Ch. 45:

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Ch. 45 Chemical Signaling in Animals
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1. Introduction to Regulatory Systems

• Hormone A chemical signal that is secreted
• into body fluids communicate regulatory
• messages.

1. Target Cells Responds to hormones.

• The two systems of internal communcation
• Nervous System Endocrine System

• Endocrine System hormone-secreting
• cells endocrine glands are ductless glands
• that secrete their chemical messengers
• directly into body fluids.

• Neurosecretory cells are specialized nerve
• cells that are a part of endocrine organs.
• 3.Ex. Of hormone Epinephrine, acts as the
• fight or flight hormone and also as a
• neurotransmitter.

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• Invertebrate reguatory systems clearly show
• endocrine and nervous system interaction

• Hormones function in reproduction
• and development.
• a. Example Mollusk Aplysia, secretes a
• hormone that stimulates the laying of eggs
• and inhibits the feeding and locomotion,
• activities that interfere with reproduction.

• Insects and crustaceans molt, triggered
• by a hormone called ecdysone.
• -Ecdysone is secreted by prothoracic
• glands
• -Ecdysone also favors the development
• of adult characteristics stimulates
• metamorphosis

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-Ecdysone production is controlled by a hormone
called brain hormone (BH).
-Ecdysone and BH are controlled by the juvenile
hormone (JH).
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1. Chemical Signals and Their Modes of Action

• Growth Factors peptides and proteins that
• stimulate cell proliferation.

• Epidermal Growth Factor (EGF)
• Accelerates epidermal development
• Insulinlike Growth Factors (IGF) produced
• in the liver essential to skeletal develop-
• ment.

• Nitric Oxide (NO)
• -Highly reactive and potentially toxic
• -acts like a neurotransmitter in neurons
• -when released by white blood cells, kills
• bacteria and cancer cells
• -dilates walls of blood vessels

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C.Prostaglandins (PGs) modified fatty
acids -in semen, stimulate contraction of
smooth muscles in the wall of the uterus
(helping sperm move towards egg) -secreted by
placental cells can cause labor in
childbirth -Defense induce fever and
inflammation, and increase pain -Examples

• Prostaglandin E (PGE) causes muscles
• to relax dilates blood vessels and
• promotes oxygenation of the blood
• Prostaglandin F (PGF) signals muscles
• to contract constricts vessels and reduces
• blood flow to lungs
• ? These two are antagonistic

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• Most chemical signals bind to plasma
• membrane proteins, initiating signal-
• transduction pathways (Ch. 11. Also see
• Activities for Ch. 45 on the Campbell website)

• Different signal-transduction pathways in
• different cells can lead to different
• responses to the same signal.
• Example Acetylcholine can produce
• different responses in different target cells.

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• One
• hormone
• can have
• a large
• effect.

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• Steroid hormones, thyroid hormones, and
• some local regulators enter target cells by
• binding to intracellular receptors.

• Examples Estrogen, progesterone,
• vitamin D, NO
• ? See Campbell website, Ch. 45 Hormone
• Activity

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1. The Vertebrate Endocrine System

• Tropic Hormones target other endocrine
• glands and are important to understandingchemica
  l coordination.

• Humans have NINE
• endocrine glands

• Hypothalamus
• releases hormones
• that stimulate and
• inhibit the anterior
• pituitary (adeno-
• hypophysis).

-Releasing hormones -Inhibiting hormones
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• Pituitary has 2
• parts
• Anterior
• Posterior

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• Hormones from the hypothalamus regulates
• anterior pituitary hormones, which stimulate
• many other hormones.

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The posterior pituitary (neurohypophysis) is a
small bulge of the hypothalamus that stores and
secretes hormones made by the hypothalamus ADH
(antidiuretic hormone) and oxytocin.
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1. Posterior Pituitary Hormones

• Oxytocin acts on muscles of the uterus
• induces contraction of the uterine
• muscles during childbirth and causes
• mammary glands to eject milk during
• nursing.

• ADH regulates osmolarity of the blood
• stimulates water reabsorption

1. Anterior Pituitary Hormones

• Growth hormone (GH)
• -protein, about 200 amino acids long
• -has a wide variety of target tissues
• -stimulates growth of bones and cartilage
• -signal the liver to produce insulinlike
• growth factors (IGFs)

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-Too much GH as a child ? gigantism -Too much GH
as an adult ? abnormal growth of bones in
hands, feet, and head acromegaly
-GH deficiencies as a child can be treated
with GH from cadavers.

• Insulinlike growth
• factors (IGFs)
• -Stimulates bone and
• cartilage growth

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• Prolactin (PRL)
• -Similar in structure to GH
• -Diverse effects Stimulates mammary
• to produce milk, regulates fat metabolism
• and reproduction in birds, delays
• metamorphosis in amphibians, regulates
• salt and water balance in fish
• ? Diversity suggests its an ancient
• hormone whose function has evolved
• during the evolution of vertebrates.

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• The tropic hormones
• 1.Follicle-Stimulating Hormone (FSH)
• stimulate gonads (testes, ovaries)
• 2.Lutenizing hormone (LH)
• stimulate gonads (testes, ovaries)
• 3.Thyroid-stimulating Hormone (TSH)
• regulates the release of thyroid
• hormones
• 4.Adrenocorticotropic Hormone (ACTH)
• stimulates the production and secretion
• of steroid hormones by the adrenal
• cortex.

