14 The Endocrine System 3.3 Flashcards
The endocrine system
Composed of ductless glands scattered thoughout the body. Their function is to produce hormones -Adrenal glands -gonads -pancreas -pineal glands -pituitary glands -Thyroid glands -parathryoid glands None of these glands are connected to each other
Hormone
(Gr) ‘impulse’, ‘Urge on’
One of their jobs is to stimulate ‘target’ cells to react in specific ways. They act as messengers to control cell metabolic rate, and regulate body fluid homeostasis.
Endocrine gland regulation systems
- positive feedback
- negative feedback
Positive Feedback
A system is activated by a stimulus. ie, a baby sucking stimulates the release of prolactin, stimulating the mammary glands.
Negative feedback
A system by which the endocrine system keeps the other system in balance. If there’s too much stimulus, the gland stops or slows production; if there’s too little stimulus, the gland increases production
Hormones controlled by the nervous system
ie, adrenaline, which is released in response to outside stimuli, such as being startled or perceiving danger.
Thyroid gland
The largest of the endocrine glands is located in the front and sides of the neck and has two lobes on either side of the trachea. Hormones:
- Thyroxine (T3) and trilodothyronine (T4) regulate metabolism in body cells
- Calcitonin stimulates the passage of calcium from the blood into the bones
T3 and T4
In the bloodstream they enable the body’s cells to consume oxygen at an increased rate, which allows the cells to use carbohydrates and break down proteins
Calcitonin (thyrocalcitonin)
Important in calcium metabolism, prevents calcium loss in the bones, lowering the amount of calcium in the blood stream. Also helps let you know when you’ve had enough to eat
Pancreas
- Located behind the stomache, it serves as an accessory digestive organ by secreting pancreatic juices which contain enzymes to digest carbohydrates, proteins, and fats
- It’s surface has clusters of microscopic cells, call the pancreatic Isles, or the Isles of Langerhan, which secrete insulin and glucagon
Insulin
Helps push glucose from our blood into our cells, which decreases blood sugar levels, and effects the way our bodies use carbohydrates, proteins, and lipids for energy.
Glucagon
Glucose is stored in the liver as glycogen. Glucagon speeds up it’s conversion to glucose, which increases the blood sugar level.
Adrenal (Suprarenal glands)
Called Suprarenal because they’re located on top of the kidney
- Cortex
- Medula
Adrenal Cortex
Helps regulate the body’s metabolism and stress responses by releasing 3 types of steroid hormones (corticosteroids)
- Cortisol (glucocorticoid) regulates the quantities of sugars, fats, and proteins in cells
- Aldosterone (mineralocorticoid) regulates the amount of salt in the body
- Estrogen and testosterone (gonadocorticoids) maintain secondary sex characteristics
Glucocorticoids
Have an anti immune/allergy effect. Given to patients to stop the body’s natural defense to allergens or irritants
- Cortisone (hydrocortisone)
- Cortisol
Cortisol
The principal steroid
- Regulates carbohydrate, protein, and fat metabolism
- Stimulates gluconeogenesis in the liver
- Increases blood sugar concentration
Gluconeogenesis
Conversion of amino and fatty acids to glucose
Androgens
- Male sex hormones, testosterone
- Small amounts are produced by the adrenal glands, which have negligible effects on the male sex drive compared to the amounts produced by the kidneys, but they are responsible for the female sex drive
Catecholamines
Hormones that help the nervous system handle any type of alarm or danger to the body
Adrenal Medula (Emergency gland)
Called the emergency gland because it releases two types of catecholamine
- Epinephrine (adrenaline),
- norepinephrine (noradrenaline)
Parathyroid
Embedded in the tissue that holds the thyroid in place. Parathyroid hormone (PTH) increases the level of calcium in the blood. Each PTH effect is balanced by an opposite effect from calcitonin, allowing the body to maintain healthy calcium levels
Epinephrine
It’s presence in the blood stream gives the body an extra burst of energy and strength by
-Increasing heart rate, blood pressure, and cardiac output
-Dilating the bronchial tubules to increase oxygen intake
-Elevating the blood sugar level
It’s Effects of the bronchial tubules make it an effective treatment for severe asthma attacks and anaphylactic shock
Norepinephrine
Reinforces the effects of epinephrine by
-dilating vessels to the brain, muscles, and heart
-constricting vessels to organs non-essential in an emergency reaction
-Acting as a neurotransmitter to heighten the ability to think quickly and clearly in an emergency
It’s vessel restricting properties are why wounds don’t bleed as profusely with adrenaline in the system and why the blood drains from your face when your angry or scared
Pituitary gland (Master Gland)
- Located in the skull, between the nasal cavity and the brain, below the hypothalamus, in a pocket of bone known as the sella turcica
- Controls hormone secretions from other glands -
Hypothalamus
The part of the brain that signals the pituitary to secrete hormones
Pituitary anterior lobe (adenohypophysis)
- Luteinizing hormone (LH) promotes ovulation
- Prolactin (PRL) promotes growth of breast tissue and milk secretion
- Growth hormone (GH, somalotropin )Stimulates the growth of bones, muscles and many other organs
- Melanocyte stimulating hormone (MSH) increases pigmentation of the skin
- Gonadotropin s ( FSH, follicle-stimulating hormone) stimulates growth of eggs and ovarian hormone secretion
- Adrenocoticotropic hormone (ACTH) stimulates secretion of hormones from the adrenal cortex, especially cortisol.
- Thyroid stimulating hormone (TSH) stimulates production of thyroxine and growth of the thyroid gland
Pituitary posterior lobe (neurohypophysis)
- Antidiuretic hormone (ADH, vasopressin) stimulates reabsorption of water by kidney tubules
- Oxytocin stimulates contraction of the uterus during labor and childbirth
Testes
Testosterone promotes growth and maintenance of secondary sex characteristics in the male
Ovaries
- Estradiol develops and maintains secondary sex characteristics in the female
- Progesterone prepares and maintains the uterus in pregnancy
