NEET Biology Neural Control & Coordination 2027 — Complete Notes, Diagrams, Action Potential and 10 Practice MCQs

NEET Biology Neural Control & Coordination 2027 is one of the highest-yield NCERT chapters from Class 11 Biology, contributing roughly 4–5 marks (1–2 questions every year) in the NEET-UG paper. This pillar guide compiles complete chapter notes on the human nervous system, neuron structure, action potential, synaptic transmission, the central nervous system (cerebrum, cerebellum, hypothalamus, brainstem), the peripheral and autonomic nervous systems, the reflex arc, and the physiology of vision and hearing — followed by 10 NCERT-style practice MCQs with detailed explanations. Last Updated: April 2026.

NEET Weightage — Neural Control & Coordination

NCERT Class 11 Biology, Chapter 21, Pages 333–349 — read these pages line by line. Diagrams of the neuron, brain (sagittal section), and reflex arc are repeatedly tested.

1. Nervous System — Overview

The nervous system in humans coordinates and integrates the activities of all organ systems through electrical impulses. It is divided into:

• Central Nervous System (CNS) — Brain + Spinal Cord. Site of information processing and control.
• Peripheral Nervous System (PNS) — All nerves outside CNS. Subdivided into Somatic NS (voluntary; skeletal muscles) and Autonomic NS (involuntary; smooth muscle, cardiac muscle, glands).
• Autonomic NS further splits into Sympathetic (fight-or-flight) and Parasympathetic (rest-and-digest).

2. Neuron — The Structural & Functional Unit

A neuron has three principal parts:

1. Cell body (cyton/soma) — Contains nucleus, Nissl granules (RER) and cytoplasm. Site of metabolism.
2. Dendrites — Short, branched cytoplasmic projections that receive impulses and conduct them towards the cell body.
3. Axon — Single long process that conducts impulses away from the cell body to the synapse. Terminal branches end in synaptic knobs (boutons) containing synaptic vesicles filled with neurotransmitters.

Types of neurons (functional)

• Sensory (afferent) — carry impulses from receptors to CNS
• Motor (efferent) — carry impulses from CNS to effectors
• Interneurons (association) — connect sensory and motor neurons within CNS

Types of neurons (structural)

• Multipolar — one axon, many dendrites (most common in cerebral cortex)
• Bipolar — one axon and one dendrite (retina, olfactory epithelium)
• Unipolar / Pseudo-unipolar — only one process; found in embryos and dorsal root ganglia

Myelinated vs Non-myelinated

Myelinated axons are wrapped by Schwann cells (in PNS) or oligodendrocytes (in CNS). The unmyelinated gaps between successive myelin segments are called Nodes of Ranvier. Myelin acts as an electrical insulator and enables saltatory conduction (impulse jumps node to node), making transmission ~100× faster than in non-myelinated fibres.

3. Generation & Conduction of Nerve Impulse

The plasma membrane of a resting neuron is selectively permeable. Inside is rich in K+ and negatively charged proteins; outside is rich in Na+ and Cl-. The Na+/K+ ATPase pump expels 3 Na+ outside and brings in 2 K+ for every ATP hydrolysed.

• Resting potential: outside positive, inside negative ≈ -70 mV; membrane is polarised.
• Depolarisation: stimulus opens voltage-gated Na+ channels → Na+ rushes in → membrane potential reverses to about +30 mV.
• Repolarisation: Na+ channels close, K+ channels open → K+ moves out → potential returns to negative.
• Hyperpolarisation (brief overshoot to ≈ -80 mV) followed by Na+/K+ pump restoring resting state.

This wave of depolarisation–repolarisation is the action potential and travels along the axon as the nerve impulse.

4. Synapse — Transmission of Impulse

A synapse is the junction where the impulse passes from one neuron to the next.

• Electrical synapse — pre- and post-synaptic membranes very close; ions flow through gap junctions; transmission is rapid; rare in mammals.
• Chemical synapse — separated by a synaptic cleft (~20 nm). Action potential opens voltage-gated Ca2+ channels in the synaptic knob → vesicles fuse with membrane → release neurotransmitter (acetylcholine, dopamine, GABA, serotonin, glutamate, noradrenaline) → binds receptors on post-synaptic membrane → opens ion channels → new action potential.

5. Central Nervous System

Brain — three primary divisions

Cerebrum

The largest part of the brain. The corpus callosum connects the two hemispheres. Surface (cerebral cortex) is folded into gyri and sulci to maximise surface area. Four lobes: frontal (motor, planning), parietal (sensory, somatosensation), temporal (hearing, memory), occipital (vision).

Hypothalamus

Lies below the thalamus. Controls body temperature, hunger, thirst, sleep–wake cycle, and emotions. Secretes neurohormones (releasing/inhibiting factors) that regulate the anterior pituitary; oxytocin and vasopressin are stored in the posterior pituitary.

