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Animal Endocrine Systems
Chapter 38
INVOLVEMENT IN GROWTH AND
DEVELOPMENT
38.1 Animal endocrine systems release chemical signals called hormones into
the blood. These signals respond to the environment, regulate growth and
development, and maintain homeostasis.
2 COMMUNICATION SYSTEMS IN ANIMALS
•2 Communication systems in animals:
•Endocrine System: acts slowly and over prolonged periods to affect broad
changes in physiological and behavioral states of animal
•Uses hormones…chemical compounds that are secreted and transported by
the circulatory system, often to distant targets
•Hormones bind to specific receptors on the surface or inside target cells that
receive their signals
•Helps an animal respond to its environment
•Is involved in growth and development
•Nervous System: responds rapidly to sensory information, providing immediate
physiological responses
•Both systems help maintain homeostasis….steady state
NEGATIVE FEEDBACK
Negative feedback: response
opposes the stimulus; stopping
mechanism
Homeostatic mechanisms:
•Body temperature
•Weight
•Calcium and potassium ions
•Blood glucose
GLUCOSE AND NEGATIVE FEEDBACK
POSITIVE FEEDBACK
Positive feedback: continues
response until completion
•Childbirth
•Arteriosclerosis and high BP
QUICK CHECK
 Diabetes mellitus is a disease characterized by high blood glucose levels. What two different physiological conditions
can produce diabetes?
ANSWER
Diabetes can result from either:
 Decreased insulin production by the pancreas
 Type 1 diabetes
 Autoimmune disease in which the insulin-producing cells in
pancreas are attacked by the immune system
 Needs daily insulin injections
 Decreased effect of insulin on target cells
 Type 2 diabetes
 Cells are not able to respond to normally circulating levels of
insulin
 Linked to obesity, family history, lack of exercise
 Need medication/insulin
CLASSES OF HORMONES
38.2 Hormones achieve specificity by binding to receptors on or inside their
target cells. Their signals are amplified to exert strong effects on their target
cells.
3 categories of hormones:
•Peptide hormones i.e.
oxytocin and ADH
•Amine hormones: I.e. epi
and nonepi
•Steroid hormones:
I.e.testosterone, progesterone,
derived from cholesterol
CELL SURFACE RECEPTORS
Peptide and amine
hormones:
•Hydrophilic
•Bind to cell surface
receptors
•Activate 2nd messenger
pathways which change the
state of the target cell
INTRACELLULAR RECEPTORS
Steroid hormones:
•Hydrophobic
•Bind to intracellular or nuclear
receptors
•Act as transcription factors to alter
the gene expression of the cell
AMPLIFYING A HORMONAL SIGNAL
•Hormones communicate by signaling
cascades
•Amplify the strength of their downstream
effect on target cells
VERTEBRATE HORMONES
VERTEBRATE HORMONES CONT.
VERTEBRATE HORMONES CONT.
ADDITIONAL HORMONE PROPERTIES
 Hormone Specificity
 Bind to receptors on the surface or inside target cells
 Therefore, the presence or absence of a receptor for a given
hormone determines which cells respond to that hormone
 Evolutionarily Conserved Molecules
 Hormones are evolutionarily conserved molecules
 Common to a diverse group of animals
 But they have evolved novel functions
 I.e. TSH…..stimulates thyroid gland for metabolic functions. Found in
snails with no thyroid.
ENDOCRINE ORGANS AND THEIR
HORMONES
38.3 In vertebrate animals, the hypothalamus and the pituitary glands control
and integrate diverse bodily functions and behaviors.
