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Signals can be of many kinds light, sound, smell, touch etc. many of which are due to chemicals.

Two systems coordinate communication throughout the body: the endocrine system and the nervous system The endocrine system secretes hormones that coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior

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Signals can be of many kinds light, sound, smell, touch etc. many of which are due to chemicals.

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  1. Two systems coordinate communication throughout the body: the endocrine system and the nervous system • The endocrine system secretes hormones that coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior • The nervous system conveys high-speed electrical signals along specialized cells called neurons; these signals regulate other cells

  2. In multicellular animals, nerve impulses provide electric signals; hormones provide chemical signals. • Hormones are secreted by cells, diffuse into the extracellular fluid, and often are distributed by the circulatory system. Hormones reach all parts of the body, but only target cells are equipped to respond • Hormones work much more slowly than nerve impulse transmission and are not useful for controlling rapid actions. • Hormones coordinate longer-term developmental processes such as reproductive cycles.

  3. Concept 45.1: Hormones and other signaling molecules bind to target receptors, triggering specific response pathways Signals can be of many kinds light, sound, smell, touch etc. many of which are due to chemicals. Chemical signals bind to receptor proteins on target cells Only target cells with the appropriate receptor respond to the signal

  4. Types of Secreted Signaling Molecules Secreted chemical signals include Hormones Local regulators Neurotransmitters Neurohormones Pheromones

  5. Local Regulators Local regulators are chemical signals that travel over short distances by diffusion Local regulators help regulate blood pressure, nervous system function, and reproduction Local regulators are divided into two types Paracrine signals act on cells near the secreting cell Autocrine signals act on the secreting cell itself

  6. Signaling by Local Regulators In paracrine signaling, nonhormonal chemical signals called local regulators elicit responses in nearby target cells Types of local regulators: Cytokines and growth factors Nitric oxide (NO) Prostaglandins

  7. Long distance signaling involves the chemical being taken by circulation to the target tissues. Usually hormones are released from a special cell or organ called an endocrine cell/organ, travel through the bloodstream, and interact with the receptor or a target cell to cause a physiological response.

  8. Fig. 45-2 Blood vessel Response (a) Endocrine signaling Response (b) Paracrine signaling Response (c) Autocrine signaling Synapse Neuron Response (d) Synaptic signaling Neurosecretory cell Blood vessel Response (e) Neuroendocrine signaling

  9. Chemical Classes of Hormones Three major classes of molecules function as hormones in vertebrates: Polypeptides (proteins and peptides) Amines derived from amino acids Steroid hormones

  10. Lipid-soluble hormones (steroid hormones) pass easily through cell membranes, while water-soluble hormones (polypeptides and amines) do not The solubility of a hormone correlates with the location of receptors inside or on the surface of target cells

  11. Fig. 45-3 Water-soluble Lipid-soluble 0.8 nm Polypeptide: Insulin Steroid: Cortisol Amine: Epinephrine Amine: Thyroxine

  12. Cellular Response Pathways Water and lipid soluble hormones differ in their paths through a body Water-soluble hormones are secreted by exocytosis, travel freely in the bloodstream, and bind to cell-surface receptors Lipid-soluble hormones diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells

  13. Signaling by any of these hormones involves three key events: Reception Signal transduction Response

  14. Fig. 45-5-1 Fat-soluble hormone Water- soluble hormone Transport protein Signal receptor TARGET CELL Signal receptor NUCLEUS (a) (b)

  15. Fig. 45-5-2 Fat-soluble hormone Water- soluble hormone Transport protein Signal receptor TARGET CELL OR Signal receptor Cytoplasmic response Gene regulation Cytoplasmic response Gene regulation NUCLEUS (a) (b)

  16. Pathway for Water-Soluble Hormones Binding of a hormone to its receptor initiates a signal transduction pathway leading to responses in the cytoplasm, enzyme activation, or a change in gene expression Animation: Water-Soluble Hormone

  17. Multiple Effects of Hormones The same hormone may have different effects on target cells that have Different receptors for the hormone Different signal transduction pathways Different proteins for carrying out the response A hormone can also have different effects in different species

  18. Fig. 45-8-1 Same receptors but different intracellular proteins (not shown) Epinephrine Epinephrine  receptor  receptor Glycogen deposits Vessel dilates. Glycogen breaks down and glucose is released. (a) Liver cell (b) Skeletal muscle blood vessel

  19. Fig. 45-8-2 Same receptors but different intracellular proteins (not shown) Different receptors Epinephrine Epinephrine Epinephrine Epinephrine  receptor  receptor  receptor  receptor Glycogen deposits Vessel dilates. Vessel constricts. Glycogen breaks down and glucose is released. (a) Liver cell (c) Intestinal blood vessel (b) Skeletal muscle blood vessel

