The Endocrine System PDF

Inhibition of natural hormone by steroid  RNB 10702 ANATOMY AND PHYSIOLOGY 2 1. THE ENDOCRINE SYSTEM  LEARNING OUTCOMES At the end of the session, the students should be able to: compare and contrast the role of the nervous and endocrine system; state the function of...

Inhibition of natural hormone by steroid  RNB 10702 ANATOMY AND PHYSIOLOGY 2 1. THE ENDOCRINE SYSTEM  LEARNING OUTCOMES At the end of the session, the students should be able to: compare and contrast the role of the nervous and endocrine system; state the function of hormones; outline the organization of the endocrine system and its main component gland; describe general characteristics of hormones ; identify three mechanisms for regulating hormone secretion; describe the locations of and relationship between the hypothalamus and the pituitary gland; describe the function of each hormone secreted by the pituitary gland.  INTRODUCTION Nervous systems and endocrine systems work together to coordinate functions of all body systems The glands in endocrine system scattered throughout the body & secrete hormone into the blood The glands are very small yet they are extremely very important  COMPARISON BETWEEN NERVOUS SYSTEM & ENDOCRINE SYSTEM (cont..) Nervous system: Control body activities through nerve impulse and neurotransmitters to causes muscles contraction or glandular secretion The effect is short duration, measured in seconds & localized Parts of the nervous system stimulate or inhibit the release of hormones Endocrine system: Controls body activities by releasing hormone The effect is last longer, broader influence & more generalized Hormones may promote or inhibit the generation of nerve impulses Hormones will influence growth, development and metabolic activities  SUMMARY OF COMPARISON BETWEEN NERVOUS SYSTEM & ENDOCRINE SYSTEM  FUNCTIONS OF HORMONES Help regulate: Chemical composition and volume of internal environment (interstitial fluid) Metabolism & energy balance Contraction of smooth cardiac muscle fibers Glandular secretion Some immune system activities Control growth & development Regulate operation of reproductive system Help establish circadian rhythm  TYPES OF GLANDS Two major types of glands in the body 1. Exocrine glands Secrete their products into ducts and the ducts carry the secretions to the target site Example are sweat gland, sebaceous gland, mammary gland & the glands that secrete digestive enzymes 2. Endocrine glands Do not have duct (ductless gland) Release hormones directly into blood capillaries or lymph & circulate throughout the body  ENDOCRINE GLANDS Located throughout the body Major Glands 1. Pituitary gland (hypophysis) 2. Thyroid gland 3. Parathyroid glands 4. Adrenal glands 5. Panreatic Islets of Langerhanns Minor glands Thymus & pineal gland OTHER HORMONE-PRODUCING STRUCTURES It is not part of endocrine system Kidneys Gastrointestinal mucosa Skin Liver Small intestine Placenta Heart – atrial muscle cells secrete atrial natriuretic peptides (ANP) RECAP - ORGAN PRODUCING HORMONE  CHEMICAL NATURE OF HORMONES Chemically hormone are classified as either protein or steroid Most hormone in the body are proteins or protein derivate The receptor of these hormones are located on the cell membrane Their fundamental building blocks are amino acids Difficult to administer orally as will inactivated by the acid & pepsin in the stomach – must administered by injection Example – adrenalin, noradrenalin, insulin, glucagon  CHEMICAL NATURE OF HORMONES (cont..) The sex hormones & those from adrenal cortex are steroids The receptor of these hormones are located inside the cell These hormone derivatives from lipid (fat) These lipid-soluble hormone can be taken orally Example – steroids (glucocorticoids, mineralcorticoids) & thyroid hormones  MECHANISMS OF HORMONE ACTION Hormones are carried by the blood throughout the entire body Hormone affect only certain cells The specific cells that respond to a given hormone have receptor sites for that hormone If the hormone fits the receptor site, then there will be an effect If a hormone & the receptor site do not match, then there is no reaction The cell that have receptor site for a specific hormone make up the target tissue for that hormone MECHANISMS OF HORMONE ACTION (cont..)  