The Russian account I have read (translated) said the cavalry withdrew after recieving significant casualties from the Highlanders, who were initially hidden until they stood up from cover, and the artillery (definately British Artillery). The Scots' version says they first fired at 1000 yards with their rifles (something the Turkish troops could not have done) but did not have effect. However, the second and third volleys (according to the Russian account) wounded many and persuaded them to wheel away and retire. If some of the Turkish troops had indeed stood with the Highlanders, their fire would have been less important than their actual appearance in support in persuading the Russians to turn away.
However, the British accounts are always biased and tend to continually dismiss the Turks as 'unreliable, lazy or downright cowardly'. This has to be taken in context: many of the writers had a 'death before dishonour' complex (see The Charge of the Light Brigade), and Turkish withdrawal after spiking the guns is understandable when they were severly outgunned. The British army in the first year of that war was an army recruited from volunteers from other regiments who had stayed behind. Their 'gung-ho, lets get at them Ruskies' attitude, combined with superior firearm technology, tended also to make them do things on the battlefield that no sensible general would allow. The Turks were not cowards, but the Brits were a bit mad and treated them as such.