Endocrinology Handout PDF

Endocrinology Endocrine Endo- within Crine- Gk to separate Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct. Hormone Gk hormon -set in motion Hormones are special chemical messengers in the bod...

Endocrinology Endocrine Endo- within Crine- Gk to separate Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct. Hormone Gk hormon -set in motion Hormones are special chemical messengers in the body that are created in the endocrine glands  What is endocrinology? Endocrinology = Intercellular Chemical Communication Endocrinology is about communication systems & information transfer. Two systems coordinate communication throughout the body The endocrine system secretes hormones that coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior The nervous system conveys high-speed electrical signals along specialized cells called neurons; these signals regulate other cells  Hormonal Classes Proteins & peptides chemcases.com/olestra/ images/insulin.jpg Lipids (steroids, eicosanoids chem.pdx.edu/~wamserc/ ChemWorkshops/ gifs/W25_1.gif Amino acid derived (thyronines, neurotransmitters website.lineone.net/~dave.cushman/ epinephrine.gif Gases (NO, CO)  hormone receptor Hormone Receptors are cellular proteins that bind with high affinity to hormones Receptors Principles Mechanisms of transmitting the hormone signal to the cell function Specificity Sensitivity Amplification Cross talk Glands of the endocrine system A simple endocrine pathway Pathway Example − Stimulus Low pH in duodenum S cells of duodenum secrete the hormone Negative feedback secretin Endocrine cell Hormone Blood vessel Target Pancreas cells Response Bicarbonate release A simple neuroendocrine pathway Pathway Example + Stimulus Suckling Sensory neuron Hypothalamus/ posterior pituitary Positive feedback Neurosecretory cell Posterior pituitary secretes the Neurohormone neurohormone oxytocin ( ). Blood vessel Target Smooth muscle in cells breasts Response Milk release Hypothalamus The hypothalamus is responsible for the direct control of the endocrine system through the pituitary gland. The hypothalamus contains special cells called neurosecretory cells—neurons that secrete hormones: Pituitary Gland The pituitary gland, also known as the hypophysis. made of 2 completely separate structures: posterior pituitary anterior pituitary  Figure 45.14 Cerebrum Pineal gland Thalamus Hypothalamus Cerebellum Pituitary Spinal cord gland The posterior pituitary stores and secretes hormones that are made in the Hypothalamus hypothalamus Posterior The anterior pituitary pituitary makes and releases hormones under regulation of the Anterior hypothalamus pituitary  Tropic hormones & target endocrine glands hypothalamus thyroid-stimulating hormone posterior antidiuretic (TSH) pituitary hormone Thyroid gland (ADH) anterior pituitary Kidney tubules Muscles of uterus gonadotropic hormones: Adrenal follicle- cortex stimulating hormone (FSH) & luteinizing hormone (LH) Melanocyte Bone Mammary and muscle glands Testes Ovaries in mammals Pineal Gland The pineal gland produces the hormone melatonin that helps to regulate the human sleep-wake cycle known as the circadian rhythm. The activity of the pineal gland is inhibited by stimulation from the photoreceptors of the retina. This light sensitivity causes melatonin to be produced only in low light or darkness. Increased melatonin production causes humans to feel drowsy at nighttime when the pineal gland is active. Thyroid Gland The thyroid gland is a butterfly-shaped gland located at the base of the neck and wrapped around the lateral sides of the trachea produces 3 major hormones: Calcitonin Triiodothyronine (T3) Thyroxine (T4) Calcitonin is released when blood calcium levels rise- reduces the blood calcium levels T3 and T4 work together to regulate the body’s metabolic rate. Increased levels of T3 and T4 lead to increased cellular activity and energy usage in the body. Parathyroid Glands The parathyroid glands are 4 small masses of glandular tissue found on the posterior side of the thyroid gland. Produce parathyroid hormone (PTH) involved in calcium ion homeostasis. PTH is released when blood calcium drops PTH stimulates the osteoclasts to break down the calcium containing bone matrix to release free calcium ions into the bloodstream. PTH also triggers the kidneys to return calcium ions filtered out of the blood back to the bloodstream so that it is conserved.  