Chemical Signals in Animals

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Chapter 45
Chemical Signals in Animals
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Hormones

• Hormones are chemical signals.
• The endocrine system consists of
• Endocrine cells which are hormone-secreting cells
  and
• Endocrine glands which are hormone-secreting
  organs.
• Specific target cells respond to specific
  hormones.

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Primary Function of Hormones

• Homeostasis
• Growth and Development
• Reproduction
• Energy Metabolism
• Behavior

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Negative Feedback Loop
blood glucose low
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Biological Cycles
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Mechanism of Action on Target Cells
response
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Mechanism of Action on Target Cells
response
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Tropic vs Nontropic Hormones
Tropic hormones- stimulate the production and
secretion of hormones by other endocrine glands
ex. TSH Nontropic hormones- stimulates cellular
growth, metabolism, or other functions ex.
thyroxine
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Invertebrate nervous systems clearly illustrate
endocrine and nervous system interactions

• Invertebrates have a wide variety of hormones
  that are involved in the regulation of
  homeostasis.

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• An example from hydra
• One hormone stimulate asexual reproduction.
• Another hormone prevents sexual reproduction.
• An example from a mollusk
• The hormone that regulates egg laying also
  inhibits feeding and locomotion.

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• Arthropods have extensive endocrine systems
  regulating molting in insects and crustaceans.
• The regulation of molting in insects.
• Ecdysone also promotes the development of adult
  features.
• Neurosecretory cells in the brain produce
  Prothoracicotropic hormone (PTTH), which
  regulates the secretion of ecdysone.
• Juvenile hormone (JH) promotes the retention of
  larval characteristics.

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

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Frog Metamorphosis
thyroxin
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Fig. 45-10
Major Endocrine Organs
Major endocrine glands
Hypothalamus
Pineal gland
Pituitary gland
Organs containing endocrine cells
Thyroid gland
Thymus
Parathyroid glands
Heart
Liver
Adrenal glands
Stomach
Pancreas
Kidney
Testes
Small intestine
Kidney
Ovaries
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Endocrine Organs of the Brain
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Pineal Gland
Produces melatonin (synthesized from seratonin, a
derivative of tryptophan)

• Secreted directly in CSF to blood
• High levels at night make us sleepy low level
  during day
• Pineal gland is stimulated by darkness and
  inhibited by light
• Function in regulating circadian rhythms (sleep,
  body temp, appetite) ? biological clock

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Pituitary Gland
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Posterior Pituitary
Hypothalamus
Posterior Pituitary
Anterior Pituitary
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Hormones of the
Posterior Pituitary
Antidiuretic Hormone (ADH) Oxytocin ( feedback)
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Anterior Pituitary
Hypothalamus
Posterior Pituitary
Anterior Pituitary
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Hormones of the
Anterior Pituitary

• Growth Hormone (GH)
• Dwarfism
• Gigantism Acromegaly
• Thyroid Stimulating Hormone (TSH)
• Adrenocorticotropic Hormone (ACTH)
• Gonadotropins (FSH, ICSH, LH)
• Prolactin (PRL)
• Melanocyte-stimulating Hormone (MSH)

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Growth Hormone (GH)

• Acts on the liver, stimulating it to release
  several polypeptide hormones.
• Stimulates amino acid uptake and protein
  synthesis in target cells.
• Ultimately stimulates cell growth (cell size and
  number), especially in muscle and bone.
• Also stimulates fat breakdown.

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GH Levels
sleep
awake
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Dwarfism
hyposecretion of GH
Little People Big World
Kenadie - worlds smallest girl due to primordial
dwarfism
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Gigantism
hypersecretion of GH
Bao Xishun, a 7ft 8.95in herdsman from Inner
Mongolia
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Acromegaly
hypersecretion of GH
7 ft 1 ¼ inches
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Thyroid-Stimulating Hormone (TSH)

• Acts on the thyroid gland, stimulating it to
  release T3 T4
• These thyroid hormones increase glucose
  catabolism and body heat production.
• Negative feedback mechanism involved in
  regulating levels.

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Adrenocorticotropic Hormone (ACTH)

• Acts on the adrenal cortex, stimulating it to
  secrete glucocorticoids (e.g., cortisol).
• Glucocorticoids promote the synthesis of glucose
  from noncarbohydrate sources such as amino acids,
  and fatty acids
• Negative feedback mechanism involved in
  regulating levels.

