Unit 2 Enodcrine-Thyroid, Parathyroid, Pancreas, Pineal, Thymus Flashcards
Where is the Thyroid Gland located, and what shape is it?
Located in the anterior portion of the neck; butterfly-shaped
What does the Thyroid gland secrete and where does it get the orders from?
The thyroid gland secretes T3 and T4 under orders from the pituitary gland.
What are T3 and T4 called?
Thyroid hormones
Except T3 and T4, what does the thyroid gland secrete?
It secretes calcitonin, which is involved in calcium storage.
What does T3 and T4 contain?
Iodine (body does not produce iodine)
What does T3 and T4 control?
They control metabolism and growth
what does over or under-production of T3 and T4 cause?
They cause a variety of clinical symptoms because the level of these hormones is essential in controlling the growth and metabolism of body tissue, particularly in the nervous system.
What outside source from the body contains iodine, and why do we need to consume iodine?
Table salt contains iodine to ensure people get enough iodine in their diets to make thyroid hormones.
What does the thyroid control?
Control metabolism, growth, and many other bodily functions.
What are the main hormones of the Thyroid Gland?
T3 and T4
What is essential for T3 and T4, and where is it absorbed by?
Iodine is essential for T3 and T4 and is absorbed by the small intestine.
What is the thyroid hormone?
It is the body’s major metabolic hormone meaning it is dealing with the production of energy.
What are the two forms of the thyroid hormone?
T3 and T4
Mott: We just need to know that T4 has iodine.
How many iodine atoms does T3 have, and what does it must be converted to?
Three iodine atoms and must be converted to T4 at tissue level.
What is thyroid hormone release regulated by?
TH release is regulated by negative feedback loop.
What does Falling TH levels stimulate?
Stimulates the release of thyroid-stimulating hormone.
What do rising TH levels provide?
Rising TH levels provide negative feedback inhibition on TSH.
Where is Thyroid stimulating hormones?
Anterior Pituitary
What can TSH also be inhibited by?
TSH can also be inhibited by GHIH, dopamine, and increased levels of cortisol and iodine.
What does the Hypothalmaus do?
The hypothalamus is doing thyrotropin-releasing hormone
What can the Hypothalamic thyrotropin-releasing hormone (TRH) do?
It can overcome negative feedback during pregnancy or exposure to cold, especially in infants, so it helps us upregulate our thyroid hormones.
Mott: So, in pregnancy, we need some higher levels of thyroid hormones. The hypothalamus can come down say actually, we need to override this, we need to play this up, we need to shut down the negative feedback loop. ASK CAMILE
Steps of Thyroid Synthesis (1): What is the Synthesis of Thyroglobulin?
Thyroglobulin does not contain any iodine, and it is a precursor protein.
Steps of Thyroid Synthesis (2): What is the iodine uptake?
We don’t have any Iodine yet, so iodine enters the thyroid from the bloodstream through active transport.
Steps of Thyroid Synthesis (3): What is the Iodination of thyroglobulin?
We need to iodize it. We need to latch the iodine on.
Steps of Thyroid Synthesis (4): What is the storage?
Thyroid hormones are bound to thyroglobulin for storage
Steps of Thyroid Synthesis (5): how many percent is T3 and T4 that are released?
T3: 20%
T4: 80%
Mott: So what we need to know. We have a precursor that does not have iodine on it. We pull in some iodine and bind the iodines on it. And where we are ready for releasing it, T4 is 80%, and T3 is 20%. If we need to go back, T3 is what needs to be ASK CAMILE
How are the thyroid hormones going to impact the body? (heart)
Increase heart rate
Increase stroke volume
Increase cardiac output and contractility.
How are the thyroid hormones going to impact the body? (lungs)
Thyroid hormones stimulate the respiratory centers and lead to increased oxygenation because of increased perfusion.
Perfusion: Perfusion refers to the flow of blood through the body’s tissues and organs, delivering oxygen and nutrients while removing waste products.
How are the thyroid hormones going to impact the body? (Skeletal muscles)
Thyroid hormones cause increased development of type II muscle fibers.
Type II: sprinters
How are the thyroid hormones going to impact the body? (Metabolism)
Thyroid hormone increases the basal metabolic rate.
Thyroid hormones do not change the blood glucose level, but they can cause increased glucose reabsorption, gluconeogenesis, glycogen synthesis, and glucose oxidation.
How are the thyroid hormones going to impact the body? (Growth during childhood)
In children, thyroid hormones act synergistically with growth hormones to stimulate bone growth.
Thyroid hormone also helps with brain maturation by axonal growth and the formation of the myelin sheath.
Mott: This is why having an adequate intake of iodine is so important.
What is Hyperthyroidism?
