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  1. 1. The Nervous System of Arthropods Insect (arthropod) vs. Humans
  2. 2. Arthropod <ul><li>Background Info </li></ul><ul><ul><li>Arthropods are the largest phylum of animals and include insects, crustaceans, and arachnids. </li></ul></ul><ul><ul><li>They have a segmented body and usually have many appendages on each segment. </li></ul></ul><ul><ul><li>All arthropods have a strong outer exoskeleton made of chitin. </li></ul></ul>
  3. 3. Pictures Examples <ul><li>Crustacean </li></ul><ul><li>Arachnid </li></ul><ul><li>Insect </li></ul>
  4. 4. Arthropod vs. Human <ul><ul><ul><li>Insect Nervous system not centralized </li></ul></ul></ul><ul><ul><ul><li>Behaviors like feeding, locomotion, and mating is controlled by segmental ganglia instead of the brain.   </li></ul></ul></ul><ul><ul><ul><li>arthropod nerve cells tend to be much larger and fewer in number than those of vertebrates </li></ul></ul></ul><ul><ul><ul><li>Invertebrates have neurons that are unipolar and vertebrates have neurons that are multipolar </li></ul></ul></ul><ul><ul><ul><li>For fast conduction speed, invertebrates have myelin sheaths while invertebrates have giant axons. </li></ul></ul></ul><ul><ul><ul><li>Sometimes the brain may innervate or inhibit activity in the segmental ganglia. These signals aren’t necessary for survival </li></ul></ul></ul><ul><ul><ul><ul><li>A headless insect can survive for days or weeks until it dies of starvation or dehydration if only it’s neck is sealed to prevent the loss of blood! </li></ul></ul></ul></ul>
  5. 5. Arthropod Nervous System <ul><li>Arthropods have a nervous system which is composed of ganglia. It is connected by the ventral nerve cord. </li></ul><ul><ul><li>The ventral nerve cord has segmented ganglia which is connected by nerve fibers. </li></ul></ul><ul><ul><li>A ganglion is a dense group of interconnected neurons </li></ul></ul><ul><ul><ul><li>Their purpose is to process sensory information and control motor functions. </li></ul></ul></ul><ul><li>Most commonly, each body segment of the arthropod will have one ganglion on each side. </li></ul><ul><li>Some ganglia are fused and form the brain </li></ul>
  6. 6. Arthropod Brain <ul><li>The arthropod’s brain is composed of six ganglia which are fused together. They are located near the backside within the head capsule. </li></ul><ul><ul><li>There are three parts of the brain and each controls certain activities in the body: </li></ul></ul>
  7. 7. Protocerebrum <ul><li>Protocerebrum: This is the first pair of ganglia which are responsible for vision; they stimulate the nerves that react with the ocelli. </li></ul><ul><ul><li>The ocelli are like miniture eyes that are capable of sensing light. They are also photoreceptor organs </li></ul></ul><ul><ul><li>Arthropods generally have two ocelli, the lateral ocelli and dorsal orcelli. </li></ul></ul>
  8. 8. Deutocerebrum <ul><ul><li>Deutocerebrum:The deutocerebrum is the second pair of ganglia which is responsible for processing the sensory information that is collected by the antennae. </li></ul></ul>
  9. 9. Tritocerebrum <ul><li>Tritocerebrum: The tritocerebrum is the third pair of ganglia which integrates the sensory inputs from the protocerebrum and the deutocerebrums. </li></ul><ul><li>The tritocerebrum also links and connects the brain to the rest of the ventral nerve cord. </li></ul>
  10. 10. Other important ganglia <ul><li>Subesophageal ganglion </li></ul><ul><ul><li>Located in the head </li></ul></ul><ul><ul><li>Stimulates the madibular nerves which are partly responsible for sensations of the face. </li></ul></ul><ul><ul><li>Also stimulates the pharynx, salivary glands, and neck muscles. </li></ul></ul><ul><ul><li>Thoracic Ganglia </li></ul></ul><ul><ul><ul><li>Controls movement for traveling by innervating the legs and wings </li></ul></ul></ul><ul><ul><li>Abdominal ganglia </li></ul></ul><ul><ul><ul><li>Controls the movement of the abdominal muscles </li></ul></ul></ul>
  11. 11. The Stomodeal Nervous System <ul><li>The internal organs are stimulated by the Stomodeal Nervous System </li></ul><ul><ul><li>  There are a pair of frontal nerves near the base of the tritocerebrum that link the brain with the frontal ganglion on the anterior wall of the esophagus.   </li></ul></ul><ul><ul><ul><li>This ganglion activates and stimulates the pharynx and muscles associated with swallowing.   </li></ul></ul></ul><ul><ul><ul><li>The gut and the heart get activated </li></ul></ul></ul>
  12. 12. Pictures
  13. 13. <ul><li>The End </li></ul>