Endocrine System PDF

Endocrine System NERVOUS SYSTEM Rapid communication using electrical signals. Releases neurotransmitters into synapses (Fewer targets). Neurotransmitters typically producer shorter-term effects. - Short term, localized. ENDOCRINE SYSTEM Slower communication through blood. Multiple, distant targ...

Endocrine System NERVOUS SYSTEM Rapid communication using electrical signals. Releases neurotransmitters into synapses (Fewer targets). Neurotransmitters typically producer shorter-term effects. - Short term, localized. ENDOCRINE SYSTEM Slower communication through blood. Multiple, distant targets. VERY Specific Hormones typically produce longer-term effects on physiology of target. Message sent from gland, goes through the blood (Circulating and slowly), getting through its target cell, changing the function of the cell. - Shorter longer distance. - Hormone = chemical messenger, secreted by endocrine cell/organ that changes the function of another cell. Endocrine System Functions Hormones Control (Organism Level) - Reproduction - Growth & development ® growth factors, insulin, thyroid (basal metabolic rate) etc. - Mobilization of body defences - Maintenance of homeostasis - Regulation of metabolism Hormonal Control Receptor specificity ® ability for cells to respond to the fit of a hormone (lock and key) Receptor affinity ® how tight the fit is, ­ affinity = less hormones needed Hormone agonist ® allows certain glands to release/inhibit their hormones. Hormone antagonist ® oppose or reverse the effects of a hormone. Synergistic effect ® two hormones with similar effects produce an amplified response. (i.e., sperm and egg) - Upregulation = ­ number of receptors. - Downregulation = ¯ number of receptors on the cell. ¯ sensitivity. - Permissiveness = one hormone being mandatory for other hormones to work. Gland Type Review Endocrine Glands (e.g., pancreas, liver etc.) Ductless glands and empty hormonal Products directly into blood Exocrine Glands (e.g., tear ducts) Glands that have ducts and deliver secretions to a body surface. (e.g., tear ducts) Mixed Gland (testes, ovaries) Gland or organ that secretes products both into the bloodstream, and onto a body surface. Intercellular Communication: Short Paracrine Signaling Synaptic Signaling Gap Junction Signaling Intercellular Communication: Long Long distance signaling. Hormonal Signaling Hormonal Secretion Hormone Action Direct gene activation Second messenger system Target cells must have specific protein receptors. Target cells activation ® depends on the number of hormones in the blood. Consider affinity. Chemistry of Hormones Classified as Amino-acid based (hydrophilic) or Steroids (can enter plasma membrane) ® made from cholesterol. or Prostaglandins ® Lipid-derivatives ® local hormones produced by every single cell in the body, response to local and mechanical stimuli. - Short-lived, short half-life. - Promote pain responses. - Induce fever. - Help mobilize white cells. - Can have local vasodilation. - Dilate or constrict respiratory bronchioles. - Help vasodilate renal vessels. - Inhibit platelet aggregation. Hormone Action Cellular Change membrane permeability (Aldosterone, Insulin, Epinephrine) Active/inactivate enzymes (insulin) Stimulate/inhibit cell division (growth hormones) Promote/inhibit secretion (tropic hormones) Turn on/off gene transcription (erythropoietin) Hormone Action Hormones initiate their effects through: - Direct gene activation ® friend that walks into a house. - Second-messenger system (includes a secretary!!) ® friend that must ring a doorbell. Direct Gene Activation 1) Diffuses through plasma membrane of target cells. 2) Binds to specific hormone receptor. 3) Hormone-receptor complex binds to specific sites on cell’s DNA. 4) Specific genes activated to create messenger RNA. 5) mRNA is translated in the cytoplasm. 