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Question
Explain the role of Na+ in the generation of action potential.
Solution
- Sodium ions play an important role in the generation of action potential. When a nerve fibre is stimulated, the membrane potential decreases.
- The membrane becomes more permeable to Na+ ions than to K+ ions. As a result, Na+ diffuses from the outside to the inside of the membrane. This causes the inside of the membrane to become positively charged, while the outer membrane gains a negative charge. This reversal of polarity across the membrane is known as depolarization.
- The rapid inflow of Na+ ions causes the membrane potential to increase, thereby generating an action potential. In the resting state, there is an abundance of negative ions in the axoplasm and positive ions in the tissue fluid.
- There is an accumulation of positive ions on the outer surface of the neurite, or neurilema, and negative ions on the inner surface. There is a positive charge of 70 mV on the outer surface of the nerve cell and a negative charge of 70 mV on the inner surface. In this situation, the nerve sheath, or neurilema, remains in an electrical or depolarized state.
- A lot of potential energy is stored in the neurilema due to the electrical muscle difference around the nerve section. This energy is called resting state potential. Its energy is used in transmission of inspiration.
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| Application of stimulus on a resting nerve |
| ⇓ |
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| ⇓ |
| ______________________________ |
| ⇓ |
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| ⇓ |
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| ⇓ |
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| a. Resting potential | i. Chemicals involved in the transmission of impulses at synapses. |
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| c. Synaptic cleft | iii. Electrical potential difference across the resting neural membrane |
| d. Neurotransmitters | iv. An electrical wave like response of a neuron to a stimulation |
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