Transcript Animal Hormones

Animal Hormones
Chemical Messaging
Hormones
• component of homeostatic control
– slower signals (vs. nervous signals)
• secreted by endocrine cells
• diffuse to blood vessels
• delivered by circulatory system
hormone delivery
Figure 42.1
Hormones
• component of homeostatic control
– broadcast signals
• dispersed throughout the body
• received by target cells with receptors
• response is determined by target cells
• e.g. epinephrine (adrenaline) targets
heart
liver
blood vessels
adipose tissues
Hormones
• cellular mechanisms of control
– hormone release
• nervous system control
• feedback control
– receptor availability
• genetic control
• feedback control
multiple receptors and
transduction pathways
Hormones
• cellular mechanisms of control
– signal transduction
• pathway - specificity
• cascade - amplification
– hormone half-life
Hormones
• component of homeostatic control
– controlled responses include
• developmental responses
• physiological responses
• behavioral responses
autocrine hormones bind source cells
Figure 42.1
Hormones
• not all hormones travel far
– autocrine hormones bind source cell
– paracrine hormones bind nearby cells
• histamine released by mast cells
• interleukin-1 released by macrophage
cells
• neurotransmitters
neurotransmitters are paracrine signals
Figure 42.1
Hormones
• identical hormones are found in different
animals
– roles may be different
• stimulus may differ
• target cells may differ
• responses may differ
– e.g. cAMP
Hormones
• endocrine cells may be single or organized
into an organ (gland)
• different endocrine cells may be present in an
endocrine gland
• in humans, nine endocrine glands make up the
endocrine system
glands
of the
human
endocrine
system
Figure 42.2
an invertebrate example
• insect development
– larval stages - instars
separated by
– shedding of rigid exoskeleton - molt
an invertebrate example
• Rhodnius
– 5 molts
– molts are triggered by blood meals
Rhodnius
headless molting
Figure 42.3
transfer
from one
individual
to another
Figure 42.3
an invertebrate example
• Rhodnius
– two hormones trigger molting
• brain hormone
–produced in brain
–stored in corpora cardiaca
–released by blood meal stimulus
an invertebrate example
• Rhodnius
– two hormones trigger molting
• ecdysone
–produced in prothoracic gland
–released in response to brain hormone
–diffuses to target tissues
–stimulates molting
molting and development are not equivalent
• Rhodnius
– proper development is controlled by another
hormone
– corpora allata produce juvenile hormone
– if corpora allata are intact, instars molt to
instars
– 5th instar linked to 4th instar molts to 6th
instar rather than adult
brain hormone,
ecdysone, juvenile
hormone
interaction
is common among
insects -
complete
metamorphosis
Figure 42.4
human endocrine system
• pituitary gland - master gland
– attached to hypothalamus
– links nervous system with endocrine system
• produces & secretes hormones
or
• secretes brain hormones
– controls many endocrine glands
human endocrine system
• pituitary gland - master gland
– two-part gland
• posterior pituitary
–outgrowth of the hypothalamus
–stores & secretes neurohormones
• antidiuretic hormone (ADH)
• oxytocin
posterior pituitary
Figure 42.5
human endocrine system
• pituitary gland - master gland
– two-part gland
• anterior pituitary
–outgrowth of mouth cavity
–produces and secretes several hormones
–responds to hypothalamic control
»neurohormones to portal vessels
»portal vessels to ant. pit.
