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Bio11 schedule Lecture – Endocrine system Lecture exam 2 next Thursday Feb 24 Ch 15 Endocrine System Same format as before Covers Ch 5-8, 11-15 Study guide will be posted Posted: Your total points so far (your “grade” in class) Extra credit is due in 2 weeks (Mar 3) The nervous and endocrine systems coordinate body functions Both systems use chemical signals to regulate the activity of other body systems Nervous system Endocrine System Controls body activities thru nerve impulses and neurotransmitters Act locally and quickly Endocrine system Controls body activities by releasing hormones Slower responses, broader influence Copyright 2009, John Wiley & Sons, Inc. Copyright 2009, John Wiley & Sons, Inc. Why do hormones only affect certain cells? Hormones are carried by the blood to target cells Endocrine cell Membraneenclosed sacs Blood vessel Hormone molecules Target cell Adrenal glands (type of endocrine gland), which sit atop the kidneys Endocrine glands release hormones into bloodstream Hormones are carried to all cells of the body, but only affect certain cells Regulate the metabolism of target cells Receptor protein Figure 25.1 Hormones only affect target cells, cells that have receptors for that specific hormone Target cell Receptor protein Hormones have a wide range of targets Some, like sex hormones, affect most of the tissues of the body Others, like glucagon, have only a few kinds of target cells (in this case, liver and fat cells) Some target other endocrine glands Classes of hormones Peptide hormones For example, the hypothalamus targets the pituitary Some hormones elicit different responses in different target cells Short chains of amino acids Most common type of hormone Water soluble, circulate in a “free” form (not attached to plasma proteins) Steroid hormones Lipid-soluble Bind to transport proteins in blood, can diffuse thru cell membranes Copyright 2009, John Wiley & Sons, Inc. Action of steroid hormones Action of peptide hormones Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. Hormone binds to a receptor in the plasma membrane. Hormone binds to a plasma membrane receptor Activates a signal transduction pathway in the cell Alters cell functions peptide hormone (first messenger) 1. activated receptor protein enzyme 2. 2. Binding leads to activation of an enzyme that changes ATP to cAMP . plasma membrane ATP 3. cAMP (second messenger) 3. cAMP activatesan enzyme cascade. 4. Many molecules of glycogen are broken down to glucose, which enters the bloodstream. glucose (leaves cell and goes to blood) glycogen steroid hormone 1. Hormone diffuses through plasma membrane because it is lipid soluble. capillary 4. Diffuse thru membrane Bind to receptors inside target cells The hormone-receptor complex binds to the DNA and alters gene expression New proteins are made that change the cell’s activity plasma membrane cytoplasm nucleus 2. Hormone binds to receptor inside nucleus. protein DNA receptor protein mRNA 3. Hormone-receptor complex activates gene and synthesis of a specific mRNA molecule follows. Action of epinephrine on muscle ribosome mRNA 4. mRNA moves to ribosomes, and protein synthesis occurs. “Master” endocrine glands: the hypothalamus and pituitary Hypothalamus – major link between nervous and endocrine system Hypothalamus secretes 9 hormones, the pituitary secretes 7. Together these hormones regulate virtually all aspects of growth, development, metabolism, and homeostasis Copyright 2009, John Wiley & Sons, Inc. The Hypothalamus Is the main control center of the endocrine system. As part of the brain, the hypothalamus receives information from the nervous system and sends out appropriate responses. It controls secretion of hormones by the pituitary gland Pituitary Gland The posterior pituitary The pituitary gland is located in the sphenoid bone and is differentiated into two lobes Anterior pituitary Posterior pituitary The anterior pituitary Composed of endocrine cells that synthesize and secrete numerous hormones directly into the blood Posterior pituitary Infundibulum (stalk) Anterior pituitary Anterior pituitary hormones Anterior pituitary Most hormones are released in short bursts Hormone secretion is controlled by 1. FSH, LH, and prolactin Hormones from the hypothalamus Negative feedback 2. 3. Signals from the nervous system Chemical changes in the blood Other hormones Human growth hormone Thyroid stimulating hormone (TSH) Infundibulum Anterior pituitary Follicle stimulating hormone (FSH) Luteinizing hormone (LH) Prolactin (PRL) Adrenocorticotropic hormone (ACTH) Melanocyte-stimulating hormone (MSH) TSH Most hormone secretion is regulated by negative feedback Human growth hormone (hGH) Such as ADH Control of Hormone Secretion Secretion regulated by Posterior pituitary Infundibulum (stalk) Is actually an extension of the hypothalamus It stores and secretes hormones made in the hypothalamus Has a broad effect on the body Causes cells in liver, muscles, bones and other tissues to grow and multiply Increase breakdown of fat in adipose tissue Releases fatty acids for ATP production Pituitary gland disorders Pituitary