Hearty Har Har
Today's post is by Prabarna Ganguly, a Ph.D. student in the Psychology Department at Northeastern University. Thanks again, Prabarna!
Sit down, place two fingers on your wrist or neck, and feel the thump, thump as your heart follows its rhythmic routine. How does it feel? Like you are alive, right? We usually notice those booming thuds when attempting to admit romantic feelings, or while pulling a (hopefully rare) Vincent Vega.
A heart’s function in humans can be broken down into physiological and psychological responses. Physiological tasks are the ones we were taught in school:
· Sending blood loaded with oxygen all over the body
· Giving cells the nutrients they need to survive
· Sending waste to the liver and kidneys
Psychological studies show that various emotional states cause individuals to experience different rhythmic patterns. Stress, anger, and frustration show incoherent rhythmic patterns, while positive behaviors such as appreciation, love, and compassion show more regular, streamlined waves.
Many organisms, all vertebrates for example, contain blood within their vessels. On the other hand, invertebrates (spiders, insects, shellfish, etc.) can have hemolymph, a fluid that flows freely throughout the body and isn’t contained in vessels. A tube in the upper body collects hemolymph in the abdomen, passes it through the heart, and toward the head. Evolution has played a decisive role in developing how the heart behaves and functions within various animals.
But not all animals have a heart. So what about the others? The heartless ones?
You could find these creatures in the oceans and the mucky ground below. Some marine animals like sponges, jellyfish, sea anemone, and the Portuguese Man o’ War lack a circulatory system. How do they survive? These animals use a process called direct diffusion, absorbing nutrients and oxygen through their outermost layers of protection, and releasing carbon dioxide and other bodily leftovers as waste. Because this diffusion only has to happen over a very short distance, their very special, heartless body is stable. This wouldn’t be the case for more 3D animals (aka us) because we have many layers of skin that need nutrients faster than diffusion can carry them.
Sometimes these organisms can be BFFLs, largely by using each other. Sponges and jellyfish can be besties with various types of blue-green algae and fish by offering shelter to each other. The freeloading flatworm enjoys a one-way relationship with the horseshoe crab, eating scraps of leftover food, without the crab’s knowledge. These relationships are found in abundance once you are down in the no-heart, single-celled organismic realm (bacteria in our gut, for instance). Perhaps these are slight indications that having no heart does not make one heartless after all!
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