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29 Cards in this Set
- Front
- Back
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What is the CNS, and what does it consist of?
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Central nervous system, brain and spinal cord.
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What is the PNS, and what does it consist of?
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Peripheral nervous system, nerves outside of CNS.
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Major parts of a neuron:
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Cell body
Dendrites Axon |
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Neuron cell body
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contains a nucleus and organelles
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Dendrites
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Receive signals from sensory receptors or other neurons.
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Axon
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Conducts nerve impulses
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Sensory Neurons
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Receive signals from a sensory receptor.
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Interneurons
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Process signals from sensory neurons.
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Motor Neurons
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Transmit impulses from CNS to an effector, such as a muscle fiber, gland, or organ.
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Neuroglia types
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More abundant than neurons.
1. Astrocytes 2. Microglia 3. Oligodendrocytes |
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Astrocytes
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Nourish and produce hormones that help maintain neurons.
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Microglia
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Consume foreign debris and bacteria.
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Oligodendrocytes
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Produce myelin sheath in CNS.
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Myelin sheath
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forms when oligodendrocytes or Schwann cells wrap around an axon. Leaves gaps called nodes of Ranvier. Good for fast messaging.
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Nodes of Ranvier
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Gaps along an axon wrapped in myelin sheath.
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White matter
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White because it has myelinated axons. Gray matter lacks myelin.
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Schwann cells
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Form the myelin sheath for neurons outside CNS. Can regenerate and form a new axon. Axons in CNS cannot regenerate.
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Resting potential
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Potential energy within a neuron because of polarized condition, when not conducting impulse.
Positive outside due to Na+, negative inside. |
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Permeability of neuron's cell membrane at rest
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Permeable to potassium, not to sodium. K+ diffuses out of the cell to join Na+ ions.
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Charge held by neuron at rest:
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-65 millivolts (mV)
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Sodium-potassium pump
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In neuron cell membrane, keeps neuron recharged by pumping Na+ out thru gated channels, allowing some K+ to flow into neuron.
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Action potential
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a. Stimulus activates axon of neuron.
b. Depolarization: Protein channels open, allowing Na+ ions to flow into cell, changes to positive charge. c. Repolarization: Na+ channel gates close, K+ gates open. Neuron is back to resting potential. |
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Neuron Threshold
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Stimulus must cause neuron to reach threshold to initiate action potential. Neuron then fires or not, nothing in-between.
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Depolarization
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Sudden switch in polarity changes action potential from -65 to -40 to +40. Electrical charge changes from negative to positive.
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Gray matter (unmyelinated axons)
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Produces slow impulses because each section of the axon must go thru an action potential. In brain, where speed isn't so important.
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White matter (myelinated)
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Rapid saltatory conduction from one node of Ranvier to another.
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Saltatory conduction
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Jumping from one gap to the next.
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Neural Transmission
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Occurs between two neurons or a neuron and a target tissue. Neurotransmitter is released across a synapse between the end of one axon and the dendrites of the next neuron.
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Neurotransmitter
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Chemicals that can slow down or speed up stimulus. Dopamine, serotonin, some drugs.
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