Lec: Endocrine System
I. Endocrine Glands are glands without ducts
1. Secrete HORMONES (“ to set in motion ”) into the intercellular spaces and they pass directly into the blood and is then distributed to all parts of the body via they circulatory system.
2. Hormones
a. chemical secretions of the endocrine glands; different types of hormones.
b. Some are proteins others are amines still others are steroid
c. act to maintain homeostasis by altering cellular activity.\
d. effect organ or groups of organs directly (“target organ(s)”)
e. effect other endocrine glands called “target glands”
II. Nervous System vs. Endocrine System
Nervous System Endocrine System
Effects rapid & short-lasting slower & longer lasting
Controls muscles & glands activities of cells:
Both influence
· metabolism; reproduction; stress responses; fluid-electrolyte balance; acid-base balance; energy balance
List of Endocrine GlandsHypothalamus Located below the thalamus in the brain, is the master control center. Makes ADH, OxytocinReleasing and Inhibiting Factors
Pituitary Gland located in the brain, also produces growth hormones and endorphins (the body’s natural painkillers). FSH, LH, ACTH, TSH, HGH, PRL, The release of the pituitary gland hormones is controlled by hormone in the hypothalamus and pituitary glands (FSH and LH). Stores ADH, Oxitosin
Has two lobes (Anterior and Pitutiary)Two lobes of pituitary:
Pineal Gland links environmental light conditions with activities that show daily or seasonal rhythms. It cues reproductive activity and sleep patterns. It secretes malatonin.
Thyroid and Parathyroid regulates development and metabolism: located in the throat. Hormones throxine and calcitonin. Parathyroxin Hormone
Thymus produces the hormone thymosin involved in development of the immune system
Adrenal glands mobilize responses to stress. (located on top of each kidney). It releases epinephrine and norepinephrine, cortisol, aldosterone
Pancreatic hormones manage cellular fuel found near the stomach: involved in digestion, secretion of digestive enzymes, and Insulin (hormone) that lowers the levels of glucose and glucogon that raises the level of glucose by releasing the stores of glycogen.
The gonads (Ovaries and Testes ) secrete sex hormones /Hypothalamus
1. It receives information from the nerves about internal and external conditions.
2. It signals the pituitary gland when to secrete hormones using inhibiting and releasing factors.
i.e. the hormone oxitocin, induces contraction of the uterine muscle is secreted by the pituitary gland and is regulated by releasing hormones.
3. It stimulates the medulla of the adrenal gland
Pituitary Gland has two lobes
Anterior Pituitary Lobe
A. Adrenocorticotropin -- (ACTH)
· promotes growth of the Adrenal Cortex
· stimulates the secretion of Cortical Hormones
· stimulates Fat Catabolism & Glycogenesis
B. Thyriod Stimulating Hormone (TSH) -
· promotes growth of the Thyroid Gland
· stimulates the secretion of the Thyroid Hormone
C. GrowthHormone (GH) – Somatotrophic Hormone (STH) promote enlargement of body parts,
Increases Growth and Maintenance of Organs by:stimulating protein anabolism and promoting fat catabolism (use of fat rather than sugars for energy)
Abnormal Secretions of STH
Giantism -- hypersecretion during childhood ( before epiphyseal plates close). Poor health due to 2o effects on blood sugar.
Acromegaly -- hypersecretion during adulthood; Extremities (feet, hands face) get very large.
