In ________, children talk and exchange toys or materials

Tim has a flat face, small nose, eyes that appear to slant upward because of small folds of skin at the inside corner, short arms and legs, and small squarish hands. These physical features are typical of a chromosomal disorder called

a) phenylketonuria. b) Down syndrome. c) Tay-Sachs disease. d) Fragile X syndrome.

If sodium is prevented from passing through the neuronal membrane,

a. the neuron has just fired. c. both a & b b. the neuron is in the refractory period. d. none of these