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अध्याय 18: तंत्रिकीय नियंत्रण एवं समन्वय

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CBSE • कक्षा XI • Biology • अध्याय 18

अनुमानित समय: 45 Mins

प्रगति: अध्ययनरत

तंत्रिकीय नियंत्रण एवं समन्वय

In Class 11 Biology, "Neural Control and Coordination" provides an authoritative, curriculum-verified master resource aligned with the 2026–27 NCERT syllabus.

अध्याय CBT ऑनलाइन टेस्ट दें सभी अध्याय देखें

प्रस्तावना अध्याय अवधारणाएँ अध्याय सारांश स्व-मूल्यांकन अभ्यास टेस्ट दें

🧠 Have You Ever Wondered?

How can a professional tennis player see a $200\text{ km/h}$ tennis serve, process its trajectory through 100 billion brain neurons, and swing a racket to return it within 0.2 seconds? The human nervous system executes bio-electrical action potentials at 120 meters per second.

यह अध्याय क्यों महत्वपूर्ण है

In Class 11 Biology, "Neural Control and Coordination" provides an authoritative, curriculum-verified master resource aligned with the 2026–27 NCERT syllabus.

अध्ययन से पूर्व (आवश्यक ज्ञान)

Reflex arc from Class 10.
Neurons and synapses.
Brain anatomy.

इस अध्याय के लक्ष्य

Describe the structure of a Neuron (Cell body/Soma, Dendrites, Axon, Myelin sheath, Nodes of Ranvier, Synaptic knobs).
Explain Conduction of a Nerve Impulse: Resting Membrane Potential ($-70\text{ mV}$, $Na^+-K^+$ pump), Depolarization ($Na^+$ influx, Action Potential $+30\text{ mV}$), Repolarization ($K^+$ efflux), and Saltatory Conduction.
Explain Synaptic Transmission: Chemical synapse, Neurotransmitters (Acetylcholine), synaptic vesicles, and receptor binding.
Analyze Human Central Nervous System (CNS): Forebrain (Cerebrum, Thalamus, Hypothalamus - thermoregulation/hormones, Limbic system - emotions), Midbrain (Corpora quadrigemina), and Hindbrain (Cerebellum - balance, Pons, Medulla oblongata - involuntary centers).
Describe Human Eye (Cornea, Iris, Lens, Retina: Rods/Rhodopsin vs Cones/Photopic color vision, Fovea centralis) and Ear (Organ of Corti, Vestibular apparatus - semicircular canals/crista for dynamic balance).

अध्याय रूपरेखा एवं प्रगति

1 1. The Action Potential ($120\text{...

2 2. The Human Brain Architecture

3 3. Eye & Ear Sensory Mechanisms

सम्पूर्ण सैद्धांतिक एवं वैचारिक अध्ययन

1. The Action Potential ($120\text{ m/s}$)

In resting state, axonal membrane is polarized ($-70\text{ mV}$ inside): maintained by active $Na^+-K^+$ ATPase Pump ($3\text{ Na}^+$ pumped out for every $2\text{ K}^+$ pumped in!).
• Depolarization: Stimulus opens voltage-gated $Na^+$ channels → explosive $Na^+$ influx reverses polarity to $+30\text{ mV}$ (Action Potential!).
• Repolarization: $Na^+$ channels close; voltage-gated $K^+$ channels open → $K^+$ efflux restores negative resting potential.
• Saltatory Conduction: In myelinated axons, action potentials leap from one Node of Ranvier to the next, accelerating conduction 50 times!

2. The Human Brain Architecture

Forebrain: Cerebral Hemispheres connected by nerve tract Corpus Callosum (seat of intellect/memory). Hypothalamus: Master regulator of body temperature, hunger, thirst, and endocrine hormones. Limbic System + Amygdala: Emotional brain (rage, fear, motivation).
Midbrain: Four rounded swellings: Corpora Quadrigemina (visual and auditory reflexes).
Hindbrain: Cerebellum (intricate surface maintaining muscular balance and precision), Pons (pneumotaxic center), Medulla (regulates heartbeat, respiration, swallowing, vomiting).

