Multiple choice questions on feedback loops and thermoregulation.

Here are the answers to the questions:

1. In the negative feedback loop of controlling blood glucose, glucagon acts as the:
Glucagon is a hormone that increases blood glucose levels. It is released in response to low blood glucose and acts on target cells (effectors) to bring the level back to normal. Therefore, it is an effector signal.
The correct option is c).

c) Effector signal.

2. Unlike negative feedback, positive feedback mechanisms typically:
Positive feedback amplifies the initial stimulus, leading to a rapid change in the same direction, rather than counteracting it to maintain stability.
The correct option is c).

c) Amplify the initial stimulus, leading to a rapid change.

3. The release of glucagon by pancreatic alpha cells is stimulated by:
Glucagon's primary role is to raise blood glucose levels when they are too low.
The correct option is b).

b) A decrease in blood glucose levels.

4. The shivering response to decreased body temperature is an example of:
Shivering involves rapid, involuntary contractions of skeletal muscles, which generate heat to raise body temperature. This process is called thermogenesis.
The correct option is c).

c) Thermogenesis through skeletal muscle contraction.