Endocrine System Lecture 1 PDF

THE ENDOCRINE SYSTEM A/Prof Jacolene Kroff Associate Professor Division of Physiological Sciences Department of Human Biology Email: [email protected] Learning Objectives 1. Gain knowledge and understanding of a general overview of homeostasis; and the endocrin...

THE ENDOCRINE SYSTEM A/Prof Jacolene Kroff Associate Professor Division of Physiological Sciences Department of Human Biology Email: [email protected] Learning Objectives 1. Gain knowledge and understanding of a general overview of homeostasis; and the endocrine system secretions and functions 2. Gain knowledge and understanding of the endocrine glands, their hormone productions, secretions and functions in the body: The Pituitary Gland, The Thyroid gland, The Parathyroid Glands, Adrenal glands 3. Gain knowledge and understanding of the endocrine organ, the pancreas, its hormone secretions and functions 4. Gain knowledge on the pathophysiology and an understanding of the symptoms, complications and treatment of certain endocrine disorders: Diabetes Mellitus Type II, Hyperthyroidism and Addison’s Disease  Quick overview - Homeostasis WHAT IS HOMEOSTASIS? Homeostasis is the body or organism’s ability to maintain stable internal conditions/ maintain internal stability. WHAT CONDITIONS WITHIN THE BODY IS UNDER HOMEOSTASTIC CONTROL? Concentration of nutrient molecules Concentration of O2 and CO2 Concentration of waste products pH Concentration of water, salt and other electrolytes (body fluids) Plasma volume and blood pressure Body Temperature  General Overview of the Endocrine System HOW IS HOMEOSTASIS CONTROLLED FOR DIFFERENT CONDITIONS? Feedback Control Negative feedback Positive Feedback Feedforward Control This is less frequently used type of control. Response happens in anticipation of a change that is going to happen, normally happens with the secretion of hormones to promote cellular uptake of nutrients while food is still in digestive track, for example insulin is secreted with the presence of glucose in the small intestine.  Quick Overview of Homeostasis Hypothalamus Homeostasis is the body or organism’s ability to maintain stable internal conditions/ maintain internal stability. Main reduce internal temperature mechanism to Hypothalamus heat loss shuts off maintain homeostasis is via negative feedback ↑ internal temperature Hypothalamus heat promoting center shut off Hypothalamus EXAMPLE OF NEGATIVE FEEDBACK  Quick Overview of Homeostasis Homeostasis is the body or organism’s ability to maintain stable internal conditions/ maintain internal stability. EXAMPLE OF Lactation POSITIVE FEEDBACK ↑ oxytocin ↑ prolactin smooth Milk muscle production contraction mechano- receptors Milk ejection Baby suckling Positive feedback Physiological change causes an even greater change in (self amplified cycle) the same direction  Quick Overview of Homeostasis Text summary of homeostasis. Maintain internal stability in the body internal body temperature fluctuate between 36 – 37 ℃ homeostasis mostly occur via negative feedback – body senses a change – activate mechanism to negate or reverse it. BODY TEMPERATURE Example of a negative feedback homeostatic control. When body temperature rise – detected by the hypothalamus – send signals – vasodilation of blood vessels close to skin- increase sweat glands activation – sweat – cool body down – negative feedback – tell the hypothalamus to shut the heat loss center down. When body temperature decreases– detected by the hypothalamus – send signals – vasoconstriction of blood vessels to send blood to internal organs not extremities - increase shivering elicited - increase in body temperature - increase negative feedback by shutting off heat promoting centers in the brain.  Quick Overview of Homeostasis Text summary of homeostasis. LACTATION Example of positive feedback loop. Self-amplifying cycle Baby suckling – positive feedback to hypothalamus to stimulate the release of prolactin and oxytocin – prolactin will help with milk production and oxytocin helped for milk flow - both causing milk flow. To maintain internal stability positive feedback can be dangerous because of this self-amplifying capability which can quickly change the internal state of the body to something far from its homeostatic, setpoint.  