Verna Bloom, who in her first feature film, the semidocumentary “Medium Cool,” moved anxiously through the rioting in Chicago during the 1968 Democratic National Convention, and who a decade later played the lustful wife of the stiff-necked college dean in “National Lampoon’s Animal House,” died on Wednesday in Bar Harbor, Me. She was 80.

Her husband, the critic and screenwriter Jay Cocks, said the cause was complications of dementia.

While “Animal House” was probably her best-known role, “Medium Cool” offered Ms. Bloom an auspicious beginning.

She had been acting mostly onstage when a small role in Studs Terkel’s play “Amazing Grace” led Mr. Turkel to recommend her for “Medium Cool” (1969), the cinematographer Haskell Wexler’s first feature as a director.

Shot in cinéma vérité style, “Medium Cool” is the story of a local news cameraman (Robert Forster) who meets Eileen (Ms. Bloom), a poor woman from West Virginia raising her teenage son in Chicago, while covering the city’s social unrest.