What does Apamin do to nerve activity?
Apamin is the smallest neurotoxin polypeptide known, and the only one that passes the blood-brain barrier. Apamin thus reaches its target organ, the central nervous system. Here it inhibits small-conductance Ca2+-activated K+ channels (SK channels) in neurons.
What does the action potential graph show?
Graph of Action Potential Plotting voltage measured across the cell membrane against time, the action potential begins with depolarization, followed by repolarization, which goes past the resting potential into hyperpolarization, and finally the membrane returns to rest.
How does hyperpolarization affect action potential?
Hyperpolarization is a change in a cell’s membrane potential that makes it more negative. It is the opposite of a depolarization. It inhibits action potentials by increasing the stimulus required to move the membrane potential to the action potential threshold.
Is bee venom a neurotoxin?
Apamin in bee venom is a neurotoxin that acts on the spinal cord. Adolapin inhibits prostaglandin synthetase and has antiinflammatory actions, and it has been postulated that it may be useful in the treatment of arthritis. The two most lethal factors in honey- bee venom are phospholipase A2 and mellitin.
What is honey bee venom?
Honey bee venom (HBV, Apis mellifera) is a bitter, colorless liquid, and its active portion contains a mixture of proteins that, cause local inflammation and act as anti-coagulants.
What causes undershoot in action potential?
The voltage-gated potassium channels stay open a little longer than needed to bring the membrane back to its resting potential. This results in a phenomenon called “undershoot,” in which the membrane potential briefly dips lower (more negative) than its resting potential.
What happens when a cell Depolarizes?
In biology, depolarization (British English: Depolarisation) is a change within a cell, during which the cell undergoes a shift in electric charge distribution, resulting in less negative charge inside the cell compared to the outside.
Why does hyperpolarization prevent an action potential?
Part of the importance of hyperpolarization is in preventing any stimulus already sent up an axon from triggering another action potential in the opposite direction. In other words, hyperpolarization assures that the signal is proceeding in one direction.
Why is the membrane hyperpolarized at the point on the graph labeled 6?
Why is the membrane hyperpolarized at the point on the graph labeled 6? All voltage-gated channels, both sodium and potassium, are fully open at this point. The membrane is temporarily more permeable to sodium than to potassium. The membrane is more temporarily more permeable to potassium than to sodium.
What does tetraethylammonium do to neurons?
Tetraethylammonium depresses the effect of nicotine receptor stimulants at postganglionic autonomic neurons either by blocking nicotine receptors or the receptor-regulated sodium channel.
Which is an example of an action potential?
Sufficient current is required to initiate a voltage response in a cell membrane; if the current is insufficient to depolarize the membrane to the threshold level, an action potential will not fire. Examples of cells that signal via action potentials are neurons and muscle cells.
What causes depolarization on an action potential graph?
First, channels open that cause the cell to reach threshold, increasing the voltage from the resting membrane potential, which is a normal membrane potential. Resting potential is a flat line on the action potential graph, which increases in slope during threshold. Depolarization is caused by voltage-gated sodium channels opening]
Where does the action potential take place in the axon?
The action potential is initiated at the beginning of the axon, at what is called the initial segment (trigger zone). Rapid depolarization can take place here due to a high density of voltage-gated Na + channels.
When does an action potential do not fire?
Sufficient current is required to initiate a voltage response in a cell membrane; if the current is insufficient to depolarize the membrane to the threshold level, an action potential will not fire.