Time difference between the process getting scheduled and process getting executed is called dispatch latency.
Lets see what Wiki (http://en.wikipedia.org/wiki/Scheduling_(computing)#Dispatcher ) says -
Dispatcher - It is the module that gives control of the CPU to the process selected by the short-term scheduler. Which involves
1. Switching context
2. Switching to user mode
3. Jumping to the proper location in the user program to restart that program.
Dispatcher analyses the values from Program counter and fetches instructions, loads data into registers.
The dispatcher should be as fast as possible, since it is invoked during every process switch. During the context switches, the processor is idle for a fraction of time. Hence, unnecessary context switches should be avoided. The time it takes for the dispatcher to stop one process and start another running is known as the dispatch latency.