»release or inhibit ant. pit. secretion
anterior
pituitary
Figure 42.7
human endocrine system
• pituitary gland - master gland
– two-part gland
• anterior pituitary
–four tropic hormones control endocrine
glands
»thyrotropin
»adrenocorticotropin
»luteinizing hormone
»follicle-stimulating hormone
human endocrine system
• pituitary gland - master gland
– two-part gland
• anterior pituitary
–five non-tropic hormones or groups
»growth hormone
»prolactin
»melanocyte-stimulating hormone
»endorphins & enkephalins
global control of hormonal release
• hypothalamus receives information
• hypothalamus stimulates or inhibits pituitary
• pituitary secretion controls effectors directly or
indirectly
• negative feedback loops convey internal
information to hypothalamus or pituitary
negative
feedback
control of
hormone
production
Figure 42.8
control of thyroxine production
• thyroid gland produces thyroxine (T4 & T3)
• thyroxine
– elevates cellular metabolic rate
– promotes use of carbohydrate over fat
– increases basal metabolic rate in response to
prolonged cold
– promotes uptake of amino acids/protein
synthesis during development
control of thyroxine production
• failure of control can produce goiter
– hyperthyroidism
• autoimmune stimulation of thyrotropin
receptor
– hypothyroidism
• e.g. iodine deficiency
• loss of feedback inhibition
thyroid & parathyroid glands
control of blood calcium
• calcitonin
– produced by thyroid gland
– reduces level of circulating calcium
• reduces osteoclast activity
• stimulates osteoblast activity
control of blood calcium
• parathyroid hormone
– produced by parathyroid glands
– stimulated by low blood calcium
– stimulates osteoclasts
– increases calcium reabsorption by kidneys
– enhances dietary uptake of calcium
control of blood calcium
• antagonistic activities of pairs of hormones
such as calcitonin and parathyroid hormone
are common among homeostatic regulatory
systems
antagonistic activities of calcitonin
and parathyroid hormone balance
blood calcium
Figure 42.9
control of blood glucose
• insulin
– produced by islet of Langerhans cells in the
pancreas
– produced when blood glucose is high
– stimulates target cells to
• take up glucose
• synthesize glycogen
• synthesize fat
control of blood glucose
• glucagon
– produced in other islet cells
– produced when blood glucose is low
– stimulates liver to break down glycogen
control of blood glucose
• antagonistic activities of insulin and glucagon
maintain glucose at set point
• failure of control may lead to diabetes
– when insulin or its receptors are absent, cells
use fat and proteins for fuel
control of blood glucose
• somatostatin overrides steady state control
– produced in pancreas
– response to rapid glucose/amino acid rise
– inhibits insulin and glucagon release
– reduces digestive activity of gut
– increases time of absorption/use of dietary
nutrients
– also produced by hypothalamus to inhibit
thyrotropin & growth hormone release
the adrenal glands
Figure 42.10
adrenal glands
• located on top of kidneys
• two parts
• adrenal medulla
–produces epinephrine & norepinephrine
–derived from nervous tissue
–under nervous system control
–mediates the “fight-or-flight” response
adrenal glands
• located on top of kidneys
• two parts
• adrenal cortex
–produces several corticosteroid
hormones
–under control of adrenocorticotropin
–slower to respond than adrenal medulla
corticosteroids come
from cholesterol
Figure 42.11
adrenal cortex
• corticosteroids are derived from cholesterol
– mineralocorticoids affect
• ionic balance of extracellular fluids
• aldosterone causes kidney to
–conserve Na+
–excrete K+
adrenal cortex
• corticosteroids are derived from cholesterol
– glucocorticoids affect
• blood glucose
• fat, protein, carbohydrate metabolism
• cortisol
–shifts non f-or-f cells to fat/protein
catabolism
–blocks immune system function
–“slow stress response”
adrenal cortex
• corticosteroids are derived from cholesterol
– cortisol
• responds to adrenocoritcotropin (ACTH)
• ACTH-releasing hormone produced by
hypothalamus
• negative feedback by cortisol reduces
ACTH-releasing hormone
• ability to recover from stress can decrease
with age
adrenal cortex
• corticosteroids are derived from cholesterol
– sex steroids affect
• sexual development
• reproductive activities
sex steroids
• produced predominantly in gonads
– progesterone & estrogens (estradiol)
• female sex steroids
– androgens (testosterone)
• male sex steroid
sex steroids
• mediate development of reproductive organs
in fetus
• mediate sexual maturation & development of
secondary sexual characteristics
sex steroids
• sex steroid control circuit
– in males, LH causes androgen production in
testes
– in females, LH, FSH, cause female sex
steroid production in ovaries
sex steroids
• GnRH stimulates gonadotropin production
– luteinizing hormone
– follicle-stimulating hormone
• sex steroids limit GnRH production by
negative feedback
• sensitivity of GnRH-producing cells to sex
steroids decreases to initiate puberty
Take Home
• hormone secretion is under multi-level control
– hypothalamus collects external information
– pituitary responds to hypothalamus
– pituitary controls many functions directly or
through other endocrine glands
– many endocrine functions are controlled by
feedback mechanisms
– many effectors are controlled by the
antagonistic activities of two or more
hormones
Table 42.1