Some discoveries while reading my txtbook

Membranes:

You may have experienced this effet even though you are a homeotherm, or "warm-blooded" organism: On chilly days, your fingers and toes can get so cold that the membranes of sensory nerve endings cease to function, resulting in temporary numbness.) (Becker, Kleinsmith and Hardin, 2006)

At temperatures much above 45 degree celcius, probably because nerve cell membranes become so leaky to ions that ion gradients cannot be maintanined and overall nervous function is disabled. (Becker et al, 2006)

Becker, W.M.. , Kleinsmith, L.J. , Hardin, J. (2006) The world of the cell, 6th edition. Chapter 7, pg.170, 3p