THE ENDOCRINE SYSTEM READINGS: CHAPTER 45;

Transcription

1 Winter 08 1 of 12 THE ENDOCRINE SYSTEM READINGS: CHAPTER 45; COORDINATION Animals use two systems to coordinate many of their functions: signals system Useful for term changes Slow response time ( ) Hormones travel through signals system term responses Very rapid response time ( ) Action potentials travel along CHEMICAL SIGNALS Allow for communication between cells of the body To coordinate and regulate various functions Hormones are products of endocrine glands Hypothalamus Pituitary Thyroid & Parathyroid Pancreas Kidney Adrenal Testes/Ovaries signals A signal is produced, released, and binds to a receptor on the signals A signal is produced, released, and binds to a receptor on a signals A signal is produced, released, enters the, and binds to a receptor on a Neuroendocrine signals

2 Winter 08 2 of 12 Chemical signals are released into the to modify behaviour in A GLAND BY ANY OTHER NAME Not all glands in our body are part of the endocrine system glands Secrete directly into circulation or other body fluids Those just mentioned Hormones travel to and act on target cells/tissues glands Secrete various products through to the external environment Mucus glands, sebaceous, mammary, sweat, liver, pancreas Mucus, sweat, digestive enzymes HORMONE STRUCTURE What exactly are hormones? or peptides insulin derivatives thyroid hormones (triiodothyronine) (cholesterol) derivatives sex hormones CONTROL OF SECRETION Release of most hormones is highly Only released when a response is Dysregulation leads to Three mechanisms exist to regulate hormone secretion The action of a on an endocrine gland The action of the system on endocrine glands The action of a produced by one endocrine gland on another gland

3 Winter 08 3 of 12 NONHORMONAL REGULATION Blood levels and the Cells in the islets of Langerhans detect blood sugar levels and respond Glucose is a non-hormone signal If levels are Alpha-cells secrete Glucagon blood sugar If levels are Beta-cells secrete Insulin blood sugar NERVOUS REGULATION Neurons can glands and hormone-releasing cells release regulates hormone secretion by the target gland An external stimulus is perceived Sends a signal to the hypothalamus Release of hormones HORMONAL REGULATION A fairly common regulatory mechanism The hypothalamus and pituitary gland release a lot of hormones which can regulate secretion by other glands hormones hormones Hormones released by one gland travel to another and cause release of a second hormone HORMONE EFFECTS In order for a target cell/tissue to respond to a hormone, the cell(s) must have a to detect its presence Like, these receptors are specific Without the right receptor, the cell the hormone This is important for the target specificity of hormones

4 Winter 08 4 of 12 Responses to hormones are generally More hormone = response = Amplitude-modulation REGULATION OF RESPONSE Different cells have the ability to regulate their responses to hormones regulation of surface hormone receptors Have receptors regulation of surface hormone receptors Have receptors INVERTEBRATE HORMONES Hydra A freshwater Cnidarian capable of regeneration If they lose a it isn't a big deal If they lose their entire head it s Coordination of mouth and tentacle regeneration is a hormone that promotes development of the Insects use a series of hormones to coordinate two major events of moulting Getting rid of Promote the production of the Hormones secreted by brain and other glands hormone (a steroid hormone) Hormones also determine what the becomes hormone When it is time to moult brain hormone is released from the Travels in the hemolymph to the Causes release of An example of hormonal regulation of hormone secretion

5 Winter 08 5 of 12 Ecdysone Travels in the hemolymph to the Initiates of the old cuticle And of the new cuticle Juvenile hormone Not directly involved in moulting, but determines what the insect will Concentration starts out in the larvae JH larval characteristics Concentration with age Lower concentration ( ) adult characteristics What if these hormones don t work properly If no brain hormone or ecdysone: No If no decrease in juvenile hormone: No into the adult form and therefore no Who would benefit from this? The plants that produce hormones which disturb this process Disrupt and in insects Fewer insects to VERTEBRATE HORMONES The major vertebrate endocrine glands are the and Produce and secrete hormones which regulate most of the other glands HYPOTHALAMUS & PITUITARY The pituitary gland develops in part as an extension of the hypothalamus The pituitary hypophysis

6 Winter 08 6 of 12 And in part from the back of the mouth The pituitary hypophysis THE POSTERIOR PITUITARY Receives neural input from the hypothalamus Axons enter the neurohypophysis Neurons synthesize Hormones that come from a nerve (ADH) Travels to the kidney tubules to increase water Released during childbirth or suckling of newborn Effects contractions of: smooth muscle Smooth muscle in HORMONAL DISTURBANCE ADH is released when osmoreceptors detect increased blood (too many solutes) Effects on: Kidney tubules water reabsorption Diabetes insipidus The neurons in the posterior pituitary do not release ADH Not enough Copious amounts of dilute urine Water stays Leads to increased osmolality of body fluids THE ANTERIOR PITUITARY Connected indirectly to hypothalamus via a special pituitary system Veins which carry blood between Neurosecretory cells of the hypothalamus can control the products of the anterior pituitary

