CAS BI 325 Chapter Notes - Chapter 5: Chemical Synapse, Gap Junction, Excitatory Synapse

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2 Jan 2018

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-presynaptic and postsynaptic membranes @ chem. synapses are separated by of gap junctions. -cleft filled with fibrous ecm proteins; glue" for pre & post membranes. Action potential in the motor axon always causes an action potential in muscle cell it innervates. Presynaptic terminal contains large number of active zones. Postsynaptic membrane ( motor endplate ) contains shallow folds packed w nt receptors. -----pre active zones aligned w these folds; ensure nt released onto large surface of chemically sensitive membrane. Major nt fall into 3 categories: (1) amino acids. -peptides are long a. a. chains; stored and released from secretory granules. Fast synaptic transmission : 10-100ms; @ cns synapses mediated by gamma-aminobutyric acid (gaba), glycine (gly) -glutamate and glycine = part of 20 a. a. building blocks; found in every type of cell including neurons. -gaba and the amine nt made primarily by neurons --contain specific enzymes for synthesizing nt from different precursors.

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The junction specialized for the transmission between a neuron and another cell is called a (1) _____ ______. Usually, the signal being sent to the receiving cell is carried by chemical messengers called (2) _____. (3) _____ is an example of this type of chemical messenger, which diffuses across the synaptic cleft, combines with protein receptor molecules on the muscle cell membrane, and soon thereafter is rapidly broken down by enzymes. At an (4) ____ synapse, the membrane potential is driven toward the threshold value and increases the likelihood that depolarization and an action potential will occur. At an (5) ____ synapse, the membrane potential is driven away form the threshold value, and the receiving neuron becomes hyperpolarized and is less likely to achieve an action potential. A specific transmitter substance can have either excitatory or inhibitory effects depending on which type of protein channel it opens up in the (6) ____ membrane. (7) ____ are neuromodulators that inhibit perceptions of pain and may have roles in memory and learning, emotional states, temperature regulation, and sexual behavior. (8) ____ ________ at the cellular level is the moment-by-moment tallying of all excitatory and inhibitory signals acting on a neuron. Incoming information is (9) ____ by the cell bodies, and the charge differences across the membranes are either enhanced or inhibited. Some narrow-diameter neurons are wrapped in lipid-rich (10) _______ produced by specialized neuroglial called Schwann cells; each of these is separated from the next by a(n) (11) ________ ________ - a small gap where the axon is exposed to extracellular fluid. A (12) ____ is an involuntary sequence of events elicited by a stimulus. During a (13) _______ ________, a muscle contracts involuntary whenever conditions cause a stretch in length; many of these help you maintain an upright posture despite small shifts in balance. Imbalances can occur at chemical synapses; a neurotoxin produced by Clostridium tetani blocks the release of GABA and glycine, thus freeing the motor neurons from (14) _____ control, which may cause tetanus â a prolonged, spastic paralysis that can lead to death. A. Excitatory H. Stretch reflex B. Inhibitory I. Summed C. Myelin J. Neurotransmitters D. Chemical synapse K. Postsynaptic E. Synaptic integration L. Endorphins F. Exposed node M. Acetylcholine (ACh)

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CAS BI 325 Chapter Notes - Chapter 5: Chemical Synapse, Gap Junction, Excitatory Synapse

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