The term autonomic nervous system (ANS) refers to collections of motor neurons (ganglia) situated in the head, neck, thorax, abdomen, and pelvis, and to the axonal connections of these neurons (Figure 1).rain and spinal cord pathways regulating autonomic outflow. Preganglionic neurons for parasympathetic and sympathetic autonomic outflow are located in the brainstem and in thoracic, upper lumbar and sacral regions of the spinal cord (Figure 1). Several different brain centres control these preganglionic neurons.
A: Moon phases are caused by the motions of the Earth and moon as they relate to the sun. Phases occur as the Earth-facing side of the moon changes over the course of 29.5 days when the moon revolves around the planet. When the angle of sunlight reflecting off the moon changes, humans observe different lighting levels from the moon.
When the Moon moves between Earth and the Sun, it casts a small shadow on Earth, and people inside that shadow see a solar eclipse. Both these events are rare, happening only about every 6 months. Moon phases are the result of the Moon's own shadow -- like Earth, only one half of the body is lit at a time. Sometimes the lit side is pointed toward Earth, and we see the reflected light. Sometimes the shadow or night side is pointed toward Earth, and we only see a crescent Moon.