Essen%al knowledge standards

Transcription

1 Essen%al knowledge standards 2.C.1: Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes 3.B.2: A variety of intercellular and intracellular signal transmissions mediate gene expression 3.D.1: Cell communicabon processes share common features that reflect a shared evolubonary history 3.D.2: Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling

2 I will be able to: FLT Describe evidence that steroid hormones have intracellular receptors, while water-soluble hormones have cell-surface receptors Explain how the hypothalamus and the pituitary glands interact and how they coordinate the endocrine system Explain the role of tropic hormones in coordina%ng endocrine signaling throughout the body By comple1ng Ch. 45 Lecture Notes

3 Ch. 45: Hormones and the Endocrine System 3

4 Overview 4

5 Overview: Hormones Animal hormones are chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body. Hormones reach all parts of the body, but only target cells are equipped to respond. 5

6 Overview: Coordina%on Two systems coordinate communication throughout the body: the endocrine system and the nervous system. Nervous System Precise Arrangement AcBon PotenBals (electrical signals) Depends on anatomical arrangement Short durabon Endocrine System Widely Dispersed Chemical signals (through circulatory system) Depends on receptors on target cells Long durabon 6

7 What role do hormones play in transforming a caterpillar into a bujerfly?

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9 The endocrine and nervous systems act individually and together in regula%ng animal physiology Signals from the nervous system inibate and regulate endocrine signals. 9

10 Coordina%on of Endocrine and Nervous Systems in Vertebrates The hypothalamus receives informa%on from the nervous system and ini%ates responses through the endocrine system. AJached to the hypothalamus is the pituitary gland composed of the posterior pituitary and anterior pituitary. 10

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12 Recall Signal Transduc%on Pathway Signaling by any of these hormones involves three key events: Reception Signal transduction Response 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. 12

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14 I. Chemical Signals 14

15 Chemical signals Hormones and other signaling molecules bind to target receptors, triggering specific response pathways Chemical signals bind to receptor proteins on target cells. Only target cells respond to the signal. Secreted chemical signals include Hormones Local regulators NeurotransmiPers Neurohormones Pheromones 15

16 A. Hormones Hormones = Endocrine signals that travel through the bloodstream and mediate responses to environmental stimuli and regulate growth, development, and reproduction 16

17 A. Hormones The solubility of a hormone correlates with the location of receptors inside or on the surface of target cells. 17

18 Hormones differ in form and solubility Water-soluble Lipid-soluble Polypeptide: Insulin 0.8 nm Steroid: Cortisol Amine: Epinephrine Amine: Thyroxine

19 B. Endocrine Glands Endocrine glands = ductless (no tubes) glands that secrete hormones directly into surrounding fluid 19

20 Exocrine Glands Exocrine glands = Glands that have ducts and secrete substances onto body surfaces or into body cavities (for example, tear ducts). à NOT part of the endocrine system 20

21 Paracrine and Autocrine (add) Local Regulators = 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 nearby cells Autocrine signals act on the secreting cell itself. 21

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23 Intercellular communica%on by secreted molecules Blood vessel Response (a) Endocrine signaling Response (b) Paracrine signaling Response (c) Autocrine signaling

24 D. Endocrinology Endocrinology = branch of physiology and medicine focusing on endocrine glands and hormones 24

25 E. Hormones are grouped into 3 classes 1. Steroid Hormones (lipid-soluble) Pass directly through the plasma membrane and bind to receptors INSIDE the cell nucleus Directly control the function of a cell, including gene regulation 25

26 E. Hormones are grouped into 3 classes 1. Steroid Hormones (lipid-soluble) Steroid hormones include testosterone, estrogens, glucocorticoids, and mineralocorticoids 26

27 E. Hormones are grouped into 3 classes 2. Amino Acid hormones Water-soluble Cannot pass through the cell membrane. Must bind to receptor molecules on the cell SURFACE. This will trigger a signal transducbon pathway. 27

28 E. Hormones are grouped into 3 classes 2. Amino Acid hormones Water-soluble Include hormones such as epinephrine, tryptophan, and melatonin 28

29 E. Hormones are grouped into 3 classes 3. Pep%de hormones - made of polypep%de chains Also water-soluble and rely on receptors on the surface of a cell Include molecules such as oxytocin and growth hormones 29