Dwarfism -- hyposecretion during childhood
Cachexia (Simmond’s Disease) – hyposecretion during adulthood
causes premature ageing and atrophy of organs
D. Prolactin (PRL) promotes breast development during pregnancy
stimulates mammary glands to produce milk after delivery
E. Gonadotropins – FSH and LH
1. Follicle Stimulating Hormone (FSH)
a. female - stimulates the Ovarian Follicles to Develop and produce ova
- stimulates the Ovarian Follicles to secrete Estrogens
b. male - stimulates the production of sperm
- stimulates the secretion of Testosterone
2. Luteinizing Hormone (LH)
a. female - associated with FSH in development of the Ovarian Follicles
- stimulates development of the Corpus Luteum following ovulation
- stimulates Corpus Luteum to secrete Progestrone
b. male - stimulates the Inerstitial Cells to secrete Testosterone
(also called Interstitial Cell Stimulating Hormone [ICSH])
Posterior lobe releases hormones made by the hypothalamus
a. antidiuretic hormone (ADH) promotes water retention
b. oxitosin (prostate gland in males and uterus and mammary gland in females)
Posterior Pituitary Lobe
1. Antidiuretic Hormone (ADH) - produced in the hypothalamus and collected and
secreted by the posterior lobe
a. increases the permeability of the kidney tubules to water
b. promotes the reabsorption of the water from the urinary filtrate
resulting in a smaller volume of urine
c. Diabetes insipidus - condition resulting in larger volumes of
urine produced - may be treates with vasopressin
2. Oxytocin
a. stimulates powerful contractions of uterus at during delivery
b. causes milk ejection from the lactating breast
III. Thyroid Gland
A. Location - lower aspect of larynx and upper trachea
B. Histology & Physiology
Thyroid Gland Produces two hormones, thyroxine and calcitonin. They function in metabolic homeostasis and in calcium homeostasis.
· Thyroxine controls early development of bone and nerve cells. It maintains normal blood pressure, heart rate, muscle tone and digestive and reproductive functions “metabolic rate”.
· Calcitonin lowers blood Ca+2. Stimulates Osteoblast activityCalcitonin (hormone) affects Ca+2 levels by affecting its distribution in a) bones b) uptake in intestines and c) uptake in kidneys.
· The thyroid also regulates the amount of calcium in cells.
· Calcium is involved in blot clotting, transport of molecules across membranes, muscle contractions and more.
Thyroxine Action –
a. Calorigenic Effects – increases Catabolism and produces extra body heat
b. Growth & Development – Works with STH to produce growth and development of tissues and organs
- Nervous Tissue particularly effected
- hyposecretion results in Mental Retardation
c. Metabolic Effects –
a. diuretic
b. protein and carbohydrate catabolism (stimulates cellular uptake)
c. increases activity of nervous system
d. increases heart rate
e. causes muscular weakness
d. Parafolliclar Cells – secrete Thyrocalcitionin (TCT)
a. decreases excretion of Calcium & Phosphate ions
b. increases Osteoblast activity –[Ca+2 & PO-3 deposition in bone
Disorders of the Thyroid
a. Hyperthyroidism (Grave’s disease)
- increases nervousness and irritability; elevated BMR
- exophthalmos – results in edema behind the eyes
b. Hypothyroidism
Cretinism – occurs if the hyposecretion is during fetal or early developmental life. Results in reduced metabolism, results in reduced growth, results in mental retardation
Myxedema – occurs if the hyposecretion is during adult life
- Results in reduced metabolism, results in mental & physical activity, results in increased blood pressure, results in accumulation of subcutaneous fluids
c. Iodine deficiency: Thyroid gland enlarges, the hormone is not produced.
IV. Parathyroid Glands
Parathyroxin hormone raises blood Ca+2. Stimulates Osteoclast.
A. Location – 4 or 5 small round bodies on the posterior surface of the lateral lobe of the thyroid gland
B. Function – secretes the Parathyroid hormone that controls Blood Calcium homeostasis
1. increases Ca+2 and Mg+2 absorption from the Intestines,
Kidneys and Bones [raises blood calcium levels]
Disorders of parathyroid activity
1. Hyposecretion of PTH leads to Hypocalcemia (blood calcium drops)
- results in Tetany [muscle spasms and convulsions]
2. Hypersecretion of PTH leads to Hypercalcemia
- results kidney stones, osteoporosis
VI. Adrenal Glands: Location - consists as two glands. They sit on the kidneys
B. Adrenal Cortex – secretes the Cortical Hormones during long-term stress.
1. Glucocorticoids produced by cells A. Cortex. Pituitary ACTH stimulates the adrenal gland to secrete glucocorticoids in response to stress.