  20. Hormones Endocrine signals (hormones) are secreted into extracellular fluids and travel via the bloodstream Endocrine glands are ductless and secrete hormones directly into surrounding fluid Hormones mediate responses to environmental stimuli and regulate growth, development, and reproduction Exocrine glands have ducts and secrete substances onto body surfaces or into body cavities (for example, tear ducts)

  21. Fig. 45-10 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

  22. Concept 45.2: Negative feedback and antagonistic hormone pairs are common features of the endocrine system Hormones are assembled into regulatory pathways • A negative feedback loop inhibits a response by reducing the initial stimulus • Negative feedback regulates many hormonal pathways involved in homeostasis

  23. Coordination of Endocrine and Nervous Systems in Invertebrates In insects, molting and development are controlled by a combination of hormones: A brain hormone stimulates release of ecdysone from the prothoracic glands Juvenile hormone promotes retention of larval characteristics Ecdysone promotes molting (in the presence of juvenile hormone) and development (in the absence of juvenile hormone) of adult characteristics

  24. Fig. 45-13-3 Brain Neurosecretory cells Corpus cardiacum PTTH Corpus allatum Low JH Prothoracic gland Ecdysone Juvenile hormone (JH) EARLYLARVA LATER LARVA PUPA ADULT

  25. Coordination of Endocrine and Nervous Systems in Vertebrates The hypothalamus receives information from the nervous system and initiates responses through the endocrine system Attached to the hypothalamus is the pituitary gland composed of the posterior pituitary and anterior pituitary The pituitary gland of mammals is a link between the nervous system and many endocrine glands and plays a crucial role in the endocrine system.

  26. Fig. 45-14 Cerebrum Thalamus Pineal gland Hypothalamus Cerebellum Pituitary gland Spinal cord Hypothalamus Posterior pituitary Anterior pituitary

  27. The posterior pituitary stores and secretes hormones that are made in the hypothalamus:these hormones are called neuroendocrine hormones The anterior pituitary makes and releases hormones under regulation of the hypothalamus

  28. Fig. 45-15 Hypothalamus Neurosecretorycells of thehypothalamus Axon Posterior pituitary Anterior pituitary HORMONE Oxytocin ADH TARGET Kidney tubules Mammary glands,uterine muscles

  29. ADH • The function of antidiuretic hormone (ADH) is to increase water conservation by the kidney. • If there is a high level of ADH secretion, the kidneys resorb water. • If there is a low level of ADH secretion, the kidneys release water in dilute urine. • ADH release by the posterior pituitary increases if blood pressure falls or blood becomes too salty. • ADH causes peripheral blood vessel constriction to help elevate blood pressure and is also called vasopressin.

  30. Oxytocin induces uterine contractions and the release of milk Suckling sends a message to the hypothalamus via the nervous system to release oxytocin, which further stimulates the milk glands This is an example of positive feedback, where the stimulus leads to an even greater response

  31. Fig. 45-17 Tropic effects only:FSHLHTSHACTH Neurosecretory cellsof the hypothalamus Nontropic effects only:ProlactinMSH Nontropic and tropic effects:GH Hypothalamicreleasing andinhibitinghormones Portal vessels Endocrine cells ofthe anterior pituitary Posterior pituitary Pituitary hormones HORMONE FSH and LH TSH ACTH Prolactin MSH GH TARGET Testes orovaries Thyroid Adrenalcortex Mammaryglands Melanocytes Liver, bones,other tissues

  32. Tropic Hormones A tropic hormone regulates the function of endocrine cells or glands The four strictly tropic hormones are Thyroid-stimulating hormone (TSH) Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Adrenocorticotropic hormone (ACTH)

  33. Nontropic Hormones Nontropic hormones target nonendocrine tissues Nontropic hormones produced by the anterior pituitary are Prolactin (PRL) Melanocyte-stimulating hormone (MSH) • Prolactin stimulates lactation in mammals but has diverse effects in different vertebrates • MSH influences skin pigmentation in some vertebrates and fat metabolism in mammals

  34. Growth Hormone Growth hormone (GH) is secreted by the anterior pituitary gland and has tropic and nontropic actions It promotes growth directly and has diverse metabolic effects It stimulates production of growth factors An excess of GH can cause gigantism, while a lack of GH can cause dwarfism

  35. Figure 42.6 Effects of Excess Growth Hormone

  36. Releasing and Release inhibiting Neurohormones of the Hypothalumus

  37. Anterior Pituitary Hormones Hormone production in the anterior pituitary is controlled by releasing and inhibiting hormones from the hypothalamus For example, the production of thyrotropin releasing hormone (TRH) in the hypothalamus stimulates secretion of the thyroid stimulating hormone (TSH) from the anterior pituitary

  38. Hormone Cascade Pathways A hormone can stimulate the release of a series of other hormones, the last of which activates a nonendocrine target cell; this is called a hormone cascade pathway The release of thyroid hormone results from a hormone cascade pathway involving the hypothalamus, anterior pituitary, and thyroid gland Hormone cascade pathways are usually regulated by negative feedback

