What controls the pupillary response?

The pupillary light reflex allows the eye to adjust the amount of light reaching the retina and protects the photoreceptors from bright lights. The iris contains two sets of smooth muscles that control the size of the pupil (Figure 7.2).

What is the function of the pupillary?

The pupil is the opening in the center of the iris (the structure that gives our eyes their color). The function of the pupil is to allow light to enter the eye so it can be focused on the retina to begin the process of sight. Typically, the pupils appear perfectly round, equal in size and black in color.

Which nervous system regulates our pupillary response?

parasympathetic nervous system
The parasympathetic nervous system is the main system responsible for pupil constriction in response to light.

How is the pupil regulated?

The size of the pupil is controlled by the activities of two muscles: the circumferential sphincter muscle found in the margin of the iris, innervated by the parasympathetic nervous system: and the iris dilator muscle, running radially from the iris root to the peripheral border of the sphincter.

What causes pupil restriction?

What Causes Pupils to Constrict? Pupil constriction and dilation are controlled by the sympathetic and parasympathetic nervous systems in the brain. Normally, when the parasympathetic nerve is activated, it causes pupils to constrict, or narrow. When the sympathetic nerve is stimulated, pupils dilate.

How are the pupils regulated?

How do you control your pupils?

If you aren’t able to dim the surrounding lighting, you can still dilate your pupils by turning to face away from windows and light source. Try tensing your stomach. Suck your stomach in and keep the muscles tight as you watch yourself in a mirror, to see whether your pupils increase.

What nerve dilates the pupil?

Therefore, the oculomotor nerve is responsible not only for a wide variety of eye movements but also for pupillary constriction and lens accommodation. A variety of pathologies may affect this nerve, but it will result in ptosis, the eye rotated downward and outward and with a fixed, dilated pupil.

How does the eye pupil work?

The colored part of the eye which helps regulate the amount of light entering the eye. When there is bright light, the iris closes the pupil to let in less light. And when there is low light, the iris opens up the pupil to let in more light. Focuses light rays onto the retina.

How does the pupil reflex work?

A greater intensity of light causes the pupil to constrict (miosis/myosis; thereby allowing less light in), whereas a lower intensity of light causes the pupil to dilate (mydriasis, expansion; thereby allowing more light in). Thus, the pupillary light reflex regulates the intensity of light entering the eye.

How is the pupillary diameter of the eye controlled?

Pupillary diameter, or more precisely iris size, is controlled by two muscles, the sphincter pupillae, which is primarily under the control of the parasympathetic nervous system, and the dilator pupillae, which is primarily under the control of the sympathetic nervous system.

Is the pupil under sympathetic or autonomic control?

The pupil is under competing autonomic control in response to light levels hitting the retina. The sympathetic system will dilate the pupil when the retina is not receiving enough light, and the parasympathetic system will constrict the pupil when too much light hits the retina.

Which is part of the nervous system controls pupillary constriction?

Pupillary Control: The Basics The physiology behind a “normal” pupillary constriction is a balance between the sympathetic and parasympathetic nervous systems. Parasympathetic innervation leads to pupillary constriction. A circular muscle called the sphincter pupillae accomplishes this task.

Is there such a thing as a normal pupillary response?

There are a handful of pupillary abnormalities that every clinician should know. Here we review the basic physiology then describe these abnormal pupillary responses and how to find them. The physiology behind a “normal” pupillary constriction is a balance between the sympathetic and parasympathetic nervous systems.