Biology 30 Unit II - The Endocrine System Nelson Biology chapter 14 Biology Directions chapter 18 The Endocrine System The endocrine system, like the nervous system is responsible for allowing communication between the cells of the body. Unlike the nervous system, the endocrine system does not rely on a complex system of cells and support, just the existing circulatory system to transport the chemical messengers of the endocrine system - hormones. The time required for a hormonal response is much longer than that ofthe nervous response, and the effect is much longer lasting. The endocrine and nervous systems overlap in the brain - the pituitary and hypothalamus. The hypothalamus stimulates the pituitary gland via a nerve, and the pituitary affects the hypothalamus with hormones! Hormones (meaning "set in motion") are chemical regulators produced by cells of endocrine glands in one part of the body that affect cells in other parts of the body. They can be divided into two types: -target hormones- affect specific cells in the body (e.g. gastrin stimulates stomach cells) -nontarget hormones- have broad effects in the body (e.g. growth hormoneaffects the growth of long bones) Endocrine glands are ductless organs, producing their messengers and secreting them directly into the bloodstream, whereas other glands (exocrine glands) produce their chemicals and excrete them into a duct (ex. digestive enzymes, sweat). The effect of hormones has been studied in animals by removing a gland or organ and then analyzing the effects. Removal of the testicles in cattle produces less tough meat, and removal of the pancreas in dogs lead to what we now identify as symptoms of diabetes. Although this shed some light on the endocrine system, many glands produce more than one hormone, and levels of some hormones affect the level of other hormones. To study hormones today, scientists inject radioactive tracers into the organ and follow the organ's products throughout the body. Hormones. Hormones will act in one of two ways based on their chemical structures: steroid hormones - include sex hormones and cortisol -made from cholesterol (fat soluble) - cause a protein to be produced *** enter the cell hormonec=:)capilla~ interstitial flu ice:::) into cell c=:) attach to receptor in cytoplasm ~ protein production =J message to ribosome ::J activate gene :::J attach to DNA<:=Jnucleus ~ Biology 30 - Unit II page 1
protein hormones - include insulin, growth hormone and epinephrine -made from amino acids (water soluble) - increase rate of normal cell functions hormoneq capillaryq interstitial flui~ receptor on cell surface~activates adenyl catalase~ normal cell functions <==:activate cytoplasmic enzymes :=Jconvert ATP~cyclic AMP ~ ** hormone production will be regulated in most cases by negative feedback systems. Once the desired outcome is reached, the outcome will inhibit the hormone release Hormones are also classified as: Tropic- have endocrine glands as their target Non-tropic- don't have endocrine glands as their target Biology 30- Unit II page 2
Overview of the Endocrine System (see diagram Some Human Endocrine Glands) Gland Hormone Target Action Mech.controlling secretion Pineal Melatonin??? Circadian rhythms in chickens (brain) Role in sexual maturation Hypothalamus Oxytocin Posterior Stored in the pituitary for later Nervous system (Connected to pituitary release the pituitary by a Anti-diuretic Posterior Stored in the pituitary for later Blood osmolarity stalk) hormone (ADH) pituitary release (concentration of solutes in I urine) Other regulating Posterior Inhibit/stimulate release of control all pituitary hormones factors pituitary pituitary hormones -ve: cortisol level (-ve to pituitary) -ve: thyroxine level (-veto pit.) Somatostatin Anterior Inhibits growth hormone (GH) Nervous system pituitary release -ve: GH concentration Dopamine Anterior Inhibits prolactin (PRL) secretion pituitary --------- ---- --- -------- ** glands and hormones in bold will be tested in the endocrine unit ** glands and hormones in italics will be tested in the reproduction unit ** other glands and hormones will not be tested but are there for completeness **digestive system hormones (gastrin, secretin & pacreozymin) are omitted, as is the thymus gland ' Biology 30 - Unit II page 3
