Unit 17 The Endocrine System PDF

Unit 17: The Endocrine System Lecture Outcomes Role of Hypothalamus: Explain the hypothalamus's role in maintaining homeostasis. Hypothalamo-Pituitary Relationship: Discuss importance in maintaining homeostasis. Feedback Mechanisms: Distinguish positive vs. negative f...

Unit 17: The Endocrine System Lecture Outcomes Role of Hypothalamus: Explain the hypothalamus's role in maintaining homeostasis. Hypothalamo-Pituitary Relationship: Discuss importance in maintaining homeostasis. Feedback Mechanisms: Distinguish positive vs. negative feedback mechanisms with examples from endocrine system. Functions of the Endocrine System Maintain homeostasis: Regulates blood sugar, calcium levels, blood pressure, thirst, and hunger. Growth and Metabolism: Hormones involved in growth and metabolic processes. Stress Responses: Hormones like adrenaline and cortisol respond to stress. Digestion Regulation: Hormonal control over digestive processes. Circadian Rhythms: Hormonal regulation of sleep-wake cycles. Reproduction: Influences secondary sex characteristics, childbirth, lactation, and gamete production. Endocrine vs. Exocrine Glands Endocrine Glands Ductless: Hormones are secreted directly into surrounding tissues and carried by blood. Target Cells: Cells respond due to receptor proteins that interact with hormones Exocrine Glands Ducted: Secrete substances other than hormones directly to a surface or hollow cavity (e.g., sweat, saliva). Function: Release non-hormonal substances via ducts. Functions of Hormones Homeostatic Regulation: Blood sugar, water balance, and hematopoiesis. Growth & Metabolism: Regulate energy production and utilization. Reproductive Functions: Influence aspects of reproductive health and function. Stress Response: Mediate the body's response to stressors. Digestion Regulation and Circadian Rhythm: Influence digestive system and biological clock. Types of Hormones Main classes of hormones and mechanisms of action Amines: Dopamine, epinephrine, norepinephrine o Water-soluble, act via second-messenger systems in target cells o Thyroid hormones are amines but not water-soluble. Peptides and Proteins: Insulin, glucagon, hypothalamus hormones, anterior pituitary hormones o Water-soluble: can’t cross cell membranes directly. They bind to membrane receptors, triggering internal second-messenger cascades (e.g., cyclic AMP)  Steroids: Testosterone, estrogen, progesterone, aldosterone, cortisol derived from cholesterol o Fat-soluble, pass through cell membranes and bind to intracellular receptors, leading to gene transcription and protein synthesis. Water-Soluble Hormones Secreted by endocrine glands and diffused into the bloodstream. Cannot cross cell membranes directly; utilize second-messenger systems. o Bind to a receptor protein on the extracellular side of the membrane o Cause a change in protein structure which stimulates another molecule inside the cell (second messenger) to cause a response within the cell Examples: o Glucagon: Stimulates gluconeogenesis in liver; increases blood sugar levels o Oxytocin: Enhances uterine contractions and releases during breastfeeding o Epinephrine/Norepinephrine: Prolongs fight or flight response through adrenal medulla stimulation Fat-Soluble Hormones Also secreted by Endocrine gland and diffused into the bloodstream. Require carrier proteins to go to target tissues due to their hydrophobic nature. Diffuses directly across the target cell membrane Bind to a receptor protein inside the cell, then diffuse directly into nucleus to stimulate transcription of specific genes  Increases mRNA production for specific proteins and therefore increases protein synthesis Example: o Testosterone: Stimulates muscle and sperm production. o Estrogen: Promotes uterine lining development and mammary tissue growth. o Progesterone: Prepares the uterus for pregnancy and supports fetal development Glands: Hypothalamus and Pituitary Interaction The hypothalamus releases hormones or inhibits hormones that travel through the hypophyseal portal system to the anterior pituitary o Produces antidiuretic hormone ADH and oxytocin, transported to the posterior pituitary Posterior Pituitary: Secretes hormones; does not synthesize them. o ADH: Increases water reabsorption in kidneys and raises blood pressure. o Oxytocin: Stimulates contractions and milk release, promotes social bonding. Hormones of Anterior Pituitary Produces hormones in response to stimulation from hypothalamic releasing hormones Major Hormones: identify the endocrine glands or structures that produce them, name the target tissue(s), and explain the main function of each o Growth Hormone: Encourages growth, metabolism, calcium incorporation into bone. ▪ Bone, muscle, adipose tissue o Prolactin: Stimulates milk production.  ▪ Mammary glands o Thyroid-stimulating hormone (TSH): Triggers thyroid hormone release ▪ Thyroid gland o Follicle-Stimulating Hormone (FSH): Stimulates the production of sperm in males and maturation of egg follicles in females ▪ Gonads (testes and ovaries) o Luteinizing Hormone (LH): Triggers ovulation in females and stimulates testosterone production in males ▪ Gonads (testes and ovaries) o Adrenocorticotropic Hormone (ACTH): Stimulates adrenal cortex release of stress hormones ▪ Adrenal glands Thyroid Gland Functions Composed of thyroid follicles that secrete thyroid hormones (T3, T4, calcitonin). o produced in response to stimulation by the anterior pituitary hormone TSH o Fat-soluble parathyroid gland: consists of four tiny glands which sit on the posterior side of the thyroid – produces parathyroid hormone Hormone production requires tyrosine, iodine and selenium. T4 is converted to t3 (more active form) Functions: o Regulates cellular respiration and BMR (Basal Metabolic Rate) o Stimulates growth hormone and enhances sympathetic nervous system activity o Improves nervous system functions and skin secretion rates. Thyroid Gland Abnormalities Hypothyroidism: insufficient production of thyroid hormone Unable to utilize nutrients to formulate energy = weight gain, cold sensitivity, fatigue, depression Example: Hashimoto’s disease (autoimmune) Hyperthyroidism: excessive production of thyroid hormone Symptoms: increased heart rate, anxiety, weight loss. Example: Graves’ disease Both conditions can result in goiter. Adrenal Glands and Stress Response Respond to physical and emotional stress by increasing the release of cortisol from the adrenal cortex and epinephrine/norepinephrine from the adrenal medulla. Corticotropin-releasing hormone (CRH): from hypothalamus, stimulates adrenocorticotropin hormone (ACTH) release from anterior pituitary, triggering cortisol production in the adrenal cortex. Circadian Rhythm and Cortisol Cortisol secretion follows a diurnal pattern; highest in the morning for energy and lowest at night. Cushing's Syndrome: Related to excessive cortisol secretion. Pancreas Functions Endocrine: Secretes insulin and glucagon to regulate blood glucose. Exocrine: Produces digestive enzymes. Hormonal Control of Blood Glucose Glucagon: Raises blood sugar levels when low. Insulin: Lowers blood glucose by facilitating cellular uptake. Gonadal Hormone Production Gonads stimulated by anterior pituitary hormones (LH and FSH). Testosterone: Develops male characteristics. Estrogen and Progesterone: Support female reproductive functions Summary of the Endocrine System Involves multiple glands that produce hormones targeting various body cells. Key glands: hypothalamus, pituitary, thyroid, pancreas, adrenal glands, gonads. Hormonal functions: homeostasis, growth, metabolism, reproduction, digestion. Key Points on Hormones Types: Hormones classified as either water-soluble or fat-soluble. Pituitary Functions: Posterior pituitary stores, anterior pituitary produces hormones. Pancreatic Hormones: Insulin and glucagon are crucial for blood glucose regulation.