In Traditional Chinese Medicine (TCM), Tian Ma belongs to the 'Herbs that pacify Internal Liver Wind and stop Tremors' category. These herbs are used to treat so-called 'hyperactive Liver Yang'. Concretely this translates into high blood pressure as well as seizures, spasms, convulsions, dizziness and vertigo. These herbs often seem to have a powerful antispasmodic effect on the nervous system.
Furthermore Tian Ma is Neutral in nature. This means that Tian Ma typically doesn't affect the balance in your body. Balance between Yin and Yang is a key health concept in TCM. Eating too many "Hot" (Yang) ingredients can lead to an imbalance whereby one has a Yang Excess. The inverse is true as well: too many "Cold" (Yin) ingredients can lead to a Yin Excess. The Neutral nature of Tian Ma means that you don't have to worry about that!
Tian Ma also tastes Sweet. The so-called 'Five Phases' theory in Chinese Medicine states that the taste of TCM ingredients is a key determinant of their action in the body. Sweet ingredients like Tian Ma tends to slow down acute reactions and detoxify the body. They also have a tonic effect because they replenish Qi and Blood.
The tastes of ingredients in TCM also determine what Organs and Meridians they target. As such Tian Ma is thought to target the Liver. In TCM the Liver is often referred as the body's "general" because it is in charge of regulating the movements of Qi and the Body Fluids. It also takes a leading role in balancing our emotions.