“…More importantly, sympathetic neurones do not fire at such high rates. For instance, the median firing rate of single sympathetic neurones in the renal, splenic and mesenteric nerves in the anaesthetized cat is 0.9 Hz (Meckler & Weaver, 1988;Stein & Weaver, 1988), and in awake humans, individual cutaneous vasoconstrictor and sudomotor neurones discharge very irregularly with an average frequency of 0.5-0.6 Hz during the specific increases in sympathetic drive associated with cold-induced vasoconstriction (Macefield & Wallin, 1999b) or heat-induced sweating (Macefield & Wallin, 1996). Moreover, human muscle vasoconstrictor neurones There is evidence in experimental animals that, in addition to receiving fusimotor drive, muscle spindles are subject to modulation by the sympathetic nervous system.…”