Download Endocrine System

Chemical
Signaling
Endocrine System
 Hormones
Chemical signal secreted
into body fluid for
communication
Secreted by neurosecretory cells
Received by target cells
 Slow
 Long duration
 Often “talks” with
nervous system
Endocrine System
Local regulators: influence nearby
cells
Growth factors: peptides &
proteins that stimulate cell growth,
division, & development
Prostaglandins (PGs): modified
fatty acids act as local regulators,
esp. in reproductive & defense
systems
Endocrine System
Two pathways
1) Hormone binds to receptor on
target cell  signal transduction
pathway  response
Response
depends
on target
cell type
Endocrine System
2) Hormone enters target cell &
nucleus  signal transduction
pathway (acting as transcription
factor)  response (change in
gene expression through protein
synthesis)
Steroids,
thyroid
hormones
Vertebrate Endocrine System
Overview of hormones, including
tropic hormones
Have other endocrine organs as
target
Vertebrate Endocrine
System
Hypothalamus
Lower brain
Receives info from nerves & brain
Sends appropriate hormone
response based on environmental
conditions
Have two sets of neurosecretory
cells
Secretions stored in or regulate
activity of pituitary gland
Vertebrate Endocrine System
 Pituitary gland
Two discrete parts
1) Anterior pituitary
(adenohypophysis)
Secretes directly into blood
“On” if releasing hormones
were secreted from
hypothalamus
“Off” if inhibitory hormones
were secreted
Vertebrate Endocrine System
Tropic hormones include:
Thyroid-stimulating hormone
(TSH)
Follicle-stimulating hormone
(FSH)**
Leutinizing hormone (LH)**
Adrenocorticotropic hormone
– stimulates adrenal cortex
Vertebrate Endocrine System
**gonadotropins – stimulate gonad
activity
Other hormones
Growth hormone (GH) – protein;
stimulates liver to produce
insulinlike growth factors (IGF),
which stimulates bone & cartilage
growth
Prolactin (PRL) – protein;
mammary growth & milk
production in mammals (different
in other species)
Vertebrate Endocrine System
Melanocyte-stimulating
hormone (MSH) –
regulates skin pigment &
fat metabolism
Endorphins – inhibit pain
perception
Vertebrate Endocrine System
2) Posterior pituitary (neurohypophysis)
Extension of the brain
Hormones include:
Antidiuretic hormone (ADH) –
regulates osmolarity of blood 
If osmolarity increases, osmoreceptors
in hypothalamus shrink & send impulse
to release ADH 
Signal-transduction pathway in kidney
tubules to increase water permeability,
which will stop ADH release (neg
feedback)
Vertebrate Endocrine System
Oxytocin – acts on uterus
to contract during birth &
mammary glands to eject
milk during nursing
Vertebrate Endocrine System
Pineal gland
Center of brain
Secretes melatonin (amino acid)
Regulates function (mostly
reproductive) based on changes in
day length
Secreted at night
Has light-sensitive cells or
connections from eyes
Vertebrate Endocrine System
 Thyroid gland
Two lobes on ventral surface
of trachea
Hormones:
Triiodothyronine (T3) – 3 I atoms
Thyroxine (T4) – 4 I atoms –
predominant secretion –
converted to T3
Calcitonin – lowers Ca2+ in blood
Vertebrate Endocrine System
Embryonic brain development
Vertebrate development &
maturation
Homeostasis
Bp, hr, muscle tone, digestion,
reproduction
Metabolism
Vertebrate Endocrine System
Malfunctions
Hyperthyroidism
Hypothyroidism
Cretinism (in infants –
muscular & skeletal retardation)
Goiter
Enlarged thyroid
Iodine deficiency
Vertebrate Endocrine System
Parathyroid
4
Embedded in thyroid
Homeostasis of Ca2+ ions
Hormones:
Parathyroid hormone (PTH)
Raises blood levels of Ca2+
Vertebrate Endocrine System
Induces osteoclasts to
decompose bone minerals
and put into blood, increases
kidney 7 intestine absorption
of calcium
Malfunctions
Tetany – convulsive contraction
of skeletal muscles due to lack
of PTH
Vertebrate
Endocrine System
 Pancreas
Islets of Langerhans – endocrine cell
clusters
Secrete glucagon (through alpha
cells) & insulin (through beta cells)
Regulate glucose in blood (negative
feedback)
Insulin lowers blood sugar, slows
glycogen breakdown in liver, inhibits
a.a. & glycerol conversion to sugar
Liver is extremely sensitive to
glucagon
Vertebrate Endocrine System
Malfunctions
Diabetes melliuts
High blood sugar
Excessive thirst, frequent
urination, sugar in urine
Use fat breakdown for cell
respiration instead of sugar –
can lower blood pH
Two types
Vertebrate Endocrine System
Type I (insulin-dependent)
Immune system attacks
pancreas
Childhood
Destroys ability to make insulin
Insulin injections
Type II (insulin-independent)
Deficiency of insulin or reduced
responsiveness in target cell
(change in receptors)
Vertebrate Endocrine System
Adulthood
More than 90% of diabetics
Managed by diet & exercise
 Adrenal glands
Sit on top of both
kidneys
Two glands
Vertebrate Endocrine System
Adrenal medulla (central portion)
Works with nervous system
Cells derived from neural crest
Hormones:
Epinephrine (adrenaline)
Norepinephrine (noradrenaline)
Both known as
catecholamines, from a.a
tyrosine
Vertebrate Endocrine System
Secreted in response to + & stress
Inc. availability of energy sources
Boost metabolic rate
Work with circ. & resp. systems to
inc. O2 flow & divert blood to
heart, brain, & muscles
Works with sympathetic portion of
the autonomic nervous system
When nerves stimulated, release
acetylcholine in medulla, which
causes release of epinephrine
Vertebrate Endocrine System
Norepinephrine works to
sustain blood pressure
Adrenal cortex (outer portion)
Reacts to stress, but responds to
endocrine rather than nervous
system
Hypothalamus secretes  anterior
pituitary releases ACTH  adrenal
cortex secretes corticosteroids
(glucocorticoids, such as cortisol,
& mineralocorticoids, such as
aldosterone)
Vertebrate Endocrine System
Glucocorticoids – work on
bioenergetics, specifically
glucose metabolism
They promote synthesis of
glucose from
noncarbohydrate sources like
muscle proteins
High doses suppress immune
system, but are used to fight
inflammation
Vertebrate Endocrine System
Mineralocorticoids – salt &
water balance
They stimulate kidney
cells to reabsorb sodium &
water
Vertebrate
Endocrine System
 Gonads
 Hormones affect growth,
development, reproductive
regulation, sexual behavior
 Secrete 3 types of steroids (testes of
males, ovaries of females)
Androgens
Primary steroid of testes
(testosterone)
In embryo, development of male
organs
Secondary sex characteristics of male
Vertebrate Endocrine System
Estrogens
Estradiol
Female development &
secondary sex characterstics
Progestins
Progesterone
Prepare & maintain uterus
Controlled by gonadotropins, FSH,
LH, GnRH of hypothalamus