Pupillary reflex
Pupillary Reflex
Pupillary reflex (pronunciation: pyoo-pil-er-ee ree-fleks) is a physiological response that regulates the diameter of the pupil, in response to the intensity of light that falls on the retina.
Etymology
The term "pupillary reflex" is derived from the Latin word "pupilla", which means "little doll", and the Latin word "reflexus", which means "bent back". The term "pupillary" refers to the pupil, the central transparent area of the eye, and "reflex" refers to an involuntary and nearly instantaneous movement in response to a stimulus.
Function
The pupillary reflex serves to protect the retina from sudden changes in light intensity. It is controlled by the autonomic nervous system, specifically the parasympathetic and sympathetic divisions. The parasympathetic division causes the pupil to constrict (miosis) in response to bright light, while the sympathetic division causes the pupil to dilate (mydriasis) in response to low light.
Types
There are two types of pupillary reflexes: the direct and consensual reflex. The direct pupillary reflex is the constriction of the pupil in response to light shone into the same eye. The consensual pupillary reflex is the constriction of the pupil in response to light shone into the opposite eye.
Related Terms
- Pupil: The central transparent area of the eye, forming a black dot, through which light enters the eye.
- Retina: The light-sensitive layer of tissue at the back of the inner eye.
- Autonomic Nervous System: The part of the nervous system responsible for control of the bodily functions not consciously directed, such as breathing, the heartbeat, and digestive processes.
- Direct Pupillary Reflex: The constriction of the pupil in response to light shone into the same eye.
- Consensual Pupillary Reflex: The constriction of the pupil in response to light shone into the opposite eye.
External links
- Medical encyclopedia article on Pupillary reflex
- Wikipedia's article - Pupillary reflex
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