Disorders of the thyroid gland can result in excess T3 and T4 production
How many types of Hypothyroidism do we have?
3
Primary, Secondary, Tertiary
What is Primary hypothyroidism?
Decreased production of thyroid hormones by the thyroid gland causes a compensatory increase of TSH
There are going to be some questions on this because it is related to the feedback loop. Why, if we’re saying thyroid hormone damaged at the level, why would we see an increase in TSH?
So if we have still have a damage at the thyroid, pituitary gland is still working. Pituitary gland is saying hey there’s not enough level of thyroid hormone, I need to release some TSH. And then it gets the feedback blood comes past again and it says wow that wasn’t enough TSH, it still didn’t release. Im gonna need to release more. It’s not giving any feedback of the thyroid’s damages, it is only getting the feedback of howmuch thyroid hormone is in the blood. So it’s going to be releasing TSH. So we’re going to end up with a high level of TSH.
What is Secondary hypothyroidism caused by?
By pituiary disorders causing decreased TSH release and decreased T3/T4 levels.
The thyroid gland has two small pairs of glands, what are they called?
Parathyroid glands, embedded in its posterior surface.
What do the Parathyroid glands produce?
They produce Parathyroid Hormone (PTH)
What does PTH do?
It regulates the levels of calcium in the blood stream.
What happens to the parathyroid glands when the calcium levels get too low?
If calcium levels get too low, the parathyroid glands are stimulated to release PTH, which stimulates bone-dissolving cells and releases calcium into the bloodstream.
Bone dissolving cells: osteoclasts
What does the parathyroid have and where is it located?
Parathyroid has four small glands in the posterior side of the thyroid gland.
What is the main function of Parathyroid
Main function is the production and secretion of parathyroid hormone.
What provides negative feedback to the parathyroid hormone?
Both Calcium and vitamin D
What happens as levels of calcium and vitamin D increase? (negative feedback loop of PTH)
They bind receptors at the parathyroid glands and inhibit the production and release of PTH.
What is the function of the Parathyroid?
Stimulate osteoclasts to digest bone matrix and release calcium to blood.
What is the function of the Parathyroid? (2)
Enhances reabsorption of calcium and secretion of phosphate by kidneys.
What is the function of the Parathyroid? (3)
Promotes activation of vitamin D by kidneys, which leads to increased absorption of calcium by intestinal mucosa.
Parathyroid systematic effects on the skeletal system.
PTH works at the cellular level by INDIRECTLY stimulating osteoclasts to break down bone.
GONNA BE ON THE EXAM
Mott: Paradoxical: is what we don’t expect.
So it’s paradoxical that we indirectly stimulate. (GONNA BE ON THE EXAM)
What is the net effect of the Parathyroid on the skeletal system?
Increased osteoclast activity increases calcium resorption.
Mott:
So what we have to know for the exam is that the net effect of parathyroid hormones is that it decrease calcium excretion and increase phosphate excretion in the kidneys.
Renal system acts on the kidneys.
Mott: So, big action goes to the bone to cause the bone breakdown to increase calcium. Goes to the kidneys to say let’s decrease how much calcium we’re gonna rid off, we’re going to get rid off some phosphates in exchange. And we go to the stomach and say let’s dig in some calcium and let’s convert vitamin D to it’s active form.
What can hyperparathyroidism lead to?
Hyperparathyroidism can lead to dangerously elevated levels of calcium in the blood.
What is “moans, stones, bones” in Hyperparathyroidism?
Someone is going have bone pain, kidney pain, and will moan because of it.
What are symptoms that are commonly seen with hypercalcemia?
Nausea, vomiting, constipation, kidney stones, bone pain, and altered mental status.
What is Hypoparathyroidism, and what can it lead to?
It is the decreased function of the parathyroid glands and can lead to low calcium levels.
What is calcium necessary for?
For muscle and nerve functions especially our heart function.
What is the big symptom of Hypoparathyroidism?
Perioral numbness or tingling. (Around the lip region)
What are the symptoms of severe Hypoprathyroidism?
weakness, paresthesis, muscle cramps, and seizure can result from severe hypocalcemia.
What is the king of the endocrine system?
Pancreas
Mott: Three main things to study for the exam:
1; Pituitary gland
2: Cortisol
3: Pancreas
What is pancreas responsible for?
Controlling blood sugar
Why are glucose levels important?
Glucose levels are important because all cells need glucose for cellular respiration.
What does blood glucose levels affect?
Blood glucose levels affect the fluid balance of the cells.
What is the pancreas gonna do if the blood sugar rises?
The pancreas releases insulin. This helps glucose get into cells and causes excess glucose to be stored as glycogen in the liver.
What is the pancreas gonna do if the blood sugar falls?
The pancreas releases glucagon. This causes glucose to be released from the liver.
