Chapter 49 introduce to nervous systems. After completing this unit, you should be able to compare and contrast the nervous systems of: hydra, sea star, planarian, nematode, clam, squid, and vertebrate. Distinguish between the following pairs of terms: central nervous system, peripheral nervous system; white matter, gray matter; bipolar disorder and major depression. List the types of glia and their functions, compare the three divisions of the autonomic nervous system. | Chapter 49 Nervous Systems Overview: Command and Control Center The circuits in the brain are more complex than the most powerful computers. Functional magnetic resonance imaging (MRI) can be used to construct a 3-D map of brain activity. The vertebrate brain is organized into regions with different functions. Scientists map activity within the human brain Figure How? For the Discovery Video Novelty Gene, go to Animation and Video Files. Nervous systems consist of circuits of neurons and supporting cells The simplest animals with nervous systems, the cnidarians, have neurons arranged in nerve nets. A nerve net is a series of interconnected nerve cells. There is no central pathway / or directional organization. More complex animals have nerves. Nerves are bundles that consist of the axons of multiple nerve cells. Sea stars have a nerve net in each arm connected by radial nerves to a central nerve ring. Nervous system organization (e) Insect (arthropod) Segmental ganglia Ventral nerve cord Brain (a) Hydra (cnidarian) Nerve net Nerve ring Radial nerve (b) Sea star (echinoderm) Anterior nerve ring Longitudinal nerve cords (f) Chiton (mollusc) (g) Squid (mollusc) Ganglia Brain Ganglia (c) Planarian (flatworm) Nerve cords Transverse nerve Brain Eyespot Brain (d) Leech (annelid) Segmental ganglia Ventral nerve cord Brain Spinal cord (dorsal nerve cord) Sensory ganglia (h) Salamander (vertebrate) Figure Hydra (cnidarian) Nerve net Nerve ring Radial nerve Sea star (echinoderm) Figure , b Nervous system organization Bilaterally symmetrical animals exhibit cephalization. Cephalization is the clustering of sensory organs at the front end of the body. Relatively simple cephalized animals, such as flatworms, have a central nervous system (CNS). The CNS consists of a brain and longitudinal nerve cords. Planarian (flatworm) Nerve cords Transverse nerve Brain Eyespot Brain Leech (annelid) Segmental ganglia Ventral nerve cord Figure Nervous . | Chapter 49 Nervous Systems Overview: Command and Control Center The circuits in the brain are more complex than the most powerful computers. Functional magnetic resonance imaging (MRI) can be used to construct a 3-D map of brain activity. The vertebrate brain is organized into regions with different functions. Scientists map activity within the human brain Figure How? For the Discovery Video Novelty Gene, go to Animation and Video Files. Nervous systems consist of circuits of neurons and supporting cells The simplest animals with nervous systems, the cnidarians, have neurons arranged in nerve nets. A nerve net is a series of interconnected nerve cells. There is no central pathway / or directional organization. More complex animals have nerves. Nerves are bundles that consist of the axons of multiple nerve cells. Sea stars have a nerve net in each arm connected by radial nerves to a central nerve ring. Nervous system organization (e) Insect (arthropod) Segmental ganglia .
