Endocrine System Flashcards

• Hormones send chemical messages from one body part to another to regulate the body, they communicate in order to coordinate the whole body. Regulation allows for daily homeostasis and regulation of large scale changes such as:
• - Solute levels in blood (glucose, ca++, salts, etc.) 
• - metabolism
• - growth and development
• - maturation and reproduction

• 1. The endocrine system:
• - It is a system of ductless glands
• - it secretes chemical signals into the blood
• - chemicals travel to target tissues with receptors
• - have a slow, long lasting response
• 2. The nervous system:
• - It utilizes neurons
• - Transmits "electrical" signals and releases neurotransmitters to target tissue
• - have a fast, short-lasting response

Neurotransmitters are release by neurons, hormones are released by endocrine glands. Prostoglandins are hormones that have a localized effect only.

• 1. Lipid based hormones (also called steroids, (oids=steroids):
• These hormones are hydrophobic & lipid-soluble, they diffuse across cell membrane and enter cells. They bind to DNA as transcription factors (turn on genes (transcription and translation)). They need an off hormone to turn off (antagonistic),
• 2. Protein-based hormones
• They are hydrophilic & not lipid soluble and cannot difuse across cell membranes. Instead they bind to receptor proteins in the cell membrane and either pass through these channels and enter or initiate a seconday messenger pathway (receptors relay the messages). These hormones activate internal cellular responses (enzyme action, uptake or secretion of molecules) and dissolce over time (turned off by time).

• 1. The hypothalamus which is the "master nerve control center." It receives information from nerves around the body about inernal/external conditions and sends messages to the medulla oblangata (ANS control), this is part of the nervous system it is linked too. The hypothalamus also regulates the release of hormones from pituitary, where it is linked to the endocrine system.
• 2. The pituitary gland (master gland) controls the endocrine system and secretes a broad range of "tropic" hormones regulating other glands in the body.

Tropic means a hormone that stimulates glands to make (targets endocrine glands). Non-tropic are hormones that regulate other glands in the body.

• In negative feedback loops too much of something will cause a gland to secrete a hormone that lowers body condition, while too little will cause a gland to secrete a hormone that raises body condition. 
• With body temperature if temp. is high the hypothalamus detects it and sends nerve signals that cause sweat glands to sweat and surface blood vessels to dilate if it is too low the hypothalamus will send a nerve signals to shiver and constrict surface blood vessels.

In regulating metabolism the hypothalamus will secrete TRH (TSH-releasing hormone) which is tropic. TRH will cause the anterior pituitary to release TSH (Thyroid stimulating hormone), also tropic. Which will cause the thyroid to produce thyroxine hormones if there is too much thyroxine receptors in the hypothalamus fill up and turn the production of TRH off stopping the entire loop, too much TSH will also have the same effect.

• Thyroxine hormones perform metabolism and development. This includes bone growth, mental development, metabolic use of energy, blood pressure and heart rate, muscle tone, digestion and reproduction.
• A goiter is caused when an iodine deficieny causes the thyroid to enlarge as it attempts to produce thyroxine hormones but cannot as iodine is a key element in producing them. Iodine is gotten from vegetables and iodized salt. The solution to goiters is eating more iodine or thyroxine injections.

The endocrine system controls calcium levels in the blood via a negative feedback loop. If blood calcium level is too high then the thyroid will create calcitonin too cause the kidney to reabsorb less ca2+ (pee it out) and cause it to be stored in bones. If calcium levels are too low, the parathyroid will secrete parathyroid hormone (PTH) which will cause the kidneys to reabsorb more ca2+, the bones to release ca2+ and cause increased ca2+ uptake in the intestines. The base level for calcium in blood is 10mg/100mL

• Thyroid:
• Thyroxine - Increases Metabolism in the Body
• Calcitonin - Decreases calcium levels in blood by making bones store calcium and the kidneys excrete calcium
• Parathyroid:
• PTH (parathyroid hormone) - Causes bones to release calcium and kidneys and intestines to absorb calcium in order to increase blood calcium levels