6) New proteins are synthesized. Second Messenger 1) Hormone (first messenger) binds to a receptor protein plasma membrane. 2) Activated receptor initiates reactions that activate an enzyme. 3) Enzyme catalyzes a reaction that produces a second-messenger molecule (Such as cyclic AMP) 4) Second messenger molecule is involved in additional changes promoting desired response. Hormone Level Regulation Nearly all hormones are regulated by negative feedback. ® responding to a change or stimuli ­ blood sugar levels = insulin release = ¯ blood sugar levels. Hormone Release Regulation Hormonal = hormones releasing hormones Humoral = local monitoring/response to blood stuff levels (could be sugars, minerals, hormones) Neural = direct neural communication Hormonal Control 1) Hormonal Stimulus - Hypothalamus secretes hormones. - The hormones stimulate the anterior pituitary gland to secrete hormones. - The hormones stimulate other endocrine glands to secrete hormones. (thyroid, adrenal cortex, gonad “testis”) - Hypothalamus ® anterior pituitary gland ® thyroid gland, adrenal cortex, gonad.  2) Humoral Control - Capillary blood contains low concentration of Ca2+. - This stimulates secretion of parathyroid hormone (PTH) by parathyroid glands. 3) Neural Control - Preganglionic sympathetic fiber which stimulates the adrenal medulla cells. - This secretes catecholamines (epinephrine and norepinephrine). Endocrine Reflexes 1) Endocrine Reflex 1 - Example: control of calcium levels by parathyroid hormones and calcitonin; control of blood glucose levels by insulin and glucagon 2) Endocrine Reflex 2 - Example: hypothalamic control of hormone production by the anterior pituitary; to control the adrenal cortex, thyroid gland, and reproductive glands. Hypothalamus and Pituitary Gland Hypothalamus ® creates hormones and uses inhibitory or activator hormones. Releases tropic hormones so that they can circulate in the blood. Infundibulum Pituitary Sphenoid Neurohypophysis = the posterior lobe of the hypophysis (pituitary gland), which stores and releases oxytocin and vasopressin produced in the hypothalamus. - Can stop hemorrhaging. - Increase contractions. Posterior Pituitary: Oxytocin Released during: Childbirth and nursing! Posterior Pituitary: Antidiuretic Hormone Released during: Decreased H2O concentration of blood. Low blood volume/pressure - Pull in PURE WATER, which fills the blood volume, which ­ BP. - Detects solute concentration levels. Hypertonic, hypotonic, isotonic. Looks primarily at sodium. Hypothalamus and Anterior Pituitary Gland Adenohypophysis = a lobe of the gland that regulates several physiological processes (including stress, growth, reproduction and lactation). Tropic Hormones TSH, ACTH, FSH, LH Anterior Pituitary Gland Anterior Pituitary Hormones - Growth hormone (somatotropin) o Growth of skeletal muscles and long bones. o Role in determining final body size. - Prolactin (lactotropin) o Milk production following childbirth. ® stimulating milk production and maintaining it. Gonadotropic Hormones o Follicle-stimulating hormone (FSH) o Luteinizing hormone (LH) - Adrenocorticotropic hormone  - Thyrotropic hormone o Thyrotropin-releasing hormone (TRH) o Thyroid stimulating hormone (TSH) o Adrenocorticotropic hormone (ACTH) ® ADRENAL CORTEX Gonads Ovaries - Estrogen = development and regulation of female characteristics (hips, nipple, pubic hair, fat storage etc.) - Progesterone = menstrual cycle, breast enlargement, embryogenesis etc. IN CONJUCTION WITH ESTROGEN o Helps prepare breasts for lactation. o Prepares embryo fertilization. Testes - Testosterone ® essential for production of sperm. Regulates FSH and LH  ® Enhances libido. Bones and muscles maintained. ® pubic