HYPOTHALAMUS & PITUITARY GLAND
•Hypothalamus: “Boss”
•Signals to pituitary glands
•Which acts as a “control center”
for most other endocrine glands
POSTERIOR PITUITARY HORMONES
Hypothalamus makes hormones released by posterior pituitary: 2 hormones
•Oxytocin: stimulates contractin of uterus/childbirth and releases milk from mammary
glands
•ADH (Antidiuretic Hormone or Vasopressin): enhances water reabsoprtion by
kidneys and sweat glands
ANTERIOR PITUITARY HORMONES
•Anterior Pituitary Gland: controlled by the hypothalamus
•Tropic Hormones: when anterior pituitary acts on other endocrine glands to cause
release of other hormones
•TSH: acts on thyroid gland
•Gonadotropic hormones – FSH and LH, which act on male & female gonads
(ovaries and testes)
•ACTH: acts on the adrenal glands
•Growth Hormone (GH): stimulates growth of bones, muscles, other body tissues
•Prolactin: stimulates milk production and secretion
TROPIC HORMONE - TSH
TSH (Thyroid Stimulating Hormone)
•Acts on thyroid gland
•Thyroid releases thyroxine (T4) and
triiodothyorine (T3)
•Help regulate cellular metabolism
throughout body
•Needs iodine (I)…..iodized salt, kelp,
seaweed
•Deficiency…goiter….causes thyroid
enlargement
•Hyperthyroidism: overly active
metabolism….weight loss, increased
apetite
•Hypothyroidism: slow metabolic
rate…I.e. fatigue
TROPIC HORMONE – FSH AND LH
Follicle Stimulating Hormone (FSH)
•Stimulates production of ova by
ovaries in females
•And sperm production by testes in
males
Leutenizing Hormone (LH)
•Causes ovulation by ovaries, and
changes follicle into corpus luteum
•Stimulates secretion of sex
hormones: estrogen from ovaries &
progesterone from corpus luteum
•And stimulates testes to secrete
testosterone from testes
TROPIC HORMONE – ACTH
Adrenocorticotropic
Hormone (ACTH)
•Acts on adrenal cortex to
secretelong-term stress
hormones, I.e. cortisol,
aldosterone
CALCIUM HOMEOSTASIS BY THYROID &
PARATHYROID GLANDS
Thyroid Gland:
•Releases calcitonin
•Good for you
•If calcium blood levels too high,
the release of calcitonin lowers
blood calcium 3 ways:
•Calcium deposition into
bones
•Reduces calcium
reabsoprtion in intestines and
kidneys
Parathyroid Glands:
•Releases parathyroid hormone
(PTH)….bad for you
•If blood calcium levels fall too low, PTH
takes calcium out of bones (from
osteoclast activity)
•Opposite of calcitonin
ADRENAL GLANDS
Adrenal Medulla (inner): short-term stress
•Releases epinephrine (adrenaline) and
norepinephrine (noradrenaline)
•These are catecholamines that regulate
“fight or flight” response
•Raises blood glucose, increases metabolic
activities, constricts certain blood vessels,
increases heart rate, increases BP
•Target organs: heart, blood vessels, liver
Adrenal Cortex (outer): long term stress
hormones
•Releases glucocorticoids….cortisol and
hydrocortisone
•These steroids raise your blood glucose
•Make you retain fat
•Decrease immune function
•Releases aldosterone
•Promotes reabsoprtion of sodium and water
by kidneys
GLUCOSE HOMEOSTASIS BY PANCREAS
Pancreas: responsible for blood
glucose homeostasis
•Releases insulin to lower blood
glucose
•Signals liver to convert
glucose into storage
glycogen; stored in liver and
muscles
•Releases glucagon to raise
blood glucose
•Signals liver and muscles
to release glycogen and
then liver breaks it down to
glucose
•Type I Diabetes Mellitus:
autoimmune disorder with elevated
blood glucose
•Type II: Not an autoimmune disorder
PINEAL GLAND
Pineal Gland: located in
thalamic region of brain
•Responds to signals from ANS
•Secretes melatonin
…..hormone of wakefulness
and sleep, biological rhythms,
and mood
•When melatonin levels
rise..animals sleep
MODES OF CHEMICAL SIGNALING
38.4 Chemical communication can also occur
locally between neighboring cells or, through
the release of pheromones, between individuals.
Local signaling:
•Paracrine signals: act locally for short term effects
to affect neighboring cells; i,.e. growth factor;
histamine
•Synaptic signals: release neurotransmitters
between 2 nerve cells or a nerve cell and muscle cell
PHEROMONES
Pheromones: chemical signals released into the air or water; signaling behavioral
cues between individuals of a species.
•Sex pheromones
•Territorial pheromones/male’s dominance or breeding area
•Alarm pheromones/predatory threats
•Trail pheromones/location of food sources
TRAIL PHEROMONES
PHEROMONES FOR SOCIAL
INTERACTIONS