3. Eye & Ear Sensory Mechanisms

Retina: Rods (contain visual purple Rhodopsin with Vitamin A; scotopic twilight vision); Cones (photopic daylight and trichromatic Red-Green-Blue color vision). Fovea Centralis: Thinned-out central pit packed purely with cones → highest visual acuity/resolution!
Ear: Organ of Corti on basilar membrane converts fluid sound waves into auditory impulses. Vestibular Apparatus (3 semicircular canals with ampulla crista + otolith macula) maintains dynamic and static body balance and posture!

Neural Control and Coordination - Key Biological & Anatomical Model

अध्याय का सार संक्षेप एवं 10 मुख्य निष्कर्ष

मुख्य बिंदु 1

Sodium-Potassium ATPase: Electrogenic pump transporting $3\text{ Na}^+$ out for $2\text{ K}^+$ in.

मुख्य बिंदु 2

Action Potential: Rapid transient membrane polarity reversal to $+30\text{ mV}$ propagating nerve signals.

मुख्य बिंदु 3

Corpus Callosum: Giant nerve bridge connecting left and right cerebral hemispheres.

मुख्य बिंदु 4

Fovea Centralis: Dense pure cone retinal focal point delivering maximum optical resolution.

मुख्य बिंदु 5

Vestibular Crista: Semicircular canal sensory hair cells maintaining rotational body balance.

स्व-मूल्यांकन अभ्यास (Check Your Understanding)

मूल वैचारिक स्पष्टता की जांच के लिए नैदानिक प्रश्न। पहले स्वयं हल करें, फिर उत्तर देखें।

Explain the mechanism of generation and conduction of a nerve impulse (action potential) along an unmyelinated axon.

उत्तर एवं व्याख्या देखें

उत्तर: (1) Resting State ($-70\text{ mV}$): Axon membrane is polarized, negatively charged inside due to $Na^+-K^+$ pump ($3Na^+$ out, $2K^+$ in) and impermeable negative proteins. (2) Depolarization ($+30\text{ mV}$): A stimulus increases membrane permeability to $Na^+$; rapid $Na^+$ influx reverses polarity, creating an action potential (nerve impulse). (3) Conduction: The local current flows ahead on inner surface and backward on outer surface, depolarizing the adjacent membrane and propagating the wave of excitation. (4) Repolarization: $K^+$ efflux rapidly restores resting membrane potential.
Polarized resting potential (-70 mV) -> Na+ influx action potential (+30 mV) -> K+ efflux repolarization.

What is the 'Corpus Callosum'? What is its function in the human brain?

उत्तर एवं व्याख्या देखें

उत्तर: The corpus callosum is a prominent, thick curved band of myelinated nerve fibers that bridges and connects the left and right cerebral hemispheres of the forebrain, facilitating inter-hemispheric communication and coordination.
Thick tract of nerve fibers connecting left and right cerebral hemispheres.

Describe the structural and functional differences between Rods and Cones in the human retina.

उत्तर एवं व्याख्या देखें

उत्तर: Rods: Contain the purplish-red photopigment Rhodopsin (derived from Vitamin A), specialized for twilight (scotopic) vision, sensitive to dim light, do not perceive color. Cones: Contain photopic iodopsin pigments specialized for bright daylight vision, provide sharp visual acuity and color vision through three types of cones sensitive to Red, Green, and Blue light.
Rods (Rhodopsin, dim twilight vision, no color) vs Cones (daylight vision, sharp acuity, color).

Which part of the human ear is responsible for maintaining the dynamic equilibrium and balance of the body?

उत्तर एवं व्याख्या देखें

उत्तर: The Vestibular Apparatus of the inner ear, specifically the Crista Ampullaris located in the ampulla of the three semicircular canals (detects rotational angular movements) and the Macula in the Otolith organs (detects linear acceleration and gravity).
Vestibular apparatus: Crista in semicircular canals and Macula in otolith organs.

What is a Chemical Synapse? How does a nerve impulse travel across it?

उत्तर एवं व्याख्या देखें

उत्तर: A chemical synapse is a microscopic junction between two neurons separated by a fluid-filled synaptic cleft. When an action potential reaches the axon terminal, it triggers calcium influx, causing synaptic vesicles to fuse with the pre-synaptic membrane and release neurotransmitters (like Acetylcholine) into the cleft. Neurotransmitters diffuse across and bind to specific receptors on the post-synaptic membrane, opening ion channels to generate a new action potential.
Neurotransmitter release across synaptic cleft binds post-synaptic receptors.

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अभ्यास के लिए तैयार?

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