Final answer:
The statement is True; glucose counter-regulatory hormones such as glucagon counter the effects of insulin by raising blood sugar levels when they fall too low. This action is part of a negative feedback mechanism crucial for maintaining blood glucose homeostasis.
Step-by-step explanation:
Glucose counter-regulatory hormones such as glucagon indeed oppose the actions of insulin. Therefore, the statement 'Glucose counter-regulatory hormones oppose the actions of insulin' is True (A). Insulin and glucagon are both crucial for maintaining blood glucose homeostasis.
When there is an increase in blood glucose levels after eating, the beta cells of the pancreas secrete insulin, which facilitates the uptake of glucose by the cells, thereby reducing blood glucose levels. On the other hand, when blood glucose levels fall, the alpha cells of the pancreas secrete glucagon, which stimulates the catabolism of glycogen into glucose and the production of new glucose, raising the blood glucose levels.
This system of balance is regulated by a negative feedback loop, where the action of one hormone inhibits the release of another to maintain a stable internal state. For example, rising blood glucose levels inhibit further glucagon production and secretion. Conversely, conditions like diabetes mellitus, characterized by high blood glucose levels due to the lack of insulin production (Type I diabetes) or target cell resistance to the effects of insulin (Type II diabetes), highlight the importance of this hormone balance for health.