1 / 19

The Nervous System

The Nervous System. By Lydia Chang, Lauren Lee, and Diana Zheng. Evolution of the Nervous System. Porifera: no nervous system Cnidaria: nerve net all throughout body—can react to stimuli from all sides Platyhelminthes: cephalization ; ganglia, eyespots, two main ventral nerve cords

caroun
Download Presentation

The Nervous System

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. The Nervous System By Lydia Chang, Lauren Lee, and Diana Zheng

  2. Evolution of the Nervous System • Porifera: no nervous system • Cnidaria: nerve net all throughout body—can react to stimuli from all sides • Platyhelminthes: cephalization; ganglia, eyespots, two main ventral nerve cords • Rhynchocoela: dorsal nerve cord, two lateral nerve cords • Nematoda: ring of nervous tissue around pharynx attached to dorsal and ventral nerve cords • Annelida: pair of brain-like cerebral ganglia and subpharyngeal ganglion • Mollusca: ranges from simple nervous system to relatively complex systems that rival those of mammals • Arthropoda: cerebral ganglion (brain!); sense organs concentrated on head • Echinodermata: decentralized nervous; no brain but have ganglia along radial nerves in some species; sensory neurons within podia

  3. Evolution of the Nervous System • Vertebrates: very centralized and cephalized; well-developed sensory organs; dorsal, hollow nerve cord (spinal cord) • Lampreys and hagfishes: no myelin sheath • Fish: enlarged cerebellum • Amphibians: growing importance of forebrain, but midbrain still important • Reptiles/Birds: many connections between thalamus and hemispheres • Birds: larger cerebellum • Mammals: brain completely dominated by cerebral hemispheres; large surface area; controlled mainly by cortex; large thalamus

  4. The Human Nervous System • Brain: about 2% human body mass • Neocortex: outer layer of brain • Human cerebral cortex (aka pallium): flat sheets of cells in six layers • Frontal lobe: reasoning, speech, motor cortex • Parietal lobe: speech, taste, reading, somatosensory cortex • Temporal lobe: hearing, smell, auditory • Occipital lobe: sight • Cerebellum: ballistic movements, balance, coordination, helps in learning and remembering motor skills

  5. From “Vertebrate Nervous System”

  6. The Brain, cont’d • Diencephalon: major integrating centers information, act as relay stations for info flow • Thalamus: main relay center for sensory information • Hypothalamus: maintains homeostasis • Brain stem: includes the pons, medulla oblongata • transfers info between peripheral and central nervous systems • helps coordinate large-scale body movements (e.g. running) • nerve crossing: right side of brain controls left side of body and vice versa • Midbrain/RAS (reticular activating system): centers for receiving and integrating several types of sensory info • Corpus callosum: connects brain hemispheres

  7. From Wikipedia

  8. Evolutionary Trends • More complex! • This system is necessary for complexity and sophisticated behaviors/responses to environment • Increases chance of survival: more complex NS = more complicated nerve connections, behaviors, movements • The nervous system controls all other body systems!! Except maybe skeletal

  9. Neurons • Neurons • Sensory neurons • Interneurons • Motor neurons

  10. How Neurons work • Resting potential: negative relative to the outside • Sodium-potassium pumps in the plasma membrane • Transport sodium out of the cell and potassium into it • Very few sodium channels • Net negative charge inside cell

  11. Action Potential • Depolarization • Rising phase of the action potential • Falling phase of the action potential • Undershoot: Potassium channels close to bring it back to the concentration needed to be at resting potential • refractory period

  12. Conduction of the Action Potential • Action potential: a “wave” from dendrite to axon • Speed is determined by axon diameter • Evolutionary trend: Because vertebrate axons have narrow diameters, vertebrates have adapted the myelin sheath to enable more efficient conduction • Nodes of Ranvier (nodes between gaps in myelin sheath) allows for saltatory conduction • current jumps from node to node

  13. Synapses • Electrical synapses: contain gap junctions to allow electrical currents to flow from one neuron to another • Chemical synapses (most synapses): neurotransmitter • Examples of neurotransmitters: acetylcholine, biogenic amines (serotonin)

  14. Disorders and Diseases • Cerebrovascular accident (stroke) • Parkinson's disease: • decreased stimulation of the motor cortex by the basal ganglia caused by the insufficient formation and action of dopamine • Multiple sclerosis: immune system damages the myelin • When myelin is lost, the axons can no longer effectively conduct signals

  15. Works Cited and Consulted • AP Bio book • http://faculty.washington.edu/chudler/nsdivide.html • http://parasitology.informatik.uni-wuerzburg.de/login/n/h/0941.html • http://www.daviddarling.info/encyclopedia/V/vertebrate_nervous_system.html • http://infusion.allconet.org/webquest/PhylumMollusca.html • http://www.mindcreators.com/Images/NB_Neuron.gif  • http://en.wikipedia.org/wiki/File:Neurons_big1.jpg

More Related