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Zoology Exam 3 - ZoologyExam3 Neuroscience Nervoussystems...

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Zoology Exam 3 01:53 Neuroscience Nervous systems Integrate internal + external info Neurons   Cells that send and receive electrical or chemical signals Similar across species More complex organisms have more complex nervous systems and more neurons The human brain has 100 billion neurons When increasing complexity   more neurons, more organized In Vertebrates: CNS  = the brain and spinal cord Central nervous system PNS  = nerve cells outside the CNS Peripheral nervous system Sensory Neurons  Sense, info from PNS   CNS Long Interneurons Integrate, talk to each other  Motor Neurons
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CNS   PNS Long Dendrites – receive signals Cell body – contains cell machinery  Axon Hillock – integrates signals, “decider” Axon – send signals to terminal branches aka axon terminals Terminal branches – send signals to other cells Neuron form matches function
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Brain has      glial cells      (or glia)     More glial cells in brain than neurons 1. Form myelin sheath Pink-insulation, wraps around axon, travels more quickly  Oligodendrocytes  (CNS) Provide myelin sheath for CNS Schwann  (PNS) provide myelin sheath for PNS Multiple Sclerosis Can have difficulty moving/breathing 2. Astrocytes metabolic support to neurons form blood brain barrier electrical properties of neurons are similar across species Across its plasma membrane, every cell has a voltage Called membrane potential  (difference of voltage) The inside of a cell is negative Relative to outside
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The Resting Potential Membrane potential of a neuron that is not sending signals  Depends on ionic gradients  that exist across the plasma membrane  Differences of ions across the plasma membrane The inside of the cell is relatively more negative than outside  A ions also inside = why more negative Channels are selectively permeable to K+ and Na+ At rest = channels are closed (sometimes can be leaky) Sodium Potassium Pump Actively transports Na+ out of the cell and K+ into cell Active transport of ions help maintain resting potential Electrochemical Gradient  Ions under pressure Electrical  – opposite attract Chemical  – move away from other ions Passive transport  What happens when Na+ channel opens?
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The inside of the neuron becomes more positive  Electrical signals from other neurons cause ion channels to open or close  Voltage-gated channels Will open or close ion channels Some stimuli trigger a depolarization  – when Na+ channels open a reduction in the magnitude of the membrane potential (inside more +) – Na+ comes in  and makes more positive Other stimuli trigger a hyperpolarization  – when K+ channels open
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