Gland Hormone Target Action Mech. Controlling secretion I Pituitary- Thyroid stimulating Thyroid Stimulates the release of +ve thyroid releasing factor I Anterior Lobe hormone (TSH) thyroxine from the thyroid (from nerve cells in (forebrain) (regulates cell metabolism) hypothalamus when ' as TSH ~. thyroxine ~ metabolic rate too low) ** considered secreted when thyroxine too low -ve: thyroxine blood levels the master Adrenocorticotropic Adrenal Stimulates the release of gland hormone (ACTH) cortex hormones involved in stress -ve: cortisol level **responds response directly to as ACTH~. ~adrenal cortex hypothalamus hormones Growth hormone Most cells Promotes growth by stimulating Hypothalmic releasing (GH) uptake of amino acids and fat factors (HGH) metabolism - ~ mitosis rate Somatostatin as HGH ~. growth ~ (until -18yrs) Follicle stimulating Ovaries Females- stimulate follicle dev. & Blood estrogen hormone (FSH) Testes estrogen release Hypothalmic releasing Males- stimulate sperm prod. factors (GnRH) Luteinizing hormone Ovaries Females- stimulate ovulation, Progesteron (or testosteron) (LH) Testes corpus luteum formation, blood levels estrogen & progesterone release Hypothalmic releasing Males - stimulate testosterone factors (GnRH) production Prolactin (PRL) Mammary Stimulates and maintains milk Hypothalmic releasing glands production in females factors -- - --- - -- -- gy 30 -Unit II 'ge 4
Gland Hormone Target Action Mech. controlling secretion Pituitary- Oxytocin Uterus Initiates contractions Nervous system Posterior Lobe Mammary Triggers milk production. (forebrain) glands Antidiuretic Kidney Increases water reabsorption Concentration of solutes in hormone (ADH) as ADH ~.urine volume~. blood the blood pressure~ Adrenal- Epinephrine Many cells Increases blood sugar level, heart Stimulated by sympathetic Adrenal Medulla (adrenaline) rate, breathing rate, cell nervous system during times (inside) metabolism, dilate blood vessels of stress (on top of Norephinephrine and iris of eye (Ep only- ~ TSH, kidneys) (noradrenaline) ~ ACTH)- Ep stress, NEp- cold Adrenal- Cortisol Liver Converts amino acids into ACTH stimulates release Adrenal Cortex (glucocorticoids) Muscles glucose, reduces inflammation (outside) (on top of kidneys) Aldosterone Kidney Increase sodium retention and Level of sodium and (mineralocorticoids) water reabsorption (maintain fluid potassium in the blood levels) Sex hormones. Pancreas Islets Insulin Liver, Increases glucose usage by cells Stimulated by high blood of Langerhans ((3 cells) muscles and by increasing permeability sugar levels, inhibited by low (near stomach) others (~glycogen in liver) blood sugar levels Glucagon Liver Stimulates conversion of glycogen Stimulated by low blood (a cells) back to glucose sugar levels, inhibited by high blood sugar levels Biology 30 - Unit II page 5
Gland Hormone Target Action Mech. controlling secretion Thyroid Gland Thyroxine All cells Regulate cellular metabolism - Stimulated by TSH (from the (base of the Triiodothyronine stimulates increased sugar pituitary) neck in front of utilization, increases heat the trachea) released Calcitonin Bones Inhibits Ga 2 + loss from bones Ca 2 + concentration in the blood I! Parathyroid Parathyroid hormone Gl tract, Raises blood Ca 2 + levels by ~ Ca 2 + concentration in the Glands (either (PTH) bones absorption from the Gl & blood side of thyroid) stimulates Ca 2 + release from bones Placenta Progesterone, Ovary Maintains uterine lining during Estroge,n Uterus pregnancy Chorionic Gonadotropin Testis Testosterone Testis, Stimulate spermatogenesis, FSH, LH androgens many other development of 2 sex cells characteristics, sex drive, bone growth, muscle development Ovary Estrogen (follicle) Uterus, e- promotes dev't of 2o sex FSH, LH Progesterone many other characteristics, thickening of (corpus luteum, follicle) cells endometrium, prep. for pregnancy p- stimulates endometrium, prevents ovulation, prevents uterine contractions, r 1Y 30 - Unit II 16 6
