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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