1. Describe the role of voltage-gated Na+ channels in RMPs, GPs, and APs 2. Give
ID: 3475342 • Letter: 1
Question
1. Describe the role of voltage-gated Na+ channels in RMPs, GPs, and APs 2. Given the mechanism of action of tetrodotoxin (TTX), what do you predict would happen to RMP, GP and AP in someone who has ingested this poison? What is the role of GP's in the CNS? 3. The cardiac cells also generate Action Potentials, and are also impacted by TTX, although their channels are a little different, and respond individually to TTX. Describe the normal mechanism and role of F-type V-G Na+ channels in creating myocardial Pacemaker Potential in slow fibers (SAN, AVN) and in fast fibers (Purkinje).Explanation / Answer
1.Voltage-gated ion channels typically are closed at the resting membrane potential but open upon membrane depolarization. These channels detect changes in electric potential across the membrane through a domain responsible for sensing voltage. The voltage sensor spans the membrane and is thus exposed to the electric field across the phospholipid bilayer.
In a neurone, the Potassium leak channel and Sodium-Potassium pump maintain the resting potential. The voltage gated sodium channels and the voltage gated potassium channels are involved in the progression of an action potential along the membrane.The voltage gated sodium channels begin to open and the membrane potential begins to slowly depolarises and sodium enters the cell down its concentration gradient. All the voltage gated Sodium channels open when the membrane potential reaches around -55 mV and there's a large influx of Sodium, causing a sharp rise in voltage. As the potential nears +30mV, the rate of depolarisation slows down as the voltage gated Sodium channels become saturated and inactivate, preventing further sodium ions from entering the cell.
fast sodium channel- These sodium channels are voltage-dependent, opening rapidly due to depolarization of the membrane, which usually occurs from neighboring cells, through gap junctions. They allow for a rapid flow of sodium into the cell, depolarizing the membrane completely and initiating an action potential.
2.Tetrodoxin is produced by puffer fish and number of other animals.Tetrodotoxin is quite specific in blocking the Na+ ion channel and therefore the flow of Na+ ions while having no effect on K+ ions.
Stimulation of the axon results in an action potential which arises from a flow of Na+ ions into the cell and the generation of a positive membrane potential.It inhibits the firing of action potentialsin neurons by binding to the voltage-gated sodium channels in nerve cell membranes and blocking the passage of sodium ions (responsible for the rising phase of an action potential) into the neuron.
Tetrodoxin causes no change in the resting membrane potential.
Gap junctions are intercellular channels which directly connect the cytoplasm between neighboring cells. In the central nervous system (CNS) various kinds of cells are coupled by gap junctions, which play an important role in maintaining normal function.Neuronal gap junctions are involved in electrical coupling and may also contribute to the recovery of function after cell injury.
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