Chapter 45-Hormones and the Endocrine System Pathway Example – Simple Hormone Pathways Stimulus Low Ph in Duodenum
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Chapter 45-Hormones and the Endocrine System Pathway Example – Simple Hormone Pathways Stimulus Low pH in duodenum •Hormones are released from an endocrine cell, S cells of duodenum travel through the bloodstream, and interact with secrete secretin ( ) Endocrine the receptor or a target cell to cause a physiological cell response Blood vessel A negative feedback loop Target Pancreas cells Response Bicarbonate release Insulin and Glucagon: Control of Blood Glucose Body cells •Insulin and glucagon are take up more Insulin antagonistic hormones that help glucose. maintain glucose homeostasis Beta cells of pancreas release insulin into the blood. The pancreas has clusters of endocrine cells called Liver takes islets of Langerhans up glucose and stores it as glycogen. STIMULUS: Blood glucose Blood glucose level level declines. rises. Target Tissues for Insulin and Glucagon Homeostasis: Blood glucose level Insulin reduces blood glucose levels by: (about 90 mg/100 mL) Promoting the cellular uptake of glucose Blood glucose STIMULUS: Slowing glycogen breakdown in the liver level rises. Blood glucose level falls. Promoting fat storage Alpha cells of pancreas release glucagon. Liver breaks down glycogen and releases glucose. Glucagon Glucagon increases blood glucose levels by: Stimulating conversion of glycogen to glucose in the liver Stimulating breakdown of fat and protein into glucose Diabetes Mellitus Type I diabetes mellitus (insulin-dependent) is an autoimmune disorder in which the immune system destroys pancreatic beta cells Type II diabetes mellitus (non-insulin-dependent) involves insulin deficiency or reduced response of target cells due to change in insulin receptors The endocrine and nervous systems act individually and together in regulating animal physiology •Signals from the nervous system initiate and regulate endocrine signals The hypothalamus receives Cerebrum information from the nervous system and initiates responses through the Pineal Thalamus endocrine system gland Hypothalamus Cerebellum Pituitary gland Spinal cord Attached to the hypothalamus is the pituitary gland composed of the posterior pituitary and anterior pituitary Hypothalamus The posterior pituitary Posterior pituitary Anterior The anterior pituitary pituitary Posterior Pituitary Hormones Hypothalamus •The two hormones released from the posterior pituitary act directly on nonendocrine tissues Neurosecretory cells of the Axon hypothalamus Posterior Oxytocin pituitary Anterior pituitary HORMONE ADH Oxytocin TARGET Kidney tubules Mammary glands, uterine muscles •This is an example of positive feedback, where the stimulus leads to an even greater response Pathway Example Stimulus Suckling + Sensory neuron •Suckling sends a message to the hypothalamus via the Hypothalamus/ nervous system to release oxytocin, which further posterior pituitary stimulates the milk glands. Neurosecretory cell Posterior pituitary Blood secretes oxytocin ( ) vessel Positive Positive feedback Target Smooth muscle in cells breasts Response Milk release Antidiuretic hormone (ADH) or vassopressin Anterior Pituitary Hormones Tropic effects only: FSH Neurosecretory cells LH of the hypothalamus TSH •Hormone production in the anterior ACTH pituitary is controlled by releasing and Nontropic effects only: inhibiting hormones from the Prolactin MSH hypothalamus Nontropic and tropic effects: GH Hypothalamic Portal vessels releasing and inhibiting hormones Endocrine cells of Posterior pituitary the anterior pituitary Pituitary hormones HORMONE FSH and LH TSH ACTH Prolactin MSH GH TARGET Testes or Thyroid Adrenal Mammary Melanocytes Liver, bones, ovaries cortex glands other tissues For example, the production of thyrotropin releasing hormone (TRH) in the hypothalamus Pathway Example Stimulus Cold Sensory neuron – Hypothalamus secretes thyrotropin-releasing hormone (TRH ) Neurosecretory cell Blood vessel Hormone Cascade Pathways •A hormone can stimulate the release of a series of – Anterior pituitary secretes other hormones, the last of which activates a thyroid-stimulating nonendocrine target cell; this is called a hormone hormone (TSH cascade pathway or thyrotropin ) Negative Negative feedback Thyroid gland secretes thyroid hormone (T and T ) The release of thyroid hormone results from a 3 4 hormone cascade pathway involving the hypothalamus, anterior pituitary, and thyroid gland. Target Body tissues cells Increased cellular Response metabolism •Hormone cascade pathways are usually regulated by negative feedback Tropic Hormones Tropic effects only: FSH Neurosecretory