Directors of The Citizens National Bank have appointed J. Donald Henyon chairman and chief executive officer of the commercial bank, based in Laurel.

Henyon, who will continue as president, replaces Sherwood S. Shreaves. Shreaves retired Dec. 31 after 10 years with Citizens National.

A 22-year veteran of the bank, Henyon said he will take on overall responsibility for the day-to-day operations of the bank's 16 branches as well as acting as liaison with Citizens' parent company, Mercantile Bankshares Corp. in Baltimore.

Citizens, the second-largest of 17 banks affiliated with Mercantile, has one main office in Laurel and 15 branch offices in four counties: Prince George's, Anne Arundel, Howard and Montgomery.

In addition to his responsibilities with the bank, Henyon always has devoted a large part of his spare time to community programs. He is chairman of the Corridor Information Center, which directs two tourist information centers on I-95, and is a director of the Laurel-Beltsville Hospital Foundation.

"I owe an obligation to the different counties that the bank is in," Henyon said. Henyon is a past chairman of the Howard County Industrial Revenue Bond Committee. After several years in that capacity, he said, he left to join the Prince George's County Economic Advisory Committee, where he still serves.

Economic development agencies, he said, depend very heavily on bank officers and personnel for their volunteer support. "They have the strength of the bank behind them and the time" to devote, he said. COMMUNICATIONS

The Public Broadcasting Service, the nonprofit organization that provides public television programming in the United States and overseas, has appointed Paula A. Jameson general counsel, effective March 1. Jameson manages the legal, government affairs and labor relations activities for Dow Jones & Co. Inc., which publishes The Wall Street Journal and Barron's.

McGraw-Hill Inc. has named William P. Giglio regional vice president in Washington in addition to his responsibilities as the New York publishing company's liaison with federal and state governments. In his new post, Giglio will oversee all corporate and operating activities in Washington and will help in identifying new markets in the area. PROFESSIONAL SERVICES

Ernst & Whinney has appointed Andrew W. Finley, Stephen A. Sacks and Theodore B. Stone senior managers in the national tax department in Washington. All have been with the international accounting firm either six or seven years.

Pennie & Edmonds, a New York law firm specializing in patent, trademark and copyright law, has named former assistant attorney general Shiro Kashiwa counsel in its Washington office. Kashiwa was the first American of Japanese descent to be appointed an assistant attorney general or to become a federal judge.

Engineer John T. DeBell, principal and formerly senior vice president and treasurer of Bengtson, DeBell, Elkin & Titus, has taken over as president of the Centreville engineering and landscaping firm. DeBell succeeds Paul E. Bengtson, who is planning to retire in a few years. Bengtson will remain with the firm as senior vice president in charge of the civil division.

Dynalectron Corp. in McLean has named Raymond J. Mulligan vice chairman of the board of the diversified high-tech services firm. Mulligan, a consultant to Nabisco Brands Inc. and the former president and chief executive officer of the Liggett Group Inc., has been a director at Dynalectron since 1978.

Walter C. Lenahan, formerly deputy assistant secretary of Commerce for textiles and apparel, will become executive vice president of International Business and Economic Research Corp., an economic consulting firm specializing in international trade. FINANCIAL SERVICES

The Student Loan Marketing Association, the federally chartered corporation that replenishes supplies of student credit by buying student loans, has appointed Charles W. Grande vice president for systems architecture. Formerly a division vice president for computer systems at Bankers Trust Co. in New York, Grande will oversee the development and implementation of a major new automated student loan servicing system.

Washington Redskins head coach Joe J. Gibbs has been elected to the board of directors of Security National Bank. The appointment brings the number of directors to 18.

Former investment banker Ulric Weil has retired from Morgan Stanley Inc. in New York to form Weil & Associates, a financial consulting firm in Washington. A senior analyst with Morgan Stanley, Weil specialized in high-technology industries. INSURANCE

Former astronaut Michael Collins has been elected a director of Avemco Corp., an aviation insurance company in Frederick, Md. Since leaving the space program in 1970, Collins has been director of the National Air and Space Museum, vice president for Washington operations of LTV Aerospace and Defense Co. and currently heads his own consulting firm.

The Overseas Private Investment Corp., the federal organization that provides political risk insurance to encourage private investment overseas, has named Travis P. Dungan Jr. vice president and treasurer. Dungan, formerly deputy assistant secretary for finance at the Commerce Department, succeeds C. Dale Duvall, who recently was confirmed by the Senate as commissioner of the Interior Department's Bureau of Reclamation.