Covers NCERT Class 11 Biology, Chapter "Neural Control and Coordination" — neuron structure, nerve impulse generation/conduction, synaptic transmission, reflex action, and the organisation of the central and peripheral nervous systems.
Resting membrane potential and the Na⁺/K⁺ pump stoichiometry, the exact sequence of depolarisation/repolarisation during an action potential, saltatory conduction along myelinated axons, chemical vs electrical synapse comparison, reflex arc pathway and its survival advantage (bypassing conscious brain processing), and the count/naming of cranial and spinal nerves.
A neuron has three parts: dendrites (receive signals), cell body/soma (contains Nissl granules, the metabolic centre), and axon (conducts the impulse away, ending in synaptic knobs).
Resting membrane potential (~ −70 mV, inside negative relative to outside) is maintained by the Na⁺/K⁺ pump, which actively pumps out 3 Na⁺ for every 2 K⁺ pumped in, plus the membrane's much higher resting permeability to K⁺ than Na⁺.
A stimulus above threshold opens voltage-gated Na⁺ channels → rapid Na⁺ influx → depolarisation (inside becomes positive, action potential). This is followed by Na⁺ channel inactivation and K⁺ efflux through voltage-gated K⁺ channels → repolarisation, restoring the negative resting potential.
In myelinated axons, the impulse jumps from one Node of Ranvier to the next — saltatory conduction — which is markedly faster than continuous conduction along an unmyelinated axon.
At a chemical synapse, the electrical impulse triggers neurotransmitter release from synaptic vesicles into the synaptic cleft; the neurotransmitter binds receptors on the postsynaptic membrane, converting the signal back into an electrical one. Electrical synapses instead allow direct current flow through gap junctions — faster but far less common, and lack the delay/modifiability of chemical synapses.
A reflex arc (e.g. the knee-jerk or withdrawal reflex) routes the signal through the spinal cord without waiting for the brain to process it consciously — this shortens response time and is the physiological basis of involuntary, protective reflexes.
The forebrain includes the cerebrum (higher mental functions, divided into lobes), thalamus (sensory relay) and hypothalamus (regulates temperature, hunger, thirst and links the nervous and endocrine systems via the pituitary). The hindbrain includes the cerebellum (fine motor coordination and balance) and medulla oblongata (controls involuntary functions — heart rate, breathing, blood pressure).
The peripheral nervous system comprises 12 pairs of cranial nerves (arising from the brain) and 31 pairs of spinal nerves (arising from the spinal cord), further divided functionally into the somatic (voluntary) and autonomic (involuntary — sympathetic/parasympathetic) nervous systems.
Original questions modelled on recurring NEET question types — not verbatim reproductions of any official paper.
Scaled from direct NCERT recall (Q1–Q6) to mixed NEET-level difficulty (Q7–Q15).
3 Na⁺ pumped out, 2 K⁺ pumped in, every cycle, using ATP — this asymmetry (3 positive charges leaving vs 2 entering) is itself part of why the inside stays net negative at rest.
Depolarisation comes before Repolarisation, alphabetically and physiologically — and within each, Na⁺ drives the first (depolarisation), K⁺ drives the second (repolarisation). Both pairs are in the same "comes first" order as their letters.
"Cerebrum thinks, cerebellum balances, medulla keeps you alive" — cerebrum: higher mental function; cerebellum: coordination/balance; medulla oblongata: heartbeat, breathing, blood pressure (damage here is immediately life-threatening, unlike damage to the other two).