hair, facial hair, aggressive behaviour etc. Gonadotropic Hormones - Follicle Stimulating Hormone (FSH) - Luteinizing Hormone (LH) Pineal Gland Releases melatonin! Thyroid Gland Thyroid Hormones: - Thyroxin (T4) - Triiodothyronine (T3) - TSH Response - Calcitonin o Has a hormone antagonist = opposite of whatever the effects of calcitonin. (parathyroid hormone) o Responds to high level calcium levels. o Breaks down bone tissues = ­ calcium o Decrease reabsorption of calcium in the intestinal wall. - T3 and T4 o These can be held for a long period of time by the thyroid gland. T4 controls metabolic rate. Parathyroid Glands Parathyroid Hormone (PTH) - ­ osteoclast activity, building up more hormone. - ­ blood calcium - Vitamin D helps with the reabsorption of calcium and lays down calcium. Blood Calcium Regulation - Only 1% of calcium in our blood. Bone Remodeling Adult bone undergoes remodeling: - Osteoclasts remove old/damaged bone. - Osteoblasts lay new bone. In response to: - Blood Ca+ levels - Forces of life (gravity, muscle tension, injury etc.) - Regular exercise increases bone density. - Helps slow age-related bone loss and prevent/limit osteoporosis. Controlled by: - Growth hormones - Thyroid hormone - Estrogen - Testosterone - Some stress hormones Thymus Thymosin ® helps T-cells mature. - Stimulate the production of T-cells. Adrenal Glands Ad- = above -renal = kidney Adrenal Medulla ® middle Adrenal Cortex ® outside Adrenal Medulla Hypothalamus Catecholamines - Epinephrine (stimulator in metabolic activities, releasing blood glucose, etc) - Norepinephrine SNS Result in more O2 and glucose in the blood and faster circulation to skeletal muscles, brain, heart, lungs, liver, eyes. Short term response: Epinephrine & Norepinephrine 1) ­ heart rate & BP 2) Liver converts glycogen to glucose and releases glucose to blood. 3) Dilation of bronchioles. 4) Changes in blood flow patterns, leading to ­ alertness and ¯ digestive and kidney activity. 5) ­ metabolic rate. Adrenal Cortex 3 Different Zones 1) Zona glomerulosa - Mineralocorticoids (e.g aldosterone) o Affects electrolyte balances. o ­ potassium expiration. o Pulling in more sodium. 2) Zona fasciculata - Glucocorticoids (e.g cortisol) 3) Zona reticularis - Sex hormones (e.g androgens) Aldosterone Secretion Renin-Angiotensin Plasma (Na+) or K+ ACTH ® inhibits zona glomerulosa. - Stops producing aldosterone. - Less potassium, more sodium. ANP ­ ALDOSTERONE­ = HIGH BP = TOO MUCH SODIUM RAAS System: Renin Renin - Initiates cascade resulting in Angiotensin 2. - Secreted by: o Specialized cells in nephrons o JGA - In response to: o Decreased BV o Decreased BP o Sympathetic stimulation RAAS System: Angiotensin 2 Angiotensin 2 - Increase BP and volume. - Effects: o Constricts afferent arterioles. o Increases Na+, Cl-, and H2O. o Reabsorption at kidney. o Causes adrenal cortex to release Aldosterone. Adrenal Cortex: Glucorticoids E.G CORTISOL Essential for survival Stress hormones Synergistic with catecholamines Cleared by liver, excreted by skins. Converts amino acids and fats into glucose. Adrenal Cortex Glucocorticoids - Cortisol and cortisone Long term stress - Na+ and H2O retention - Increased blood volume/BP - Gluconeogenesis - Increased BG - Immunosuppression Sex hormones Non-Endocrine Organ Endocrine Function Heart: Secreted by: Atrial cells In response to: Blood volume ­ Atrial Natriuretic Peptide Effects: - ¯ Na+ reabsorption - ¯ H2O Reabsorption - ¯ Secretion of aldosterone - ¯ secretion of ADH Glycogenolysis If body activities require additional ATP Glycogen can be broken down into glucose (to be released into the blood). Liver responds to hormone Glucagon and Epinephrine. Causing catabolic reactions. Skeletal muscle unable to directly break glycogen down to glucose.