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Chapter 9 Endocrine system – cells, tissues, or organs that secrete hormones
Hormone – substance that stimulates changes in cells and regulate metabolic processes
Hormones are target specific, meaning the target cells have specific receptors that bind to specific hormones.Functions of hormones:
A. control chemical reactionsB. regulate water and electrolytes
C. regulate growth and reproductionD. aid in transport of substances into/out of cellE. defend against stressorsF. regulate energy and metabolism
Types of hormones:A. Local – not considered to be ‘true’ hormones because
they are released and act locally, but they have functions similar to hormones:
Paracrine – affect neighboring cellsAutocrine – affect only secretory cells
Prostaglandins are lipid-based local hormones. Prostaglandins are released due to local irritation or by actions of other hormones. Effects:
A. relax smooth muscles in blood vessels and lungs
B. cause smooth muscle contractions in uterus and small intestines
C. inhibit stomach excretion of HCl D. affect movement of sodium water in kidneysE. induce inflammation, fever, painF. enhance blood clotting
B. Steroid derived hormones – contain rings of carbon and hydrogen atoms, are insoluble in water and soluble
in lipids, can easily diffuse across the membrane, and are transported through the membrane.
Actions:1. hormone diffuses through cell membrane2. hormone forms a complex protein, which activates the 3. DNA to start protein synthesis4. Transcription and translation forms proteins, which
carries out the effects of the hormone
C. Amines, peptides, and protein derived hormones.
Actions:1. hormone binds with a receptor on cell membrane2. biochemical changes occur within the cell (known as
the first messenger)3. chemicals respond to the first messenger (known as
second messenger) stimulate the formation of cAMP (cyclic adenosine monophosphate)
4. cAMP activates proteins in the cell that carry out hormone’s effects
Hormones are continuously broken down in the liver and excreted in the urine. Hormones are controlled by three different negative feedback mechanisms:
1. Hypothalamus control –monitors blood hormone concentrations and stimulates release of hormones from other organs.
2. Nervous system – directly stimulates release of hormone via SNS
3. Endocrine glands – directly respond to changes in blood composition
Endocrine Glands are glands that release hormones1. Pituitary – part of hypothalamus – made of two parts:
a. anterior lobeb. posterior lobe
Anterior lobe secretes hormones controlled by releasing hormones of the hypothalamus.
Hormones of anterior lobeA. Somatotropin (growth hormone) effects:
1. ↑ in cell size, ↑ cell division2. ↑ speed of cell’s use of fats and carbohydrates3. ↑ movement of amino acids into cells
Hypersecretion leads to gigantism in children, acomegaly in adults of hands, feet, and face
Hyposecretion leads to dwarfism in children (normal body proportions and mental abilities)
Jyoti Amge - Nagpur, India, Friday, Dec. 16, 2011. Amge, 18, was declared shortest woman in the world measuring 62.8 centimeters (24.7 inches) by the Guinness World Records. (AP Photo/Manish Swarup)
B. Prolactin – stimulates production of milk after birth
Hypersecretion leads to galactorrhea, cessation of menstrual cycle, impotence in males
Hyposecretion leads poor milk production
C. Thyroid stimulating hormone (TSH) – controls secretions of the thyroid gland
D. Andrenocorticotropic hormone (ACTH) – regulates hormones released from adrenal gland
E. Follicular stimulating hormone (FSH) regulates the production of sex hormones
Females – causes follicles to mature and stimulate estrogen production
Males - ↑ testosterone production
F. Luteinizing hormone (LH) regulates the production of sex hormones
Females – triggers ovulation and production of progesterone
Males – ↑ testosterone production
Posterior lobe hormones – release is controlled by nerve impulses from the brain. Types of posterior hormones:
A. Antidiuretic hormone (ADH) – regulated by osmoreceptors (detect changes in body fluid pressure) located in brain
When there is an increase in dissolved solutes and a decrease in water (ex: dehydration), the brain stimulates the posterior pituitary to release ADH. ADH is also released in response to pain, low blood pressure, and sever hemorrhage.
ADH – released into bloodstream, travels to kidneys, causes kidney to ↓ urine output
Hyposecretion leads to diabetes insipidus and causes increased urine output and thirst.
B. Oxytocin is released in response to stretching of the uterus and nursing.Effects:1. ↑ uterine contractions during childbirth2. ↑ release of milk after childbirth
2. Thyroid gland is located inferior to the larynx. There are two lobes, one on either side of the trachea, and are connected by an isthmus. There are two types of secretory cells:
1. follicular 2. Parafollicular
Hormones of follicular cells:A. thyroxine – T4 – most abundant – contains 4 iodine
atomsB. triiodothyronine – T3 – formed from conversion of T4
TSH controls the release of thyroxin and triiodothyronine.
Effects (same for both hormones):1. regulate metabolism2. determines BMR – basal metabolic rate3. stimulate breakdown and metabolism of lipids4. ↑ rate of protein synthesis
Hypersecretion – Graves disease – due to autoimmunity against the thyroid gland. The symptoms of Graves disease are: increased metabolic rate, excessive perspiration, irregular heart beat and nervousness, weight loss, and exophtalamos (protruding eyeballs).
GOITER
Exophtalamos – Graves disease
Hypothyroidism occurs when there is not enough thyroxine in the blood stream. This can be due to:
A. lack of iodine in diet (goiter –inflammation of thyroid)
B. defective thyroid glandC. problems with release of TSH
Cretinism – in children – will result in cretin dwarf. The children will have short and disproportioned bodies and mental deficiencies.
