HP-06: Neural Control — NEET Cheat Sheet

NON-NEGOTIABLE VALUES (Memory MUST):

Resting potential = -70 mV (INSIDE NEGATIVE)
Action potential peak = +30 mV
Na+/K+ pump: 3 Na+ OUT, 2 K+ IN
Synaptic cleft = 20 nm
Rods = 120 million; Cones = 6-7 million
Ossicular amplification = 20-fold
Spinal nerves = 31 pairs (8C+12T+5L+5S+1Cx)
Cranial nerves = 12 pairs

ION MOVEMENTS (Critical):

DEPOLARIZATION = Na+ IN (Na+ in = up)
REPOLARIZATION = K+ OUT (K+ out = down)
Mnemonic: NDKR = Na Depolarizes, K Repolarizes

BRAIN FUNCTIONS (Most Tested):

CEREBRUM → INITIATES voluntary movement (motor cortex)
CEREBELLUM → COORDINATES movement (NOT initiate); damage = ATAXIA
THALAMUS → Relay centre (ALL senses EXCEPT smell)
HYPOTHALAMUS → Homeostasis + controls pituitary
MEDULLA → Vital involuntary (CV + respiratory)
PONS → Pneumotaxic centre; relay cerebrum ↔ cerebellum
MIDBRAIN → Visual and auditory REFLEXES

PHOTORECEPTORS:

RODS = Rhodopsin = dim light (scotopic) = 120M = peripheral retina
CONES = Iodopsin = colour (photopic) = 6-7M = FOVEA

LENS/EYE DEFECTS:

MYOPIA → image IN FRONT of retina → CONCAVE (−) lens
HYPERMETROPIA → image BEHIND retina → CONVEX (+) lens
PRESBYOPIA → age, lens inelastic → BIFOCAL
ASTIGMATISM → irregular cornea → CYLINDRICAL lens
CATARACT → cloudy lens → SURGERY
GLAUCOMA → ↑intraocular pressure → damages optic nerve

EAR OSSICLES:

MIS: MALLEUS → INCUS → STAPES → OVAL WINDOW
Stapes = SMALLEST BONE in human body
Amplification = 20x
Cochlea = HEARING (organ of Corti, hair cells)
Vestibular apparatus = BALANCE (3 semicircular canals + utricle + saccule)

ANS QUICK REFERENCE:

SYMPATHETIC $\frac{fight}{flight}$: ↑HR, ↑BP, Dilates pupils + bronchi, ↓digestion → Norepinephrine (postganglionic)
PARASYMPATHETIC $\frac{rest}{digest}$: ↓HR, ↓BP, Constricts pupils + bronchi, ↑digestion → ACh (postganglionic)
ALL preganglionic = ACh (both divisions)

NEUROTRANSMITTER DISEASE LINKS:

Dopamine deficit → Parkinson's disease
Serotonin deficit → Depression
GABA deficit → Seizures / anxiety
Glutamate excess → Excitotoxicity
ACh deficit (NMJ) → Myasthenia gravis

REFLEX ARC ORDER:

Receptor → SENSORY (afferent) neuron → INTERNEURON → MOTOR (efferent) neuron → Effector
Knee-jerk = MONOSYNAPTIC (no interneuron — direct sensory → motor)