BIOM20002 Lecture 16: 8. Lecture 16 Neuromuscular junction and E-C coupling

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roseturtle504

22 Aug 2018

School

University of Melbourne

Department

Biomedicine

Course

BIOM20002

Professor

All

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Document Summary

The neuromuscular junction is the site where the neuronal axon terminals (synaptic terminal) of a motor neuron come in contact with the plasma membrane of the skeletal muscle fiber (motor end plate). In reality there is no physical contact between the two membranes, but rather a small gap exists, being similarly functional to the synaptic cleft of a chemical synapse. The synaptic terminal of the neuron is of a sausage-like shape being embedded within the muscle fiber rather than lying over the the cell. The neuromuscular junction usually refers to the interaction of an motor neuron with a skeletal muscle fiber. The neuronal synaptic terminals are cholinergic and secrete acetylcholine (ach) a neurotransmitter that promotes contraction of the skeletal muscle fibers. Ach introduces different effects over smooth muscle and striated muscle acting through different types of receptors. Skeletal muscle fibers contain nicotinic cholinergic receptors whereas the smooth muscle cells consist of muscarinic cholinergic receptors that are both excitatory and inhibitory.

Related Questions

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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BIOM20002 Lecture 16: 8. Lecture 16 Neuromuscular junction and E-C coupling

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