Nervous Tissue – Ch 12 – Flashcards
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the larger of the two nerve cells, they generate and transmit nerve impulses
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neuron
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the biosynthetic center of the neuron
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cell body
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process of the neuron that carries a nerve impulse away from the cell body towards the target cell
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axon
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branching process of the neuron that carries information towards the cell body
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dendrite
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a fatty sheath found around certain axons that increases the speed of conduction of a nerve impulse
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myelin sheath
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spaces between segments of the myelin sheath along a nerve fiber
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node of ranvier
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junction between neuron and target cells
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synapse
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found at the end of the telodendria, they contain synaptic vesicles
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axon terminals
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a vesicle containing neurotransmitters in the axon terminal of a neuron
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synaptic vesicle
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fluid-filed space at a synapse through which neurotransmitters diffuse
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synaptic cleft
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in the nervous system, the neuron that sends the message. In the peripheral nervous system, this is the efferent neuron
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presynaptic neuron
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in the nervous system, the neuron that receives the message. In the peripheral nervous system, this is the afferent neuron
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postsynaptic neuron
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an electrical impulse conducted along the neuron membrane
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action potential
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event in which the resting potential becomes less negative because of an influx of cations; the beginning stage of an action potential
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depolarization
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event in which the resting membrane potential returns to a negative value because of the outward flow of cations; the end stage of an action potential
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repolaization
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in the generation of an action potential across a a synapse , may be inhibitory or excitatory in the postsynaptic neuron depending on the neurotransmitter
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local potential
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event duing an action potential in which the resting membrance potential becomes moe negative than it is normally at rest because of the continues outward flow of cations
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hyperpolarization
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Describe the three neuron loop
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neuronal action potential reaches the axon terminal of neuron 1 -> neurotransmitters are released from axon terminals by exoxytosis -> neurotransmitters diffuse across the synaptic cleft -> neurotransmitters bind to the postsynaptic membrane of neuron 2 and generate an excitatory local potential ->excitatory local potentials summate -> local potentials spread through the plasma membrane to the trigger zone/axon hillock -> axon hillock is a depolarized to threshold ->action potential generated -> voltage gated Na+ channels open, causing depolarization -> voltage gated Na+ channels close, and K+ ion channels open -> K+ ions exit the cytosol, causing repolarization -> K+ ions continue to exit until the membrane in hyperpolarized -> the action potential is propagated along the axon -> the action potential reaches the axon terminals of neuron 2 -> neurotransmitters are released from the axon terminal by exocytosis -> neurotransmitters diffuse across the synaptic cleft -> neurotransmitters cause an excitatory or inhibitory local potential in the postsynaptic membrane of neuron 3
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multipolar neuron
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neurons with one axon and many dendrites
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oligodendrocytes
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form the myelin sheath in the CNS
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astrocytes
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anchor neurons and blood vessels, maintain extracellular environment around neurons, assist in the formations of the blood brain barrier
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microglial cells
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phagocytic cells of the CNS
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schwann cells
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create the myelin sheath in the PNS
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satellite cells
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surround the cell bodies of neurons in the PNS
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ependymal cells
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ciliated cells in the CNS that form and circulate cerebrospinal fluid
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What is the funtion of the myelin sheath?
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The myelin sheath protects and insulates the fibers and increases speed of transmission of action potential
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Which part of the neuron is capable of generating an action potential?
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axon
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Put the following events of the neuronal action potential in the correct order, placing number 1 next to the first event, number 2 next to the second event, and so on.
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1. Voltage-gated sodium ion channels open, and the axon depolarizes
2. Voltage-gated sodium ion channels close, and voltage-gated potassium ion channels open
3. Potassium ions exit the cell, causing repolarization
4. Potassium ions continue to exit the cell, causing hyperpolarization
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Neurotransmitters that bind the postsynaptic membrane generally generate a/an
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local potential
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Where are synaptic vesicles located?
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axon terminals
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What triggers exocytosis of synaptic vesicles?
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the influx of calcium ions into the axon terminal
