www.teamtalk.com
Midfielder Norwood, 20, joined Scunthorpe on loan in September and has made a total of 17 appearances, scoring one goal.
Goalkeeper Johnstone, 18, arrived at Glanford Park a fortnight after Norwood and has featured 13 times in all competitions despite dislocating his finger during that time.
Another Scunthorpe loanee, central defender Shane Duffy, returned to his parent club Everton last week.
Any reproduction, publication or redistribution of this material without the written agreement of 365 Media Group is strictly forbidden.