Boulder ultrarunner Jay Rawlings still remembers the day 10 years ago he learned his mother had been diagnosed with multiple sclerosis.

Visions of people in wheelchairs and hospital beds flashed through his mind as he thought of his own mother, now 60-year-old Annie Hayashi, living with the disease that attacks the central nervous system.

On Monday, Rawlings will begin his leg of the 3,000-mile MS Run the U.S. relay. Rawlings' relay leg is a 182-mile jaunt from Barstow, Calif., to Las Vegas. He joins 14 other runners for the relay, which started in Los Angeles on April 15 and ends in New York City on September 6.

The runners aim to raise $500,000, which will be donated to the National MS Society to fund research for a cure.

Rawlings, a technical support analyst in Boulder, will run 26 miles a day for seven days -- almost a marathon a day -- to complete his leg of the relay. Since her diagnosis, Rawlings said he's learned how tough his mom is, who is continuing to work full time and not letting the disease get in her way.

"Her fighting spirit is what inspired me to do something of this magnitude," Rawlings said.

The relay's organizer, Ashley Kumlien, started the run in 2010 as a solo trip across the United States. Kumlien ran from San Francisco to New York by herself, but decided that a 15-runner relay would help with spreading awareness about MS.

In a way, Kumlien said, running represents the "endurance event" people living with MS finish every day.

"Waking up each day and living with the symptoms they have from the disease and trying to remain positive and healthy," she said. "That's their own event they do, day in and day out."

Rawlings' mother Hayashi said she's "incredibly proud" of her son for running the relay and fundraising. As a divorced single mother raising Rawlings, Hayashi said she always told her son they were a team -- they're still close today even though Rawlings lives in Boulder and Hayashi lives in the Chicago suburb of Northfield, Ill.

When Rawlings approached her with the idea of running the relay, Hayashi said initially she was worried about talking about her disease publicly. For most of her life with MS, Hayashi said she's been living "in the closet" with the disease, only telling her closest friends and family members.

But when Rawlings told her about the relay, Hayashi said she decided it was a time to stop hiding the illness.

Her son's commitment to run 182 miles across the Mojave Desert helped her realized that, she said.

"As freeing as he finds running," she said, "this experience and this run has, in many ways, freed me."

--Follow Sarah Kuta on Twitter: @SarahKuta.