Transcript Chapter 36

Chapter 36
Signaling Molecules:
1)
2)
Neurotransmitters
Local signaling Molecules
a) Secreted into extracellular fluid
b) Short lived
c) Very local effects
3)
Pheromones
a) Signal other individuals
b) Sensed by vomeronasal organ
4)
Hormones
Hormones

Produced by endocrine system
– Endocrine glands/cells
– Some neurons

Delivered by blood then interstitial fluid

Received by target cells
– Cells with membrane receptors for that
specific hormone
– Lipid hormones diffuse through cell
membrane (they are non-polar)

Intracellular receptors
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Bind lipid Hormones
like steroids

Testosterone &
thyroid hormones

Often affect
promoters regulating
transcription

Why do they need
carrier proteins in
blood?
Intracellular Receptor
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Membrane Receptors
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Bind peptide/protein
hormones
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Binding produces 2nd
messenger mols. Like
cAMP

cAMP initiates chain
reaction

resulting series of
chem. rxns is called a
cascade

Example: Glucagon
Glucagon induced cascade
Anterior Pituitary Hormones
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Regulated by Hypothalamus
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Hypothalamus monitors blood levels of
thyroid hormones (T3/T4) and cortisol
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Low levels of T3/T4 or cortisol cause
hypothalamus to signal Anterior Pituitary
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Neurons in hypothal. make releasing
hormones (_RH) that signal the anterior
pituitary to begin secreting hormones
Releasing Hormones
Produced by hypothalamus
 CRH = Corticotropin Releasing Hormone

 In response to low cortisol levels
 Coritsol helps maintain blood glucose levels
 High cortisol levels may result from stress
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TRH = Thyrotropin Releasing Hormone
 In response to low thyroid hormone level in blood
Negative feedback loops

Slow production of Releasing hormones by
Hypothalamus

High blood thyroid hormone levels = slow
TRH production

High blood cortisol levels in blood = slow
CRH production
Transmission of ___RH

Releasing hormones produced in
hypothalamus neruons flow into
hypothalamus capillary bed

Blood & hormones flow to 2nd capillary
bed in anterior pituitary where TRH and
CRH bind to receptors in anterior pituitary
Anterior Pituitary Response

RHs binding to receptors on Ant. Pituitary cells
begin cascade of rxns leading to…..
Release of TSH (thyroid stimulating hormone) or
ACTH (adreno corticotropin)
 TSH also called thyrotropin


-tropins stimulate other glands

These hormones travel through blood to their
target endocrine glands
Thyroid Gland Response
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TSH binds to thyroid receptors
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Cascade of reactions results in release of
T3 and T4 (thyroxins)

High T3/T4 levels result in negative
feedback to Hypothalamus and Anterior
pituitary..stops TRH and TSH production

T3/T4 regulate metabolism, growth &
maturation
Adrenal Gland Response

ACTH binds to adrenal cortex receptors

Cascade of reactions results in release of
cortisol

High cortisol levels in blood cause
negative feedback to Hypothalamus and
Anterior pituitary..stops CRH and ATCH
production

cortisol regulates blood glucose levels,
stress response, excess = poor
growth/imune system, cushings syndroms
Other Ant. Pit. Hormones

FSH – Follicle-stimulating Hormone

 Stimulates follicle to release egg (see ch 44)
 Stimulates sperm production in males
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LH – Luteininzing Hormone
 Stimulates gamete formation (see ch 44)
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Prolactin –
causes lactation
Growth Hormone- duhh
Posterior Pituitary Function
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Hormones produced in cell bodies in the
hypothalamus
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Axons of hypothamamic nerves extend
into the posterior pituitary
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Action potentials trigger the release of
hormones into capillaries

Blood carries hormones to target organs
Posterior Pituitary Hormones
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ADH – AntiDiuretic Hormone
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* Controls water excretion by kidney
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Oxytocin – controls….
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* Uterine contractions/ lactation
Pancreatic Hormones
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Hormones produced in Pancreatic Islets
3 types of cells in islets
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1) alpha cells = glucagon
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2) beta cells = insulin
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3) Delta cells = somatostatin
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Glucagon = peptide hormone
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Low blood glucose triggers alpha cells
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Glucagon produced, binds to liver cells
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Cascade causes breakdown of glycogen
into glucose
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High blood glucose levels = neg. feedback
Insulin
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High blood glucose levels trigger beta cells
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Produce insulin
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Insulin  cascade resulting in uptake of glucose
– (only hormone to do this)
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Targets skeletal muscle, fat & liver cells
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Promotes:
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protein, fat & glycogen synthesis
Low glucose levels = Neg. feedback
Somatostatin
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Produced by Delta cells
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Regulated digestion
Inhibits

insulin

glucagon
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Diabetes mellitus
Cells do not take up glucose properly
 Type I = autoimmune attack on
B cells (juvenile onset diabetes)
 Type II = target cells ignore insulin
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 Beta cells constant production of insulin  fail
 Insulin shots required
 Caused by genetics & obesity
Symptoms of Diabetes
Sugar accumulated in blood/ urine upsets
water-solute balance  kidney damage
 Cells burn protein/fats in absence of
glucose

Produces ketones  ketoacidosis
Affects brain, bloodvessels & nerves
amputations