High blood glucose:
Insulin–>Glucose enters cells–>blood glucose lowered
Low blood glucose:
Glucagon–>liver releases glucose from glycogen–> blood glucose raised
Is all of the pancreas is an endocrine gland?
No, only portions of the pancreas are endocrine glands.
How is the Endocrine portion of the Pancreas arranged?
They are arranged as discrete islets of Langerhans. These are discrete cells on the pancreas. Those are technically the component that are part of the endocrine system.
The endocrine portion of the Pancreas are composed of five different endocrine cell types, what are they?
Alpha-glucagon
Beta-insulin
Delta-somatostatin
Epsilon-ghrelin
Upsilon-pancreatic polypeptide
What is glucagon?
It’s going to be important for our hyperglycemic agent. It helps to bring blood sugars back up.
What is Glucagon triggered by?
Glucagon is triggered by decreased blood glucose levels, rising amino acid levels, or sympathetic nervous system.
How does Glucagon raise blood glucose levels?
By targeting liver to break down glycogen into glucose via Glycogenolysis. It also synthesizes glucose from lactic acid and other noncarbohydrates via Gluconeogenesis. Ultimately releasing glucose into blood.
What is net effect of Glucagon?
Glucose is going to rise in the blood
When is Insulin secreted?
Secreted when blood glucose levels increase
What is insulin synthesized as?
Synthesized as proinsulin that is then modified into useful form.
How many ways does insulin lower blood glucose levels?
Three ways
What does insulin do?
Lower blood glucose levels.
What are the three ways that insulin lowers blood glucose levels? (1)
Enhances membrane transport of glucose into fat and muscle cells.
“Yes, let’s put some glucose into the cells instead of leaving it in the blood.”
What are the three ways that insulin lowers blood glucose levels? (2)
Inhibits breakdown of glycogen to glucose
What are the three ways that insulin lowers blood glucose levels? (3)
Inhibits conversion of amino acids or fats to glucose.
What is diabetes indicated with?
Pancreas
What is Type 1 Diabetes?
Chronic autoimmune disease in which the beta cells of islets of the pancreas are destroyed resulting in insulin deficiency.
Juvenile: Type 1 diabetes
What is Type 2 Diabetes?
It is a progressive disease that develops due to a continued decline in beta-cell function and/or due to a defect in insulin sensitivity that causes hyperglycemia.
Diabetes can be due to what two things?
Hyposecretion of insulin: type 1
Hypoactivity of insulin: type 2
ON THE EXAM
What are the three cardinal signs of Diabetes
Polyuria
Polydipsia
Polyphagia
What is Polyuria? three cardinal signs of Diabetes
ON THE EXAM
Huge urine output
Glucose acts as osmotic diuretic 이뇨제
So, if we have increased levels of blood glucose, we have this diuretic effect
What is Polydipsia? three cardinal signs of Diabetes
ON THE EXAM
Excessive thirst
From water loss due to polyuria
What is Polyphagia? three cardinal signs of Diabetes
ON THE EXAM
Excessive hunger and food consumption
Because cells cannot take up glucose and are “starving”
Where is the pineal gland found?
within diencephalon
What does pineal gland produce?
Melatonin
What is the role of Pineal gland?
Circadian cycle of sleep and wakefulness through melatonin
What does melatonin modulate?
Melatonin modulates the circadian rhythm of sleep.
What upregulates the production of melatonin?
Darkness
What deregulates the production of melatonin?
When exposed to light
Where is the Thymus gland located?
In the upper thorax
What does the thymus gland play an important role in?
Plays an important function in the immune system
What does the Thymus gland produce, and what does it do?
Produces thymosin, which helps with the maturation of white blood cells during childhood, to fight infection.
WHAT WE NEED TO KNOW OF THYMUS
Responsible for the production and maturation of immune cells.
What does gonads include?
Testes and Ovaries
What is the main function of the gonads?
To produce and store gametes.
What do the Gonads also produce other than gametes?
They produce a number of sex hormones that control reproduction.
Testosterone in men
Estrogen in women
What does Gonads produce that are same as adrenal cortex?
Gonads produce same steroid sex hormones as adrenal cortex, but in lesser amounts.
What does ovaries produce?
Estrogens and Progesterone
What are the roles of the Estrogen?
Maturation of reproductive organs
Appearance of secondary sexual characteristics
What is the role of progesterone?
Causes breast development and cyclic changes in uterine mucosa.
What does Testes produce?
Testosterone
What are the roles of testosterone?
Initiates maturation of male reproductive organs
Causes appearance of male secondary sexual characteristics and sex drive
Necessary for normal sperm production
What does Placenta secrete?
Placenta secretes estrogens, progesterone, and human chorionic gonadotropin (hCG)
