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Published byPiers Esmond Kennedy Modified over 9 years ago
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Warm-Up 5/8 1.The sympathetic nervous system has what effect on the body? 2.What portion of the nervous system is responsible for voluntary movement? 3.Support or contradict this statement: If two individuals receive exactly the same sensory information, their “integration” of that information will always be identical.
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NEURON STRUCTURE & NEURAL CELL TYPES
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NERVOUS TISSUE CELLS
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2 Neural cell types: Neurons & Neuroglial cells A.K.A: -Neuroglia -Glia -Glial cells AMAZING variety in shapes and sizes! NERVOUS TISSUE CELLS
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Neurons transmit nerve impulses known as “Action Potentials” (AP) Neuroglia carry out a variety of functions to aid and protect the nervous system. Neural Cell Functions
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STRUCTURE OF NEURON
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Neurons: Nerve cells. Unique structure – cell body with many extensions or processes (nerve “fibers”) which conduct impulses. 1. Dendrites – shorter, more numerous. These, along with the cell body, form the receptive surfaces of neurons. 2. Axons – single, long “fiber” which conducts impulse away from the cell body. Sometimes it is “branched” (collaterals). End has many fine branches called AXON TERMINALS 3. Soma – Cell body
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On peripheral axons, a fatty MYELIN SHEATH surrounds and insulates the axon. Functions to speeds up signal transmission.
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MEMBRANE POTENTIAL/ NERVE IMPULSE
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Here is a Neuron. Charged particles and ions exist both inside and outside of the cell. However, distribution of these charged particles is not identical inside and outside.
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OUTSIDE CELL (Extracellular) INSIDE CELL (Intracellular) Lots of Sodium (Na + ) ions Few Potassium (K + ) Lots of Potassium (K + ) Few Sodium (Na + ) ions
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Extracellular Intracellular (Na + ) (K + ) (Na + ) So they spend energy (ATP) to keep Sodium out and Potassium in! Neurons NEED this distribution of ions to function! Ions will SLOWLY leak across membrane via diffusion.
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Burns ATP for energy to do work. Pushes sodium ions out of the cell and potassium ions into the cell. EXTRACELLULAR INTRACELLULAR Na + /K + pump Protein in cell membrane that moves ions!
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Cell at REST. (Unstimulated) + ++++++++ ------------------ Outside has more positively charged particles. Inside the cell there is an excess of negative charges caused in part by the negative charge on most proteins
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(Na + ) (K + ) (Na + ) This difference in concentration and charge causes a force on the particles to move across the membrane! + ++++++++ ------------------ Electro-Chemical Gradient! This “force” across the membrane creates something known as the “membrane potential”
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Lots of (Na + ) Few (Na + ) FORCE + +++++ ------------ Membrane Potential RESTING MEMBRANE POTENTIAL (RMP)- difference in electrical charge across the membrane at “rest” Measured in milli-volts (mV) RMP of cell = -70mV -70mV
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Stimulation + +++ Some input opens a channel in the membrane! (touch, temperature, neurotransmitter etc.) Most neurotransmitter receptors are simply doors for ions that are unlocked by a their target neurotransmitter. + +++ -70mV
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+ +++ Channel opens and lets some sodium sneak into the cell! This causes slight depolarization of membrane! + +++ Stimulation -70mV + ++ -63mV
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+ +++ If enough positive ions can get into the cell to get the membrane potential to -55mV (threshold) it will stimulate an Action potential! + +++ Stimulation -70mV + ++ -63mV-55mV ACTION POTENTIAL! THRESHOLD!
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When an action potential occurs… 1.Sodium ions rush into the neuron causing a positive charge inside the axon
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When an action potential occurs… 2. This influx of Na+ (sodium) causes a similar change in the next region of the axon
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When an action potential occurs… 2. This influx of Na+ (sodium) causes a similar change in the next region of the axon
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When an action potential occurs… 3. The electrical nerve impulse (positive charge) moves like a wave down the axon
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4.K+ channels open to repolarize the membrane 5.The Na+/K+ pump restores the original balance of ions to resting levels
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END. VIDEO! Muahahaha….
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