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Chemical signals in Animals

Chemical signals in Animals. Ch 45 – Endocrine system. Human Endocrine system. Both the nervous system & the endocrine system send message to the body Nervous – messages for quicker, more specific responses Endocrine – messages for broader, more widespread responses

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Chemical signals in Animals

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  1. Chemical signals in Animals Ch 45 – Endocrine system

  2. Human Endocrine system Both the nervous system & the endocrine system send message to the body Nervous – messages for quicker, more specific responses Endocrine – messages for broader, more widespread responses http://www.youtube.com/watch?v=gjmS4_7kvDM

  3. Lactation- example of interaction between nervous & endocrine systems

  4. Chemical Signals 1) endocrine 2) paracrine & autocrine 3) synaptic & neuroendocrine - neurosecretory cells secrete molecules (neurohormones) into the blood stream 4) pheromones - chemicals released into external environment

  5. Local Regulators • Cytokinases – polypeptide regulators, carry signals locally between cells • Growth factors • Nitric oxide – gas, produced by many cells causes changes within seconds in target cell & then breaks down • Prostaglandins- promote fever and inflammation and intensify the sensation of pain, also active in female reproductive system – ie. Inducing labor in childbirth

  6. Hormones – long distance signals • Three classes: • 1) Polypeptides – Water soluble (hydrophilic) • i.e. insulin • 2) Steroids – Lipid soluble (Hydrophobic) • i.e. testosterone, estradiol • 3) Amines – most are water soluble • i.e. thyroxin, epinephrine

  7. Water soluble hormones – bind to cell-surface receptor cells • This starts the signal transduction pathway • Causes changes in cytoplasm, enzyme activation, or changes in gene expression

  8. Lipid soluble – can pass through cell membrane, bind to receptors in cytoplasm or nucleus • Cause possible change in gene expression, or cytoplasmic response

  9. (b) Skeletal muscleblood vessel (c) Intestinal bloodvessel Same receptors but differentintracellular proteins (not shown) Different receptors Different cellularresponses Different cellularresponses Epinephrine Epinephrine Epinephrine  receptor  receptor  receptor Glycogendeposits Vesseldilates. Vesselconstricts. Glycogenbreaks downand glucoseis releasedfrom cell. (a) Liver cell

  10. Hypothalamus & Pituitary gland • The hypothalamus – at the base of the brain • Helps integrate nervous & endocrine systems • Receives nervous signals • Releases hormones to control the anterior pituitary

  11. Pituitary Gland Anterior • Secretes four tropic hormones: • TSH – thyroxin stimulating hormone • LH – luteinizing hormone • FSH – follicle stimulating hormone • ACTH – adrenocorticotropic hormone • Tropic hormones – control other endocrine glands • Also releases other peptide hormones (prolactin, growth hormone)

  12. Pituitary Gland Posterior • Hypothalamic neurons extend into the posterior • Secretes 2 neurohormones: • ADH – antidiuretic hormone • Oxytocin

  13. Hormone Feedback loops • Many used to maintain Homeostasis • Negative feedback helps maintain pre-existing state • Some homeostatic control systems have two antagonistic negative feedback pathways, that balance each other

  14. Control of Blood Glucose • Pancreas produces 2 hormones that control glucose level: • Glucagon • Made by alpha cells in pancreas • Increases glucose levels by targeting liver cells – stimulates glycogen hydrolysis, release glucose into bloodstream • Insulin • Made by beta cells in pancreas • Lowers glucose levels by stimulating body cells to take up glucose from blood • Slows glycogen breakdown in liver

  15. Insulin Body cellstake up moreglucose. Beta cells ofpancreasrelease insulininto the blood. Liver takesup glucose and stores itas glycogen. STIMULUS:Blood glucose level rises (for instance, after eating acarbohydrate-rich meal). Blood glucoselevel declines. Homeostasis:Blood glucose level(70–110 mg/m100mL) STIMULUS:Blood glucose level falls (for instance, afterskipping a meal). Blood glucoselevel rises. Liver breaksdown glycogenand releasesglucose intothe blood. Alpha cells of pancreasrelease glucagon intothe blood. Glucagon

  16. Diabetes • Chronic disease where there are high levels of sugar in the blood • Symptoms: frequent urination, blurred vision

  17. Diabetes • Type 1– insulin dependent • Beta cells produce little or no insulin, so glucose builds up in blood • Autoimmune system destroys beta cells • Type 2 – non insulin dependent • Target cells do not respond to insulin • Suppression of target cells, so pathway doesn’t function

