Muscles will contract or relax when they receive signals from the nervous system. The neuromuscular junction is the site of the signal exchange. The steps of this process in vertebrates occur as follows:(`) The action potential reaches the axon terminal. The development of the neuromuscular junction requires signaling from both the motor neuron's terminal and the muscle cell's central region. During development, muscle cells produce acetylcholine receptors (AChRs) and express them in the central regions in a process called prepatterning. A motor neuron (or motoneuron) is a nerve cell (neuron) whose cell body is located in the spinal cord and whose fiber (axon) projects outside the spinal cord to directly or indirectly control effector organs, mainly muscles and glands. Motor neurons' axons are efferent nerve fibers that carry signals from the spinal cord to the effectors to produce effects. Types of motor neurons are alpha motor neurons, beta motor neurons, and gamma motor neurons. There are upper motor neurons and lower motor neurons, with the cell type described above being a lower motor neuron. Upper motor neurons are cortico-spinal interneurons that arise from the motor cortex and descend to the spinal cord where they activate the lower motor neurons through synapse The CNS activates alpha motor neurons in the spinal cord, which cause extrafusal muscle fibers to contract and thereby resist further stretching. This process is also called the stretch reflex. 1  Beta motor neurons innervate intrafusal muscle fibers of muscle spindles, with collaterals to extrafusal fibres. Motor neurons' axons are efferent nerve fibers that carry signals from the spinal cord to the effectors to produce effects. Types of motor neurons are alpha motor neurons, beta motor neurons, and gamma motor neurons. There are upper motor neurons and lower motor neurons, with the cell type described above being a lower motor neuron. Upper motor neurons are cortico-spinal interneurons that arise from the motor cortex and descend to the spinal cord where they activate the lower motor neurons through synaps A neuromuscular junction (sometimes called a myoneural junction) is a junction between nerve and muscle; it is a chemical synapse formed by the contact between the presynaptic terminal of a motor neuron and the postsynaptic membrane of a muscle fiber. The development of the neuromuscular junction requires signaling from both the motor neuron's terminal and the muscle cell's central region. During development, muscle cells produce acetylcholine receptors (AChRs) and express them in the central regions in a process called prepatterning. Excitability is thus described in terms of the qualitatively different transitions neurons exhibit as they go from resting to spiking states. Underlying a neuron’s excitability is a host of ion channels that allow sodium, potassium, calcium, etc. to go in and out of the cell. There is a relationship between the types of rest-to-spiking transitions neurons can make and the type and number of ion channels they express (see for example pdf). Working in model systems like Drosophila, we can change the levels of channel expression in neurons and see how their excitability changes. Furthermore, we can target these manipulations to groups of cells, like motor neurons, to ask how changing their excitability affects motor behaviors. Below is an example of a genetic manipulation of potassium currents in Drosophila motor neurons (article available here) that I’ve used in my work (unpublished to date). Part IV of the “Help me decide…” series. See parts I, II, and III. Motor neurons send signals to muscles, causing them to contract. You’d think understanding their role in the production of movements like breathing and walking would be simple. Furthermore, we can target these manipulations to groups of cells, like motor neurons, to ask how changing their excitability affects motor behaviors. Below is an example of a genetic manipulation of potassium currents in Drosophila motor neurons (article available here) that I’ve used in my work (unpublished to date). The process being controlled (the 'plant') generates output that is compared to a target. The difference between the target and the output (error) is fed into a controller, which outputs a control signal. This signal is fed back into the plant, driving its output to target by minimizing the error. Over time, the model re-tunes itself to produce stable bursting (bottom panel). Homeostatic regulation of neuronal excitability refers to the collective phenomena by which neurons alter their intrinsic or synaptic properties to maintain a target level of electrical activity (see Fig. 1 & 2). It is at the neuromuscular junction that a motor neuron is able to transmit a signal to the muscle fiber, causing muscle contraction. The development of the neuromuscular junction requires signaling from both the motor neuron's terminal and the muscle cell's central region. During development, muscle cells produce acetylcholine receptors (AChRs) and express them in the central regions in a process called prepatterning.
https://en.wikipedia.org/wiki/Neuromuscular_junction https://en.wikipedia.org/wiki/Motor_neuron https://en.wikipedia.org/wiki/Motor_neuron https://en.wikipedia.org/wiki/Neuromuscular_junction https://emckiernan.wordpress.com/2013/03/09/the-excitability-of-motor-neurons/ https://emckiernan.wordpress.com/2013/03/09/the-excitability-of-motor-neurons/ http://scholarpedia.org/article/Homeostatic_Regulation_of_Neuronal_Excitability https://en.wikipedia.org/wiki/Neuromuscular_junction
what is motor excitability