![]() It is given intravenously, by injection into a muscle, by inhalation, or by injection just under the skin. It may also be used for asthma when other treatments are not effective. Inhaled epinephrine may be used to improve the symptoms of croup. As a medication it is used for a number of conditions including: anaphylaxis, cardiac arrest, and superficial bleeding. Excessive activation of VDCCs is a major component of excitotoxicity, as severely elevated levels of intracellular calcium activates enzymes which, at high enough levels, can degrade essential cellular structures.Įpinephrine, also known as adrenalin or adrenaline, is primarily a medication and hormone. VDCCs have been immunolocalized in the zona glomerulosa of normal and hyperplastic human adrenal, as well as in aldosterone-producing adenomas (APA), and in the latter T-type VDCCs correlated with plasma aldosterone levels of patients. ![]() Activation of particular VDCCs allows Ca2+ to rush into the cell, which, depending on the cell type, results in activation of calcium-sensitive potassium channels, muscular contraction, excitation of neurons, up-regulation of gene expression, or release of hormones or neurotransmitters. The concentration of calcium (Ca2+ ions) is normally several thousand times higher outside of the cell than inside. They are activated (i.e., opened) at depolarized membrane potentials and this is the source of the "voltage-dependent" epithet. At physiologic or resting membrane potential, VDCCs are normally closed. These channels are slightly permeable to sodium ions, so they are also called Ca2+-Na+ channels, but their permeability to calcium is about 1000-fold greater than to sodium under normal physiological conditions. Voltage-dependent calcium channels (VDCC) are a group of voltage-gated ion channels found in the membrane of excitable cells (e.g., muscle, glial cells, neurons, etc.) with a permeability to the calcium ion Ca2+. ![]() There are, however, many exceptions to these rules: neurons that lack dendrites, neurons that have no axon, synapses that connect an axon to another axon or a dendrite to another dendrite, etc. At the majority of synapses, signals are sent from the axon of one neuron to a dendrite of another. The cell body of a neuron frequently gives rise to multiple dendrites, but never to more than one axon, although the axon may branch hundreds of times before it terminates. Nerve fibers are often bundled into fascicles, and in the peripheral nervous system, bundles of fascicles make up nerves (like strands of wire make up cables). An axon (also called a nerve fiber when myelinated) is a special cellular extension (process) that arises from the cell body at a site called the axon hillock and travels for a distance, as far as 1 meter in humans or even more in other species. Dendrites are thin structures that arise from the cell body, often extending for hundreds of micrometres and branching multiple times, giving rise to a complex "dendritic tree". The term neurite is used to describe either a dendrite or an axon, particularly in its undifferentiated stage. A typical neuron consists of a cell body (soma), dendrites, and an axon. Specialized types of neurons include: sensory neurons which respond to touch, sound, light and all other stimuli affecting the cells of the sensory organs that then send signals to the spinal cord and brain, motor neurons that receive signals from the brain and spinal cord to cause muscle contractions and affect glandular outputs, and interneurons which connect neurons to other neurons within the same region of the brain, or spinal cord in neural networks. Neurons are the core components of the brain and spinal cord of the central nervous system (CNS), and of the ganglia of the peripheral nervous system (PNS). Neurons can connect to each other to form neural networks. These signals between neurons occur via synapses, specialized connections with other cells. A neuron also known as a neurone or nerve cell) is an electrically excitable cell that processes and transmits information through electrical and chemical signals. A specialized cell transmitting nerve impulses a nerve cell.
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