CHEMICAL SIGNALS IN ANIMALS

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CHAPTER 45

• CHEMICAL SIGNALS IN ANIMALS

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• ENDOCRINE SYSTEM
• PRODUCE HORMONES
• MAINTAIN HOMEOSTASIS
• REGULATE REPRODUCTION
• REGULATE GROWTH DEVELOPMENT

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• HORMONES
• CHEMICAL MESSENGERS, PRODUCED IN ONE AREA AND MAY
  EFFECT ANOTHER AREA (TARGET CELLS)
• TRANSPORTED IN THE BLOOD
• MINUTE AMOUNTS MAY CREATE A HUGE PHYSIOLOGICAL
  RESPONSE
• MAY BE STEROIDS, PEPTIDES OR AMINO ACIDS

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• BRAIN (CNS)
• MONITORS THE EXTERNAL ENVIRONMENT AND INTERNAL
  ENVIRONMENT OF THE ORGANISM
• JOB IS TO CONTINUALLY INTEGRATE INFORMATION IN
  ORDER TO MAINTAIN HOMEOSTASIS

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• NEUROSECRETORY CELLS SECRETE HORMONES INTO THE
  BLOOD
• PITUITARY GLAND
• MASTER ENDOCRINE GLAND
• CONTROLS OTHER GLANDS

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• POSTERIOR PITUITARY (ADH OXYTOCIN) ARE STORED
  HERE. PRODUCED IN THE HYPOTHALAMUS AND STORED,
  RELEASED AS NEEDED
• ANTERIOR PITUITARY RELEASE TROPIC HORMONES.
• HORMONES THAT TARGET CELLS ARE OTHER ENDOCRINE
  GLANDS. ESSENTIALLY REGULATE THESE GLANDS

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• PANCREAS
• ISLETS OF LANGERHANS MADE UP OF 2 CELL TYPES
  AND RELEASE HORMONES THAT ARE ANTAGONISTIC IN
  FUNCTION
• BETA CELLS SECRETE INSULIN WHEN THE BLOOD
  GLUCOSE LEVEL RISES (EATING). INSULIN STIMULATE
  THE LIVER AND OTHER BODY CELLS TO ABSORB GLUCOSE
  SO THE RESULT IS BLOOD GLUCOSE LEVELS DECREASE
• ALPHA CELLS SECRETE GLUCAGON BLOOD GLUCOSE
  LEVEL DECREASES (EXCERSISE) GLUCAGON STIMULATES
  THE LIVER TO RELEASE GLUCOSE. STIMULATES THE
  CONVERSION OF GLYCOGEN TO GLUCOSE

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• CALCIUM BALANCE
• PARATHYROID GLAND (PTH) PARATHYROID HORMONE
  STIMULATES CALCIUM REABSORPTION IN THE KIDNEYS
  AND (OSTEOCLASTS) TO RELEASE CALCIUM IONS INTO
  THE BLOOD
• THROID GELEASES CALCITONIN, WHICH HAS THE
  OPPOSITE EFFECT OT PTH. LOWERS BLOOD CALCIUM
  LEVELS

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• 2 WAYS TO TRIGGER TARGET CELL ACTIVITY
• 1. HORMONE (USUALLY A STERIOD) DIFFUSES THROUGH
  THE PLASMA MEMBRANE THROUGH THE CYTOPLASM INTO
  THE NUCLEUS. THE HORMONE WILL BOND TO A RECEPTOR
  PROTEIN IN THE NUCLEUS AND THE RECEPTOR PROTEIN
  ACTIVATES A PROTEIN TO TURN ON SPECIFIC GENES
  (GENE ACTIVATION)

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• 2. HORMONE (A PEPTIDE) BINDS TO A RECEPTOR
  PROTEIN ON THE PLASMA MEMBRANE (RECEPTOR MEDIATED
  ENDOCYTOSIS). THE RECEPTOR PROTEIN THEN
  STIMULATES THE PRODUCTION OF SECONDARY
  MESSENGERS

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• A. CYCLIC AMP (camp) IS PRODUCED FROM ATP,
  CYCLIC AMP THEN WILL TRIGGER AN ENZYME THAT WILL
  GENERATE A SPECIFIC CELLULAR RESPONSE
• B. INOSITOL TRIPHOSPHATE (IP3). PRODUCED FROM
  MEMBRANES PHOSPHOLIPIDS, IP3 THEN WILL TRIGGER
  THE RELEASE OF CALCIUM FROM THE E.R. WHICH WILL
  ACTIVATE ENZYMES TO GENERATE CELLULAR CHANGES

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• HYPOTHALAMUS
• PITUITARY GLAND
• THYROID GLAND
• PARATHYROID GLAND
• PANCREAS
• ADRENAL GLANDS
• GONADS
• PINEAL GLAND
• THYMUS

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