PTH Parathyroid gland (behind thyroid) STIMULUS: Falling blood Ca2+ level Homeostasis: Blood Ca2+ level (about 10 mg/100 mL)  Figure 45.20-2 Increases Ca2+ Active uptake in vitamin D Stimulates Ca2+ intestines uptake in kidneys PTH Parathyroid Stimulates gland (behind Ca2+ release thyroid) from bones STIMULUS: Blood Ca2+ Falling blood level rises. Ca2+ level Homeostasis: Blood Ca2+ level (about 10 mg/100 mL) Adrenal Glands A pair of roughly triangular glands found immediately superior to the kidneys. 2 distinct layers-with own unique functions outer adrenal cortex inner adrenal medulla Adrenal cortex: produces many cortical hormones Glucocorticoids Breakdown of proteins and lipids to produce glucose. reduce inflammation and immune response. Mineralocorticoids regulate the concentration of mineral ions in the body. Androgens produced at low levels -regulate the growth and activity of cells that are receptive to male hormones (testosterone) Adrenal medulla produces Epinephrine and norepinephrin Under stimulation by the sympathetic division of the autonomic nervous system. Both of these hormones help to increase the flow of blood to the brain and muscles to improve the “fight-or-flight” response to stress. increase heart rate, breathing rate, and blood pressure decreasing the flow of blood to and function of organs that are not involved in responding to emergencies.  Figure 45.21 (a) Short-term stress response (b) Long-term stress response and the adrenal medulla and the adrenal cortex Stress Nerve Hypothalamus Spinal cord signals Releasing (cross section) hormone Nerve cell Anterior pituitary Blood vessel Nerve cell ACTH Adrenal medulla secretes epinephrine and norepinephrine. Adrenal cortex secretes mineralo- Adrenal corticoids and gland glucocorticoids. Kidney Effects of epinephrine and norepinephrine: Effects of Effects of mineralocorticoids: glucocorticoids: Glycogen broken down to glucose; increased blood glucose Retention of sodium Proteins and fats broken Increased blood pressure ions and water by down and converted to kidneys glucose, leading to Increased breathing rate increased blood glucose Increased metabolic rate Increased blood Change in blood flow patterns, leading to volume and blood Partial suppression of increased alertness and decreased digestive, pressure immune system excretory, and reproductive system activity  Effects of stress on a body Stress Nerve Hypothalamus Spinal cord signals (cross section) Releasing hormone Nerve cell Anterior pituitary Blood vessel adrenal medulla Nerve cell secretes epinephrine Adrenal cortex & norepinephrine secretes ACTH mineralocorticoids & glucocorticoids Adrenal gland Kidney (A) SHORT-TERM STRESS RESPONSE (B) LONG-TERM STRESS RESPONSE Effects of epinephrine and norepinephrine: Effects of Effects of mineralocorticoids: glucocorticoids: 1. Glycogen broken down to glucose; increased blood glucose 1. Retention of 1. Proteins & fats broken 2. Increased blood pressure sodium ions & down & converted to 3. Increased breathing rate water by kidneys glucose, leading to 4. Increased metabolic rate increased blood 2. Increased blood 5. Change in blood flow patterns, leading glucose volume & blood to increased alertness & decreased pressure 2. Immune system digestive & kidney activity suppressed Pancreas A large gland located in the abdominal cavity just inferior and posterior to the stomach, is connected to the duodenum. The heterocrine gland -Contains both endocrine and exocrine tissue. The endocrine cells- about 1% of the total mass found in small groups throughout the pancreas called islets of Langerhans. 2 types of cells - α and β cells. α cells produce glucagon responsible for raising blood glucose levels. triggers muscle and liver cells to break down the polysaccharide glycogen to release glucose into the bloodstream. β cells produce insulin responsible for lowering blood glucose triggers the absorption of glucose from the blood into cells, where it is added to glycogen molecules for storage.  