The Endocrine System Endocrine system Comprised of ductless glands that secrete hormones into the blood stream Hormones travel through circulation until they reach their target cell Results in a slow but a prolonged response Exocrine glands have ducts and secrete a substance onto the surface of the skin or into a cavity Major glands of the endocrine system 1 Anterior pituitary gland 2 Posterior pituitary gland 3 Thyroid gland 4 Parathyroid glands 5 Adrenal glands 6 Pancreas 7 Testes 8 Ovaries 9 Thymus gland 10 Pineal gland The Pituitary Located beneath the hypothalamus which helps to regulate its functioning Divided into the anterior and posterior pituitary The two components operate in different ways Anterior pituitary gland Controlled by hypothalamic releasing and hypothalalmic inhibiting hormones Hormones produced by the anterior pituitary 1 Thyroid stimulating hormone TSH stimulates the thyroid to produce thyroid hormones 2 Adrenocorticotropic hormone ACTH stimulates the adrenal cortex to produce cortisol 3 Gonadotropic hormones stimulate gonads to produce sex cells and hormones 4 Prolactin PRL stimulates mammary glands to develop and produce milk only after childbirth 5 Growth hormone GH promotes skeletal and muscular growth What happens when the body produces too much or too little GH Pituitary dwarfism too little GH is produced during childhood results in small stature Giagantism too much GH is produced during childhood results in excessive growth Acromegaly overproduction of GH as an adult that results in larger than normal feet hands and face Posterior pituitary gland Neurons in the hypothalamus have axons that extend down into the posterior pituitary the synaptic knobs of these neurons release hormones directly into circulation Antidiuretic hormone ADH released in response to dehydration Decreases urine production Oxytocin stimulates uterine contractions during childbirth and promotes milk let down plays a role in ejaculation in males Thyroid gland A large gland located below the larynx Iodine is needed in the diet to allow the thyroid gland to produce the hormones Tetraiodothyronin and thyroxine T3 T4 regulates metabolism The thyroid also secretes calcitonin helps lower blood Ca2 levels by stimulating the deposition of calcium in the bones What if someone lacks iodine in their diet Can they still produce T3 and T4 TSH continues to stimulate the thyroid to secrete T3 and T4 Forms a goiter Hyposecretion of T3 and T4 Hypothyroidism low blood levels of thyroid hormones A Congenital hypothyroidism thyroid does not develop properly and is characterized in a short stocky person that may be mentally retarded B Myxedema hypothyroidism in adults characterized by lethargy weight gain loss of hair cold intolerant and thick puffy skin Hyperthyroidism excess thyroid hormones in the blood A Graves disease characterized by enlargement of the thyroid gland protrusion of the eyes increased heart rate weight loss and insomnia B Thyroid tumor can also cause hyperthyroidism Parathyroid glands Small glands embedded in the surface of the thyroid gland Produces parathyroid hormone PTH Acts to increase blood Ca2 levels by promoting osteoclast activity Promotes reabsorption of Ca2 by the kidneys Adrenal glands Located on top of the kidneys 2 parts to each gland Adrenal medulla Inner portion of the adrenal glands Epinephrine adrenaline Norepinephrine Adrenal medulla controlled by the sympathetic nervous system Adrenal cortex portions are controlled by ACTH from the anterior pituitary Hypothalamus initiates stimulation of hormone secretion in the adrenal medulla Produces hormones that allow a short term response to stress fight or flight response Adrenal cortex Outer portion of the adrenal glands Produces hormones that provide a long term response to stress 2 major hormones Mineralcorticoids Aldosterone secreted in response to low blood volume targets the kidney increases sodium reabsorption Glucocorticoids Cortisol increases blood glucose levels how Promotes the break down of protein and fats and gluconeogenesis suppresses the body s inflammatory response inhibits the functioning of the WBCs Hyposecretion of glucocorticoids Addison s disease hyposecretion of glucocorticoids and aldosterone by the adrenal cortex Characterized by bronzing of the skin Hypoglycemia and dehydration are common symptoms Hypersecretion of glucocorticoids Cushing syndrome hypersecretion of cortisol by the adrenal cortex characterized by weight gain in the trunk of the body but not arms and legs Pancreas Located behind the stomach Composed of 2 tissues Exocrine produces and secretes digestive juices Endocrine produces and secretes hormones Alpha cells produce and secrete glucagon Beta cells produce and secrete insulin Actions of glucagon Glucagon is secreted in response to low blood glucose levels Acts to return blood glucose levels to normal How Promotes the break down of triglycerides and proteins Promotes gluconeogenesis and glycogenolysis Actions of insulin Insulin is secreted in response to high blood glucose levels Acts to return blood glucose levels to normal How Promotes glucose uptake by cells of the body Promotes the synthesis of glycogen and triglycerides Diabetes Amellitus Inability to control blood glucose levels There are two types Type 1 and Type 2 18 million people in the US have diabetes General symptoms Frequent urination Unusual hunger and or thirst Unexplained change in weight Blurred vision Sores that heal slowly or not at all Excessive fatigue Long term effects are blindness loss of limbs nerve deterioration kidney and cardiovascular disease Diabetes Understanding the 2 types Type 1 Usually early onset Autoimmune disorder Beta cells are under attack and cannot produce insulin Need insulin injections Type 2 Usually adult onset and most common type Tends to occur in obese sedentary people Cells do not respond to insulin Testes Gonads found in males Usually diet and exercise are important for controlling this and may even prevent this Produce androgens ex testosterone T Stimulates growth of the penis and testes Responsible for secondary sex characteristics such as facial underarm and pubic hair Prompts the larynx and vocal cords to enlarge resulting in a lower voice Promotes muscular strength Ovaries Gonads found in females Produce estrogen E and progesterone Stimulates growth of the vagina and uterus Responsible for egg maturation Regulates the menstrual cycle Thymus gland Lies beneath the sternum
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