Critical Numbers for NEET
Membrane Potential Values
| Value | What it Represents |
|---|---|
| -70 mV | Resting membrane potential |
| +30 mV | Peak of action potential (depolarization) |
| -90 mV | K+ equilibrium (Nernst) potential |
| +62 mV | Na+ equilibrium (Nernst) potential |
| Threshold ≈ -55 mV | Level at which AP is triggered |
Na+/K+ Pump
| Ion | Direction | Number per cycle |
|---|---|---|
| Na+ | OUT | 3 |
| K+ | IN | 2 |
| Net charge moved | Outward | 1 positive charge per cycle (electrogenic) |
Synapse
| Parameter | Value |
|---|---|
| Synaptic cleft width | 20 nm |
| Ca2+ required for | NT exocytosis |
| ACh degraded by | Acetylcholinesterase |
Eye
| Parameter | Value |
|---|---|
| Number of rods | ~120 million |
| Number of cones | ~6-7 million |
| Rods pigment | Rhodopsin (opsin + retinal from Vitamin A) |
| Cones pigment | Iodopsin (3 types: R, G, B) |
| Cones concentrated at | Fovea |
| Rods distributed | Peripheral retina |
Ear
| Parameter | Value |
|---|---|
| Ossicular amplification | ~20-fold |
| Ossicle order | Malleus → Incus → Stapes |
| Smallest bone in body | Stapes |
| Semicircular canals per ear | 3 (perpendicular planes) |
Spinal Nerves
| Region | Pairs |
|---|---|
| Cervical | 8 |
| Thoracic | 12 |
| Lumbar | 5 |
| Sacral | 5 |
| Coccygeal | 1 |
| TOTAL | 31 |
| Cranial nerves | 12 pairs |