If jelly fish don't have a brain then how do they know how to move, or swim or do anything they do?

Answer 1

Jellyfish are part of philum cnidaria. At the most primitive cnidaria(hidrozoars) the nervous sistem is called a diffuse nervous sistem: it has multipolar neurons on the surface of it's body. Here we find the simplest reflex in the animal kingdom. The nervous system in jellyfish(scifozoars) is more complex because it is concentrated more on the region of the umbrella. So they do not have a brain, but they have brain cells and they are organised well enough to fulfill the needs of the jellyfish.


Like the hydra, the jellyfish has a nervous system characterized by a series of interconnected nerve cells (a nerve net). The nerve net conducts impulses around the entire body of the jellyfish. The strength of a behavioral response is proportional to the stimulus strength. In other words, the stronger the stimulus, the larger the response.
Some jellyfish (for example, Aurelia) have specialized structures called "rhopalia". These rhopalia have receptors for:


light (called ocelli)
balance (called statocysts)
chemical detection (olfaction),
touch (called sensory lappets)

When the animal moves and body is tilted, the statocyst makes contact with the cilium. When the cilium bends, it causes action potentials to fire in a nerve. This provides information to move muscles.

Answer 2

Jellies can swim. Just not against the ocean current, making them the largest form of plankton.

They may not have a "brain" as we know it, but they do have a large nerve net. Rhopalia around the bell margin are ganglia (concentrations of nerves). These help coordinate the movements of the jelly. They contain all sorts of sensory mechanisms to sense chemicals in the water, touch, which way is up and down, and can even detect light.

Answer 3

I know I cheated, but your question made me curious. Jelly Fish actually use the current of the water to move. That you for sparking my want to learn something new. : )

Answer 4

They do not swim, the float on the current and burn anything that touches them and eat anything that swims to them