Insulin Beta cells of pancreas release insulin into the blood. STIMULUS: Blood glucose level rises (for instance, after eating a carbohydrate-rich meal). Homeostasis: Blood glucose level (70–110 mg/100 mL) Body cells Insulin take up more Beta cells of glucose. pancreas release insulin into the blood. Liver takes up glucose and stores it STIMULUS: as glycogen. Blood glucose level rises Blood glucose level declines. (for instance, after eating a carbohydrate-rich meal). Homeostasis: Blood glucose level (70–110 mg/100 mL) Figure 45.13b-1 Homeostasis: Blood glucose level (70–110 mg/100 mL) STIMULUS: Blood glucose level falls (for instance, after skipping a meal). Alpha cells of pancreas release glucagon into the blood. Glucagon  Homeostasis: Blood glucose level (70–110 mg/100 mL) STIMULUS: Blood glucose Blood glucose level level rises. falls (for instance, after skipping a meal). Alpha cells of pancreas release glucagon into Liver breaks the blood. down glycogen Glucagon and releases glucose into the blood.  Gonads The gonads-ovaries in females and testes in males Responsible for producing the sex hormones Determine secondary sex characteristics of adult females and adult males.  Testes Produce the androgen testosterone Causes growth and increases in strength of the bones and muscles- accelerated growth of long bones during adolescence. During puberty- controls the growth and development of the sex organs and body hair of males, including pubic, chest, and facial hair. In men who have inherited genes for baldness testosterone triggers the onset of androgenic alopecia, commonly known as male pattern baldness. Ovaries Produce the female sex hormones Progesterone and Estrogens Progesterone- most active during ovulation and pregnancy Maintains appropriate conditions in the human body to support a developing fetus. Estrogens- primary female sex hormones. The release of estrogen during puberty triggers the development of female secondary sex characteristics Uterine development, breast development, and the growth of pubic hair. Estrogen also triggers the increased growth of bones during adolescence that lead to adult height and proportions. Thymus The thymus is a soft, triangular-shaped organ found in the chest posterior to the sternum. Produces hormones called thymosins help to train and develop T-lymphocytes during fetal development and childhood. The T-lymphocytes produced in the thymus go on to protect the body from pathogens throughout a person’s entire life. The thymus becomes inactive during puberty and is slowly replaced by adipose tissue throughout a person’s life.  Other Hormone Producing Organs Heart Cardiac muscle produce atrial natriuretic peptide (ANP) in response to high blood pressure levels. ANP reduce blood pressure by triggering vasodilation reduces blood volume and pressure by salt excretion by kidneys  Kidneys produce the hormone erythropoietin (EPO) in response to low oxygen in the blood. EPO released by the kidneys travels to the red bone marrow stimulates an increased production of red blood cells. The number of red blood cells increases the oxygen carrying capacity of the blood, eventually ending the production of EPO.  Digestive System Produce hormones Cholecystokinin (CCK), Secretin, Gastrin All help to regulate the secretion of pancreatic juice, bile, and gastric juice in response to the presence of food in the stomach CCK is also instrumental in the sensation of satiety or “fullness” after eating a meal.  Adipose Produces the hormone leptin involved in management of appetite and energy usage by the body. Leptin is produced at levels relative to the amount of adipose tissue in the body A sufficient level of adipose (energy storage)- level of leptin tells the brain that the body is not starving ( work normally) If the level of adipose or leptin decreases- body enters starvation mode and attempts to conserve energy by increased hunger (food intake) and decreased energy usage. Adipose tissue also produces very low levels of estrogens in both men and women. In obese people the large volume of adipose tissue may lead to abnormal estrogen levels.