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How would Damaged heart tissue affect mean electrical axis?
damages or disease of the heart could cause changes of the path of depolarization (mean electrical axis). such affects would result in abnormalities in ECG trace. ultimately causing MEA to be off
How does acetylcholine induce a decrease in heart rate?
Yes it does. Acetylcholine decreases the heart rate. It acts on the muscarinic (m2) receptor which decreases the activity of adenylate cyclase. This in turn decreases the production of cycliac AMP -> decreases the amount of protein kinase a activated -> decreases the amount of calcuim entry -> decreased activity of myocytes in heart- which results in decreased permeability of l type voltaged gated calcuim channels and decreases the length of time they are open for -> decreased calcuim levels -> decreased heart rate.
How can sodium channel blockers terminate re-entry in cardiac arrhythmia?
Cardiac arrhythmia is cause by the presence of an ectopic focus or a re-entry mechanism where an action potential is delayed for some reason and enters nearby muscle fibres that are no longer refractory causing depolarisation and establishing a circuit movement. There are three classes of anti-arrhythmic drugs which block sodium channels: Class IA drugs block open Na+ sodium and can increase the effective refractory period. They produce a frequency-dependent block As they dissociate slowly away from these Na+ channels, they can prevent the Na+ channel from contributing towards an action potential if the frequency is high. Disopyramide one such example. It is used to treat ventricular arrhythmia by resulting in a negative inotropic effect. Class IB drugs block closed Na+ sodium. It is often used to treat ventricular arrhythmia after an acute myocardial infraction. Lidocaine is one such example. It has little effect on normal cardiac tissues as it dissociates quickly from the Na+ channels. However, many Na+ channels are closed in ischemic cases due to anoxia. Lidocaine can hence act on these closed Na+ channels. Class IC drugs are the most potent when it comes to blocking Na+ channels. They slowly dissociate from the Na+ channels and it leads to depressed conduction in the myocardium. These agents can prolong the RP and QRS intervals. Flecainide is one such example and it is used the treat atrial fibrillation.
What is responsible for causing accretion?
gravitation
What will happen if Mt Rainier erupts?
Even a relatively small eruption at Mount Rainier could melt the snow and ice at the volcano's summit. This could mix with volcanic ash as well as sediment around the volcano, forming mudflows called lahars. These could potentially devastate nearby towns and even the city of Tacoma. The mud could then clog river channels, causing the rivers to back up and flood portions of Seattle.
What characterizes depolarization the first phase of the action potential?
Depolarization is the initial phase of the action potential characterized by a rapid influx of sodium ions into the cell, causing a change in membrane potential from negative to positive. This occurs when voltage-gated sodium channels open in response to a threshold stimulus, leading to the depolarization of the cell membrane.
Depolarization of the nerve membrane begins with?
The opening of voltage-gated sodium channels in response to a stimulus. Sodium ions flow into the cell, causing depolarization as the inside becomes more positively charged.
A neuron will generate action potentials when it?
reaches a certain threshold level of depolarization, typically around -55 mV. This threshold is reached when excitatory signals outweigh inhibitory signals received by the neuron. Once the threshold is reached, voltage-gated sodium channels open, allowing a rapid influx of sodium ions and causing depolarization of the cell membrane, leading to an action potential.
What opens first in response to a threshold stimulus?
The activation gates of voltage-gated Na+ channels open, and Na+ diffuses into the cytoplasm.
What is the primary action during depolarization of an action potential?
Sodium ions flow into the neuron via voltage-gated sodium ion channels, driving the membrane potential into the positive. Beyond the threshold, more sodium ion channels are opened, causing the influx of sodium further downstream, and the process repeats, propagating the action potential down the axon.
What causes rapid depolarization phase of a pacemaker cell?
Rapid depolarization happens after the membrane threshold has been reached and Na+ ions start to flow into the cell. As more Na+ ions flood in the cell becomes more and more positive. This causes the voltage gated Na+ channels to open creating a flood of Na+ ions and thus a rapid phase of depolarization. Shortly after this rapid phase K+ ions are released from the cell causing the cell to become more negative closing the Na+ channels and thus repolarizing the cell.
How is excitatory postsynaptic potential produce?
Excitatory postsynaptic potentials (EPSPs) are produced when neurotransmitters bind to excitatory receptors on the postsynaptic membrane, causing a depolarization of the neuron. This depolarization results in the opening of ion channels that allow positively charged ions, such as sodium and calcium, to enter the neuron, further depolarizing it. The cumulative effect of EPSPs from multiple synapses can reach the threshold for action potential initiation.
What causes NA plus channels to open?
NA plus channels open in response to a change in the membrane potential, causing the channel to undergo conformational changes that lead to its opening. This change in membrane potential can be initiated by various stimuli, such as neurotransmitter binding or depolarization of the cell.
The action potential is generated when a stimulus?
The action potential is generated when a stimulus causes a change in the electrical potential across the cell membrane, resulting in the opening of voltage-gated ion channels. This allows an influx of sodium ions, causing depolarization of the membrane and initiation of the action potential.
What causes the inside of the membrane to reverse charge and begin action potential?
During an action potential, voltage-gated ion channels open in response to depolarization, causing an influx of sodium ions into the cell. This influx of positive ions triggers the reversal of charge inside the membrane, producing an action potential.
Is an action spike an impulse created by an excitable membrane when it reaches the threshold?
Yes, an action potential spike is generated when the membrane potential of a neuron reaches a certain threshold, causing a rapid depolarization and repolarization of the membrane. This creates a brief electrical impulse that propagates along the neuron's axon.
What happen during the rising phase of an action potential?
During the rising phase of an action potential, voltage-gated sodium channels open in response to a depolarizing stimulus. This allows sodium ions to rush into the cell, causing a rapid depolarization of the cell membrane. This results in the cell reaching its threshold and firing an action potential.
