E.5b Brain Function

20/01/2014 § Leave a comment

I’ve been listening to a lot of ’80s music these days. It helps deal with the senioritis.


So one of the questions on the syllabus is “Explain sympathetic and parasympathetic control of the heart, movements of the iris, and flow of blood to the gut.” Well, okay, the sympathetic and parasympathetic controls are important in the autonomic nervous system, the heart, the blood flow of the gut, and the iris. GO FIGURE.

The sympathetic control of the ANS is for fight-or-flight while the parasympathetic control is for restorative, resting, and digestive purposes.In the heart, sympathetic control accelerates the heart, thus pumps more blood to the muscles while parasympathetic control does the opposite, slowing down the heart and pumping less blood to the muscles, letting the body relax. In the blood flow to the gut, the sympathetic control is to constrict the blood vessels, thus decrease the blood flow, and by contrast, the parasympathetic control is to dilate the blood vessels and increase the blood flow. Finally in the iris of the eye, the sympathetic control is for the radial muscles to contract, which in turns dilates the pupils (and lets it take in more light), and by contrast the parasympathetic control contracts the circular muscle fibers to contract to constrict the pupil and close it off from light.

Also, have a brief definition of the pupil reflex, which is when a bright light shines into one eye, both eyes’ pupils will constrict. And okay okay okay, the brain is also the organ that perceives pain, responding by releasing endorphins to inhibit pain. Brains. Very cool.

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