gland disorders Disorders of hGH secretion Overproduction of hGH during childhood Giantism Overproduction of hGH during adulthood results in acromegaly Hormones regulate the rate of metabolism Athletes abuse hGH to bulk up their muscles Abuse can lead to Disfigurement Heart failure Multiple cancers Located in the neck Thyroid follicles produce thyroid hormones T4 = Thyroxine T3 = Triiodothyronine Both increase BMR, stimulate cell metabolism Secreted by the thyroid gland Increases the metabolic rate hGH Insulin T3 and T4 production Low blood T3/T4 or low metabolic rate Release of TRH 1 Low blood levels of T3 and T 3 or low metabolic rate stimulate release of Hypothalamus TRH 2 TRH, carried by hypophyseal portal veins to anterior pituitary, stimulates release of TSH by thyrotrophs 5 Elevated T3inhibits release of TRH and TSH (negative feedback) TSH Release of TSH 3 TSH released into blood stimulates thyroid follicular cells Copyright 2009, John Wiley & Sons, Inc. Thyroxine (T3/T4) Thyroid Gland Underproduction of hGH during childhood Dwarfism Enlarged bones in hands, feet and face Abuse of hGH Disorders of hGH secretion Synthesis of T3 and T4 by thyroid gland Negative feedback Anterior pituitary 4 T3 and T4 Thyroid follicle released into blood by follicular cells Thyroid Gland Disorders: hypothyroidism Actions of T3/T4 Affect most body cells Increase basal metabolic rate (BMR) have receptors for thyroid hormones increase body temperature Growth and development Stimulate protein synthesis Increase use of glucose and fatty acids for ATP production Why does the thyroid gland enlarge? Congenital hypothyroidism during fetal life or infancy → severe mental retardation (cretinism) Excess thyroid hormones The most common form of hyperthyroidism is Graves’ disease X enlargement of the thyroid gland Hyperthyroidism X Too little thyroid hormone Results from dietary deficiency of iodine or from a defective thyroid gland Sx: Goiter an autoimmune disease. Produce antibodies that mimic the action of TSH and continually stimulate the thyroid gland Sx: enlarged thyroid, protruding eyes (exophthalmos) Copyright 2009, John Wiley & Sons, Inc. Hormones and homeostasis Control of blood glucose Insulin Glucagon Calcium homeostasis Calcitonin Parathyroid hormone (PTH) Vitamin D (calcitriol) Blood glucose homeostasis Insulin Glucagon Body cells take up more glucose Insulin Pancreas Pancreas releases insulin into the blood Produces two antagonistic hormones that regulate the body’s energy supplies: Insulin reduces Blood glucose level falls to a set point; stimulus for insulin release diminishes Glucose level Homeostasis: Normal blood glucose level Glucose level blood sugar levels Liver takes up glucose and stores it as glycogen Stimulus: Rising blood glucose level (for example, after eating a carbohydrate-rich meal) Blood glucose level rises to set point; stimulus for glucagon release diminishes Glucagon increases blood sugar levels In the absence of insulin, the glucose transporters reside within the cell When insulin binds to its receptor, it initiates a cascade of events Glucose transporters are moved to plasma membrane They are inserted in the membrane, and glucose transport is activated Glucagon Figure 25.9-6 How insulin stimulates glucose uptake Pancreas releases glucagon into the blood Liver breaks down glycogen and releases glucose to the blood Copyright 2009, John Wiley & Sons, Inc. Stimulus: Declining blood glucose level (for example, after skipping a meal) Pancreatic Disorders Diabetes Mellitus Most common endocrine disorder Caused by an inability to produce or use insulin Sx: high blood glucose, glucose “spills” into urine Type 1 diabetes (insulin-dependent diabetes) Type 2 diabetes Insulin level is low because the person’s immune system destroys the pancreatic Beta cells Target cells are less sensitive to insulin due to lower # of insulin receptors Gestational diabetes Copyright 2009, John Wiley & Sons, Inc. Type I Diabetes Autoimmune disease Occurs most often in children and young adults Without insulin, cells use fatty acids for energy Complications: damage to blood vessels in retina and kidneys Rx: insulin injections Type 2 diabetes 90% of diabetics 55% are obese Insulin resistance Insulin and type 1 diabetes (4:03) http://www.youtube.com/watch?v=OYvav8aDGCc Most common form body tissues more resistant to the actions of insulin Lower uptake of glucose Can be controlled by diet, exercise and weight loss Gestational diabetes Pregnant women who have never had diabetes before but who have high blood glucose levels during pregnancy Affects about 4% of all pregnant women It may precede development of type 2 diabetes Why is calcium important? Calcium homeostasis Calcitonin Parathyroid hormone Calcitriol (vitamin D) Calcium Homeostasis Bone formation Muscle contraction Cardiac muscle action potential Blood clotting Neurotransmitter release Three hormones regulate blood calcium levels Calcitriol (vitamin D) Copyright 2009, John Wiley & Sons, Inc. Calcitonin and PTH are antagonists The two hormones have opposite effects on blood calcium levels Figure 25.10 Calcitonin Parathyroid hormone (PTH) Calcitriol (vitamin D)
