The Chief Medical Officer is in charge of the health of the crew. They make sure that the Medical Doctors are treating people effectively, and making sure the Virologists. Geneticists, and Chemists are working for the good of the station.
This role is an extremely important one. If you know what you're doing, as a Medical Doctor (Otherwise known as a Surgeon or a Nurse) you will save lives. Nearly every death can be prevented, provided you reach the victim in time. Since Medical Doctors are the only ones with the tools and the in character experience to save them, Medical Doctors tend to make a lot of friends.
The Paramedic is the first responder to medical emergencies outside the sanctity of the Medbay. With your ambulance and space suit, you can reach personnel in extremely hazardous conditions. If you pay attention to the tracking computer, a portable monitor, keep an eye on the radio, and otherwise be vigilant, you will be a lifesaver just as much, if not more so, than your doctorate wielding coworkers.
As the Coroner your job is to inspect the cause of death of any bodies that grace the halls of your domain, the morgue. You're expected to generate a full autopsy on each body you receive (yes even borged ones). You're also responsible for all the un-cloned corpses in your domain, lest you anger the lesser spotted ghost.
As a Chemist (Also known as a Pharmacist or a Pharmacologist), your job is to mix chemicals for the medical staff to use. Your work will be needed mostly by Medical Doctors as they often require important chemicals.
Congratulations Doctor, you have been selected to study and treat various types of viruses, and create valuable vaccines. So grab your latex gloves, get your breathing mask on, and head over to Virology. As a Virologist (Also known as Pathologist or a Microbiologist) your main job is to find a virus, analyze it, and then produce a cure. Additionally, you will experiment with different viruses and possibly create your very own virus that is beneficial to the station.
As the Station Psychologist (Or a Psychiatrist or a Therapist), you are tasked with identifying and improving mental health aboard the station. As required, you may perform psychiatric evaluations.