30 F. Hormone Receptors Cell-surface receptors For AA and pep%de hormones Ex/ G-protein-coupled receptor Intracellular receptors Located inside the cell Bind to hormone to form a hormone-receptor complex Hormone-Receptor Complex acts as a transcripbon factor to regulate gene expression directly 30

31 G. Pheromones Pheromones = chemical signals that are released from the body and used to communicate with other individuals in the species. Pheromones mark trails to food sources, warn of predators, and attract potential mates. 31

32 Pair-Share-Respond 1. Iden%fy two differences between the nervous and endocrine systems 2. What is a hormone, and what are the three types? 3. How do the solubili%es of hormones affect their method of signaling cells? Be specific. 4. Remind me: What is the signal transduc%on pathway, and which hormones use it? 5. Dis%nguish between endocrine and exocrine glands 32

33 Addi%onal Notes on Hormones 33

34 Mul%ple 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. 34

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36 One hormone, different effects Same receptors but different intracellular proteins Different receptors Epinephrine β receptor Glycogen deposits Epinephrine β receptor Epinephrine α receptor Glycogen breaks down and glucose is released. Vessel dilates. Vessel constricts. (a) Liver cell (b) Skeletal muscle blood vessel (c) Intestinal blood vessel

37 Simple Hormone Pathways Many hormones have antagonistic relationships and are regulated through negative feedback Antagonistic hormones = hormones that act to return body conditions to within acceptable limits from opposite extremes 37

38 A simple endocrine pathway Pathway Stimulus Example Low ph in duodenum Negative feedback Endocrine cell Blood vessel S cells of duodenum secrete secretin ( ) Target cells Pancreas Response Bicarbonate release

39 II. Endocrine System in Mammals 39

40 Recall Endocrine glands respond to diverse s%muli in regula%ng metabolism, homeostasis, development, and behavior Endocrine signaling regulates metabolism, homeostasis, development, and behavior. 40

41 A. Hypothalamus and Pituitary Gland 1. Hypothalamus = part of the brain that receives informabon from the nervous system and controls responses through the endocrine system 41

42 A. Hypothalamus and Pituitary Gland 1. Hypothalamus a. Neurosecretory cells = specialized neurons in the hypothalamus that release hormones. Also are the communicabon link between the hypothalamus and posterior pituitary. b. Releasing hormones = Hormones are released into a capillary network and transported through veins 42

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44 A. Hypothalamus and Pituitary Gland 2. Pituitary Gland = ajached to the bojom of the hypothalamus and consists of two lobes: the anterior and posterior pituitary 44

45 A. Hypothalamus and Pituitary Gland 2. Pituitary Gland Posterior pituitary = stores and secretes hormones that are made in the hypothalamus Anterior pituitary = makes and releases its own hormones under regulation of the hypothalamus 45

46 A. Hypothalamus and Pituitary Gland 2. Pituitary Gland a. Neurohypophysis = posterior lobe of the pituitary 46

47 A simple endocrine pathway Pathway Stimulus Example Low ph in duodenum Negative feedback Endocrine cell Blood vessel S cells of duodenum secrete secretin ( ) Target cells Pancreas Response Bicarbonate release

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49 Hypothalamus Hormones 49

50 Hypothalamus Hormones The hypothalamus controls pituitary hormones via the following: Thyrotrophic-releasing hormone Growth hormone-releasing hormone Cor%cotrophin-releasing hormone Gonadotropin-releasing hormone 50

51 Pituitary Hormones 51

52 Pituitary Hormones Growth Hormone Prolac%n Adrenocor%cotropic Hormone Thyroid-s%mula%ng hormone (TSH) Luteinizing hormone (LH) Follicle-s%mula%ng hormone (FSH) Posterior: Oxytocin An%diure%c Hormone 52

53 Specific Hormones 53

54 A. Hypothalamus and Pituitary Gland 3. Oxytocin 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 Oxytocin undergoes positive feedback à stimulus increases the effect 54

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56 A. Hypothalamus and Pituitary Gland 6. Prolactin (PRL) = stimulates lactation in mammals but has diverse effects in different vertebrates. 56

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58 A. Hypothalamus and Pituitary Gland 4. An%diure%c Hormone (ADH) Antidiuretic hormone (ADH) = enhances water reabsorption in the kidneys Nega%ve feedback loop: Dehydra%on à high solute concentra%on à hypothalamus s%mulated à increased ADH à Posterior pituitary releases ADH à increased water reabsorp%on in kidneys and constric%on of blood vessels 58

