The fifth-floor chapel in the senior center of the New York Avenue Presbyterian Church downtown has been temporarily converted to a classroom, where about 20 senior citizens are waiting.

Two gentlemen are slumped over, snoozing. Others chat quietly. A homeless woman wearing a red kerchief walks into the classroom and takes a seat.

They are waiting for van Gogh.

Suddenly, Joan Hart breezes into the room, posters and slides in hand. She gets a rousing "hello" from her students, who seem to come back to life, swallowing yawns and sitting up in their chairs.

Hart is from Museum One, an organization she started to take art to nursing homes and other institutions whose residents cannot easily get to museums and galleries. Of the 20 senior students in class today, some are needy and others homeless; almost all have faithfully attended her course at the center for more than a year.

Hart announces that class will begin with impressionism and lead into modernism. "La Seine a Giverny" flashes on screen, and Monet's water, sky and flowers draw oohs and ahs. Then van Gogh's intense portraits appear, greeted with quiet, reverent sighs of admiration. And then Matisse, whose bright, wild colors bring shrieks of both delight and derision.

Comments flow freely. One woman reacts to a Ce zanne still life of pears and apples, saying, "To me it has a cosmic feel," while a man complains, "The fruit looks rotten."

Museum One began when Hart, who has her master's degree in fine arts from Syracuse University, decided to offer an art appreciation class at the Washington Home, where residents are chronically ill. The wholehearted, enthusiastic response she received from patients, all physically incapacitated and some emotionally disturbed, persuaded Hart to expand her efforts.

That was 1981. Five years later, with the assistance of public and private contributions, Hart works full time managing Museum One and teaching, aided by five assistants. The organization has conducted courses at 40 sites in Maryland, Virginia and the District and visits 20 nursing homes regularly.

"Art should reach out to everybody. We bring our art courses to the people," says Hart.

She says her lessons "are a form of intellectual stimulation, and also sensory stimulation" for the institutionalized elderly, some of whom live in drab quarters with little contact with the rest of the world because of physical limitations. "What struck me when I first started was how isolated the people in the homes were," she says.

Museum One's premise is that seniors want more than games and social activities to fill their free hours. So far, Hart feels she has been proved right, having amassed loyal followings in area homes.

Dorothy Ferguson, 67, a student of Hart's at the New York Avenue Presbyterian Church for the past year, says she attends because "I learn about artists."

"I like the way Joan explains the techniques," says Adele Haddad, 53, herself an artist and avid pupil.

Classes lace learning with fun; Hart sets up the historical context of the works she displays, often devoting weeks at a time to one artistic period, then spotlighting individual artists.

She encourages class participation, and the students at New York Avenue Presbyterian are not the only ones who voice opinions freely. Different groups from area nursing homes have developed their own favorites, Hart says.

"Edward Hopper is an excellent artist to show to this group at New York Avenue Presbyterian because his scenes are of the '20s and '30s. Everyone starts saying, 'I remember that,' " she says.

"In the Washington Home, van Gogh has been so popular," she says, noting that the artist was institutionalized. "In institutions people feel cut off. What van Gogh does is, he brings out feelings about color. At the Washington Home they like 'Starry Night.' Once a student there said, 'Didn't van Gogh kill himself?' They seemed to accept it easily. I'm the one who's squeamish.

"I always point out that Degas, Renoir, Monet, they all led long lives," Hart says. "I'll point out if it's a painting done a few weeks before death, to show they were working up until then."