Chp.45: Hormones & the Endocrine System (review: Chp.11
Cell Communication) AP Bio 3/14/13
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Remember: Why cells need to communicate: Coordinate activities
in multicellular organisms Hormone actions Cell recognition To find
mates (yeast cells) Turn pathways on/off apoptosis 2
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Evolutionary ties of cell communication Cell-to-cell
communication is everywhere in biological systems from Archaea and
bacteria to multicellular organisms. The basic chemical processes
of communication are shared across evolutionary lines of descent.
Signal transduction is an excellent example 3
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Signal Transduction Animation Click on this link to access the
animation: http://www.wiley.com/college/boyer/047000
3790/animations/signal_transduction/signal_ transduction.htm 4
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Chemical Communication Outside the body Ex. Pheromones Ex.
Quorum sensing Inside the body Short Distance Long Distance 5
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Pheromones 6 Members of the same animal species sometimes
communicate with pheromones, chemicals that are released into the
environment. Pheromones serve many functions, including marking
trails leading to food, defining territories, warning of predators,
and attracting potential mates.
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Quorum sensing Quorum sensing in bacteria single celled
bacteria monitor their environment by producing, releasing and
detecting hormone- like molecules called autoinducers. 7
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Chemical Communication Inside the body Short Distance Paracrine
Example Prostaglandin Autocrine Example Interleukin Long Distance
Hormones Example Insulin 8
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Direct Contact Communication Ex. Plant cells communicate
directly through openings called plasmodesmata. 9
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Short Distance Communication Paracrine signals diffuse to and
affect nearby cells Ex. Neurotransmitters Ex. Prostaglandins
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Autocrine signals These chemicals affect the same cells that
release them. Ex. Interleukin-1 produced by monocytes and can bind
to receptors on the same monocyte. Tumor cells reproduce
uncontrollably because they self-stimulate cell division by making
their own division signals. 12
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Long Distance Communication Endocrine hormones via signal
transduction pathway: 13
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Hormones Endocrine glands produce hormones which are Chemical
signals Transported in tissue fluids Detected only by target cells
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Summary: 15
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Communication Features Secreting cell - releases the signal
Signal = chemical = ligand Receptor - accepts and temporarily joins
with the ligand forming receptor/ligand complex Target cell
contains the receptor 16
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Apply the features Insulin is secreted by beta cells of the
pancreas. Once secreted, insulin travels around the body. When
insulin docks with an integral protein on the membrane of a muscle
cell, glucose can enter the cell. What is the secreting cell, the
target cell, ligand, and the receptor? 17
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Endocrine System The human endocrine system is composed of a
collection of glands that secrete a variety of hormones. These
chemicals use long distance communication to control the daily
functioning of the cells of the body, maintain homeostasis, respond
to environmental stimuli, and growth & development. 18
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Endocrine System The endocrine system produces more than 30
different chemicals used by your body to and promote normal body
function. This system contains 9 primary glands as well as
endocrine cells found within major organs. The endocrine system is
a ductless system that employs the circulatory system when
delivering chemical signals over long distances. 19
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The Endocrine System works with the Nervous System Two systems
coordinate communication throughout the body: the endocrine system
and the nervous system. The endocrine system secretes hormones that
communicate regulatory info throughout body. The nervous system
uses neurons to transmit signals; these signals can regulate the
release of hormones.
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Table 45.1a
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Table 45.1b
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Figure 45.17 Pathway Example Stimulus Cold Sensory neuron
Hypothalamus Neurosecretory cell Releasing hormone Blood vessel
Anterior pituitary Tropic hormone Endocrine cell Hormone Target
cells Response Negative feedback Hypothalamus secretes
thyrotropin-releasing hormone (TRH). Anterior pituitary secretes
thyroid-stimulating hormone (TSH, also known as thyrotropin).