- elevates blood sugar levels by acceleration of glycogenolysis and glucogenolysis
or conversion of proteins into carbohydrates – resulting in “Tissue Wasting”
- promotes protein and fat catabolism which increases blood sugar
- promotes vasoconstriction to maintains normal blood pressure
- suppresses the bodies Inflammatory response (Remember the anti-inflammatory drug Cortisone, reduces inflammation)
2. Aldosterone is one of many Mineralocorticoids – target the kidney, to promote Na reabsorption . Sodium retention and water retention promote increased blood pressure
When blood pressure it is stimulated by Renin
When blood pressure is high it is inhibited by ANH (atria natriuretic hormone).
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3. Gonadocorticoids – produced by cells of the Zona Reticularis
a. these are the sex hormones that are produced by the adrenal
cortex in small amounts in booth males and females
4. Abnormal Adrenal Cortical Function:
a. Addison’s Disease – caused by Hyposecretion of Cortical hormones
- decreased Na+ retention and dehydration and increased K+
- decreased blood glucose levels therefore decreased stress resistance
- decreased blood pressure
b. Cushing’s syndrome – causes by Hypersecretion of Cortical Hormones
- increases tendency for diabetes mellitus
- obesity, altered carbohydrate & electrolyte metabolism
c. Adrenogenital Syndrome – caused by Hypersecretion of Gonadotropins
- results in premature sexual development in both males and females
- results in masculinization of females
C. Adrenal Medulla Hormones –Epinephrine & Norepinephrine
Epinephrine (adrenalin) and Nor-epinephrine (nor-adrenaline) are for short term stress and are produced during the sympathetic responses. Levels increase during Fight or Flight Response (i.e. stress, fear, anxiety or emergency).
Both of these hormones stimulate
1) Increased blood pressure due to increased heart rate & constriction of blood vessels
2) Increased respiratory rate and dilation of bronchioles
3) Increased blood sugar by stimulation of pancreas: the liver to secrete glucose needed to make energy for fuel
4) Increase cellular metabolism
5) Decreased digestive tract activity
VII. Pancreas– (Islets of Langerhans cells)
Produces the antagonistic hormones Insulin and Glucogon. They regulate blood glucose levels.
1. Insulin – secreted by the Beta Cells; stimulates all body cells to remove glucose from blood. Most glucose is converted to glycogen, by the liver. Glucose in Muscle cells is metabolized into energy, stored fats and proteins (Cellular Respiration)
- promotes lower blood glucose levels by:
- promoting glycogenesis, protein synthesis and lipogenesis
- promoting cellular uptake
2. Glucagon – secreted by the Alpha Cells
- promotes higher blood glucose by promoting glycogenolysis: stimulates the liver to convert glycogen to glucose or fatty acids and amino acids to glucose, when blood glucose levels fall as during a fast or during rigorous exercise.
Disorders of the Pancrease
Diabetes Mellitus: Inability of the body’s cells to take up glucose. Blood sugar is high. symptoms: sugar in urine, high blood glucose, frequent urination, thirsty. Long term effects, cardiovascular disease, kidney failure, nerdestroction and or stroke. Two types:
Type I: Pancrease doesn’t make insulin (could be environmental)
Type II: Diet induced. Cells are said to be insulin resistant.
Hypoglycemia, in contrast, individuals who are produce too much insulin causing blood glucose levels to drop severely below 70mg/100ml. Individuals become weak, hungry, sweating and nervous eventually convulsions may develop. Individuals should eat more frequently.
Gonads
Sex glands make sex hormones (androgen, estrogen and progesterone) supporting egg and sperm formation, maintains male and female secondary characteristics. All three are found in male and female. Females have a higher ratio of estrogen to androgen. Males have a high ratio of androgens (testosterone) to estrogen. The production of these hormones is regulated by the release of FSH and LH by the pituitary gland.
Estrogen stimulates the development and maintenance of female reproductive system and secondary sex characteristics (smaller body size, higher voice, breasts and wider hips). Progestin and Estrogen prepare the uterus to support the developing embryo.