Active+Reading


 * Active Reading Activity**


 * Directions:** Below is an article that may be difficult to understand due to the extensive vocabulary that is used. Your objective as a class is to locate a series of words that you don't understand and create a hyperlink for that word. The link should be attached to the word and you must attach a link to at least three words each. This assignment is worth 30 points.


 * Article: Caffeine**

Caffeine, the stimulant in coffee, has been called "the most widely used[|psychoactive] substance on Earth ." Synder, Daly and Bruns have recently proposed that [|caffeine] affects behavior by countering the activity in (5) the human brain of a naturally occurring chemical called adenosine. [|Adenosine] normally depresses [|neuron] firing in many areas of the brain. It apparently does this by inhibiting the release of [|neurotransmitters], chemicals that carry nerve impulses from one neuron to the next. (10) Like many other agents that affect neuron firing, adenosine must first bind to specific receptors on [|neuronal] membranes. There are at least two classes of these [|receptors], which have been designated A1 and A2. Snyder et al propose that caffeine, which is struc- (15) turally similar to [|adenosine], is able to bind to both types of receptors, which prevents adenosine from attaching there and allows the neurons to fire more readily than they otherwise would. For many years, caffeine's effects have been attri- (20) buted to its [|inhibition] of the production of [|phosphodi- esterase], an[| enzyme] that breaks down the chemical called cyclic AMP.A number of neurotransmitters exert their effects by first increasing cyclic AMP concentra- tions in target [|neurons]. Therefore, [|prolonged] periods at (25) the elevated concentrations, as might be brought about by a phosphodiesterase [|inhibitor], could lead to a greater amount of neuron firing and, consequently, to behav- ioral stimulation. But Snyder et al point out that the caffeine concentrations needed to inhibit the production (30) of [|phosphodiesterase] in the brain are much higher than those that produce [|stimulation]. Moreover, other com- pounds that block [|phosphodiesterase's] activity are not stimulants.