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Question

Which of the following statements is wrong regarding conduction of nerve impulse?
  1. In a resting neuron, the axonal membrane is more permeable to K+ ions and nearly impermeable to Na+ ions
  2. Fluid outside the axon has a high concentration of Na+ and low concentration of K+, in a resting neuron
  3. Ionic gradients are maintained by Na-K pumps across the resting membrane, which transport 3 Na+ ions outwards for 2K+ ions into the cell.
  4. A neuron is polarised only when the outer surface of the axonal membrane possess a negative carge and its innersurface is positively charged.

A
A neuron is polarised only when the outer surface of the axonal membrane possess a negative carge and its innersurface is positively charged.
B
Ionic gradients are maintained by Na-K pumps across the resting membrane, which transport 3 Na+ ions outwards for 2K+ ions into the cell.
C
In a resting neuron, the axonal membrane is more permeable to K+ ions and nearly impermeable to Na+ ions
D
Fluid outside the axon has a high concentration of Na+ and low concentration of K+, in a resting neuron
Solution
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In a resting neuron the resting potential is -70 mV, this means that the inside of the neuron is negatively charged.The neuronal membrane is more permeable to K+ ions and less permeable to Na+ ions. The Na+- K+ pump tries to balance the negative charge by pumping 3 Na+ ions inside and 2 K+ ions outside.When neurons receive signal, an action potential is generated and depolarization of membrane occurs. Resting membrane potential is pushed towards 0 mV. When depolarization reaches -55 mV the action potential is fired by neuron.This means outer surface still remains positively charged.
Therefore the last statement is wrong.

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Similar Questions
Q1
Sodium-potassium pump across the resting membrane transports ____ Na ions outside and ____ K ions into the cell.
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Q2

In the resting state, the axonal membrane is ___(i)____ with more ___(ii)___ charged ions outside than inside. This unequal distribution of ions is due to (1) the selective permeability of the membrane, which forms an almost impenetrable barrier to ___(iii)___ and (2) the action of the ____(iv)___, which pumps ___(v)___ Na+ out of the neuron for every ____(vi)___ K+ brought in.
Select the option that correctly fills the blanks in the paragraph.
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Q3
If a part of an axonal membrane becomes more permeable to Na+ ions, the membrane becomes .
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Q4
Read the given statements and select the correct ones.
(i) Autonomic neural system transmits impulses from the CNS to the voluntary organs and striated muscles of the body.
(ii) Unmyelinated nerve fibres do not have Schwann cells which from the myelin sheath.
(iii) Axonal membrane of a neuron while not conducting any impulse is comparatively more permeable to potassium ions (K+) than to sodium ions (Na+).
(iv) A synapse is formed by the membranes of a presynaptic neuron and a post synaptic neuron.
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Q5
Which of the following statements are correct regarding Na+ - K+ pump?

(i) Needs energy (ATP) to work.
(ii) Expels 3 Na+ for every 2K+ ions imported
(iii) Works against a concentration gradient
(iv) Maintains resting potential

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