General Overview of the Endocrine System DIFFERENCES BETWEEN NERVOUS SYTEM AND ENDOCRINE SYSTEM Nervous System neurotransmitter Short term quick response Stimulus Target Cell receptor Endocrine System Endocrine Cell Hormones OR Stimulus Endocrine Cell Long term slow response  General Overview of the Endocrine System DIFFERENCES BETWEEN NERVOUS SYTEM AND ENDOCRINE SYSTEM NERVOUS SYSTEM ENDOCRINE SYSTEM Cells Neurons Glands Chemical Signal Neurotransmitter Hormone Specificity of Action Receptors on Postsynaptic Cell Receptors on Target Cell Speed of action Seconds Seconds to Hours Very Brief May be Brief or May Last for Days Duration of action Unless Neuronal Activity Even if Secretion Ceases Continues  Overview of the Endocrine System H Amino acid DIFFERENT TYPES O derivative Bind on plasma OF HORMONES: R membrane of target cell M Peptide O Derivative N E Bind on receptor inside S Lipid cell Derivative  Overview of the Endocrine System Water soluble (Hydrophilic) vs Lipid soluble (Hydrophobic) hormones Hydrophilic hormones have receptor proteins on the surface of the Hydrophobic cell membrane hormone will of target cell have receptor eg. Most protein inside Amino acid of target cell and peptide hormones eg. Thyroid and Steriod Hormones  Overview of the Endocrine System Where do hormones come from? production of Anti-Diuretic Hormone (ADH) and oxytocin production, and regulatory hormones Thyroxine (T4) Triiodotyronine (T3) Melatonin (increase metabolism) Anterior and Posterior (sleep-wake Calcitonin cycle) (stimulate bone growth) Posterior gland secrete ADH and oxytocin Anterior pituitary secrete Parathyroid gland many hormones: (4 lobes on posterior thyroid) Parathyroid hormone – regulate Anterior calcium and phosphate in body ACTH – Adrenocorticotropin hormone TSH – Thyroid stimulating Undergoes atrophy hormone during adulthood GH – Growth hormone secretes PRL – Prolactin Thymosin – increase FSH – Follicle Stimulating immune response & Hormone help stimulate pituitary LH – Luteinizing Hormone to release GH  Overview of the Endocrine System Where do hormones come from? Insulin (decrease blood glucose) Glucagon (increase blood glucose) Kidneys Erithropoietin (stimulate red blood Cortex Medulla cell production) Cortisol adrenaline Calcitriol (deal with (epinephrine) (reabsorption stress) noradrenaline calcium) Aldosterone (nor- (sodium and epinephrine) Gonads potassium re- (flight or fight (Ovaries or Testes) absorption) response)  Overview of the Endocrine System Where do hormones come from? Digestive Testes Ovaries Adipose Tract Heart 1. Gastrin, 2. Secretin, Tissue Androgens Estrogen 3. Somatostatin, 4. CCK, Naturetic such as Progesterone Leptin 5. VIP (Vaso-active Intestinal Polypeptide), Peptides Testosterone Inhibin 6. GIP (Gastric Inhibitory Peptide) Inhibin Lowers blood play a role in 1. ↑ gastric motility, HCL secretion pressure fat metabolism Mucosal growth in stomach when there is an 2. ↑ Pancreatic juice and bicarb production & increase secretion in blood pressure 3. ↓ endocrine and exocrine secretions of pancreas 4. ↑ production and secretion of bile, ↓ gastric emptying 5. Vasodilation in GIT blood vessels, stimulate water secretion, ↓ gastric acid secretion 6. ↑ insulin secretion, ↓ gastric acid secretion  Overview of the Endocrine System The stimuli that activate the endocrine glands fall into three major categories: a) Hormonal b) Humoral c) Neural Overview of the Endocrine System 1 The hypothalamus secretes hormones that… Hypothalamus a) Hormonal Stimulus 2 …stimulate the anterior most common stimulus pituitary Anterior pituitary gland to gland secrete hormones endocrine organs are activated that… by other hormones Thyroid Adrenal Gonad gland cortex (testis) 3 …stimulate other endocrine glands to secrete hormones Overview of the Endocrine System 1 Capillary blood contains low concentration of Ca2+, which b) Humoral Stimulus stimulates… Capillary Thyroid gland (low Ca2+ (posterior view) in blood) changing of certain ions and nutrients in the blood vessels stimulate hormone release Humoral indicate various body fluids, such as Parathyroid Parathyroid blood and bile glands PTH glands 2 …secretion of parathyroid Other example: Insulin produced in response hormone (PTH) by parathyroid glands) to changing levels of blood glucose. Overview of the Endocrine System 1 Preganglionic sympathetic fiber stimulates adrenal medulla cells… CNS (spinal cord) c) Neural Stimulus Nerve impulses stimulate hormone release Preganglionic most are under the control of the sympathetic fibers sympathetic nervous system Medulla of adrenal gland Example: the release of norepinephrine and epinephrine by the adrenal medulla Capillary 2 …to secrete catecholamines (epinephrine and norepinephrine) The end Lecture 1