Topic 3

Question 1

why is the hypothalamus important?

Answer 1

regulating pituitary gland

Question 2

what is the posterior pituitary gland?

Answer 2

axon terminals connect the hypothalamus to posterior pituitary gland through a tract.

Question 3

what are two main hormones released from posterior pituitary gland? where are they formed?

Answer 3

paraventricular nuclei produces oxytocin
super optic nucleus synthesising energy antidiuretic hormone (ADH).

Question 4

where is thyroid gland located (in science terms)?

Answer 4

located inferior to the larynx and on the anterior side of the trachea.

Question 5

what hormones do the follicular cells produce?

Answer 5

thyroxine (T4) and triiodothyronine (T3)

Question 6

function of parafollicular cells and location?

Answer 6

lay between the follicles and release hormone called calcitonin which helps calcium metabolism.

Question 7

what is the steps for formation and storage of thryoid hormones?

Answer 7

1. Iodine trapping: Thyroid follicular cells trap iodine ions (I-) from the bloodstream, by actively transporting them from the blood into the cytosol.
2. Synthesis of thyroglobulin: At the same time iodine is being trapped, follicular cells are also synthesiseing thyroglobulin (TGB), produced in the rough endoplasmic reticulum, modified in the golgi complex and packaged into secretory vesicles. The vesicles undergo exocytosis, releasing TGB into the lumen of the follicle.
3. Oxidation of iodide: Tyrosine, in TBG, will have iodine attached (iodination). However, this is not chemically possible until iodine is oxidised (loses electrons). As the iodine ions are being oxidised, they pass through the membrane into the lumen of the follicle.
4. Iodination of tyrosine: the oxidised iodine ions now react with the tyrosines in the TBG molecule. One addition of ionine ions makes monoiodotyrosine (T1), and two makes diiodotyrosine (T2). The TBG that has the iodine attached becomes sticky and is stored in the lumen of the thyroid follicle. This is called colliod.
5. Coupling of T1 and T2: During the last step of synthesis, two T2 molecules join together to for T4, and one T1 and one T2 join to form T3.
6. Pinocyntosis and digestion of colloid: Droplets of colloid re-enter the follicular cells through pinocytosis and merge with lysosomes. Digestive enzymes break down TBG and cleave off T3 and T4.
7. Secretion of thyroid hormones: both T3 and T4 are lipid hormones, so they easily diffuse through the plasma membrane into the interstitual fluid and into the blood. T4 is normally secreted in larger amounts than T3, but T3 is more biologically active as the receptor has a greater affinity for it. When T4 enters the body cell, it will be converted to T3 by removing one iodine.
8. Transport in the blood: more than 995 of both T3 and T4 combine with thyroxine-binding globulin, to travel around the body to act on their target organs.

Question 8

steps of stimulation hormone release?

Answer 8

1. if there’s low levels of thyroid hormones in blood stream, the hypothalamus will identify this and act.
2. Then, the hypothalamus will release TRH hormone.
3. Thyroid stimulating hormone is released into bloodstream and act on the thyroid follicular cells
4. Cause the release of T3 and T4 into the blood from follicular cells.

Question 9

what does calcitonin impact and do?

Answer 9

bones; stimulates calcium deposition in bones
kidneys; reduces calcium uptake in kidneys
intestines; reduces calcium uptake in intestines

Question 10

what does calcitonin impact and do?

Answer 10

bones; stimulates calcium deposition in bones
kidneys; reduces calcium uptake in kidneys
intestines; reduces calcium uptake in intestines

can be used as medication for certain diseases, such as Paget’s disease and osteoporosis.

Question 11

what is the parathyroid gland?

Answer 11

partially embedded in the