Chemical Coordination: Endocrine Systems

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Chemical Coordination Endocrine Systems I.
Selective Forces -- animals must coordinate
activities with long-term changes for
development, reproduction, migration, etc. --
long-term responses to environmental stimuli are
regulated by chemicals called hormones
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Chemical Coordination Endocrine Systems II.
Hormones general characteristics A.
Definition chemicals produced in one tissue
(often a gland), released into blood in minute
amounts, and carried to target cells where they
have physiological and behavioral effects --
are slow acting alter physiology and
neurobiology -- same hormone can have vastly
different effects on different tissues ex
vasopressin (anti-diuretic hormone ADH) --
low-level signals minute amounts are released
and vastly diluted by blood require
amplification -- spread throughout body, but
must influence only certain target tissues
how is this regulated?
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Chemical Coordination Endocrine Systems II.
Hormones general characteristics B. Sources
of hormones 1. endocrine glands
ductless produce hormones that are released into
blood
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Chemical Coordination Endocrine Systems II.
Hormones general characteristics B. Sources
of hormones 2. exocrine glands have
ducts discharge hormones/secretions directly
onto tissues or surfaces
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Chemical Coordination Endocrine Systems II.
Hormones general characteristics C. Effects
of hormones 1. change enzymatic
activity/alter cellular metabolism 2.
change membrane permeability (alters nervous
response behavior) 3. cause other
glands to release their own hormones
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Chemical Coordination Endocrine Systems II.
Hormones general characteristics D.
Interaction of nervous and endocrine systems --
are tightly interlinked and influence one
another 1. some hormones function as
neurotransmitters -- oxytocin stimulates
uterine contraction in brain
neurotransmitter -- norepinephrin both
hormone neurotransmitter
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Chemical Coordination Endocrine Systems II.
Hormones general characteristics D.
Interaction of nervous and endocrine systems
2. neurosecretions (neuropeptides) produced
by neurosecretory neurons in
hypothalamus -- function as releasing
factors or releasing hormones -- how brain
regulates endocrine system ex
hypothalamus releases GnRH (gonadotropic
releasing hormone) stimulates
pituitary to release FSH (follicle stimulating
hormone) stimulates gonads to release sex
steroids
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Chemical Coordination Endocrine Systems II.
Hormones general characteristics D.
Interaction of nervous and endocrine systems
3. negative feedback loops (see below)
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Chemical Coordination Endocrine Systems III.
Hormones Mechanisms of Action -- how to
ensure they affect specific target tissues?
-- how to amplify effects of highly diluted,
minute amounts? -- how is hormone release
regulated? A. Receptors --
ability of hormone to influence a tissue depends
upon whether tissue has
receptors for that hormone -- receptor
molecules structured to bind with only one
specific hormone
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Fig. 34.2 p. 755)
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Chemical Coordination Endocrine Systems III.
Hormones Mechanisms of Action A.
Receptors 1. membrane-bound receptors 2nd
messenger concept -- used for
polypeptide hormones too big to pass through cell
membrane directly
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• hormone ( 1st messenger) binds with receptor
• embedded in cell membrane
• binding stimulates enzyme, adenylate cyclase
• adenylate cyclase catalyzes conversion of ATP
  to
• cyclic AMP (cAMP 2nd messenger)
• cAMP activates protein kinase A influences
  enzymatic
• pathways
• alters cellular metabolism and cause target
  cell response
• can produce many cAMPs for each molecule of
  hormone
• amplification
• effects of hormone on cell are indirect

capillary
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Chemical Coordination Endocrine Systems III.
Hormones Mechanisms of Action A.
Receptors 2. nuclear receptors (cytoplasmic
receptors)
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• For steroids (lipid soluble)
• hormone crosses cell membrane
• binds with receptor in cytoplasm or nucleus
• (regardless, site of activity nucleus)
• hormone receptor gene regulatory protein
• binds with specific genes alters transcription
  
• and number of mRNA copies produced
• mRNAs move into cytoplasm ? enzymes
• alters cellular metabolism and causes target
  
• cell response
• one gene regulatory protein can result in many
  mRNA copies amplification
• effects of hormone on cell are direct

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• For thyroid hormones and insect ecdysone
• hormone binds with transmembrane protein
  transport molecule
• ATP used to move hormone across membrane into
  cell
• hormone binds with receptor in cytoplasm or
• nucleus (regardless, site of activity
  nucleus)
• hormone receptor gene regulatory protein
• binds with specific genes alters transcription
  
• and number of mRNA copies produced
• mRNAs move into cytoplasm ? enzymes
• alters cellular metabolism and causes target
  
• cell response
• one gene regulatory protein can result in many
  mRNA copies amplification

(insect ecdysone)
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Chemical Coordination Endocrine Systems III.
Hormones Mechanisms of Action B. Control of
hormone secretion negative feedback loops --
hormone causes a response in target tissue that
inhibits production of the hormone