Thyroid gland secretes thyroid hormone (T 3 and T 4 ). Body tissues
Increased cellular metabolism
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The Process of Communication: Signal-Transduction Pathway Three
stages of the Signal- Transduction Pathway 1. reception 2.
transduction 3. response
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Typical Signal Transduction Pathway
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Ligand = Chemical Messenger Three major classes of molecules
function as hormones in vertebrates (ligands) Polypeptides
(proteins and peptides) Amines derived from amino acids Steroid
hormones 27
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Cellular Response Pathways Water- and lipid-soluble hormones
differ in their paths through a body Water-soluble hormones are
secreted by exocytosis, travel freely in the bloodstream, and bind
to cell-surface receptors Lipid-soluble hormones diffuse across
cell membranes, travel in the bloodstream bound to transport
proteins, and diffuse through the membrane of target cells
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Type of Receptor: Ex- G-protein linked ( Water soluble =
polypeptides & amines, cant pass cell membrane)
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Type of Receptor: Intracellular Receptor (Lipid Soluble =
Steroid Hormones, can pass cell membrane)
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Lipid- soluble hormone SECRETORY CELL Water- soluble hormone
VIA BLOOD Signal receptor TARGET CELL OR Cytoplasmic response Gene
regulation (a) (b) Cytoplasmic response Gene regulation Signal
receptor Transport protein NUCLEUS
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Plasma membrane EXTRACELLULAR FLUID CYTOPLASM
ReceptionTransduction Response Receptor Signaling molecule
Activation of cellular response Relay molecules in a signal
transduction pathway 3 2 1Recap
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Multiple Effects of Hormones The same hormone may have
different effects on target cells that have Different receptors for
the hormone Different signal transduction pathways
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The hormone epinephrine has multiple effects in mediating the
bodys response to short-term stress Epinephrine binds to receptors
on the plasma membrane of liver cells This triggers the release of
messenger molecules that activate enzymes and result in the release
of glucose into the bloodstream Multiple Effects of Hormones
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Different receptors Same receptors but different intracellular
proteins (not shown) Different cellular responses Epinephrine
receptor receptor receptor Glycogen deposits Vessel dilates. Vessel
constricts. Glycogen breaks down and glucose is released from cell.
(a) Liver cell (b) Skeletal muscle blood vessel Intestinal blood
vessel (c)
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Insulin and Glucagon: Control of Blood Glucose Hormones work in
pairs to maintain homeostasis. Insulin (decreases blood glucose)
and glucagon (increases blood glucose) are antagonistic hormones
that help maintain glucose homeostasis. The pancreas has clusters
of endocrine cells called pancreatic islets with alpha cells that
produce glucagon and beta cells that produce insulin.
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Body cells take up more glucose. Insulin Beta cells of pancreas
release insulin into the blood. Liver takes up glucose and stores
it as glycogen. Blood glucose level declines. Blood glucose level
rises. Homeostasis: Blood glucose level (70110 mg/100mL) STIMULUS:
Blood glucose level rises (for instance, after eating a
carbohydrate-rich meal). Liver breaks down glycogen and releases
glucose into the blood. Alpha cells of pancreas release glucagon
into the blood. Glucagon STIMULUS: Blood glucose level falls (for
instance, after skipping a meal). Figure 45.13
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Out of Balance: Diabetes Mellitus Diabetes mellitus is perhaps
the best-known endocrine disorder. It is caused by a deficiency of
insulin or a decreased response to insulin in target tissues. It is
marked by elevated blood glucose levels.
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Type 1 diabetes mellitus (insulin-dependent) is an autoimmune
disorder in which the immune system destroys pancreatic beta cells.
Type 2 diabetes mellitus (non-insulin-dependent) involves insulin
deficiency or reduced response of target cells due to change in
insulin receptors. Out of Balance: Diabetes Mellitus
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Insulin & Glucose Regulation
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Endocrine System Summary Assignment Copy the general Endocrine
System Negative Feedback Summary (Fig.13.10) pg.479 Then, create
your own feedback summary for any other Hormone of the Endocrine
System ***Bring Books MONDAY***