Sign Up Now
Get instant access to over 1 million+ study documents
OR
Already registered? click here to login
By creating your account, you agree to our terms of service, privacy policy and student honor code.
¶ … sodium and other ion channels considered gated?
Ions moving by facilitated diffusion can traverse the plasma membrane through channels created by proteins. These embedded transmembrane proteins allow the formation of a concentration gradient between the extracellular and intracellular contents. These ion channels are said to be 'gated' if they can be opened or closed.
Ligand gated channels open or close in response to the binding of a small signaling molecule or ligand (Keramidas et al.). Some ion channels are gated by extra cellular ligands; some by intracellular ligands. In both cases, the ligand is not the substance that is transported when the channel opens. The binding of neurotransmitter acetylcholine opens sodium channels in certain synapses. Voltage gated channels are found in neurons and muscle cells. They open or close in response to changes in the charge across the plasma membrane. For example, as an impulse passes down a neuron, the reduction in the voltage opens sodium channels in the adjacent portion of the membrane. This allows the influx of sodium into the neuron and thus the continuation of the nerve impulse.
Ion channels are highly specific filters, allowing only desired ions through the cell membrane. Voltage gated sodium channels are crucial for the propagation of action potentials in excitable membranes. They cause the cell membrane to depolarize by allowing the influx of sodium ions into the cell. However due to the size and hydrophobic nature of the channel protein, it has not been fully resolved by x-ray crystallography.
The secondary and some of the tertiary structures can only be deduced from the primary amino acid sequence. Voltage gated sodium channels consist of an ?-subunit responsible for selectivity and voltage gating (Errington, Stohr and Lees; Sands, Grottesi and Sansom). However some sodium channels also have one or two smaller subunits called ?-1 and ?-2. The protein has 4 homologous domains containing multiple potential ?-helical transmembrane segments. The segments are connected by non-conserved, hydrophilic intervening segments. The fourth transmembrane segment (S4) of each domain is highly positively charged, and thought to be a voltage sensor.
References
Errington, a.C., T. Stohr, and G. Lees. "Voltage Gated Ion Channels: Targets for Anticonvulsant Drugs." Curr Top Med Chem 5.1 (2005): 15-30.
Keramidas, a., et al. "Ligand-Gated Ion Channels: Mechanisms Underlying Ion Selectivity." Prog Biophys Mol Biol 86.2 (2004): 161-204.
Sands, Z., a. Grottesi, and M.S. Sansom. "Voltage-Gated Ion Channels." Curr Biol 15.2 (2005): R44-7.
Discussion Sodium and potassium could be seen as the dynamic duo critical for normal functioning of several processes in the body. In addition to assessing the role the sodium-potassium pump plays in the propagation of an action potential, this text will also highlight both the pathophysiologic impact of hyperkalemia on the action potential as well as the resulting clinical manifestations. The Role of the Sodium-Potassium Pump on the Propagation of an Action
When watching a scary movie alone at night, this system is likely to become engaged due to the perception of a threat; sudden noises are likely to cause an involuntary flight reaction that, of course, subsides after a moment. 8) Temporal summation in a nerve cell occurs when the length of time over which successive activation potentials occur is sufficiently long enough to allow for the potentials to continue to the
Brugada Syndrome is a hereditary illness that is categorized by irregular electrocardiogram (ECG) results (Refer to Appendix 1) and an augmented danger of unexpected cardiac arrest. It is titled after the Spanish cardiologists Josep and Pedro Brugada. It is counted amongst one of the key (Nademanee, 1997) reasons for "Sudden Unexplained Death Syndrome" (SUDS), and is the most regularly occurring reason of unexpected expiration amongst young men without knowing the
Muscle fiber type and performance The body majorly has two types of muscles, the slow-twitch and fast-twitch muscle fibers. Most people have, on estimation, 50% slow-twitch fibers and 50% fast-twitch ones. This however can significantly change depending on the type of training an athlete goes through. The slow-twitch muscles come into play for the endurance athletes hence they will develop more of this type over time with training. Fast-twitch muscle fibers
chemistry of pesticides, including characteristics and their effects on the environment. What are pesticides? They are substances, including chemical, biological, antimicrobial, or disinfectant, or some type of mixtures of these substances, that are used to control pests like weeds, insects, microbes, and other pests. The word itself comes from the Latin word "cida," which means "killer" (1). For most people, the word "pesticide" really means some kind of poison
Although tastes are not relegated to different regions on the tongue, it is important to note that there are slight differences between the major taste sensations. "The chemicals that produce salty and sour tastes act directly through ion channels, whereas those responsible for sweet and bitter tastes bind to surface receptors that trigger a bucket brigade of signals to the cells' interiors that ultimately results in the opening and closing