The protein hormone that react with receptor sites on the surface of the cell is called first messenger The hormone-receptor reaction on cell membrane activates an enzyme within the membrane which diffuse into the cytoplasm (inside) of the cell – removal of ATP occur to produce cyclic AMP Cyclic AMP which brings about the action attributed to the hormone is called a second messenger MECHANISMS OF HORMONE ACTION (cont..)  MECHANISMS OF HORMONE ACTION (cont..) Steroid hormones bind to and activate receptors within cells The activated receptors then alter gene expression which results in the formation of new proteins The new proteins alter the cells activity and result in the physiological responses of those hormones SUMMARY OF HORMONE ACTION  CONTROL OF HORMONES SECRETIONS Most hormones are released in short bursts, with little or no release between bursts It will increased the concentration of the hormone in the blood Regulation of hormone secretion normally maintains homeostasis and prevents overproduction or underproduction of a particular hormone If these regulating mechanisms do not operate properly, disorders occur  CONTROL OF HORMONES SECRETIONS (cont..) Hormone secretion is regulated by Neural stimulus Humoral stimulus (Changes in the blood) Hormonal stimulus  CONTROL OF HORMONES SECRETIONS (cont..) 1. Neural stimulus Nerve fibers stimulate hormones to be released Examples: norepinephrine and epinephrine released during stress 2. Humoral stimulus (Chemical changes in the blood) Changing blood levels of ions & nutrients will stimulate hormones to be released Examples:  Parathyroid hormone (PTH) will cause calcium to be released from bone into blood  ADH will cause water to be reabsorbed into blood 2. Hormonal stimulus  Some hormones released will stimulate other hormones to be released Most hormonal regulatory systems work via negative feedback, but a few operate via positive feedback In a negative feedback system the hormone output reverses a particular stimulus Blood Ca2+ level is controlled by the parathyroid hormone (PTH). If blood Ca2+ is low, there is a stimulus for the parathyroid glands to release more PTH. PTH then exerts its effects in the body until the Ca2+ level returns to normal. If the level gets too high the body will cease PTH production and secrete calcitonin to lower the Ca2+ level. This example shows how PTH and calcitonin have negative feedback influence on one another In a positive feedback system the hormone output reinforces and encourages the stimulus For example, during childbirth, the hormone oxytocin stimulates contractions of the uterus, and uterine contractions in turn stimulate more oxytocin release, a positive feedback effect THE HYPOTHALAMUS AND PITUITARY GLAND  HYPOTHALAMUS AND PITUITARY GLAND The hypothalamus is the major link between the nervous and endocrine systems The hypothalamus and the pituitary gland regulate virtually all aspects of growth, development, metabolism, and homeostasis It receives input from the thalamus, the RAS, and the limbic system  The pituitary gland is attached to the hypothalamus & consists 2 lobes - anterior pituitary & posterior pituitary Hormones of pituitary gland are controlled by releasing & inhibiting hormones produced by the hypothalamus 2 lobes of pituitary gland Anterior pituitary gland: also known as adenohypophysis about 75% of the total weight of the gland Posterior pituitary gland: It is extension of the brain Consists of neuron & neuroglia also known as neurohypophysis  HYPOTHALAMUS AND ANTERIOR PITUITARY LOBE Neurosecretory cell of the hypothalamus secreted hormones into capillaries in the hypothalamus & transport by veins along the infundibulum to another capillary network in anterior pituitary lobe Within anterior pituitary lobe, the releasing hormone affect the glandular epithelium to cause secretion of anterior pituitary hormone Inhibitory hormone have the opposite effect  ANTERIOR PITUITARY HORMONES Hormone Major Function/ Target Human Growth Stimulates the growth of bones, muscle & Hormone (hGH) other organs by promoting protein synthesis Thyroid Stimulates synthesis and secretion of thyroid Stimulating hormones by the thyroid gland Hormone (TSH) Promotes the development of glandular tissue in female breast during pregnancy Prolactin (PRL) Stimulate milk production after birth of the infant  ANTERIOR PITUITARY HORMONES (CONT..) Hormone Major Function/ Target Follicle Stimulates the development of egg or Stimulating ova in the ovaries & sperm in the hormone (FSH) testes In female – cause ovulation & the production and secretion of the female sex hormones (estrogen & Luteinizing progesterone) hormone (LH) In male – stimulate the testes to produce & secrete male sex hormone (testosterone)  Hormone Major Function/ Target Controls the production and Adrenocorticotropic secretion of hormones called Hormone (ACTH) glucocorticoids by the cortex of the adrenal gland Stimulate the production and release of melanin by Melanocyte melanocytes in skin and hair. Stimulating MSH signals to the brain have hormone (MSH) effects on appetite and sexual arousal Negative feedback regulation of secretion hormones by the anterior lobe of the pituitary gland ANTERIOR PITUITARY HORMONES (CLINICAL APPLICATION) cont.. Dwarfism- lack of Giantism – excessive of hGH in child hGH in a child ANTERIOR PITUITARY HORMONES (CLINICAL APPLICATION) cont.. Acromegaly – excessive of hGH during adulthood  HYPOTHALAMUS AND POSTERIOR PITUITARY GLAND The posterior pituitary gland is also known as neurohypophysis Neurosecretory cells in the hypothalamus secrete oxytocin and antidiuretic hormone (ADH) The hormone released at the axon terminals located in the posterior pituitary where they stored & subsequently released  HYPOTHALAMUS AND POSTERIOR PITUITARY GLAND (cont..) Oxytocin Targets smooth muscle in the uterus and breasts In the uterus, oxytocin stimulates uterine contractions, and in response to the sucking from an infant Stimulates “milk letdown” in the breasts Antidiuretic Hormone (ADH) Promotes reabsorption of water by kidney tubules Targets the sweat glands in the skin to minimize water loss  This graphic demonstrates the regulation of ADH secretion REGULATION OF SECRETION OF OXYTOCIN THROUGH A POSITIVE FEEDBACK MECHANISM  POSTERIOR PITUITARY HORMONES (CLINICAL APPLICATION) Nursing a baby after delivery stimulates oxytocin release promoting uterine contractions and the expulsion of the placenta. Synthetic OT (Pitocin) may be used to induce birth contractions  POSTERIOR PITUITARY HORMONES (CLINICAL APPLICATION) cont.. Insufficient of ADH Caused Diabetes insipidus – excessive water lost in urine with very diluted urine Will lead to dehydration & thirst (polydipsia) Usually caused by brain tumor, head trauma, or brain surgery that damages the posterior pituitary or the hypothalamus Ingestion of alchohol inhibits ADH secretion & results in increased urine output Excessive of ADH Will caused blood vessels to constrict which lead to increase blood pressure  RECAP/QUIZ How nervous and endocrine systems coordinate functions of all body systems? Nervous system-through nerve impulses & neurotransmitters Endocrine system controls body activities by hormone What is the different between exocrine glands & endocrine glands in their mode of secretion? Exocrine glands -secrete their products into ducts and the ducts carry the secretions to the target site– e.g sweat gland, sebaceous gland, mammary Endocrine glands - Release hormones directly into blood capillaries or lymp & circulate throughout the body  RECAP/QUIZ (cont..) How the secretion of hormone is regulated? Neural stimulus Humoral stimulus (Changes in the blood) Hormonal stimulus What is the function of Human Growth Hormone (hGH)? Stimulates the growth of bones, muscle & other organs by promoting protein synthesis What condition will happened when there is lack of hCG in child? Dwarfism  RECAP/QUIZ (cont..) Excessive of hCG during childhood will cause Giantism Excessive of hCG during adulthood will cause Acromegaly What are the 2 hormones released by the posterior pituitary gland? ADH & Oxytocin What is the function of ADH? Promotes reabsorption of water by kidney tubules Targets the sweat glands in the skin to minimize water loss  RECAP/QUIZ (cont..) What is the disease occur due to inability of the pituitary to secret ADH? Diabetes insipidus Which structure mainly controls the pituitary glands? Hypothalamus