  18. Thyroid gland • Helps regulate metabolic rate and body temperature • Also involved in calcium regulation

  19. Thyroid regulation Thyroid produces Thyroxine (T4) and similar hormone T3 (T3 is more active) (count iodines)

  20. Thyroxine – lipid soluble • Binds to intracellular receptor that stimulates transcription of several genes • These genes encode proteins involved in energy pathways – leads to general increase in cell metabolism • Important in development and growth – it promotes amino acid uptake & protein synthesis • Insufficient thyroxine – retards physical and mental development – (cretinism)

  21. Thyroxine levels are controlled by the hypothalamus and anterior pituitary • Hypothalamus releases TRH – thyrotropin releasing hormone • This stimulates the anterior pituitary to release thyroid stimulating hormone

  22. Pathway Example Cold Stimulus Sensory neuron Hypothalamus secretesthyrotropin-releasinghormone (TRH ). Hypothalamus Neurosecretory cell Releasing hormone Blood vessel Anterior pituitary secretesthyroid-stimulatinghormone (TSH, also knownas thyrotropin ). Anterior pituitary Tropic hormone

  23. Pathway Example Tohypothalamus  Anterior pituitary secretesthyroid-stimulatinghormone (TSH, also knownas thyrotropin ). Anterior pituitary Tropic hormone Negative feedback Thyroid gland secretesthyroid hormone(T3 and T4 ). Endocrine cell Hormone Targetcells Body tissues Increased cellularmetabolism Response

  24. Hormone cascade pathway • Thyroid regulation is an example of a hormone cascade pathway • One hormone stimulates a series of other hormones, which finally activates a nonendocrine target cell

  25. Thyroid issues • Too much thyroxine– Hyperthyroidism • - most commonly a result of an autoimmune disorder, where antibody binds to and activates TSH receptors • Blood TSH is low due to negative feedback from thyroxine • - Thyroid gland is always stimulated, so goiter may occur (enlarged thyroid) • - symptoms: high metabolism, feel hot, nervous, may have eyes bulge (buildup of fat)

  26. Too little thyroxine – Hypothyroidism • Most commonly – due to too little dietary iodine, so the thyroid cannot make functional thyroxine • TSH levels high, stimulates Thyroid to become bigger • Can lead to Goiter – enlarged thyroid

  27. Adrenal gland • Adrenal glands sit above the kidneys • Two parts: • Inner – Adrenal medulla – produces epinephrine and norephinephrine (catecholamines) • Outer – Adrenal cortex – produces glucocorticoids,mineralcorticoids and sex hormones

  28. Stress response – “fight or flight” • Epinephrine and norepinephrine secreted in response to positive or negative stress • Trigger the release of glucose and fatty acids into the blood • Increase oxygen delivery to body cells • Direct blood toward heart, brain, and skeletal muscles and away from skin, digestive system, and kidneys • http://www.youtube.com/watch?v=BIfK0L8xDP0 • http://www.youtube.com/watch?v=FBnBTkcr6No

  29. Stress response- longer term • Glucocorticoids are secreted from adrenal cortex (affect glucose production) • Increased blood glucose • Mineralcorticoids secreted from adrenal cortex (affect salt & water balance) • Increased blood volume & blood pressure

  30. (b) Long-term stress responseand the adrenal cortex (a) Short-term stress responseand the adrenal medulla Stress Hypothalamus Nervesignals Spinal cord(cross section) Releasinghormone Nervecell Anterior pituitary Blood vessel ACTH Nerve cell Adrenal medullasecretes epinephrineand norepinephrine. Adrenal cortexsecretes mineralo-corticoids andglucocorticoids. Adrenalgland Kidney Effects of mineralocorticoids: Effects of glucocorticoids: Effects of epinephrine and norepinephrine: • Glycogen broken down to glucose; • increased blood glucose •Proteins and fats broken down and converted to glucose, leading to increased blood glucose •Retention of sodium ions and water by kidneys • Increased blood pressure • Increased breathing rate • Increased metabolic rate •Increased blood volume and blood pressure •Partial suppression of immune system

  31. Melatonin and Biorhythms • The pineal gland, located in the brain, secretes melatonin • Light/dark cycles control release of melatonin • It is secreted at night, amount depends on length of night • Primary functions of melatonin appear to relate to biological rhythms associated with reproduction

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