cells LH of the hypothalamus A tropic hormone TSH ACTH Nontropic effects only: The four strictly tropic hormones are Prolactin MSH Nontropic and tropic effects: Thyroid-stimulating hormone (TSH) GH Hypothalamic Portal vessels releasing and inhibiting hormones Follicle-stimulating hormone (FSH) Endocrine cells of Posterior pituitary the anterior pituitary Luteinizing hormone (LH) Pituitary hormones Adrenocorticotropic hormone (ACTH) HORMONE FSH and LH TSH ACTH Prolactin MSH GH •Follicle-stimulating hormone (FSH) and TARGET Testes or Thyroid Adrenal Mammary Melanocytes Liver, bones, Luteinizing hormone (LH) ovaries cortex glands other tissues Stimulate the activities of the male and female gonads, the testes and the ovaries, respectively. Adrenocorticotropic hormone (ACTH) -stimulates the production and secretion of steroid hormones by the adrenal cortex. Nontropic Hormones •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 -regulates fat metabolism and reproduction in birds -delays metamorphosis in amphibians -regulates salt and water balance in freshwater fishes MSH influences skin pigmentation in some vertebrates and fat metabolism in mammals 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 Robert Wadlow Warwick Davis http://en.wikipedia.org/wiki/Dwarfism Endocrine glands respond to diverse stimuli in regulating metabolism, homeostasis, development, and behavior •Endocrine signaling regulates metabolism, homeostasis, development, and behavior Thyroid Hormone: Control of Metabolism and Development •Thyroid hormones stimulate metabolism and influence development and maturation http://en.wikipedia.org/wiki/Thyroid triiodothyronine (T3) http://en.wikipedia.org/wiki/Image:Triiodothyronine.svg http://en.wikipedia.org/wiki/Thyroid thyroxine (T4) http://en.wikipedia.org/wiki/Image:Thyroxine-2D-skeletal.png It produces two iodine-containing hormones: triiodothyronine (T3) and thyroxine (T4) Hyperthyroidism, Hyperthyroidism, excessive secretion of thyroid hormones, •Graves’ disease is a form of hyperthyroidism in humans Hypothyroidism •Proper thyroid function requires dietary iodine for hormone production Iodine deficiency in the diet Parathyroid Hormone and Vitamin D: Control of Blood Calcium Two antagonistic hormones regulate the homeostasis of calcium (Ca 2+) in the blood of mammals Calcitonin Parathyroid hormone (PTH) Thyroid gland releases calcitonin. Reduces Calcitonin Stimulates Ca2+ uptake Ca2+ deposition in kidneys in bones 2+ PTH increases the level of blood Ca2+ STIMULUS: Blood Ca Rising blood level declines Ca2+ level to set point 2+ It releases Ca from bone and Homoeostasis: stimulates reabsorption of Ca2+ in Blood Ca2+ level the kidneys (about 10 mg/100 mL) Blood Ca2+ STIMULUS: level rises Falling blood to set point Ca2+ level It also has an indirect effect, stimulating Stimulates Parathyroid the kidneys to activate vitamin D, which Ca2+ release gland promotes intestinal uptake of Ca2+ from from bones food. PTH Increases Ca2+ uptake 2+ in intestines Active Stimulates Ca vitamin D uptake in kidneys •Calcitonin decreases the level of blood Ca2+ It stimulates Ca2+ deposition in bones and secretion by kidneys. Study outline-Chapter 45- Hormones and the Endocrine System Understand simple hormone pathways and negative feedback Ex: insulin and glucagon: control of blood glucose Differentiate between Type I diabetes mellitus (insulin-dependent) and Type II diabetes mellitus (non-insulin dependent) Understand the coordination of endocrine and nervous systems in vertebrates -How is the hypothalmus involved? How are the posterior and anterior pituitary involved? What 2 hormones are released from the posterior pituitary that act directly on nonendrocrine tissue? Understand the process of positive feedback. Ex: oxytocin What are the functions of antidiuretic hormone (ADH)? Understand the hormone cascade pathway Differentiate between tropic and nontropic hormones. -Name the 4 tropic hormones and their functions. -Name the 2 tropic hormones and their functions. What is the function of growth hormone (GH)? Differentiate between gigantism and dwarfism. Understand thyroid hormone. -Name the two iodine-containing hormones. -Differentiate between hyperthyroidism and hypothyroidism. Understand how the parathyroid hormone and vitamin D control blood calcium Give examples of multiple effects of hormones. Name the different types of local regulators and their functions. Pathway Example – Stimulus Low pH in Describe the general structure of a hormone pathway using the duodenum figure provided. Using the same figure, explain the concept of negative feedback. S cells of duodenum secrete secretin ( ) Endocrine cell Blood vessel Target Pancreas cells Response Bicarbonate