Final answer:
Blood pressure is typically higher when sitting due to the increased gravitational force that the heart has to overcome to pump blood to the brain. In the lying down position, this gravitational challenge is reduced, often resulting in slightly lower blood pressure.
Step-by-step explanation:
The question asks whether blood pressure is different when lying down compared to sitting and which is higher. The correct answer is: b. Blood pressure is higher when sitting due to increased gravitational force. When a person sits up from a lying down position, the heart has to work against gravity to pump blood to the brain. This process is related to homeostasis and adapts to the change in body position, which can also lead to orthostatic hypotension if changes in blood pressure are not regulated properly.
While in a lying down position, the body is more level, reducing the need for the heart to work as hard against gravity and often resulting in a slight decrease in blood pressure. Therefore, when the body is in a sitting position, the action of the cardiovascular system adjusting to this new postural change and having to ensure enough blood reaches the brain despite the force of gravity leads to a temporary increase in blood pressure compared to when lying down.