All annelids and arthropods have a body plan. unlike annelids, arthropods also have . the circulatory system of annelids is , while the circulatory system of arthropods is .

All annelids and arthropods have a body plan. Unlike annelids, arthropods also have a coelom, and a segmented body. The circulatory system of annelids is closed, while the circulatory system of arthropods is opened.

Arthropods are invertebrate organism that possess a stiff exoskeleton, a segmented body, and paired jointed appendages. Arthropods include insects, crustaceans, myriapods, and arachnids. Arthropods possess an open circulatory system; a system without blood vessels. The circulatory system of arthropods is made up of a tube (the heart), and an open hemocoel (in which the blood moves).

Annelids are invertebrate animals that have a body cavity, movable bristles, and a segmented body. Annelids include earthworms, and leeches. The circulatory system of annelids is closed; blood circulates through a closed system of blood vessels.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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