Adding responsibilities to role?

[Nyon]

Can my school add more responsibilities to my role without any additional pay award? I’m a second in a core department and currently on the minimum they can pay me. Apparently the responsibilities I have are about to be adjusted to pick up slack for my HoD; can they do this (I have no job description) without adding to my pay?

I believe they can allocate tasks to you.

Of course, whether or not it's reasonable depends on the task.