Cerebellum

Coordinates voluntary muscle movements, posture and balance. Damage causes ataxia (loss of muscle coordination).

Medulla oblongata

Continuous with spinal cord. Houses cardiovascular, respiratory and gastric centres — controls heart rate, blood pressure, breathing, swallowing, vomiting.

Spinal cord

Extends from medulla through the vertebral column. Internal grey matter is shaped like the letter H; surrounded by white matter (ascending sensory and descending motor tracts). 31 pairs of spinal nerves arise from it. Centre for spinal reflexes such as the knee-jerk reflex.

6. Peripheral Nervous System

• 12 pairs of cranial nerves from brain (e.g. I-Olfactory, II-Optic, III-Oculomotor, V-Trigeminal, VII-Facial, VIII-Vestibulocochlear, X-Vagus).
• 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal. Each is mixed (sensory + motor).

Autonomic Nervous System — Sympathetic vs Parasympathetic

7. Reflex Action and Reflex Arc

A reflex action is an involuntary, near-instantaneous response to a stimulus, mediated by the spinal cord (without conscious involvement of the brain). The path of impulse is the reflex arc:

Receptor → Sensory (afferent) neuron → Spinal cord (interneuron) → Motor (efferent) neuron → Effector (muscle/gland)

Examples: knee-jerk reflex, withdrawal of hand from a hot object, blinking.

8. Sensory Reception — Eye and Ear

The eye and ear are the chief photoreceptive and mechanoreceptive organs respectively.

Human Eye

The eyeball has three concentric layers — outer sclera (continuous anteriorly with the transparent cornea); middle choroid (continuous anteriorly with the iris; the opening at the centre of the iris is the pupil whose diameter is regulated by smooth muscles of the iris); innermost retina containing photoreceptor cells. The lens is held in place by ligaments attached to the ciliary body, which alters its curvature for accommodation.

The retina contains two kinds of photoreceptor cells: rods (contain rhodopsin/visual purple — a photosensitive pigment derived from vitamin A; responsible for scotopic/dim-light vision) and cones (contain three types of photopsins — red, green, blue — responsible for photopic/colour vision). Rods are absent at the fovea centralis (region of highest visual acuity), while cones are densely packed there. The blind spot (optic disc) lacks both photoreceptors. The light-induced photochemical change in rhodopsin generates electrical signals that are conducted via the optic nerve (cranial nerve II) to the visual cortex of the occipital lobe.

Human Ear

The ear has three regions — outer (pinna + external auditory meatus + tympanic membrane), middle (three ear ossicles: malleus, incus, stapes — which transmit and amplify vibrations to the oval window) and inner (bony labyrinth + membranous labyrinth filled with endolymph). The cochlea contains the organ of Corti resting on the basilar membrane; it bears hair cells whose stereocilia bend against the tectorial membrane when the basilar membrane vibrates, generating nerve impulses carried by the auditory nerve to the temporal lobe. The vestibular apparatus (three semicircular canals + utricle + saccule) maintains balance and posture by detecting head movement and gravitational pull.

9. High-Yield Memory Hooks for NEET

• “All Tigers Have Pale Coats Mostly” — Forebrain (Olfactory + cerebrum), Thalamus, Hypothalamus, Pituitary, Corpora quadrigemina (midbrain), Medulla.
• Number of cranial nerves = 12 pairs; spinal nerves = 31 pairs. Memorise the I-XII Roman numeral list.
• Resting potential = -70 mV; threshold ≈ -55 mV; peak of action potential ≈ +30 mV.
• Na+/K+ pump ratio: 3 Na+ out : 2 K+ in per ATP hydrolysed.
• Cerebellum injuries → ataxia; medulla injuries → death (cardiorespiratory failure); hypothalamus disorders → diabetes insipidus, sleep & temperature dysregulation.
• Synaptic vesicles release neurotransmitter only after Ca²⁺ entry into the presynaptic terminal.

Practice MCQs — 10 NCERT-style Questions

Test yourself with the interactive quiz below. Each question carries detailed explanations.

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FAQ

Q1. How many marks does Neural Control & Coordination carry in NEET?

Typically 1–2 questions every year, contributing 4–8 marks. Both NCERT diagrams and physiology of the action potential are favourite picking grounds.

Q2. What is the resting potential of a typical neuron?

Approximately -70 mV — maintained by the Na+/K+ ATPase and selective potassium leak channels.

Q3. Which neurotransmitter is released at the neuromuscular junction?

Acetylcholine, which binds nicotinic receptors on the muscle membrane.

Q4. What is saltatory conduction?

The jumping of action potentials from one Node of Ranvier to the next in myelinated axons — much faster (~100×) than continuous conduction in unmyelinated fibres.

Q5. Which division of the autonomic nervous system is dominant during fight-or-flight?

The sympathetic division — increases heart rate, dilates pupils and bronchi, releases adrenaline from adrenal medulla.

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Last Updated: April 2026 — NEET Gurukul Editorial Team.