Concussion, from the Latin concutere ("to shake violently") or the Latin concussus ("action of striking together"), is the most common type of traumatic brain injury. The terms mild brain injury, mild traumatic brain injury (MTBI), mild head injury (MHI), minor head trauma, and concussion may be used interchangeably, although the latter is often treated as a narrower category. The term "concussion" has been used for centuries and is still commonly used in sports medicine, while "MTBI" is a technical term used more commonly nowadays in general medical contexts. Frequently defined as a head injury with a temporary loss of brain function, concussion can cause a variety of physical, cognitive, and emotional symptoms.

Treatment of concussion involves monitoring and rest. Symptoms usually go away entirely within three weeks, though they may persist, or complications may occur. Repeated concussions can cause cumulative brain damage such as dementia pugilistica or severe complications such as second-impact syndrome.

Maggie Siff (born June 21, 1974) is an American actress best known for her television roles, notably department-store heiress Rachel Menken Katz on the AMC drama Mad Men and Dr. Tara Knowles on the FX drama Sons of Anarchy. She also played a role in the 2009 film Push, as Teresa Stowe and in the 2010 film Leaves of Grass as Rabbi Renannah Zimmerman.

Siff was born in The Bronx, New York City. Her father is Jewish, and Siff identifies as "half" Jewish. She is a graduate of Bronx Science, and of Bryn Mawr Majoring in English and graduating in 1996, and later New York University's Graduate Acting Program at the Tisch School of the Arts with an M.F.A. in Acting.

Siff worked extensively in regional theater before her work on TV. She appears as an Alcoholics Anonymous speaker during an episode of Rescue Me in season two. She won a Barrymore Award for Best Supporting Actress in 1998 for her work in Henrik Ibsen's Ghosts at Lantern Theater Company. She also had a brief role in Funny People.

Robin Weigert (born July 7, 1969) is an American television and film actress.

Weigert was born in Washington, D.C. of Jewish heritage. After graduating from Brandeis University in 1991, Weigert attended New York University, earning a Master of Fine Arts degree in the Graduate Acting Program at the Tisch School of the Arts. After a decade as a stage actress based in New York City, she moved to Los Angeles and has appeared in various movies, TV shows and mini-series.

Weigert is best known for her much-lauded portrayal of the unkempt, foul-mooded, foul-mouthed drunkard Calamity Jane in the HBO television series Deadwood. In 2004, Weigert was nominated for an Emmy for Outstanding Supporting Actress in a Drama Series for the role.

To date, her highest profile role in film has been as Hannelore in Steven Soderbergh's The Good German (2006), with her character featured on the film's official release one sheet.

In 2010, it was announced that Weigert would be joining the cast of the FX drama Sons of Anarchy. She will play the titular motorcycle club's lawyer.

Michael "Mike" Maurer (born November 6, 1975, in Saskatoon, Saskatchewan) is a professional Canadian football fullback with the Edmonton Eskimos of the Canadian Football League and a professional mixed martial artist.

Maurer served in the Canadian Forces from 1993 to 1994. He played junior football with the Regina Rams from 1994 to 1996 and was signed as a territorial exemption by the Saskatchewan Roughriders in 1997, appearing in 39 games over four seasons with the Roughriders before being released in August 2000. He signed with the BC Lions and won the 88th Grey Cup in 2000 and appeared in 17 games in 2001. He was selected by the Ottawa Renegades in their 2002 expansion draft and appeared in 44 games with the Renegades over the next three seasons. He signed with the Eskimos on May 15, 2005, and made his impact primarily on special teams. In the 93rd Grey Cup against the Montreal Alouettes, which the Eskimos won by a score of 38-35 in overtime, he caught 4 passes for 41 yards substituting for fullback Mathieu Bertrand and won the Dick Suderman Trophy as the Most Valuable Canadian in the Grey Cup. He retired from football in May 2008.

Jahvid Andre Best (born January 30, 1989) is a running back for the Detroit Lions of the National Football League. He was selected by the Lions with the 30th pick in the 2010 NFL Draft. In college, he played for the California Golden Bears, setting several records, including most all-purpose yards in a single season and most rushing yards in a single game for Cal. Best also led the Pac-10 in total rushing yards in 2008.

Jahvid Best attended Salesian High School in Richmond, California. In his junior year he had 1,495 rushing yards on 138 attempts with 20 touchdowns. Salesian also won the North Coast Section championship in 2005 to conclude a 12–1 season. In his senior year, Best ran for 3,325 yards and 48 touchdowns, both Bay Area single-season records. Salesian once again made it to the NCS finals, but lost in the final game to St. Patrick-St. Vincent High School of Vallejo.

Best ran track as well, participating in the Arcadia Invitational in his junior and senior years. As a junior, he won the 100 meter dash with a time of 10.39 seconds with an injured foot. At the 2006 CIF California State Meet, he finished third in the 200 metres behind Bryshon Nellum and Devin Mays. As a senior he won the Arcadia Invitational 200 meter dash with a time of 21.40 seconds. Also during his senior year, Best won the CIF California State Meet 100 meters with a discounted wind assisted (2.4 m/s) time of 10.31, ahead of Charles Saseun and Randall Carroll. In the 200 metres, Best was runner-up (20.65) to Nellum (20.43), both far ahead of the competition. Best finished his senior season with personal bests of 10.36 and 20.65, the 5th and 2nd fastest times in the nation respectively.