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NEET Questions / Zoology / Neural Control And Coordination / Trasmission Of Impulses
A neuron is experimentally stimulated at multiple points along its axon. Action potentials are recorded downstream from the stimulation points. Which observation BEST supports the all-or-none principle of action potentials?
The amplitude of the action potential increases with increasing stimulus strength.
The speed of the action potential increases with increasing stimulus strength.
The amplitude of the action potential is the same regardless of the strength or location of the stimulus, as long as threshold is reached.
The frequency of action potentials increases with increasing stimulus strength, but their amplitude remains constant only at the axon hillock.
The absolute refractory period is crucial for the unidirectional propagation of action potentials. Which molecular mechanism primarily underlies this period?
Opening of voltage-gated potassium channels
Inactivation of voltage-gated sodium channels
Activity of the sodium-potassium pump
Binding of neurotransmitters to postsynaptic receptors
A researcher is studying the effects of a novel neurotoxin on synaptic transmission. They find that the toxin significantly reduces the amplitude of excitatory postsynaptic potentials (EPSPs) without affecting the presynaptic action potential. Which of the following is the MOST likely mechanism of action of the toxin?
Reduced presynaptic neurotransmitter release
Inhibition of postsynaptic receptors
Enhanced enzymatic degradation of neurotransmitter in the synapse
Increased presynaptic calcium influx
Which statement BEST describes the role of myelin in saltatory conduction?
Myelin increases membrane capacitance, allowing for greater charge storage and slower depolarization.
Myelin decreases membrane resistance, facilitating ion flow across the membrane at internodes.
Myelin increases membrane resistance, allowing depolarization to spread passively and rapidly between Nodes of Ranvier.
Myelin enhances the activity of the sodium-potassium pump, increasing the speed of repolarization.
The Nernst equation is used to calculate the equilibrium potential for a given ion. If the intracellular concentration of K+ is 150 mM and the extracellular concentration is 5 mM, what would happen to the equilibrium potential for K+ if the extracellular concentration was suddenly increased to 10 mM, assuming a temperature of 37°C?
The equilibrium potential would become more negative.
The equilibrium potential would become less negative.
The equilibrium potential would remain unchanged.
The equilibrium potential would become zero.
A drug inhibits the reuptake of a specific neurotransmitter from the synaptic cleft. Which of the following effects is MOST likely to be observed at the synapse?
Decreased synthesis of the neurotransmitter
Prolonged action of the neurotransmitter on the postsynaptic receptors
Hyperpolarization of the postsynaptic membrane
Inhibition of presynaptic action potential generation
The resting membrane potential of a neuron is primarily maintained by the:
Sodium-potassium pump
Calcium channels
Leakage of chloride ions
Voltage-gated sodium channels
What is the role of myelin sheath in nerve impulse transmission?
Increases the speed of impulse conduction
Decreases the speed of impulse conduction
Stores neurotransmitters
Produces action potentials
Which of the following is NOT a neurotransmitter?
Myosin
Acetylcholine
Dopamine
Serotonin
The process by which the membrane potential returns to its resting state after depolarization is called:
Repolarization
Depolarization
Hyperpolarization
Synaptic transmission
