natremia The presence of sodium ions in the blood. Derived terms . dysnatremia; hypernatremia; hyponatremia; natremic; Translations
A reflex arc is a nerve pathway in the body of humans and some animals that connects certain muscle groups to others, without involving the brain. These sorts of pathways primarily control involuntary movements in response to some sort of stimulus.
Describe the components of a reflex arc. 1  Reflexes, or reflex actions, are involuntary, almost instantaneous movements in response to a specific stimulus.  Reflex arcs which contain only two neurons, a sensory and a motor neuron, are considered monosynaptic.