Myxedema – in adults – decreases metabolic rate, produces dry and thick skin, puffy eyes, edema (retention of body fluids), feeling of being chilled, and weight gain.
Hormone of parafollicular cells - calcitonin
Calcitonin is released in response to an increase in blood calcium level (hypercalcemia).
Calcitonin – made by parafollicular, released with ↑ calcium (hypercalcium)
↑ kidney excretion of Ca+2 and PO4-3 ions, inhibits osteoclasts from reabsorbing bone, ↓ absorption of calcium from intestinal tract
Parathyroid glands are four glands on the posterior surface of the thyroid gland. It secretes parathyroid hormone (PTH) in response to a decrease in blood calcium level (hypocalcemia).
PTH causes kidneys to conserve water, enhance absorption of calcium from intestine, and activate osteoclasts to breakdown bone and release calcium
Adrenal glands are located atop of each kidney. They are made of two portions:
Adrenal cortex, adrenal medulla
The secretion of the hormones of the adrenal gland is regulated by the sympathetic nervous system.
Adrenal medulla releases epinephrine
Effects of epinephrine:A. ↑ breathing rateB. ↑ heart rate, blood pressure, force of heart contractionC. ↑ release of glucose into bloodD. ↓ digestive motility
Adrenal cortex releases aldosterone, cortisol, and androgens
Aldosterone helps regulate concentration of mineral electrolytes (Na+, K+, Cl-, etc.), which affects blood pressure and volume. Aldosterone is regulated by a decrease in blood pressure and the concentration of sodium and potassium ions in the blood. Aldosterone causes the kidneys to conserve sodium and potassium ions. This causes an increase in water re-absorption, which increases the volume of blood. An increase in blood volume will increase blood pressure.
Cortisol affects glucose metabolism. It is released between meals or hypsecreted during stressful situations. Effects:
1. inbibit protein synthesis2. promote release of fatty acids, ↑ usage of fat for cell
energy3. stimulates liver cells to synthesize glucose from
amino acids and fats, ↑ blood glucose level
Excess cortisol may lead to: high blood pressure, atherosclerosis, depressed immune system, ulcers
Hypersecretion causes Cushings disease. - tissues retain water (edema), hyperglycemia, loss of muscle and bone proteins, hypertension
Hyposecretion causes Addison’s disease – severe dehydration, hypotension, weight loss, decrease glucose level
Androgens are sex hormones that stimulate the development of reproductive organs. The production declines after puberty. After menopause, women convert these hormones into estrogen to help maintain reactions associated with estrogen.
5. Pancreas is posterior to the stomach and has ducts that lead into the small intestines. Islets of
Langerhans produce glucagons (from alpha cells) and insulin (from beta cells).
Pancreatic hormones:Insulin is released when blood glucose level is
elevated. Insulin decreases blood glucose by:1. promoting cell uptake of glucose 2. inhibit conversion of protein and fats into glucose3. stimulate liver to store glucose as glycogen4. promote transfer of amino acids into cells5. increase protein synthesis
Glucagon is released when the blood glucose level drops. Glucose increases blood glucose level by:
1. stimulate liver to convert glycogen into glucose2. promote proteins and lipids to form glucose
Diabetes mellitus is due to a deficiency of insulin; the blood glucose level increases (hyperglycemia). Effects:
1. ↑ glycogen formation2. excrete excess glucose into urine (glycosuria)3. abnormal water excretion by kidney4. dehydration and extreme thirst (polydispia)5. ↓ protein and fat synthesis6. proteins and fats used for energy
7. ketones released when fats used for energy – disrupts blood pH – may lead to coma8. muscles atrophy as proteins used for energy9. excess hunger and food consumption (polyphagia)10. long term: retinal disease, coronary artery disease,
nerve damage
Types of diabetes:1. Type I – autoimmune disease against the beta cells of
the islets of Langerhans – usually affects children. Since insulin is not produced, the affected individual must monitor blood glucose levels on a daily basis and take insulin injections.
2. Type II – most common and will develop milder symptoms. Insulin is produced but cells are sensitized to insulin. Fat cells produce a hormone that blocks the uptake of glucose by cells. Exercise, weight loss, and a decrease in foods with high sugar content will help control Type II diabetes.
Hypoglycemia occurs when the blood sugar level falls to dangerously low levels. The effects are:a. disorientation – lack of glucose to brainb. convulsionsc. unconsciousnessd. death - extreme
6. Pineal gland is located in the epithalamus. It releases melatonin, which helps to regulate the sleep-wake cycle.
7. Thymus gland is located between the lungs (superiorly) and secretes thymosin and thymopoietin. These
two hormones cause T-cells to mature. In adults, the thymus gland is replaced by fat.
8. Reproductive glands:a. Females – ovaries produce estrogen and
progesteroneb. Males – testes release testosterone
9. Miscellaneous hormones
a. ANP – atrial natriuretic peptide – stimulates kidneys to increase urine production
and decrease blood pressureb. gastrin – stimulate HCl release by stomachc. erythropoietin – stimulate RBC production by kidneys
Goiter
Hyperthyroidism – Graves disease
Myxedema – before and after treatment
gigantism
cretinism
Pituitary dwarfism – 17 years old
Cushing’s Disease
