After a neuron experiences an action potential, it must wait for 1 or 2 milliseconds before it can fire again. This period of time is called the __________ period

When an excitatory message reaches the dendrites, the cell becomes _________________ and the likelihood of a nerve impulse is ______________.

a. more negative...decreased b. less negative... increased c. less negative...decreased d. more negative...increased

Rapid-eye movement (REM) sleep

a. becomes more frequent as infants grow older. b. may stimulate the brain and foster growth of the nervous system. c. makes up 90 percent of newborns' sleep. d. involves steady heart rate, breathing, and brain activity.