Neuroendocrine system III – Thyroid, Parathyroid & Pancreas

Question 1

What is the Thyroid?

Answer 1

The largest endocrine gland, located in the anterior neck (inferior to larynx)
Consists of two lateral lobes connected by a median tissue mass - Isthmus
Comprised of thyroid follicles

Follicle walls formed by follicle cells

Follicular cells produce two hormones
Thyroxine (T4)
Triiodothyronine (T3)

Question 2

Only endocrine gland that stores secretory products is what?

Answer 2

Thyroid

Question 3

Hormones are released slowly - T4 = T½ 6 days | T3 = T ½ 1 day. True or False?

Answer 3

True

Question 4

What are the actions of the thyroid hormones?

Answer 4

Increase basal metabolic rate (BMR)
Simulate cellular O2 for ATP production | Increased metabolism of carbohydrate, fat & protein

Stimulate additional Na+/K+/ATPase pumps
Increased utilisation of ATP | Thermoregulation due to calorigenic effect

Regulate metabolism
Protein synthesis | Utilisation of glucose & fatty acids for ATP | Excrete cholesterol

Enhance actions of catecholamines (cell signalling molecules)
Up-regulation of β-receptors | Increased adrenaline & noradrenaline

Growth & development
Accelerate body growth| Linked to development of nervous & skeletal system