Three modifications of the small intestine that increase the surface area for absorption

Three modification of the small intestines that increase the surface area for absorption are: VILLI, MICROVILLI AND MUCOSAL FOLDS.

Explanation:

The small intestine is the longest part of the alimentary canal and its is the place, where the absorption of digested food usually take place. The modification of the small intestines that increase its surface are are villi, micro villi and mucosal folds. The inner surface of the small intestine is folded into many circular parts; this increases the surface area of the organ. The mucosal forms many projections, which give rise to the villi. The microvilli, which is the lumenar plasma membrane is also densely packed with mircrovilli. All these modification increases the surface area of the small intestines.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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