How this happens could be from one or more causes. One common view is that caffeine narrows the blood vessels by blocking the hormone that normally keeps them open â adenosine. Caffeine also can stimulate cortisol and adrenaline to be released, which can cause a direct increase in blood pressure.
Second-order levers are mechanisms which feature the input force and output force on the same side of the fulcrum, with the input force furthest from the fulcrum. A great example of a second-order lever is a wheelbarrow. Similar to first-order levers, in a second-order lever the output force will be greater than the input force. However, the output travel will be less than the input travel. In this case, both the input and output forces will act in the same direction.
A lever is any elongated, rigid object that rotates around a fixed point called the fulcrum (fig. 9.15). Familiar examples include a seesaw and a crowbar. Rotation occurs when an effort applied to one point on the lever overcomes a resistance (load) located at some other point. The part of a lever from the fulcrum to the point of effort is called the effort arm, and the part from the fulcrum to the point of resistance is the resistance arm. In the body, a long bone acts as a lever, a joint serves as the fulcrum, and the effort is generated by a muscle attached to the bone.