Gonadotropins
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• Melanocyte-Stimulating Hormone (MSH)
• regulates the activity of pigment-
• containing cells in the skin.
• It also regulates fat metabolism.

• Endorphins Class of molecules called
• natural opiates, giving a natural high
• because they inhibit the perception of
• pain. Exercise releases endorphins.
• Opiate drugs mimic endorphins.

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• Pineal Gland hormones Involved in
• biorhythms

• Melatonin Modified
• amino acid

• Melatonin is secreted at night, and the
• amount secreted depends on the length
• of the night.
• Winter more melatonin secreted
• Summer less melatonin secreted

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• Affects skin pigmentation (more
• darker skin)
• Associated with biological rhythms
• ? biological clocks

1. Thyroid hormones

• Two lobes around the trachea
• Produces Calcitoninhormone that
• controls Ca2 levels
• in blood
• c.Produces T3 T4
• hormones
• ? T4 converts to T3
• in target cells
• d.T3 and T4 are
• derived from
• amino acid tyrosine.

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• Tyroid gland plays a crucial role in
• development and maturation.
• ? Tadpole into a frog
• ? Cretinism in humans thyroid
• deficiency causes retarded skeletal
• growth and mental development.

• Tyroid gland helps maintain homeostasis
• -Blood pressure
• -Heart rate
• -Muscle tone
• -Digestion
• -Reproductive functions

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• Hyperthyroidism excess secretion of
• thyroid hormones
• g.Hypothyroidism shortage of thyroid
• hormones
• h.Goiterism shortage of thyroid hormones

Great website to visit! http//www.biosbcc.net/ba
rron/physiology/endo/thyr.htm
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• Feedback control loops regulating the
• secretion of T3 and T4.

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• Parathyroid hormones
• a. Four parathyroid glands embedded in
• the surface of the thyroid, function in
• the homeostasis of calcium ions (Ca 2 ).

-They secrete parathyroid hormone (PTH), which
raises blood levels of Ca2 (opposite of
calcitonin).
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1. Endocrine tissues

• Pancreas two tissue
• -Exocrine produces bicarbonate ions
• and digestive enzymes that are carried
• to the small intestines via the
• pancreatic duct.
• -Endocrine (1-2 of pancreas)
• 1. Islets of Langerhans
• ? secretes glucagon from its alpha
• cells
• ? secretes insulin from its beta
• cells

-Insulin and glucagon are antagonistic hormones
that regulate the concentration of glucose in
blood.
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• -Type I diabetes mellitus autoimmune
• disorder immune system attacks the
• cells of the pancreas.
• Occurs in childhood
• person cannot produce insulin
• treatment daily injections of insulin
• -Type II diabetes mellitus non-insulin
• dependent diabetes
• characterized by deficiency in insulin or
• reduced responsiveness in target cells
• due to changes in insulin receptors
• usually occurs after age 40
• 90 of diabetics are type II
• can be managed by exercise and
• dietary control
• heredity and obesity are major factors

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• Adrenal medulla and Adrenal cortex
• hormones

• Adrenal glands adjacent to the kidneys
• -Medulla central part
• -Cortex outer part

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• Catecholamines
• 1. Epinephrine (aka adrenaline)
• 2. Norepinephrine (aka noradrenaline)

• Released due to positive and negative
• stress.
• Produces a rapid bioenergetic boost
• increasing basal metabolic rate
• Produces the fight or flight response
• Increases the rate of glycogen break-
• down and glucose release into blood
• Stimulate the release of fatty acids from
• fat cells
• Increases rate and stroke volume of
• heart rate
• Increases rate of oxygen delivery to
• body

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• Moves blood away from skin, digestive
• organs, and kidneys, while increasing
• blood supply to heart, brain, and
• skeletal muscles.

• What causes the release of epinephrine
• and norepinephrine?
• -adrenal medulla is under control of
• nerve cells from the sympathetic
• division of the autonomic nervous
• system
• -Under stress, the nerve cells are excited
• and release the neurotransmitter
• acetylcholine. Acetylcholine stimulates
• the release of epinephrine.

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-Adrenal cortex secretes steroids called
corticosteroids when acted upon by ACTH (from
the anterior pituitary gland). -Three types of
corticosteroids 1.Glucocorticoids (ex.
Cortisol) promotes the synthesis of glucose
from noncarbohydrate sources (protein). ?
Glucocorticoids act on skeletal muscles to
break down protein to be converted to glucose.

• Mineralocorticoids (ex. Aldosterone)
• effects salt and water balance.
• Aldosterone stimulates the kidney to
• reabsorbe sodium and water from the
• filtrate, raising blood pressure and
• volume.

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• Sex hormones, androgen (male
• hormones) estrogen, and
• progesterone (female hormones).

9. Gonadal steroids

• Gonads produce and secrete androgens,
• estrogens, and progestins.
• All 3 are found in both males and
• females but in different proportions.
• All are produced in testes and ovaries.
• Affect growth and development and also
• regulate reproductive cycles and sexual
• behavior.
• Testes primarily produce androgens, the
• main such hormone being testosterone.
• Estrogen maintain and develop female
• reproductive system.

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• Progestins (progesterone) are primarily
• involved in preparing and maintaining
• the uterus, which supports the growth
• and development of the embryo.
• Synthesis of estrogens and androgens
• are controlled by gonadotropins FSH and
• LH. FSH and LH are controlled by the
• hormone GnRH (gonadotropin-releasing
• hormone) released by the hypothalamus.