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61 A. Hypothalamus and Pituitary Gland 5. Growth Hormone (GH) Growth hormone (GH) = Involved in multiple processes, including growth and metabolism It stimulates production of growth factors. An excess of GH can cause gigantism, while a lack of GH can cause dwarfism. 61

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63 Pair-Share-Respond 1. Dis%nguish between the anterior and posterior pituitary glands 2. Which hormones are involved with milk produc%on and secre%on in mammals? 3. Describe GH. 4. You have not been drinking enough water. Describe a nega%ve feedback mechanism your body will use to help maintain homeostasis. 63

64 Tropic Hormones 64

65 Tropic hormones = regulate endocrine cells/ glands The four strictly tropic hormones are: Thyroid-stimulating hormone (TSH) Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Adrenocorticotropic hormone (ACTH) 65

66 A. Hypothalamus and Pituitary Gland 9. Thyroid-S%mula%ng Hormone Thyroid-SBmulaBng Hormone (TSH) = helps regulate the thyroid, which is central to metabolism TSH produc%on controlled by hormones in the hypothalamus. The production of thyrotropin releasing hormone (TRH) in the hypothalamus stimulates secretion of the thyroid stimulating hormone (TSH) from the anterior pituitary 66

67 Produc%on and release of anterior pituitary hormones Tropic effects only: FSH LH TSH ACTH Neurosecretory cells of the hypothalamus Nontropic effects only: Prolactin MSH Nontropic and tropic effects: GH Hypothalamic releasing and inhibiting hormones Posterior pituitary Portal vessels Endocrine cells of the anterior pituitary Pituitary hormones HORMONE FSH and LH TSH ACTH Prolactin MSH GH TARGET Testes or ovaries Thyroid Adrenal cortex Mammary glands Melanocytes Liver, bones, other tissues

68 Hormone Cascade Pathways Hormone cascade pathway: When a hormone stimulates the release of a series of other hormones, the last of which activates a nonendocrine target cell 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. 68

69 A hormone casade pathway Pathway Stimulus Cold Example Sensory neuron Neurosecretory cell Hypothalamus secretes thyrotropin-releasing hormone (TRH ) Blood vessel

70 A hormone casade pathway + Pathway Stimulus Sensory neuron Neurosecretory cell Cold Example Hypothalamus secretes thyrotropin-releasing hormone (TRH ) Blood vessel Anterior pituitary secretes thyroid-stimulating hormone (TSH or thyrotropin )

71 A hormone casade pathway Pathway Stimulus Sensory neuron Neurosecretory cell Cold Example Hypothalamus secretes thyrotropin-releasing hormone (TRH ) Blood vessel Negative feedback Anterior pituitary secretes thyroid-stimulating hormone (TSH or thyrotropin ) Thyroid gland secretes thyroid hormone (T 3 and T 4 ) Target cells Body tissues Response Increased cellular metabolism

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73 B. The Thyroid Gland 1. Plays a major role in vertebrate development and matura%on The thyroid gland consists of two lobes on the ventral surface of the trachea. 73

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75 B. The Thyroid Gland Thyroid hormones stimulate metabolism and influence development and maturation 75

76 B. The Thyroid Gland It produces two iodine-containing hormones: triiodothyronine (T 3 ) and thyroxine (T 4 ). Proper thyroid function requires dietary iodine for thyroid hormone production. 76

77 B. The Thyroid Gland 2. Hypothyroidism Hyperthyroidism = excessive secretion of thyroid hormones = causes high body temperature, weight loss, irritability, and high blood pressure. Graves disease is a form of hyperthyroidism in humans. Hypothyroidism = low secretion of thyroid hormones = causes weight gain, lethargy, and intolerance to cold. 77

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80 B. The Thyroid Gland 3. Goiter = enlarged thyroid gland = usually caused by low iodine in diet 80

81 C. Parathyroid Gland 1. Four glands that are embedded in the surface of the thyroid and func%on in the homeostasis of calcium ions 81

82 C. Parathyroid Gland 2. Secretes Parathyroid hormone (PTH) and Calcitonin Two antagonistic hormones regulate the homeostasis of calcium (Ca 2+ ) in the blood of mammals Parathyroid hormone (PTH) is released by the parathyroid glands Calcitonin is released by the thyroid gland 82