(ex from hypothalamus)
(expituitary)
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Chemical Coordination Endocrine Systems IV.
Invertebrate Hormones -- found in all
invertebrate groups -- usually produced by
neurosecretory cells endocrine glands less
common than in vertebrates EX molting and
metamorphosis in insects -- as an insect
increases in size, it outgrows its exoskeletion
(cuticle)
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• Exoskeleton presents insects with two problems
• Must molt to grow (molting ecdysis)
• -- in insects (but not all arthropods), all
  molting occurs in larval or juvenile stages
• -- as larva increases size, outgrows exoskeleton
• -- must shed old cuticle and secrete new, larger
  cuticle

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• Exoskeleton presents insects with two problems
• Must undergo metamorphosis to become an adult (
  imago)
• -- hemimetabolous development (gradual
  metamorphosis)
• -- grasshoppers, crickets, cicadas,
  cockroaches, praying mantis, dragonflies, etc.
• -- immature stages juvenile stages or nymphs
  similar to adult, but no wings or gonads

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• Exoskeleton presents insects with two problems
• Must undergo metamorphosis to become an adult (
  imago)
• -- holometabolous development (complete
  metamorphosis)
• -- beetles, butterflies, bees, wasps, flies.
• -- immature stages larva (ex maggot or
  caterpillar) often radically different from
  adult

egg
larva
larva
imago
pupa
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Chemical Coordination Endocrine Systems IV.
Invertebrate Hormones A. Review of insect
cuticle

Exocuticle
Endocuticle

Fig. 29-1 p. 628)
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Chemical Coordination Endocrine Systems IV.
Invertebrate Hormones B. Hormonal regulation of
molting 1. neurosecretory cells in
protocerebrum produce prothoracicotropic
hormone (PTTH) released into hemolymph
2. carried to prothoracic gland
stimulates release of ecdysone 3. ecdysone
binds with nuclear receptors in cells of
epidermis ? gene regulatory protein
enters nuclei of epidermal cells
activates gene programs
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• Chemical Coordination Endocrine Systems
• IV. Invertebrate Hormones
• B. Hormonal regulation of molting
• 4. ecdysone causes 2 responses from
• epidermal cells
• secrete molting fluid
• digests old endocuticle from
• bottom up
• secrete new cuticle under old
• exocuticle
• epicuticle ? exocuticle ? endocuticle
• 5. Brain releases eclosion hormone
• causes old exocuticle to
  split insect
• crawls out (casting off old exocuticle

Exocuticle
Endocuticle
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Chemical Coordination Endocrine Systems IV.
Invertebrate Hormones C. Hormonal regulation of
metamorphosis -- ecdysone controls
molting promotes development of adult
characteristics -- juvenile hormone (JH)
promotes retention of larval characteristics
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if JH above threshold level ecdysone promotes
molting, but larval characteristics are retained
? next larval stage
JH Titer in Hemolymph
Threshold JH
if JH below threshold level ecdysone promotes
molting and development of adult characteristics
? imago
L1 L2 L3 L4 L5 Pupa Adult
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Chemical Coordination Endocrine Systems V.
Vertebrate Hormones A. Central nervous system
regulation of hormones 1. hypothalamus
-- contains neurosecretory centers --
produces releasing hormones -- carried to
pituitary, cause it to release
its own hormones
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• Chemical Coordination Endocrine Systems
• V. Vertebrate Hormones
• A. Central nervous system regulation of
  hormones
• 2. pituitary gland part of diencephalon
• a. Anterior pituitary
• -- receives releasing hormones from
• hypothalamus
• -- produces its own hormones, which
• are released in response to
• releasing hormones from hypo-
• thalamus
• tropic hormones
• -- dumped into blood cause
• other endocrine glands to
• release own hormones
• thyroid stimulating hormone (TSH)

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• Chemical Coordination Endocrine Systems
• V. Vertebrate Hormones
• A. Central nervous system regulation of
  hormones
• 2. pituitary gland part of diencephalon
• a. Anterior pituitary
• -- receives releasing hormones from
• hypothalamus
• -- releases
• prolactin
• growth hormone (GH)

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• Chemical Coordination Endocrine Systems
• V. Vertebrate Hormones
• A. Central nervous system regulation of
  hormones
• 2. pituitary gland part of diencephalon
• b. Posterior pituitary
• -- does not produce own hormones
• -- receives and stores hormones
• (neuropeptides) from
  hypothalamus
• oxytocin
• vasopressin
• (anti-diuretic hormone ADH)

