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The Endocrine System
• Similar in fxn to the Nervous System
• Both send a message-Δ fxn of cell
• Nervous System-quick on, quick off
• Endocrine System-slow on, slow off
© 2012 Pearson Education, Inc.
© 2012 Pearson Education, Inc.
Figure 18-1 Organs and Tissues of the Endocrine System
Hypothalamus
Production of ADH, oxytocin, andregulatory hormones
Pituitary Gland
Anterior lobe:ACTH, TSH, GH, PRL, FSH, LH,and MSH
Posterior lobe:Release of oxytocin and ADH
Parathyroid Glands(located on the posterior surface ofthe thyroid gland)
Parathyroid hormone (PTH)
Pineal Gland
Melatonin
p. 597
© 2012 Pearson Education, Inc.
Figure 18-1 Organs and Tissues of the Endocrine System
Thyroid Gland
Thyroxine (T4)Triiodothyronine (T3)Calcitonin (CT)
Adrenal Glands
Adrenal medulla:Epinephrine (E)Norepinephrine (NE)
Adrenal cortex:Cortisol, corticosterone,aldosterone, androgens
InsulinGlucagon
Pancreas (Pancreatic Islets)Testis
Ovary
Thymus: (Undergoes atrophyduring adulthood)Secretes thymosins
Adipose Tissue: Secretes• Leptin
Digestive Tract: Secretesnumerous hormones involved in thecoordination of system functions,glucose metabolism, and appetite
Kidneys: Secrete• Erythropoietin (EPO)• Calcitriol
Gonads:Testes (male):
Androgens (especially testosterone),inhibin
Ovaries (female):Estrogens, progestins, inhibin
Organs with SecondaryEndocrine Functions
Heart: Secretes natriuretic peptides.• Atrial natriuretic peptide (ANP)• Brain natriuretic peptide (BNP)
SeeChapter21
SeeChapter22
SeeChapter25
SeeChapters19 and 26
SeeChapters28 and 29
p. 597
• Hormone: organic chemical that changes the function of its target cell– Autocrine-– Paracrine-– Endocrine-– exocrine
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings © 2012 Pearson Education, Inc.
p. 595
• Maintenance of Homeostasis– Water/electrolytes– Enzyme function– Transport
• Regulate long term processes• Development• Growth• Reproduction
© 2012 Pearson Education, Inc.
• Circulate freely-don’t last long– Bind to receptor– b.d. by liver or kidneys– b.d. by enzymes in plasma or interstitial fluid
• Bound to a carrier-last a long time– Reserves in the blood stream– Once released from carrier-don’t last long– Same reasons as above
© 2012 Pearson Education, Inc.
Hormones
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
p. 598
© 2012 Pearson Education, Inc.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings © 2012 Pearson Education, Inc.
p. 601
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings © 2012 Pearson Education, Inc.
p. 601
Copyright © 2009 Pearson
Education, Inc., publishing as Pearson Benjam
in Cumm
ings
p. 600
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Mechanisms of Hormone Action• The Process of Amplification
– Is the binding of a small number of hormone molecules to membrane receptors
– Leads to thousands of second messengers in cell– Magnifies effect of hormone on target cell
© 2012 Pearson Education, Inc.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Mechanisms of Hormone Action• Down-regulation
– Presence of a hormone triggers decrease in number of hormone receptors
– When levels of particular hormone are high, cells become less sensitive
• Up-regulation– Absence of a hormone triggers increase in number of
hormone receptors
– When levels of particular hormone are low, cells become more sensitive
© 2012 Pearson Education, Inc.
© 2012 Pearson Education, Inc.
Figure 18-3 G Proteins and Hormone Activity
Hormone
Proteinreceptor
G proteinactivated
Hormone
Proteinreceptor
G proteinactivated
Effects on cAMP Levels
Many G proteins, once activated, exert their effects by changing the concentrationof cyclic-AMP, which acts as the second messenger within the cell.
