chapter 9: the endocrine system
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Chapter 9: The endocrine system. Bio 24. The endocrine system. One of two communication systems in the body Consists of hormones : chemicals secreted into the blood that travel throughout the body to act on specific target cells - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 9: The endocrine system
Bio 24
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The endocrine system
• One of two communication systems in the body
• Consists of hormones: chemicals secreted into the blood that travel throughout the body to act on specific target cells
• Only cells with the appropriate receptors will respond to the hormonal signal
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Functions of the endocrine system
• Hormones are essential for:– reproduction– regulation of the immune system– utilization of energy– maintenance of bone and muscle mass– growth– regulation of salt and water balance and blood pressure– regulation of our moods & emotions– many other things!
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The endocrine vs. the nervous system
Endocrine system• uses chemical signals
• chemical signals secreted into the blood
• effects take minutes or hours and may be long-lasting
Nervous system• uses chemical and
electrical signals• chemical signals travel
only across a synapse• effects take a fraction of
a second and usually mediates rapid responses
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2 main categories of hormones
• Amino acid-based hormones (most common) include proteins, peptides, and amino acid derivatives– Include insulin, growth hormone, thyroid hormones
• Steroid hormones are small lipid molecules made from cholesterol that can cross cell membranes– Include testosterone, estrogen, progesterone, and
cortisol
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Steroid hormone action
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Nonsteroid hormone action uses second messengers in the cell
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Control of hormone release
• Release of most hormones is controlled by other hormones
• Hormones that control the release of other hormones are called tropic hormones
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Control of hormone release
• Some hormones are released in response to humoral stimuli: substances in the blood that are not hormones
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Control of hormone release
• Release of some hormones is controlled by the nervous system
• The nervous and endocrine systems often work together in a coordinated fashion
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THE MAJOR ENDOCRINE ORGANS
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Endocrine organs
• Most hormones are released from epithelial cells that form endocrine glands
• Major ones are shown here
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The hypothalamus is the master controller through the pituitary glands
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Hormones of the anterior pituitary: growth hormone
• Growth hormone promotes growth of bones and muscles in children, and maintenance of muscle mass in adults
• Growth hormone excess can result in gigantism (if in childhood) or acromegaly (if in adulthood)
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Hormones of the anterior pituitary: prolactin
• Stimulates and maintains milk production
• Men make it, too, but function is unknown!
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Hormones of the anterior pituitary: adrenocorticotropic hormone (ACTH)
• ACTH is a tropic hormone that regulates the activity of part of the adrenal glands called the adrenal cortex
• Glucocorticoids released from the adrenal cortex increase blood glucose and are involved in our stress response; mineralocorticoids regulate salt and water balance by controlling urine composition
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Hormones of the anterior pituitary: follicle-stimulating hormone (FSH) and luteinizing
hormone (LH)
• Both these hormones control the hormonal activity of the gonads: testes and ovaries
• Both are essential for the development of both sperm and eggs
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Hormones of the anterior pituitary: Thyroid-stimulating hormone (TSH)
• TSH influences the growth of and hormone release from the thyroid gland
• The thyroid gland releases thyroid hormones, which contain amino acid-like molecules bound to iodine atoms and also calcitonin, which regulates calcium deposition in bones
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Structure of the thyroid
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Thyroid hormone targets
• Thyroid hormones act on essentially every cell in the body
• Control metabolic rate and energy utilization• Also important for normal growth and
development and reproductive function• Thyroid disease is quite common!
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Thyroid deficiency• Hypothyroidism (underactive thyroid) is most
often caused by autoimmune disease that attacks the thyroid
• Symptoms include fatigue, persistent feeling of cold, bloating and weight gain, dry skin, and mental slowness
• Can be very well treated by taking thyroid hormone pills
• Thyroid deficiency in children can cause mental retardation and dwarfism, known as cretinism
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Thyroid excess• Hyperthyroidism (overactive
thyroid) can also result from autoimmune disease or a benign tumor of the thyroid
• Graves’ disease is one form of hyperthyroidism that also causes exophthalmos (bulging eyes)
• Symptoms include rapid heart rate, heat intolerance, and nervous behavior
• Hyperthyroidism is harder to treat
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Goiter
• A goiter is an enlarged thyroid
• Can be caused by hyperthyroidism or hypothyroidism
• Traditionally caused by dietary iodine deficiency