Essential Knowledge • 2.e.2 – Timing and coordination of physiological events are regulated by multiple mechanisms (11.1). • 3.b.2 – A variety of intercellular and intracellular signal transmissions mediate gene expression (11.1 & 11.4). • 3.d.1 – Cell communication processes share common features that reflect a shared evolutionary history (11.2 & 11.2). • 3.d.2 – Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling (11.1 & 11.2).
Essential Knowledge • 3.d.3 – Signal transduction pathways link signal reception with cellular response (11.3). • 3.d.4 – Changes in signal transduction pathways can alter cellular response (11.4).
Introduction • Endocrine system deals with chemical control and communication • Uses hormones • Hormone: chemical signal usually transported through bloodstream, elicits a specific response from target cell • Produced by endocrine cells (neurosecretory cells) • Specialized nerve cells • Hormones regulate activity of other cells and organs • Hormones bind to cell surface receptors
Introduction • Hypothalamus and pituitary gland coordinate • Produce many hormones that control production of other hormones in other endocrine glands/organs • Nervous system: coordinates and communicates • Endocrine system: produces hormones which regulate bodily processes
Pathways for signals • A receptor/sensor detects a change (stimulus) • Receptor notifies the control center • Control center sends out an efferent signal which directs a response by effector • Endocrine cells: acts as both sensor and control center • Sends out either hormones or signal • Usually controlled via negative feedback loop
Hormones • Three groups/classes of hormones: • Peptide/Protein (water-soluble) • Amine (water-soluble) • Steroid • Types of signals: • Hormones: within body (long distance) • Local regulators: neighboring cells • Phermones: communication between individual organisms
Hormones • Hormones bind to target cell receptors • Initiate pathways/signals that end in specific cell responses • Steps of signal response: • Reception: Signal binds to specific protein receptor on target cell • Signal transduction: signal’s message is transmitted via target cell • Response: the end result, how the target cell responds
Hypothalamus • Hypothalamus and pituitary integrate the endocrine system functions • Hypothalamus: • Situated in lower brain • Integrates endocrine and nervous system • Receives nerve signals from body • It’s neurosecretory cells release hormones • These hormones are stored in or regulate by the pituitary gland
Pituitary gland • Pituitary gland: • Located at the base of hypothalamus • Regulate and stores hormones produced by hypothalamus • Two parts: • Posterior: stores and secretes two hormones from hypothalamus • Anterior: makes at least 6 hormones (tropic hormones), important to chemical coordination
Hormone examples • Antidiuretic hormone (ADH) • Functions in osmoregulation • Increases water retention by kidney (decreases urine volume) • Produced in posterior pituitary • Oxytocin • Induces uterine contractions during birth • Induces milk ejection during nursing • Produced in posterior pituitary • Thyroid-stimulating hormone (TSH) • Regulates production of thyroid hormones • Produce in anterior pituitary gland
Hormone examples • Follicle-stimulating hormone (FSH) and luteinizing hormone (LH): • Stimulate gonad activity • Produced in anterior pituitary • Prolactin (PRL) • Mammals: milk production and secretion • Amphibians: delays metamorphosis • Fish: osmoregulation • Produced in anterior pituitary • Endorphin: • Pain perception • Can resemble opiate drugs (giving you a sense of well-being!) • Produced in anterior pituitary
Hormone examples • Growth hormone (GH): • Variety of target tissues • Signals release of IGFs (Insulin-like growth factors) • Gigantism (human growth disorder caused by excessive GH) • Produced by anterior pituitary • IGFs: • Produced by liver • Stimulate bone and cartilage growth • T3 and T4: • Produced by thyroid gland • Secretion controlled by negative feedback • Critical to development and maturation
Hormone examples • T3 and T4, cont.: • Contributes to homeostasis • Maintain normal blood pressure, heart rate, muscle tone, digestion, reproductive function • Blood calcium hormones: • Parathyroid hormone (PTH): stimulate Calcium resabsorption in kidney, activate vitamin D which helps uptake of Ca in intestines • Calcitonin: hormone that lowers calcium levels in blood
Hormone examples • Blood glucose hormones: • Glucagon: raises glucose concentrations by stimulating liver to increase breakdown of glycogen • Insulin: lowers glucose concentration by promoting movement of glucose from blood into other body cells • Produced by pancreatic cells • Diabetes mellitus: absence of insulin in bloodstream or loss of response to insulin • Type-I: autoimmune disorder, treated by regular insulin injections • Type-II: 90% of diabetics, insulin deficiency, controlled via exercise and diet control
Hormone examples • Stress hormones: • Epinephrine (adrenaline) • Norepinephrine (noradrenaline) • Sustain blood pressure • Produced by adrenal glands • Increase availability of energy sources • Increase metabolic rate • Gonadal sex hormones: • Produces by testes and ovaries • Affect growth, development and reproductive cycles and behaviors
Hormone examples • Gonadal sex hormones, cont.: • Three groups: • Androgens: • Produced primarily by testes • Ex: testosterone (determines gender, stimulate development of male reproductive system) • Estrogens • Produced by ovaries • Regulate development and maintenance of female reproductive system • Progestins • Help prepare and maintain uterus for growth of embryo
Hormone examples • Melatonin: • Secreted and produced in pineal gland (near center of brain) • Regulate functions related to light and changes in day length • Secretion at night functions with biological clock for daily or seasonal activities (such as sleeping, mating, nesting)
Exclusion Statements • Memorization of the names, molecular structures, and specific effects of hormones or features of the brain are responsible for these physiological phenomena is beyond the scope of the course and the AP Exam.