Central Nervous System

1. Central Nervous System

2. Central Nervous System (CNS) • Consists of the brain and spinal cord • Integrates and processes information by nerves

3. Peripheral Nervous System (PNS) • Divided into Somatic and Autonomic systems Somatic Nervous System (Voluntary) • Consists of sensory receptors • Nerves that carry sensory information or instructions to the CNS to the skeletal muscles Autonomic Nervous System (Involuntary) • Controls glandular secretions • Sympathetic and parasympathetic

4. Autonomic Nervous System (Involuntary) • Autonomic Nervous System • Sympathetic nervous system • allow body to function under stress • fight or flight • Parasympathetic nervous system • controls vegetative functions • feed or breed or rest • constant opposition to sympathetic system

5. The Organization of the Brain

6. Cells of the Nervous System • Two main cells: • Neurons • Specialized cells to respond to physical and chemical stimuli • Release chemicals that regulate various body processes • Individual neurons are organized into tissues called nerves

7. Cells of the Nervous System Cont… 2) Glial Cells • Supports the nervous system tissue • Removes waste • Defend against infections

8. The structure of a neuron • Specialized cell structures that enable them to transmit nerve impulses Features: • Dendrites • Receive nerve impulses from other neurons and sends back to the cell body 2) Cell body • Site of metabolic reactions • Processes input from dendrites and sends to the axon

9. The structure of a neuron cont… 3) Axon • Conducts impulses away from the cell body • Releases chemical signals to the receptors and dendrites • Myelin sheath protects the neuron and speeds up the rate of nerve impulse transmission

10. Classifying Neurons

11. Nerve Impulse Generation and Resting Membrane Potential

12. Nerve Impulses • Galvani and Volta performed experiments using leg muscles • Muscles contracted after experiencing stimulation from electric currents • Resting neuron: the outside of the cellular membrane is negative, relative to the inside • This causes a potential difference between the inside and outside of the neuron

13. More on Resting Potential • Potential difference across the membrane of a resting neuron • Remains relatively constant for all neurons, approximately -70 mV • Controlled by electrochemical gradients, protein presence and active transport

14. Electrochemical Gradient • Large, negatively charged proteins cause the inside of the membrane to be charged • Potassium and sodium ions control the electrochemical gradient • Gradient is adjusted, maintained and controlled through active transport

15. Blue – Sodium Yellow – Chlorine Orange – Anions Purple - Potassium Controlled by various channel proteins such as the one used for potassium shown in the diagram

16. Action Potential

17. What Is It? • Movement of electrical impulse • Rapid change in polarity • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html

18. History • Discovered by 2 British Scientists • Used giant squid • Revealed that action potential is dependant on voltage gated Na and K channels

19. When does this occur? • Occurs when Threshold Potential occurs • Threshold Potential Varies • Strength of stimulus does not = strength of Action Potential

20. Events • Action Potential triggered by Threshold Potential • Voltage gated Sodium channels open • Sodium channel closed Potassium Channels open • Potassium Channels closes after hyperpolarization • Membrane Potential brought back to -70mV

21. Does natural = safe? • Natural and synthetic neurotoxins work by blocking the “action potential” • Tetrodoxin (pufferfish) blocks sodium channel • Dendrotoxin (black mamba) blocks potassium channel • Applications: chemical weapons? Insecticides?

22. Extended Information • Tetraodontidae (Pufferfish) • Contains Tetrotoxin (1200x more poisonous than cyanide)

23. Synaptic Transmission

24. Synaptic Transmission Synaptic cleft Presynaptic neuron Postsynaptic neuron (protein) http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__chemical_synapse__quiz_1_.html

25. Reflex Arc

26. Reflex Arc and Feedback • Reflex arc: simple connection of neurons that results in a reflex action in response to a stimulus

27. Reflex Arc and Feedback • Your nervous system reacts to sensory input through a basic impulse pathway • Reflexes: Sudden involuntary responses to certain stimuli • Requires 3 neurons (sensory input, integration, motor output)

28. Sensory Input Neuron • Sensory receptors such as those in the skin, receive stimuli and form a nerve impulse • Sensory neurons transmit impulses from the sensory receptors to the central nervous system

29. Integration Neurons • Interneurons are found entirely within the central nervous system • They act as a link between the sensory and motor neurons • They process and integrate incoming sensory information and relay outgoing motor information

30. Motor Output • Motor neuron transmits information from the central nervous system to effectors • Effectors include muscles, glands and other organs that respond to impulses from motor neurons

31. Putting it all together 1. receptors in skin sense the pressure or temperature change 2. Impulse is carried by the sensory neurons then activates the internuron in the spinal cord 3. The interneuron signals the motor neuron to instruct the muscle

32. Loss of Homeostasis • What can be seen through synaptic transmission? • Parkinson’s • Dopamine • Controls body movements • Sensations of pleasure • Serotonin • Regulates temperature and sensory perception • Depression

33. Deep Brain Stimulation

34. Take Home Message • Synapse = connection between neurons or neuron and effector • Impacts homeostasis through neurotransmitters • Movement • Temperature • Natural painkilling • Danger/stress reactions