one
cell to regulate another cell and may be
delivered in an endocrine, paracrine,
autocrine or pheromonal route.
But what about all those neuro messengers?
“Neuro Is As Neuro Does”
• Neurotransmitters are released
by neurons and travel only
across the synaptic
cleft/neuromuscular junction
• Neuromodulators are released
by neurons to affect other
neurons but are not
immediately taken up or
metabolized like NTs
• Neurohormones are hormones
produced by a nerve cell and
released into the blood to reach
their target cells
Control by the Nervous and Endocrine
Systems
• The nervous and endocrine systems act
together to coordinate all systems of the body.
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Credit: Dr. Michael Ormsbee, Florida State University
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Hormone Delivery Review
• Endocrine where the messenger is bloodborne.
• Neuroendocrine where the hormone
released by a nerve is blood borne.
• Paracrine where the released hormone
diffuses to adjacent target cells through the
immediate extracellular space.
• Autocrine where the hormone may feedback
to the cell of origin to regulate it’s own
release.
Continued
• Neuromodulator is a hormone that modulates
the response of a neuron to a neurotransmitter
or other hormone. (all act as NM- feedback
loops)
• Pheromone is a chemical messenger released to
the exterior of one animal to stimulate a
response in another member of the same
species.
• Chalones (K-lone) are putative cellular mitotic
inhibitors
• Growth factors are mitogenic peptides which
may later become known as hormones.
Hormone Activity
Hormones are either:
• Lipid-soluble
– Steroid hormones, thyroid hormones, nitric oxide (NO)
• Water-soluble
– Amine hormones, peptide and protein hormones,
eicosanoid hormones
• Water-soluble hormones circulate freely in the plasma;
Lipid-soluble hormones circulate bound to transport
proteins.
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Credit: Dr. Michael Ormsbee, Florida State University
Where Do Hormones Come From?
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Where Do Hormones Come From?
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Physiological Role of Hormones
A.K.A. : What do hormones do?
1. Hormones affect cellular synthesis and
secretion of other hormones within other
endocrine glands and neurons.
2. Hormones affect anabolic and catabolic
processes.
3. Hormones affect contraction, relaxation, and
metabolism of muscle.
Continued
4. Hormones control reproductive processes
such as gondal differentiation, maturation, and
gametogenesis.
5. Hormones stimulate and inhibit cellular
proliferation, thus affecting growth. Hormones
regulate cell division and differentiation of the
fertilized egg.
Continued Some More
6. Hormones regulate the excretion and
reabsorption of inorganic cations and ions.
7. Hormones have a permissive action on other
hormones
8. Hormones play an important part in animal
behavior.
How Do Hormones Exert Their Influence??
Short answer: RECEPTORS
• Receptors (proteins or glycoproteins) provide
specificity for hormone-cell interaction.
• Receptors may be components of the cell
membrane or they may by cytosolic or
nuclear receptors. (steroid/thyroid/vitamin d)
• Cells do not possess receptors for all
hormones but rather have a limited number
of receptor types.
Hormone Activity
• Hormones traveling throughout the body will
only affect target cells that possess specific
protein receptors.
• Receptors are continually being synthesized
and broken down.
• Receptors may be down-regulated in the
presence of high concentrations of hormone.
• Receptors may be up-regulated in the
presence of low concentrations of hormone.
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Mechanisms of Hormone Action
Lipid-soluble
hormones bind to
receptors within
target cells.
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Mechanisms of Hormone Action
Water-soluble hormones
bind to receptors on the
exterior surface of the
target cell.
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Mechanisms of Hormone Action
How a target cell responds to a hormone is
based on:
– The hormone’s concentration in the blood
– The number of hormone receptors on the target
cell
– Influences exerted by other hormones
– Some hormones work more effectively when a
second hormone is present to assist them
(synergistic effect).
– Some hormones oppose the action of others
(antagonistic effect).
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Control of Hormone Secretion
Hormones are secreted in short bursts when
needed.
Secretion is regulated by:
– Signals from the nervous system
– Chemical changes in the blood
– Other hormones
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Control of Hormone Secretion
Most hormone regulation
is achieved via negative
feedback.
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Control of Hormone Secretion
A few hormones operate
via positive feedback.
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Control of Hormone Secretion
Interactions Animation:

Hormonal Cycles
You must be connected to the Internet and in Slideshow Mode to
run this animation.
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Neurotransmitters (NT)
• NT’s are chemical messengers released from
neurons into the synapse between the nerve
and its effector cells
• Secretory cells, muscle cells, or other neurons.
• Usually act in a paracrine fashion
• Many peptide hormones that function in a
classical sense are also synthesized in specific
neurons and may function as NT’s.
Neurohormones
NT’s that diffuse beyond the synapse and enter
the blood stream are termed Neurohormones.
– i.e. Dopamine
NT’s act very rapidly in comparison to
neuromodulators which exert a more sustained
response.
Neuromodulatory hormones may originate from
non-neuronal sources
– i.e. corticosteroids, androgens, estrogens.