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Thyroid Gland
larynx
thyroid
trachea
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Thyroid Follicles
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Thyroid Hormones
Thyroid gland selectively uptakes iodine to
produce T3 T4

• Thyroxine (T4)
• Triiodothyronine (T3)
• Both control metabolic rate and cellular
  oxidation
• Calcitonin (from parafolicular cells)- lowers
  blood CA levels and causes CA reabsorption
  in bone

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Thyroid Hormone Regulation
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Thyroid Disorders

• Hyperthyroidism (Graves, Goiter)
• Hypothyroidism (Cretinism, Myxedima)

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Goiter
Lack of iodine in diet hyposecretion of T3 T4
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hyposecretion of T3 T4
Cretinism
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Myxedemahyposecretion of T3 T4
After thyroid treatment
myxedema
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Exophthalmos- hyperthyroidism
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Parathyroid Glands
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Parathyroid Hormone (PTH)

• PTH release
• stimulates osteoclasts
• enhances reabsorption of Ca by kidneys
• increases absorption of Ca by intestinal
  mucosal cells
• Hyperparathyroidism- too much Ca drawn out of
  bone could be due to tumor
• Hypoparathyroidism- most often follow parathyroid
  gland trauma or after removal of thyroid---
  tetany, muscle twitches, convulsions if
  untreated?respiratory paralysis and death

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PTH Effects
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Pancreas
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Pancreas

• Regulates glucose uptake by cells
• Controlled via negative feedback insulin
  glucagon
• Blood sugar level 90 mg/mL

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Islets of Langerhan
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Insulin

• Produced by the ? cells of the Islets of
  Langerhan
• Catalyze oxidation of glucose for ATP production
• Lowers blood glucose levels by promoting
  transport of glucose into cells.
• Stimulates glucose uptake by the liver and
  muscle cells.
• Stimulates glycogen synthesis in the liver and
  muscle cells.
• Also stimulates amino acid uptake and protein
  synthesis of muscle tissue

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Glucagon

• Produced by the ? cells of the Islets of
  Langerhans
• Stimulates change of glycogen to glucose in the
  liver.
• Synthesis of glucose from lactic acid and non
  carbohydrate molecules such as fatty acids and
  amino acids
• Causes ? in blood glucose concentration

hypoglycemic- low blood sugar? deficient in
glucagon
   
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Regulation of Blood Sugar Levels
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Diabetes Melitus
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Type I Diabetes hyposecretion of
insulin insulin dependant juvenile onsetType
II Diabetes late onset (adult) insensitivity of
cells to insulin manage by exercise diet
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Adrenal Glands
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Hormones of the Adrenal Medulla

• Adrenalin (epinephrine) converts glycogen to
  glucose in liver
• Noradrenalin (norepinephrine) increases blood
  pressure
• (sympathetic nervous system)
• Corticosteroids? glucose levels)

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Hormones of the Adrenal Cortex

• Glucocorticoids- cortisol
• Decrease protein synthesis
• Increase release and use of fatty acids
• Stimulates the liver to produce glucose from non
  carbs
• Mineralcorticoids- aldosterone
• Stimulates cells in kidney to reabsorb Na from
  filtrate
• Increases water reabsorption in kidneys
• Increases blood pressure
• Sex Steroids- small amts (androgens)
• Onset of puberty
• Sex drive

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Cushings Syndrome
Hypersecretion of cortisone may be caused by an
ACTH releasing tumor in pituitary Symptoms
trunkal obesity and moon face, emotional
instability Treatment removal of adrenal gland
and hormone replacement
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Addisons Disease
Hyposecretion of glucocorticoids and mineral
corticoids Symptoms- wt loss, fatigue,
dizziness, changes in mood and personality, low
levels of plasma glucose and Na levels, high
levels of K Treatment- corticosteroid
replacement therapy
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Thymus
Located anterior to the heart Produces-
thymopoetin and thymosin? helps direct maturation
and specialization of T-lymphocytes (immunity)
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Gonads
Ovaries- produce estrogen and progesterone?respons
ible for maturation of the reproductive organs
and 2ndary sex characteristics in girls at
puberty
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Female Reproductive System
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Gonads
Testes- produce sperm and testosterone (initiates
maturation of male repro organs and 2ndary sex
characteristics in boys at puberty)
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Male Reproductive System