NEET
- Exam
- NEET
- Subject
- Zoology
- Chapter
- Neural Control and Coordination
NEET · Zoology · Neural Control and Coordination
Order of Sequence Events A. Third 1. Sequence of impulse is...
| Order of Sequence | Events |
|---|---|
| A. Third | 1. Sequence of impulse is repeated along the length of the axon and consequently the impulse is conducted. |
| B. Fourth | 2. A rise in permeability to K |
| C. Second | 3. Ionic gradients across the resting membrane are maintained by the active transport of ions by the sodium-potassium pump which transports 3 Na⁺ outwards for 2 K⁺ into the cell- Resting potential |
| D. First | 4. Stimulus applied, hence membrane becomes permeable to Na⁺ |
Options
- AA - 1, B -2 , C -3 , D - 4
- BA - 1, B -2 , C - 4, D -3
- CA -2 , B -4 , C -3 , D - 1
- DA -3 , B -1 , C -2 , D - 4
Correct answer
B. A - 1, B -2 , C - 4, D -3
Step-by-step solution
When a neuron is not conducting any impulse, i.e., resting, the axonal membrane is comparatively more permeable to potassium ions (K⁺ ) and nearly impermeable to sodium ions (Na⁺). Similarly, the membrane is impermeable to negatively charged proteins present in the axoplasm. Consequently, the axoplasm inside the axon contains high concentration of K⁺ and negatively charged proteins and low concentration of Na⁺. In contrast, the fluid outside the axon contains a low concentration of K⁺ , a high concentration of Na⁺ and thus form a concentration gradient. These ionic gradients across the resting membrane are maintained by the active transport of ions by the sodium-potassium pump which transports 3 Na⁺ outwards for 2 K⁺ into the cell. As a result, the outer surface of the axonal membrane possesses a positive charge while its inner surface.