Transcript Chemical Signaling in Animals

Chemical Signals in Animals
• 2 communication systems in body.
• 1Nervous system, 2endocrine
system.
• Endocrine system - glands and
tissues that secrete hormones,
chemical messengers produced by
cells to act on other cells.
http://scienceblogs.com/clock/upload/2006/06/endocrine%20system.jpg
• Some hormones act on nearby cells
(paracrine signals) others on same
cells that made them (autocrine
signal).
• Signals in endocrine system take
longer to reach destination (carried
by blood), longer lasting than
nervous impulses.
http://home.earthlink.net/~dayvdanls/paracrine.gif
• Endocrine glands secrete hormones
directly into bloodstream.
• Exocrine secretions do not contain
hormones; released through ducts
into body compartment.
• Example - pancreas in digestion.
http://www.daviddarling.info/images/exocrine_gland_types.gif
• Hormones classified into 2 groups:
steroid hormones, peptide
hormones.
• Both must bind to protein receptor
on target cell, peptide hormones
must bind to receptors on cell
surface since they cannot cross
membrane.
• Causes signal to be transmitted to
inside of cell.
http://web.indstate.edu/thcme/mwking/epinephrinephosphorylase.gif
• Signal can activate 2nd messengers,
which amplify signal and alter cell
activities - called signal
transduction cascade because
process amplified as it continues
down path.
• Steroid hormones usually smaller
and can pass through membrane.
• Most come from cholesterol and
usually enter nucleus of cell,
altering protein synthesis
(transcription).
• Steroid hormones not stored, unlike
protein hormones - need to be
regulated in order to be secreted.
http://fig.cox.miami.edu/~cmallery/150/memb/c11x10hormone-receptors2.jpg
Endocrine glands
• Regulation of production and
secretion of hormones done
through feedback loop.
• Some hormones regulate release of
other hormones.
• 1Hypothalamus and pituitary – found
in forebrain, located above
pituitary gland.
• Pituitary has 2 parts: anterior
pituitary, posterior pituitary.
• Posterior - vasopressin (antidiuretic
hormone or ADH) - acts on kidney
to conserve water; oxytocin - aids
in childbirth.
http://www.becomehealthynow.com/images/organs/nervous/glakgar_pit_hypothalamus.jpg
• Hormones made in hypothalamus,
pass through posterior pituitary secreted.
• Anterior pituitary regulated by
hypothalamus through portal blood
circulation - carries blood directly
from hypothalamus to pituitary.
http://www.brainexplorer.org/brain-images/hypothalamus.jpg
• Hypothalamus stimulated releasing factors into portal blood
circulation carried to pituitary cause release of hormone from
anterior pituitary.
• Growth hormone promotes growth
in body tissues.
http://www.3dscience.com/img/Products/Images/clip_art/endocrine_hypothalamus_pituitary_web.jpg
• Thyroid stimulating hormone (TSH)
stimulates thyroid to secrete
thyroxin.
• Adrenocorticotrophic hormone
(ACTH) stimulates adrenal cortex
to secrete corticosteroids in
response to stress.
http://media.allrefer.com/s1/l/t0200300-thyroid-gland.jpg
• Prolactin - responsible for milk
production.
• Follicle-stimulating hormone (FSH)
promotes maturation of
seminiferous tubules in males,
ovaries in females.
• Luteinizing hormone (LH) promotes testes to secrete
testosterone in males; causes
ovulation of egg in females.
http://www.discount-herbal-nutritional-supplements.com/weight_loss_supplements/images/brain2.gif
• Endorphins act on central nervous
system to block pain signaling (like
opiates).
• 2Thyroid gland – thyroxine
accelerates metabolism.
• Person deficient can develop goiter,
lethargy, obesity.
• Hyperthyroidism causes profuse
sweating, weight loss, increased
BMR.
http://www.hoslink.com/encocrineimages/hyperthyroid1.jpg
• Thyroxine secretion stimulated by
hypothalamus in response to
environment (like cold), acts on
thyroid gland.
• Thyroid gland also produces
calcitonin - regulates calcium
concentration in blood.
http://www.cvm.okstate.edu/instruction/mm_curr/histology/HistologyReference/hrendo7.jpg
• Calcitonin increases stimulates bone
formation, decreases bone
destruction.
• Calcitonin opposed by parathyroid
hormone.
• 3Parathyroid glands – located on
backside of thyroid gland, secretes
parathyroid hormone - regulates
calcium, phosphate balance between
blood, other tissue.
http://cyber.law.harvard.edu/blogs/static/heydan/parathyroid.jpg
• Increased parathyroid hormone
increase bone resorption, elevates
plasma calcium.
• Decreased calcium in blood causes
secretion of parathyroid hormone
which increases activity of
osteoclasts (bone breaking cells) remodels bones to release calcium.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• 4Pancreas – performs both
exocrine, endocrine functions.
• Endocrine function occurs in islets
of Langerhans which contain alpha
and beta cells that secrete
glucagon and insulin.
• Insulin stimulates muscles and
other cells to release glucose from
blood.
http://images.medicinenet.com/images/illustrations/pancreas.jpg
• Causes muscles and liver to convert
glucose to glycogen (storage form
of glucose).
• Glucagon responds to low levels of
blood glucose - stimulates
breakdown of glycogen to glucose.
• Diabetics cannot control levels of
insulin.
• 5Adrenal glands – found on top of
kidneys, consist of adrenal cortex
on exterior + adrenal medulla on
inside of gland.
• Medulla responsible for epinephrine
and norepinephrine in response to
stress.
http://training.seer.cancer.gov/module_anatomy/images/quiz_dd_adrenal_gland.jpg
• Epinephrine responsible for
adrenaline release as well as causing
blood to shunt away from skin,
digestive organs, kidneys; increases
blood flow to heart, brain, skeletal
muscle.
• Also increases metabolic activity.
http://services.epnet.com/GetImage.aspx/getImage.aspx?ImageIID=4680
• Cortex responsible for secretion of
corticosteroids - regulated by
nervous system in response to
stress, 3 types.
• AGlucocorticoids help to raise blood
glucose levels.
• High doses help in inflammation
response.
http://www.stanford.edu/group/hopes/treatmts/lifestyleandhd/f_an1hpaaxis.jpg
• BMineral corticoids - promote
reabsorption of Na+, excretion of K
by kidneys.
• CSex hormones – androgens
responsible in part for female sex
drive.
• 6Ovaries, Testes - testes produce
testosterone in males, estrogen and
progesterone in females.
• 7th week of development,
information on Y chromosome (if
present) starts to produce
testosterone.
• Absent - female hormones are
produced.
• ATestes – releases androgens (like
testosterone) responsible for
production of sperm and secondary
male sex characteristics.
• BOvaries – secrete estrogen and
progesterone.
http://www.redhotflush.co.uk/images/cartoons/hormones.jpg
• 1Estrogen responsible for
stimulating lining of uterus to grow
and secondary sex characteristics
of females.
• 2Progesterone responsible for
promoting lining of uterus to grow.
http://www.lef.org/magazine/mag2006/images/apr2006_report_prog_02_big.jpg
• 7Pineal gland - small mass of tissue
near center mammalian brain.
• Secretes melatonin - aids in
reproduction and cycle of light and
dark.
http://www.rickrichards.com/chakras/pituitary_brain2a.jpg