Increasedproduction
of cAMPadenylatecyclase
Acts assecond
messenger
kinase
Activatesenzymes
Opens ionchannels
If levels of cAMP increase,enzymes may be activatedor ion channels may beopened, accelerating themetabolic activity of the cell.
Examples:• Epinephrine and norepinephrine (β receptors)• Calcitonin• Parathyroid hormone• ADh, ACTH, FSH, LH, TSH• Glucagon
Examples:• Epinephrine and norepineph- rine (α2 receptors)
In some instances, G proteinactivation results in decreasedlevels of cAMP in thecytoplasm. This decrease hasan inhibitory effect on the cell.
Enhancedbreakdown
of cAMPPDE
Reducedenzymeactivity
Hormone
Proteinreceptor
G protein(inactive)
G proteinactivated
p. 600
Copyright © 2009 Pearson
Education, Inc., publishing as Pearson Benjam
in Cumm
ings©
201
2 Pe
arso
n Ed
ucati
on, I
nc.
p. 600
© 2012 Pearson Education, Inc.
Figure 18-3 G Proteins and Hormone Activity
Hormone
Proteinreceptor
G protein(inactive)
G proteinactivated
Hormone
Proteinreceptor
G proteinactivated
Effects on Ca2+ Levels
Some G proteins use Ca2+ as asecond messenger.
Examples:
• Epinephrine and norepinephrine (α1 receptors)
• Oxytocin• Regulatory hormones of hypothalamus• Several eicosanoids
Activatesenzymes
Calmodulin
PLC,DAG,and IP3
Opening of Ca2+ channels
Release ofstored Ca2+
from ER or SER
Ca2+ acts assecond messenger
p. 600
Copyright © 2009 Pearson
Education, Inc., publishing as Pearson Benjam
in Cumm
ings©
201
2 Pe
arso
n Ed
ucati
on, I
nc.
p. 600
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Endocrine Reflexes • Endocrine Reflexes
– Functional counterparts of neural reflexes– In most cases, controlled by negative feedback
mechanisms• Stimulus triggers production of hormone whose effects
reduce intensity of the stimulus
© 2012 Pearson Education, Inc.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Endocrine Reflexes • Endocrine reflexes can be triggered by
– Humoral stimuli
• Changes in composition of extracellular fluid
– Hormonal stimuli
• Arrival or removal of specific hormone
– Neural stimuli
• Arrival of neurotransmitters at neuroglandular junctions
© 2012 Pearson Education, Inc.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Endocrine Reflexes• Simple Endocrine Reflex
– Involves only one hormone
– Controls hormone secretion by the heart, pancreas, parathyroid gland, and digestive tract
• Complex Endocrine Reflex– Involves
• One or more intermediary steps
• Two or more hormones
• The hypothalamus
© 2012 Pearson Education, Inc.
© 2012 Pearson Education, Inc.
Figure 18-5 Three Mechanisms of Hypothalamic Control over Endocrine Function
Production of ADHand oxytocin
HYPOTHALAMUS
Control of sympatheticoutput to adrenalmedullae
Secretion of regulatoryhormones to control activityof the anterior lobe of thepituitary gland
Preganglionicmotor fibers
Adrenal gland
Secretion of epinephrineand norepinephrine
Adrenal medulla
Adrenal cortex
Posterior lobeof pituitary gland
Release of ADHand oxytocin
Hormones secreted by the anteriorlobe control other endocrine organs
Anterior lobeof pituitary gland
Infundibulum
p. 602
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Endocrine Reflexes• Neuroendocrine Reflexes
– Pathways include both neural and endocrine components
• Complex Commands– Issued by changing
• Amount of hormone secreted
• Pattern of hormone release:– hypothalamic and pituitary hormones released in sudden
bursts
– frequency changes response of target cells
© 2012 Pearson Education, Inc.