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Nervous System

Nervous System. So, we now know that the nervous system is the first one to form in an early embryo, so let’s talk about this in a little more detail…. What is the Nervous System?. A network of specialized cells (nerve cells) which carry messages (impulses) throughout an organism

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Nervous System

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  1. Nervous System

  2. So, we now know that the nervous system is the first one to form in an early embryo, so let’s talk about this in a little more detail…

  3. What is the Nervous System? • A network of specialized cells (nerve cells) which carry messages (impulses) throughout an organism • Two key components: • Receptors: sensitive to changes, physical forces, or chemicals both inside and outside the body • Effectors: where the impulse is sent • Responds to the receptor

  4. Nervous System Definitions • Ganglia- mass of nerve structures (cells, roots, etc.) • Ocellus- photoreceptor; “simple eyes” • Cerebral- brain • Neurons- nerve cells

  5. Neuron • Nerve Cell • Consists of: • Cell Body (largest part) • nucleus & organelles • Axon & axon terminals • transmit signals to other cells • Myelin • insulator surrounding the axon which allows for the conduction of impulses • Dendrites • receive signals from other cells

  6. Synapse

  7. Types of Neurons • Motor Neuron- transmit signals for muscle contractions • Sensory Neuron- associated with the 5 senses • Interneuron- occur entirely within the central nervous system • Mostly found within the brain • Make local connections

  8. Types of Nervous Systems…

  9. 1. Cephalization • Definition: A concentration of nervous tissue in the anterior (head) portion of an organism • Complexity increases throughout the animal kingdom

  10. 2. Nerve Net • A network of nerve cells which allows the organism to respond to the environment • Lack a brain or any cephalization • Found in hydra & other cnidarians

  11. 3. “Ladder” • Two lateral nerve cords joined by transverse nerves • Found in planarian and other flatworms • Ganglia present in the anterior end • Ocellus (eyespots) with photoreceptors sense lighting

  12. 4. Cerebral Ganglia • Ventral nerve cord with anterior ganglia • Annelids, Arthropods, and Mollusks • Brain= control center for the ganglia • Many exhibit eyes with lenses that create images • Receptors- sense touch • Increased overall number of neurons

  13. Vertebrate Brain • Central Nervous System (CNS) • Brain: the enlarged anterior end of the nerve cord • Has three parts: 1. Hindbrain- regulates organs below the level of consciousness ( , lungs) • Cerebellum & Medulla

  14. 2. Midbrain- sensory input & coordinates reflex responses • Optic Lobe 3. Forebrain- receives and integrates sensory and motor input • Cerebrum & Olfactory bulbs • Associated with higher mental capacity

  15. Cerebrum Cerebellum Brain Stem

  16. Spinal Cord • Dorsal nerve cord • Transmits impulses to and from the brain

  17. Peripheral Nervous System (PNS) • Lateral nerves: accessory nerves that transmit impulses to and from the spinal cord • Accessory sense organs: • Eyes • Ears • Nose • Taste buds • Skin 5 senses!

  18. Motor System

  19. Functions of the Nervous System • Receives sensory input • Integrate sensory input • Generate motor outputs (responses)

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