7 Winter 08 7 of 12 Many different hormones hormones Have effects on glands hormones Those that don t Hormones that effect glands targets PITUITARY TROPIC HORMONES The gonadotropins have effects on both male and female reproductive organs Follicle-Stimulating Hormone (FSH) Ovary Testes Synthesis begins at puberty Luteinizing Hormone (LH) Ovary and synthesis & release of and Testes production Adrenocorticotropic Hormone (ACTH) Travels to the Increases secretion of the hormones Thyroid-Stimulating Hormone (TSH) Secreted in response to thyroid-releasing hormone (TRH) produced by the hypothalamus Travels to the thyroid gland Stimulates thyroid follicular cells to the thyroid hormones Prolactin (PRL) Travels to mammary gland PITUITARY NONTROPIC HORMONES Stimulates Blood levels follow during menstrual cycle & increase during pregnancy Production continues as long as breast feeding

8 Winter 08 8 of 12 β Endorphins Analgesics produced in response to exercise Travel to in the brain The runner s high you get from torturing yourself GROWTH HORMONE (GH) A hormone with both and effects Tropic effects include stimulation of liver to produce other Bone elongation & increased muscle mass Nontropic effects include Metabolic effects such as HORMONAL DISTURBANCE Growth hormone abnormalities Hypersecretion Hyposecretion Not the same as achondroplastic dwarfism in that long bones are proportional THE THYROID GLAND The thyroid gland is situated just inferior to the larynx at the base of the neck Hormones are produced and stored in A lumen surrounded by endocrine cells (TH) Follicle cells synthesize thyroxine ( ) and triiodothyronine ( ) Regulates blood Ca ++ levels Deposition at bones THE THYROID HORMONES T 3 is the active form T 4 gets transformed to T 3 before it works T 3 acts on most cells of the body leading to tissue growth Important homeostatic functions maintaining normal: Blood pressure Heart rate Muscle tone Intestinal motility

9 Winter 08 9 of 12 HORMONAL DISTURBANCE Hyperthyroidism Hypothyroidism Graves Disease Nearly opposite of hyper- Increased metabolic rate May develop a goiter Weight loss, increased appetite Excessive sweating Increased heart rate Increased intestinal motility Bouts of intestinal hurry Weak skeletal muscles Increased iodide uptake Goiter ADRENAL GLAND Two structurally and functionally separate components Adrenal medulla ( ) Stimulation causes release of and Part of the fight-or-flight response Secretion is stimulated by Effects include: cardiac output blood flow to muscles ( to GI) glucose release (glycogen breakdown) digestive functions ADRENAL GLAND Adrenal Cortex ( ) Recall that hormone secretion is stimulated by ACTH Produces different types of steroid hormones Mineralocorticoids Androgens Glucocorticoids

10 Winter of 12 MINERALOCORTICOIDS The major mineralocorticoid is aldosterone Maintain balance in the body ADRENAL ANDROGENS Such as androstenedione Stimulate growth of both Increase GLUCOCORTICOIDS Hormones including cortisol Released in response to (metabolic, disease, emotional, exams) Effects fall under three categories: Gluconeogenesis, protein and fat metabolism Maturation of fetal lungs Suppression of immune system by decreasing numbers of WBCs A common treatment for a immune/inflammatory diseases THE OVARIES After puberty, LH and FSH are released from the anterior pituitary and travel to the gonads LH binds to follicle interstitial cells are synthesized sex characteristics LH & FSH stimulate of the follicle and cause the primary oocyte to meiosis I secondary oocyte Meiosis isn t completed until fertilization LH surge stimulates

11 Winter of 12 THE TESTES LH binds to interstitial cells in testes stimulating secretion sex characteristics Voice, hair Bone growth & muscle mass FSH binds to Sertoli cells THE PANCREAS The pancreas is a gland with both and functions Exocrine digestive enzymes and bicarbonate Two major endocrine hormones are produced in the islets of Langerhans: cells cells These 2 hormones work together to maintain a stable level INSULIN Released in response to blood glucose After a meal Targets: liver, muscle, adipose tissue Causes: Increased glucose Increased synthesis (storage) Effectively glucose from the blood Reasons: These effects occur after a meal Promote cellular storage of excess nutrients Also stimulates centre in hypothalamus

12 Winter of 12 GLUCAGON Released when blood glucose Between meals Targets: liver, and adipose tissue Causes: breakdown of glycogen synthesis of glucose Reasons: Mobilize stored nutrients preventing Part of the sympathetic response to mobilize stored glucose for use when needed DIABETES MELLITUS Literally means running over with honey Type I -dependent DM ~3% Autoimmune of the pancreatic beta cells in the blood to stimulate glucose uptake Controlled by insulin Type II -dependent DM ~97% Beta cells work fine, insulin is produced for insulin are non-functional Controlled primarily by LIST OF FIGURES Table 45.1