Chapter 5.3 Flashcards
What is the thyroid and what are its functions?
The thyroid gland is a endocrine organ on the anterior aspect of the trachea, just deep to the anterior neck. Its functions are to regulate metabolic rate and calcium homeostasis.
What are the three thyroid hormones?
- Triiodothyronine (T3)
- Thyroxine (T4)
- Calcitonin
Where are T3 and T4 produced? What do they contain?
In the follicular cells of the thyroid. They contain iodine
What is the function of T3 and T4?
T3 and T4 work together to increase the basal metabolic rate. The more of these hormones there are, the more cellular respiration occuring and the more calories a person naturally burns.
What is hypothyroidism?
Hypothyroidism is when thyroid hormones are in insufficient quantity. This condition is characterized by lethargy, decreased body temperature, weight gain, slowed respiratory rate, and slowed heart rate.
What is hyperthyroidism?
Hyperthyroidism is when thyroid hormones are in too high concentration. The symptoms of this are opposite those seen in hypothyroidism. Weight loss, increased body temperature, increased energy levels, higher heart rate, higher respiratory rate.
Where is calcitonin made?
In the parafollicular (or C-cells) of the thyroid.
What is Calcitonin’s function?
To decrease calcium levels in the blood.
MNEMONIC: Calcitonin tones down the calcium levels in the blood.
What are the three ways Calcitonin decreases calcium concentration in the blood?
- Calcitonin stimulates calcium excretion from the kidneys.
- Calcitonin decreases the amount of calcium absorbed by the gut.
- Calcitonin increases the amount of calcium stored in the bones.
What is a good general rule for knowing what condition causes a hormone to be secreted?
Hormones want to maintain balance and will often be secreted in response to their opposite effect being too high in the body. For example, calcitonin decreases the amount of calcium in the blood. When calcium levels in the blood are too high, calcitonin is secreted in response.
What are the parathyroid glands and what are their functions?
The parathyroid glands are 4 small glands on the thyroid gland. Their function is to increase the level of calcium in the blood.
What are 5 big roles of Calcium in the body?
- Bone structure and strength
- Release of neurotransmitters from neurons
- Regulation of muscle contraction
- Clotting of blood
- Secondary messenger
What hormone is produced by the parathyroid glands?
Parathyroid Hormone (PTH)
What are PTH’s 4 effects on the body?
- Increases calcium absorption by the gut.
- Increases bone resorption (liberating calcium from bone).
- Decreases excretion of calcium by the kidneys.
- Affect phosphorus homeostasis by increasing resorption of phosphate from bone and reducing reabsorption of phosphate in the kidney (increasing its urine excretion)
What does it mean to be antagonistic?
If something is antagonistic to something else, that means it has the opposite effects.
What is the relationship between PTH and Vitamin D?
PTH activates Vitamin D which allows calcium and phosphate to be absorbed in the gut.
What are the two effects of PTH on phosphorus homeostasis?
- PTH Increases absorption of phosphorus by the gut (by activating vitamin D)
- PTH decreases reabsorption of phosphate by the kidneys
Notice that the first effect increases phosphorus in the blood, but the second decreases it. PTH has little effect on phosphorus homeostasis because its dual effects mostly cancel out.
What are the adrenal glands?
The adrenal glands are glands located on top of the kidney that control the levels of a wide variety of hormones in the blood.
What are the two parts of the adrenal gland?
The adrenal cortex and the adrenal medulla.
What hormones are secreted by the adrenal cortex?
The corticosteroids.
What are the three classifications of corticosteroids?
- Glucocorticoids
- Mineralcorticoids
- Cortical Sex hormones
What is the function of the glucocorticoids?
Glucorticoids are steroid hormones that regulat glucose levels and affect protein metabolism.
What are the two glucocorticoids with which you should be familiar?
Cortisol and Cortisone
Describe how cortisol and cortisone affect the body.
Cortisol and cortisone raise blood glucose by increasing gluconeogenesis and decreasing protein synthesis.
They can also decrease inflammation and immunologic responses.
Finally, Cortisol is a stress hormone, which means it is released in times of stress. It makes sense because you would need high levels of energy (sugar) to deal with a stressful situation.
How are Glucocorticoids signalled to be released?
Hypothalamus secretes CRF, Anterior Pituitary releases ACTH, and then the adrenal cortex releases glucocorticoids.
What is the function of the mineralcorticoids?
The mineral corticoids are used in salt and water homeostasis.
What is the mineralcorticoid with which you should be familiar?
Aldosterone
