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.
Some reflex arcs can include a coordination centre within the spinal cord or brain prior to stimulation of the motor nerve. Reflex arcs can involve single or multiple segments up and down the body, although reflex arcs do not require brain input in order to function. However, the brain can act to modulate reflexes. The brain obtains its afferent information via the ascending sensory tracts of the spinal cord.