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Chemical Coordination Endocrine Systems V.
Vertebrate Hormones B. Hormones and vertebrate
reproductive cycle 1. types of female
reproductive cycles a. Estrous cycle
-- under influence of hormones,
females are receptive to males during
only certain, brief periods of estrus
(heat) -- lining of uterus
(endometrium) is not shed
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Chemical Coordination Endocrine Systems V.
Vertebrate Hormones B. Hormones and vertebrate
reproductive cycle 1. types of female
reproductive cycles b. Menstrual cycle
-- only in monkeys, apes, and
humans -- female receptivity occurs
throughout cycle no brief period of estrus
-- lining of uterus (endometrium) is shed
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Hormonal Regulation of Human Menstrual Cycle
p. 145

• Hypothalamus releases Gonadotropic
• Releasing Hormone (GnRH)
• 2. stimulates anterior pituitary to release
• Follicle Stimulating Hormone (FSH) and
• Luteinizing Hormone (LH)
• 3. FSH causes follicle to form in ovary
• -- releases inhibin inhibits FSH release
• by ant. pituitary
• -- releases estrogen stimulates
• development of
• endometrium
• After 13-14 days, estrogen reaches
• threshold conc. in blood causes surge of
• LH from anterior pituitary

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Hormonal Regulation of Human Menstrual Cycle

• 5. LH surge causes ovulation
• -- oocyte (ovum) is released lives
• for 12 hrs. if not fertilized, disintegrates
• Ruptured follicle creates scar
• corpus luteum transitory endocrine
• gland
• -- maintained by LH after LH surge,
• LH declines steadily back to baseline
• level thus maintenance of corpus
• luteum by LH is temporary
• -- releases estrogen and
• progesterone finish preparing
• endometrium

p. 140
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Hormonal Regulation of Human Menstrual Cycle

• If oocyte is NOT fertilized
• LH declines below level to maintain
• corpus luteum degenerates
• Without corpus luteum, estrogen
• and progesterone decline below
• level necessary to maintain uterine
• lining
• 9. menstruation

p. 146
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Hormonal Regulation of Human Menstrual Cycle

• If oocyte IS fertilized
• 10. zygote implants ? trophoblast
• (future embryo placenta) (endocrine)
• 11. trophoblast secretes
• human chorionic gonadotropin
• (hCG)
• maintains corpus luteum and
• thus uterine lining (replaces LH)
• placenta begins to produce
• estrogen and progesterone
• maintain uterine lining
• around 3rd mo. of pregnancy,
• corpus luteum degenerates
• 12. birth
• triggered by surge in estrogen
• plus decline in progesterone

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• Chemical Coordination Endocrine Systems
• V. Vertebrate Hormones
• C. Hormones and vertebrate metabolism
• 1. thyroid hormones
• thyroid gland stimulated by thyroid stimulating
  hormone (TSH) from anterior
• pituitary
• responds by producing triiodothyronin and
  thyroxine
• -- regulate growth and development of nervous
  system
• -- stimulates metabolic rate

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• Chemical Coordination Endocrine Systems
• V. Vertebrate Hormones
• C. Hormones and vertebrate metabolism
• 1. thyroid hormones
• undersecretion at early age ? impaired growth of
  nervous system ?
• cretinism

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• Chemical Coordination Endocrine Systems
• V. Vertebrate Hormones
• C. Hormones and vertebrate metabolism
• 1. thyroid hormones
• oversecretion
• -- speeded up metabolism
• -- weight loss
• -- nervousness
• undersecretion
• -- slow metabolic rate
• -- weight gain
• Production of thyroid hormones requires iodine
• -- thyroid hormones act as negative feedback on
  TSH
• -- if iodine deficient, cant produce thyroid
  hormones, TSH increases
• -- continued stimulation of thyroid lack of
  iodine causes thyroid gland
• to hypertrophy ? goiter

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• Chemical Coordination Endocrine Systems
• V. Vertebrate Hormones
• C. Hormones and vertebrate metabolism
• 2. Adrenal glands
• glucocorticoids (cortisol corticosterone)
• -- regulate food metabolism
• -- conversion of foods (amino acids, etc.) into
  glucose ( gluconeogenesis) increase blood
  glucose level to give quick energy for muscles
  and nervous tissue
• -- regulate stress response
• norepinephrin and epinephrin involved in
  sympathetic nervous system regulate
  fight-flight response
• water and salt balance
• androgens effects are similar to testosterone

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Chemical Coordination Endocrine Systems V.
Vertebrate Hormones C. Hormones and vertebrate
metabolism 3. Growth Hormone
-- produced by anterior pituitary --
acts directly on long bones to promote
cartilaginous growth and bone
development -- acts on growth
indirectly by stimulating insulin-like growth
factor (IGF) from liver --
promotes release of glycogen from liver and fat
from adipose tissue for growth -- over
secretion of IGH ? increased blood glucose ?
insulin insensitivity ( diabetes mellitus
type 2) 4. Leptin -- coded for by ob
gene -- produced by adipose tissue (white
fat cells) -- leptin receptors occur
primarily in hypothalamus and brain stem
-- regulates eating behavior part of feedback
system to inform brain of energy
status of body -- related to obesity