  39. Fig. 45-18-3 Pathway Example Stimulus Cold Sensoryneuron – Hypothalamus secretesthyrotropin-releasinghormone (TRH ) Neurosecretorycell Bloodvessel – Anterior pituitary secretes thyroid-stimulatinghormone (TSHor thyrotropin ) Negative feedback Thyroid gland secretes thyroid hormone (T3 and T4 ) Targetcells Body tissues Increased cellularmetabolism Response

  40. Thyroid Hormone: Control of Metabolism and Development The thyroid gland consists of two lobes on the ventral surface of the trachea It produces two iodine-containing hormones: triiodothyronine (T3) and thyroxine (T4) Two forms of thyroxine, T3 and T4, are made from tyrosine. T3 (triiodothyronine) has three iodine atoms. T4 has four iodine atoms. More T4 is produced in thyroid, but it can be converted to T3 by an enzyme in the blood. T3 is the more active form of the hormone.

  41. Thyroxine has many roles in regulating metabolism. • It stimulates the transcription of many genes in nearly all cells in the body. These include genes for enzymes of energy pathways, transport proteins, and structural proteins. • It elevates metabolic rates in most cells and tissues. • It promotes the use of carbohydrates over fats for fuel. • It promotes amino acid uptake and protein synthesis and so is critical for metabolism, growth and development. Insufficient thyroxine may result in cretinism.

  42. Hyperthyroidism, excessive secretion of thyroid hormones, causes high body temperature, weight loss, irritability, and high blood pressure Hypothyroidism, low secretion of thyroid hormones, causes weight gain, lethargy, and intolerance to cold

  43. A goiter is an enlarged thyroid gland associated with either very low (hypothyroidism) or very high (hyperthyroidism) levels of thyroxine. Hyperthyroid goiter results when the negative feedback mechanism fails even though blood levels of thyroxine are high. A common cause is an autoimmune disease in which an antibody to the TSH receptor is produced. This antibody binds the TSH receptor, causing the thyroid cells to release excess thyroxine. (Graves’ disease) The thyroid remains maximally active and grows larger, causing symptoms associated with high metabolic rates.

  44. Hypothalamus Anterior pituitary TSH Thyroid T3 T4 +

  45. Hypothyroid goiter results when there is insufficient thyroxine to turn off TSH production. • The most common cause is a deficiency of dietary iodine. • With high TSH levels, the thyroid gland continues to produce nonfunctional thyroxine and becomes very large. • The body symptoms of this condition are low metabolism, cold intolerance, and physical and mental sluggishness.

  46. Parathyroid Hormone and Vitamin D: Control of Blood Calcium • Two antagonistic hormones regulate the homeostasis of calcium (Ca2+) in the blood of mammals • Parathyroid hormone (PTH) is released by the parathyroid glands • Calcitonin is released by the thyroid gland

  47. Vertebrate Endocrine Systems- Calcium regulation • Calcium levels in the blood must be regulated within a narrow range. Small changes in blood calcium levels have serious effects. • Most calcium in the body is in the bones (99%). About 1% is in the cells, and only 0.1% is in the extracellular fluids. • Blood calcium levels are regulated by: • Deposition and absorption of bone • Excretion of calcium by the kidneys • Absorption of calcium from the digestive tract

  48. Calcitonin Thyroid gland releases calcitonin. Reduces Ca2+ uptake in kidneys Stimulates Ca2+ deposition in bones Blood Ca2+ level declines to set point STIMULUS: Rising blood Ca2+ level Homeostasis: Blood Ca2+ level (about 10 mg/100 mL) STIMULUS: Falling blood Ca2+ level Blood Ca2+ level rises to set point Stimulates Ca2+ release from bones Parathyroid gland PTH Increases Ca2+ uptake in intestines Stimulates Ca2+ uptake in kidneys Active vitamin D Hormonal control of calcium homeostasis in mammals

  49. Vertebrate Endocrine Systems • Calcitonin, released by the thyroid gland, acts to lower calcium levels in the blood. • Bone is constantly remodeled by absorption of old bone and production of new bone. • Osteoclasts break down bone and release calcium. • Osteoblasts use circulating calcium to build new bone. • Calcitonin decreases osteoclast activity and stimulates the osteoblasts to take up calcium for bone growth.

  50. Vertebrate Endocrine Systems • Blood calcium decrease triggers release of parathyroid hormone (PTH), from the parathyroid glands which are embedded in the posterior surface of the thyroid gland. • This in turn causes the osteoclasts to dissolve bone and release calcium. • Parathyroid hormone also promotes calcium resorption by the kidney to prevent loss in the urine. • It also promotes vitamin D activation, which stimulates the gut to absorb calcium from food. • Parathyroid hormone and calcitonin act antagonistically to regulate blood calcium levels.

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