BIOC17H3 Lecture Notes - Lecture 2: Electrical Synapse, Resting Potential, Axon Terminal

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14 Sep 2016

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Synapse is the axon terminal, synapse cleft (the space) and the postsynaptic membrane. A pre-synaptic neuron- a neuron that carrying the signal initially. Post synaptic neuron is what receiving the signal and carries it away. Different kinds of axons can be defined as where in the neuron does the synapse form. Axodendritic synapse = between the axon neuron and the dendrite of another neuron 2) 2) Axosomatic synapse = axon is forming synapse with the cell body. Axoaxonic synapse = axon from one neuron and forming a synapse with the axon of another neuron. The average presynaptic neuron forms synapses with 1000 postsynaptic neurons; the average postsynaptic neuron receives inputs from 10,000 presynaptic neurons (and up to 150,000); there are around 100 trillion synapses in the cns. A great complexity to the great central system. Divergence: signal that this neuron has initiated that has been conducted by its axon, carry this signal to thousands of neurons.

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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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BIOC17H3 Lecture Notes - Lecture 2: Electrical Synapse, Resting Potential, Axon Terminal

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