Explain why the rate of conduction of a nerve impulse is greater in a myelinated axon than in an unmyelinated axon .

解释为什神经脉冲在有髓鞘的轴突传递速率较无髓鞘的轴突为快.

In contrast to white fat , brown fat is richly vascularized and has numerous unmyelinated nerves which provide sympathetic stimulation to the adipocytes .

和白色脂肪组织比较起来，棕色组织有充分的血管浸润，而且有许多无髓鞘的神经提供交感神经对脂肪细胞的刺激。