![]() Somatic nerves and autonomic nerves both act on muscles. Acetylcholine molecules then bind their receptors on the sarcolemma to cause the opening of sodium channels which results in the production of an action potential and its propagation to the myofibril to cause muscle contraction. This permits the fusion of neurotransmitter vesicles with the axon terminal membrane to cause acetylcholine release into the junction. When an action potential reaches the axon terminal of the motor neuron, voltage-dependent calcium channels open and accommodate the influx of calcium. Motor neurons in vertebrates secrete acetylcholine into the neuromuscular junction. Muscles require innervation to contract and to maintain tone. There is a continuing interest in potential therapeutic uses for neural progenitor cells following injury. However, neural progenitors that are capable of participation in neurogenesis are present in certain regions such as the dentate gyrus of the rat, and in the subependymal of rodents. Mature neurons are unable to divide, so their destruction may lead to a neurological deficit. The variety of interactions among neurons enables the transmission of impulses to perpetrate diverse functions within the body. Graded potentials are also important to note as they vary in strength, and lose amplitude throughout their transmission. As a depolarizing threshold stimulus occurs, an action potential that is consistent in amplitude is generated and travels down the axon to the terminal. The resting membrane potential of typical neurons is around -70 mV. Potassium, sodium, and chloride ions are the greatest contributors to the membrane potential of the common neuron. ![]() Neurons propagate their potentials by ion movement through voltage-gated ion channels (though calcium channels are largely voltage-independent) across their membranes. Axonal transport is carried out by proteins such as kinesin and dynein. Axons typically end in an axon terminal at which neurotransmitters, neuromodulators, or neurohormones are released in the conversion of the electrical signal to a chemical signal which can cross the synapse or neuromuscular junction. In addition to afferent signaling, dendrites can be involved in protein synthesis and independent signaling functions with other neurons. There may be one or many dendrites associated with a single neuron depending on its function and location. The soma contains the nucleus and other organelles necessary for neuronal function. ![]() Neurons exist in a variety of forms including multipolar, bipolar, pseudounipolar, and anaxonic which differ primarily in their number and arrangement of axons and dendrites. Neurons are characterized by the long processes which extend out from the cell body or soma. Interneurons are multipolar.Neurons are unique in their ability to receive and transmit information. What neurons are unipolar, bipolar, and/or multipolar? Sensory neurons can be uni or bipolar. Axons are encased in myelin, and dendrites are not. What are differences between axons and dendrites? Axons carry messages away from your body and dendrites carry messages to your body. Synapse Impulses spread from axon of one neuron to dendrites of another. Myelin sheath A tube that protects the axon and allows for faster electrical impulse transportation. Schwann cells Forms the myelin sheath and provides protection for the axon. Axons A long or short tube that stabilizes electrical impulses as they travel through a neuron. Dendrites Long or short extensions of a neuron that connect to a cell body and start the transmission of the impulse through a nerve cell. How is an interneuron structured? Interneurons have short dendrites with short or long axons. What does a sensory neuron do? Sensory neurons are responsible for sending messages from receptors back to the CNS How is a sensory neuron structured? Sensory neurons have long dendrites with short axon What does an interneuron do? Interneurons are responsible for making sure that signals are smoothly passed between motor and sensory neurons.
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