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Endocrine System

Endocrine System. Ch. 45 AP Biology Ms. Haut. Overview: The Body’s Long-Distance Regulators. An animal hormone Is a chemical signal that is secreted into the circulatory system and communicates regulatory messages within the body Hormones may reach all parts of the body

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Endocrine System

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  1. Endocrine System Ch. 45 AP Biology Ms. Haut

  2. Overview: The Body’s Long-Distance Regulators • An animal hormone • Is a chemical signal that is secreted into the circulatory system and communicates regulatory messages within the body • Hormones may reach all parts of the body • But only certain types of cells, target cells, are equipped to respond

  3. Regulatory Systems • Endocrine System • All of an animal’s hormone-secreting cells • Secretes hormones that coordinate slower but longer-acting responses to stimuli • Endocrine glands • Ductless glands • Secrete chemical messengers directly into blood stream • Nervous System • Conveys high-speed electrical signals along specialized cells called neurons

  4. Hormones involved in Control of Development in Insects • Control molting of exoskeletons and metamorphosis in insects • After a meal, a brain hormone is released and moves to the prothorasic gland • The brain hormone stimulates the release of ecdysone which stimulates molting

  5. Brain Neurosecretory cells in the brain produce brain hormone (BH), which is stored in the corpora cardiaca (singular, corpus cardiacum) until release. 1 Neurosecretory cells Brainhormone (BH) Corpus cardiacum Corpus allatum LowJH Juvenile hormone (JH), secreted by the corpora allata, determines the result of the molt. At relatively high concen- trations of JH, ecdysone-stimulated molting produces another larval stage. JH suppresses metamorphosis. But when levels of JH fall below a certain concentration, a pupa forms at the next ecdysone-induced molt. The adult insect emerges from the pupa. 4 Prothoracicgland Ecdysone Juvenilehormone(JH) BH signals its main target organ, the prothoracic gland, to produce the hormone ecdysone. 2 EARLYLARVA LATERLARVA PUPA ADULT Ecdysone secretion from the prothoracic gland is episodic, with each release stimulating a molt. 3

  6. Pathway Example Pathway Example Example Pathway Low blood glucose Hypothalamic neurohormone released in response to neural and hormonal signals Stimulus Stimulus Suckling Stimulus Receptor protein Sensory neuron Sensory neuron Pancreas secretes glucagon ( ) Hypothalamus/ posterior pituitary Hypothalamus Endocrine cell Neurosecretory cell Blood vessel Neurosecretory cell Hypothalamus secretes prolactin- releasing hormone ( ) Posterior pituitary secretes oxytocin ( ) Blood vessel Blood vessel Target effectors Liver Anterior pituitary secretes prolactin ( ) Smooth muscle in breast Target effectors Glycogenbreakdown,glucose releaseinto blood Response Endocrine cell Blood vessel (a) Simple endocrine pathway Milk release Response (b) Simple neurohormone pathway Target effectors Mammary glands Milk production Response Figure 45.2a–c (c) Simple neuroendocrine pathway Control Pathways and Feedback Loops • There are three types of hormonal control pathways

  7. Three major classes of molecules function as hormones in vertebrates • Proteins and peptides • Amines derived from amino acids • Steroids

  8. Signaling by any of these molecules involves three key events • Reception • Signal transduction • Response

  9. Table 45.1 Major human endocrine glands and some of their hormones Page 899

  10. Page 899 Table 45.1

  11. Vertebrate Endocrine System • In addition to the glands shown here, many organs also secrete hormones • Digestive system produces at least 8 hormones (e.g. gastrin, secretin)

  12. Integration of the Hypothalamus and Posterior Pituitary • Regulation of blood osmolarity • Monitored by nerve cells (osmoreceptors) in the hypothalamus •  plasma osmolarity causes cells to shrink slightly and transmit nerve impulses to certain neurosecretory cells • Cells in posterior pituitary release antidiuretic hormone (ADH) • ADH targets kidney tubules—increasing water permeability of collecting ducts • Water diffuses to capillaries to decrease osmolarity • Homeostasis is maintained!!

  13. Integration of the Hypothalamus and Anterior Pituitary • Hypothalamus produces releasing hormones and inhibiting hormones into capillaries to affect anterior pituitary Tropic Effects Only (target endocrine glands) FSH, follicle-stimulating hormone LH, luteinizing hormone TSH, thyroid-stimulating hormone ACTH, adrenocorticotropic hormone Nontropic Effects Only (target other tissues) Prolactin MSH, melanocyte-stimulating hormone Endorphin Nontropic and Tropic Effects Growth hormone

  14. Thyroid and Parathyroid Hormones Regulated by 2 negative feedback loops • Plays role in development and maturation and homeostasis and metabolism • Produces two iodine-containing hormones, triiodothyronine (T3) and thyroxine (T4)-regulated by hypothalamus and pituitary

  15. Pancreas Islets of Langerhans-consists of clusters of 2 cell types

  16. Target Tissues for Insulin and Glucagon • Insulin reduces blood glucose levels by • Promoting the cellular uptake of glucose • Slowing glycogen breakdown in the liver • Promoting fat storage • Glucagon increases blood glucose levels by • Stimulating the conversion of glycogen to glucose in the liver • Stimulating the breakdown of fat and protein into glucose

  17. Diabetes Mellitus • Diabetes mellitus, perhaps the best-known endocrine disorder • Is caused by a deficiency of insulin or a decreased response to insulin in target tissues • Is marked by elevated blood glucose levels

  18. Type I diabetes mellitus (insulin-dependent diabetes) Is an autoimmune disorder in which the immune system destroys the beta cells of the pancreas Type II diabetes mellitus (non-insulin-dependent diabetes) Is characterized either by a deficiency of insulin or, more commonly, by reduced responsiveness of target cells due to some change in insulin receptors

  19. Adrenal Gland • Are adjacent to the kidneys • Are actually made up of two glands: the adrenal medulla and the adrenal cortex "Fight or Flight"

  20. Gonadal Steroids • Regulate growth, development, reproductive cycles, and sexual behavior • Testes • Androgens (testosterone) • Stimulate development and maintenance of male reproductive system • At puberty, high concentrations responsible for male secondary sex characteristics • Ovaries • Estrogens (estradiol) • Parallel role in females • Progestins—prepare and maintain uterus for support of offspring

  21. ↑Estrogens (secreted by follicle) = thickening and vascularization of endometrium

  22. Melatonin and Biorhythms • The pineal gland, located within the brain • Secretes melatonin • Release of melatonin • Is controlled by light/dark cycles • The primary functions of melatonin • Appear to be related to biological rhythms associated with reproduction

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