I don't own a D7000 and you are kind of annoying, but I highly doubt you have read the manual as I can almost guarantee it is in there (pages 49-55). A quick 2 minute google search and I found the answer for this question.
These options are found in the camera menu. See below.
"During shooting you can lock the focus at any time by half-pressing the shutter button. In terms of Auto Focus the D7000's movie mode offers all the options you also get in live view: you can choose between single and continuous AF and pick one of the focus area modes: normal area, wide area, face detection or subject tracking (AF-F). Nikon recommends the use of AF-S lenses in video mode as their design and quiet focusing is more suited to video requirements than the standard AF Nikkors. However, no matter what lens you use you should be aware that Auto Focusing in video mode with a large sensor camera is often a tricky affair. Due to the limited depth of field, and focussing errors are very obvious, and whilst fairly effective, AF-F can be a little 'jumpy' as it tries to keep up with the action. Focusing manually gives you more control and can yield better results. That said, AF-F performs pretty well - certainly better than we expected, and only really struggles when tracking sudden leaps from close to distant focus."