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Nervous System

Nervous System. By Melissa Ames & Andral Harmon . What is the Nervous System?. The nervous system consists of the central nervous system (CNS) and peripheral nervous system and is composed of cells called neurons that can carry rapid electrical impulses. (Assessment Statement 06.05.01) )

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Nervous System

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  1. Nervous System By Melissa Ames & Andral Harmon

  2. What is the Nervous System? • The nervous system consists of the central nervous system (CNS) and peripheral nervous system and is composed of cells called neurons that can carry rapid electrical impulses. (Assessment Statement 06.05.01)) • Nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons (Assessment Statement 06.05.03).

  3. So, what’s the point of the Nervous System? • The basis of the nervous system consist of a combination of electrical and chemical signals that enable nerve cells (neurons) to communicate with one another. • All about those nerves!!!

  4. Basic Neuron

  5. How does the Nervous System help the body stay alive? • The nervous system controls three overlapping functions of sensory input, integration, and motor output. • The nervous system is composed of neurons and supporting cells that carry out the three overlapping functions of the nervous system. • The nervous system organization tends to correlate with the body symmetry. • The brainstem conducts data and controls automatic activities essential for survival. The cerebellum controls movement and balance to support the body’s needs for every day life.

  6. Neurons • Specialized for transmitting signals from one location in the body to another • A neuron has a relatively large cell body containing the nucleus and a variety of other cellular organelles • Most distinctive feature: fiber like extensions called processes There are two types of processes: • 1. Dendrites - Convey signals from their tips to the rest of the neuron. • They are structural adaptations that increase the surface area of the neuron where it receives inputs from other neurons or sensory receptors. • 2. Axons- Conduct messages towards their tips. • Axons can be branched and each branch can give rise to thousands of specialized endings. • Axon hillock is the region where impulses that pass down the axon are usually generated.

  7. Supporting Cells (Schwann Cells) • Many axons are enclosed by an insulating layer called the Myelin Sheath, which is formed by supporting cells. • In the CNS supporting cells called ogliodendrocytes produce the myelin sheaths.

  8. Nerve Impulses • Nerve impulses begin and take place because of concentration gradients of Na+, K+, and Cl-. • The inside of the axon has a negative charge while the outside has a positive charge. • Resting potential rises above threshold level. • Voltage gated sodium channels open. • Sodium ions flow into the cell and more sodium channels open. • Inside of the cell develops a positive charge and results in depolarization

  9. Nerve Impulses 5. Voltage gated potassium channels open. 6. Potassium ions flow out of the cell. 7. Cell develops a negative charge and results in repolarization. 8. Concentration gradients restored by sodium-potassium pumps. 9. Resting potential is restored.

  10. Action Potential • http://outreach.mcb.harvard.edu/animations/actionpotential.swf

  11. Resting Potential and Action Potential (cont.)

  12. Resting Potential and Action Potential • Cells that have the ability to generate changes in their membrane potentials are called excitable cells. • -The membrane potential of an excitable cell in a resting state is called the resting potential. • -Depolarization is a reduction in the electrical gradient across the brain. • -The threshold potential is the potential that an excitable cell membrane must reach for an action potential to be initiated. • -If depolarization reaches the threshold, it results in the response called the action potential. The action potential is the nerve impulse.

  13. Synapses • Synaptic terminals - relay signals to other cells (neurons mostly) by releasing chemical messengers called neurotransmitters. • The site of contact between synaptic terminal and a target cell (neuron or effector) ex. muscle cell, is called a synapse.

  14. Synaptic Transmission • Synaptic transmission’s main function is to mobilize body systems during activities in a series of steps. • 1. Action potential reaches the end of the transmitting end of a discharge across a synapse (presynaptic) neuron. • 2. Calcium channels open • 3. Calcium ions flow into the presynaptic neuron • 4. Vesicles fuse with the plasma membrane releasing the neurotransmitter by exocytosis. • 5. Neurotransmitters diffuse across the synaptic cleft • This effect can be either direct of indirect.

  15. Synaptic Transmission Direct Synaptic Transmission Indirect Synaptic Transmission Ion channels bind to the neurotransmitter and are clustered in the membrane of the postsynaptic cell. The receptor opens and allows specific ions to diffuse across the membrane. When a neurotransmitter binds to a receptor that is not part of an ion channel. This activates a signal transduction pathway involving a second messenger in the postsynaptic cell. One pathway involves cyclic AMP (cAMP).

  16. Indirect Synaptic Transmission cont. • An example is: • when the neurotransmitter binds to the receptor, the neurotransmitter-receptor complex activates a G protein. • Then the enzyme that coverts ATP to cAMP activates protein kinase A, which phosphorylates specific channel proteins in the postsynaptic membrane, causing them to open, or in some cases, close. • This allows for the binding of a neurotransmitter molecule to a single receptor to open or close as many channels.

  17. Synaptic Transmission • http://outreach.mcb.harvard.edu/animations/synaptic.swf

  18. How has the nervous system evolved to meet the needs of humans? • Older parts of the nervous system were just for reflexes. • When people starts to evolve, our nervous system started to evolve as well. • Primates developed complex tools, as wells as idea. With that development the nervous system developed in ways that made it easier for specialized neurons to communicate with one another. • The nervous system is now associated with memory, learning and thinking.

  19. Bibliography (Pictures) • http://www.spiritualgarden.net/info/human+electricity.html • http://en.wikipedia.org/wiki/Action_potential • http://p-i-a.com/Magazine/Issue3/Physics_3.htm • http://www.daviddarling.info/encyclopedia/M/myelin.html • http://faculty.southwest.tn.edu/rburkett/A&P1_nervous_system_lab.htm • http://biologyclass.neurobio.arizona.edu/lect2b.html • http://outreach.mcb.harvard.edu/animations_S05.htm

  20. Bibliography(cont.) • http://www.lumosity.com/blog/your-nervous-system-at-work/

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