Hormones & Homeostasis Insulin and Blood Sugar Regulation the pancreas has an exocrine (digestive enzyme) and endocrine (insulin & glucagon) function - the Islets of Langerhans produce the hormones (insulin in ~ cells and glucagon in a cells) the role of insulin was discovered by Banting & Best (a new school in Calgary is named after them!) v Blood sugar ~... ~/ 1' Insulin 1' storage of glucose in cells ( 1' permeability) 1' Glucagon. Fasting ~ (&other causes) Blood sugar 1' / ~Eating (&other causes) the balance between +ve and -ve feedback provided by blood glucose levels on the Islet cells maintains homeostasis high levels of blood sugar= hyperglycemia, low blood sugar= hypoglycemia Diabetes there are three basic types of diabetes type I (insulin dependent) caused by lack of insulin production in pancreas, hereditary but may skip generations treated with insulin injections and rigid blood monitoring since insulin is a protein it would be digested if taken orally must monitor both hypoglycemia (need glucagon or glucose) and hyperglycemia (need insulin) in research: islet transplants, gene therapy (thought to have found gene) type II (insulin independent), caused bydecreased insulin production, or too much glucose produced by the liver (not enough compensation by pancreas), insulin resistance Biology 30 - Unit II
HGH cone. gestational diabetes, during pregnancy, mother develops symptoms - at a greater risk for type II later in life diabetes insipidous, which has nothing to do with insulin, but ADH production in the pituitary- a tumour or injury causes '-"ADH or response to ADH, causing frequent urination (up to 30 L per day). Treat with ADH nasal spray only type I requires daily insulin injections, type II and GDM are treated by changing diet & sometimes sulfonamides symptoms of type I and II fatigue (not enough glucose inside cells to provide an energy source - must use fat & protein) excessive thirst & urination (glucose in urine pulls out water by osmosis) increased appetite (&weight loss- type I) increased susceptibility to infection ***in type II, since it onsets slowly, there may be no symptoms initially diabetes causes many complications due to fluctuations in blood sugar and ketoacidosis (products of fat breakdown which are toxic to the body) Growth Hormone & Growth (see Igor) as long as growth hormone is secreted at appropriate gigantism levels for the age of the organism, there are no ill effects too little GH during childhood - Lorrain dwarfism (not all i acromegaly growth inhibition is caused by '-"GH, also genetic, cortisol 1--(Cushing's syndrome), hypothyroidism (Frohlich's dwarf.it!!lts!!.y..!t+l... with '-"GH), poor nutrition, disease)! age (yrs) 12 too much GH during childhood -gigantism if GH excess continues into adulthood~ acromegaly: bone growth continues in width Thyroid Gland & Metabolism - thyroxine & triiodothyronine secreted by the thyroid regulate the rate of sugar oxidation (to produce ATP and heat) compared to storing the ~ / Epinephrine ~~ (Ad. Medulla) \ ~cellular metabolic rate ~ TSH (Thyroid ). ~ \... ' - - - - - - - - thyroxine triiodothinonine sugar as fat Thyroid disorders (see pictures- goiter. mvxedema. cretinism) / 1' cellular metabolic rate Biology 30 - Unit II
if too much thyroxine is present -7 hyperthyroidism (Grave's disease) - jittery, weight loss, fast heart rate, feel warm, mood swings, hair loss, bulging eyes - treated by removing a portion of the thyroid gland (surgically or chemically) if too little thyroxine is present -7 hypothyroidism cold, fatigue, dry skin, hair loss, weight gain, sleep a lot (myxedema) in children, leads to abnormal mental and physical development, growth retardation (cretinism) if too little iodine in the diet -7 thyroid swells (goiter) iodine is required to synthesize thyroxine swelling is due to the continued stimulation by TSH (no thyroxine made), causes increase in thyroid size in an attempt to make more thyroxine Adrenal Gland & Stress The medulla of the adrenal gland releases the hormones epinephrine and norepinephrine, both of which are found as neurotransmitters in the sympathetic nervous system The adrenal medulla is also stimulated by the sympathetic nervous system to release epinephrine & norepinephrine (which work faster than other hormones) In times of stress, the adrenal gland medulla along with the sympathetic nervous system act to prepare the body for fight or flight FYI ~ Emotional stress leads to epinephrine release wher~as cold leads to norepinephrine release ~ Brittle bones may be caused by hyperparathyroidism - causing loss of Ca 2 + this is NOT the same as osteoporosis, but osteoporosis may be lessened using a calcitonin spray ~ Don't forget - environmental factors - not just internal body factors have effects on hormone production- the effect of light (SAD, jet lag), the effect of diet (type II diabetes) Biology 30- Unit II