83 C. Parathyroid Gland 2. Secretes Parathyroid hormone (PTH) and Calcitonin PTH increases the level of blood Ca 2+ It releases Ca 2+ from bone and stimulates reabsorption of Ca 2+ in the kidneys It also has an indirect effect, stimulating the kidneys to activate vitamin D, which promotes intestinal uptake of Ca 2+ from food Calcitonin decreases the level of blood Ca 2+ It stimulates Ca 2+ deposition in bones and secretion by kidneys 83

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85 Pair-Share-Respond 1. What is meant by tropic hormones? 2. Dis%nguish between thyroid hormones and parathyroid hormones 3. Explain (specifically) how nega%ve feedback helps maintain calcium levels in the blood 4. Dis%nguish between hyperthyroidism and hypothyroidism. Include applicable symptoms. 85

86 E. The Adrenal Glands 1. Synthesize Catecholamines from amino acid tyrosine The adrenal glands are adjacent to the kidneys. Each adrenal gland actually consists of two glands: the adrenal medulla (inner portion) and adrenal cortex (outer portion). 86

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89 E. The Adrenal Glands 1. Synthesize Catecholamines from amino acid tyrosine a. Epinephrine and Norepinephrine These hormones are members of a class of compounds called catecholamines. They are secreted in response to stress-activated impulses from the nervous system. They mediate various fight-or-flight responses. 89

90 E. The Adrenal Glands 1. Synthesize Catecholamines from amino acid tyrosine a. Epinephrine and Norepinephrine These hormones are part of the fight or flight response Under stress, the body increases heart rate and blood pressure (essentially increasing oxygen delivery to cells). Blood-glucose levels also increase, muscles tense, nonessential systems are shut down, etc. 90

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92 E. The Adrenal Glands Adrenal Hormones: Response to Stress a. Epinephrine and Norepinephrine Epinephrine = adrenaline = Produced by the adrenal medulla. Responds to stress by increasing your heart rate, increasing blood flow to muscles and brain, increases blood sugar level. Short-term stress response. Epinephrine binds to receptors on the plasma membrane of liver cells. This triggers the release of messenger molecules that activate enzymes and result in the release of glucose into the bloodstream. 92

93 Epinephrine G protein Adenylyl cyclase Cell-surface hormone receptors trigger signal transduc%on G protein-coupled receptor Inhibition of glycogen synthesis Promotion of glycogen breakdown GTP ATP camp Protein kinase A Second messenger

94 E. The Adrenal Glands Adrenal Hormones: Response to Stress a. Epinephrine and Norepinephrine Norepinephrine = noradrenaline = Produced by the adrenal medulla. Responds to stress by causing vasoconstriction, which results in high blood pressure 94

95 E. The Adrenal Glands 1. Synthesize Catecholamines from amino acid tyrosine Epinephrine and norepinephrine 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. The release of epinephrine and norepinephrine occurs in response to nerve signals from the hypothalamus. 95

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97 Summary: Stress and the Adrenal Gland Stress Spinal cord Nerve signals Releasing hormone Hypothalamus Nerve cell Anterior pituitary Blood vessel ACTH Adrenal medulla Adrenal cortex Adrenal gland Kidney (a) Short-term stress response (b) Long-term stress response Effects of epinephrine and norepinephrine: 1. Glycogen broken down to glucose; increased blood glucose 2. Increased blood pressure 3. Increased breathing rate 4. Increased metabolic rate 5. Change in blood flow patterns, leading to increased alertness and decreased digestive, excretory, and reproductive system activity Effects of mineralocorticoids: 1. Retention of sodium ions and water by kidneys 2. Increased blood volume and blood pressure Effects of glucocorticoids: 1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose 2. Possible suppression of immune system

98 Stress and the Adrenal Gland Stress Spinal cord Nerve signals Releasing hormone Hypothalamus Nerve cell Anterior pituitary ACTH Blood vessel Adrenal medulla Adrenal gland Kidney Adrenal cortex

99 Short-term Stress and the Adrenal Gland Adrenal medulla Adrenal gland Kidney (a) Short-term stress response Effects of epinephrine and norepinephrine: 1. Glycogen broken down to glucose; increased blood glucose 2. Increased blood pressure 3. Increased breathing rate 4. Increased metabolic rate 5. Change in blood flow patterns, leading to increased alertness and decreased digestive, excretory, and reproductive system activity