A reflex pathway is a type of neural pathway involved in the mediation of a reflex. Reflexes are involuntary reactions that occur in response to stimuli. They often bypass the brain altogether, allowing them to occur very quickly, although the brain receives information about the reflex as it happens. There are a number of different reflex pathways in the body. In patients with certain kinds of neurological disorders, these pathways become disrupted and the patient develops abnormal reflex responses.
A classic example of a reflex pathway can be seen in the knee. When the right spot on the kneecap is tapped, it triggers a reflex. Signals from the stimulus are transmitted to the spinal cord along the reflex pathway and the spinal cord activates motor neurons, causing the leg to kick out. The patient's brain is not involved in the processing of this information or the signal to kick, although it does receive sensory information to alert it to the fact that the knee was touched and the leg kicked out.
Avoiding the brain allows reflexes to occur on a hair trigger. The stimuli and response can be so closely linked that people are unaware until the reflex has already happened. Reflexes are designed to provide very specific protections to the body in response to common stimuli. Having to consciously process the stimulus and determine a response would take too long, potentially exposing the body to risks. The reflex pathway is the shortcut.
When a reflex pathway becomes damaged in some way, as may happen if nerves are severed, compressed, or demyelinated, the reflex is disrupted. A patient may have no reflexes at all, a sluggish reflex, or an abnormal reflex. This can be detected during a routine neurological exam where the patient is exposed to stimuli and the responses are noted. If a patient responds abnormally, additional testing can be used to learn more about the origins of the altered reflex. This information can be used to develop a diagnosis.
Scientific studies mapping out reflex pathways have been conducted to allow researchers to understand how reflexes work and to learn about the paths the sensory information takes as it travels from and back to the site of the reflex. These studies have also been applied to people with abnormal reflexes to see where the signal goes wrong or is missed. This can be used to help clinicians accurately diagnose patients when they present in a hospital or clinic with unusual reflex responses.