• Posterior pituitary (stores hormones): 
• Antidiruretic hormone (ADH) - increases water absorption (less urine, up in BP) in kidneys
• Oxytocin - causes the uterus to flex and the mammary glands to release milk

• Anterior pituitary (Master gland):
• human growth hormone (hGH) - causes body to grow
• Thyroid stimulating hormone (TSH) - causes thyroid to create thyroxine
• Adrenocorticotropic hormone (ACTH) - causes the adrenal cortex to make more cortisol, aldosterone and sex hormones 
• Prolactin (PRL) - caises mammary glands to make more milk
• Follicle stimulating hormone (FSH) - causes the gonads to create there respective sex cells (Sperm and eggs)
• Leutenizing hormone (LH) - causes the testes to create more testosterone in males and ovaries to make more estrogen, ovulate and cause corpus luteum formation in females

• Hypothalamus:
• It makes various tropic hormones that target the pituitary + ADH + OCT,

First both begin by having the Hypothalamus stimulate m.o. to stimulate a sympathetic nerve, which passes through the spinal cord and stimulates the Adrenal Medulla. The Adrenal Medulla secretes Epinephrine and norepinephrine (fight or flight). These hormones cause short term stress and the effects are: 1. glycogen being broken down into glucose which causes increased blood glucose, 2. increased blood pressure, 3. increased breathing rate, 4. increased metabolic rate, 5. Change in blood flow patterns, leading to increased alertness & decreased digestive and kidney activity. Short term stress is activated via nerve to make the effect short lasting and response quick.

• Stress causes the hypothalamus to secrete hormones that stimulate the anterior pituitary to make ACTH (adrenocorticotropic hormone), which causes the adrenal cortex of the adrenal gland to make Cortisol, Aldosterone and sex hormones (testosterone & estrogen). 
• Mineralocorticoids cause increased retention of water and salt in the kidneys leading to increased blood volume and pressure.
• Glucocorticoids cause proteins & fats to be brokens down and converted into glucose, leading to increased blood glucose. And they the cause immune system to be supressed.

• If blood osmolarity is high osmoreceptors in the hypothalamus will detect it and stimulate the posterior pituitary to release ADH, which leads to increased water reabsorption in the nephron and increased thirst allowing blood to become fluid and easier to pump. 
• If blood pressure is too low the adrenal gland (cortex) will make aldosterone causing increased water and salt reabsorption to raise blood pressure.

• If there is too much blood sugar the islets of langerhans beta cells on the pancreas to make insulin which will cause body cells to use up sugar, the liver to store glycogen and adipose tissue to make fat.
• If blood sugar level is low the islets of langerhans alpha cells will make glucagon which will first cause the liver to release glucose and once that is used up, cause the adipose tissue to turn fats into sugars.

• Diabetes insipidus is ADH hyposecretion causing increased urine volume and dehydration. Addisons disease is aldosterone hyposecretion causing increased salty urine production also causing dehydration.
• Diabete mellitus is insulin hyposecretion or hyperglycemia. It causes sugary urine and fatigue. Type 1 is called juvenile (genetic) and is caused by the pancrease being unable to make enough insulin. Type 2 is adult onset (caused by diet + genetics) it is caused when cells become resistant to insulin. The treatments are insulins pumps or injections or islet transplantation in liver.

It begins after menstruation after the hypothalamus makes GnRH which stimulates the pituitary to make FSH (follicle stimulating hormone) and LH (leutinizing hormone). These hormones cause the ovary to make estrogen. Estrogen promotes to growth of the endometrium (uterus lining) and causes the egg to mature and be released (ovulation). The corpus luteum will then make proegsterone which maintains uterus lining and inhibits uterus contraction. Then we reach a checkpoint if you are not pregnant, the corpus luteum breaks down, progesterone level drops and menstruation begins again. If you are pregnant a zygote will form and hcg will cause the corpus luteum to make progesterone to maintain the uterus lining.

Testes make testosterone which causes the testes to perform the primary goal of repoduction, make sperm and grow secondary sex traits in the body. The ovaries make estrogen which promotes endometrium growth and causes secondary sex traits to form in the body, and they also make progesterone which is made during pregnancy and  maintains the endometrium and inhibits uterus contraction.