Class 11 : Biology (In English) – Lesson 18: Neural Control and Coordination
EXPLANATION & SUMMARY
🌱✨ Introduction
🧠 Coordination ensures that all organs of the body work together harmoniously.
⚙️ The nervous system and endocrine system together regulate body functions through electrical and chemical signals.
🌿 This chapter focuses on the neural system, which works through neurons — specialized cells that transmit information via electrochemical impulses.
💡 Concept:
Neural control = rapid, short-term responses
Endocrine control = slower, long-term regulation
🧬 The Human Neural System
📘 Divided into:
1️⃣ Central Nervous System (CNS) — 🧠 Brain + 🧬 Spinal cord
2️⃣ Peripheral Nervous System (PNS) — cranial and spinal nerves
3️⃣ Autonomic Nervous System (ANS) — involuntary control (sympathetic & parasympathetic)
4️⃣ Somatic Nervous System — voluntary control of skeletal muscles
💡 The nervous system receives stimuli, processes them, and sends suitable responses.
🧠 Neuron: Structural and Functional Unit
🧩 Neuron = nerve cell specialized to conduct impulses.
📘 Parts:
Cell body (Soma): contains nucleus, cytoplasm (Nissl bodies)
Dendrites: receive impulses
Axon: transmits impulse away from cell body
Axon terminals: form synapses with next cell
💡 Myelinated neurons have Schwann cells forming myelin sheath → faster conduction.
Unmyelinated neurons conduct slower.
🔹 Types of Neurons
1️⃣ Sensory (Afferent): carry impulses from receptors to CNS
2️⃣ Motor (Efferent): carry impulses from CNS to effectors
3️⃣ Interneurons: connect sensory and motor neurons within CNS
⚡ Transmission of Nerve Impulse
🧠 Based on resting membrane potential and action potential.
1️⃣ Resting Potential
Inside neuron: negative (–70 mV)
Due to Na⁺/K⁺ pump (3 Na⁺ out, 2 K⁺ in)
Membrane is polarized
2️⃣ Action Potential (Depolarization)
Stimulus opens Na⁺ channels → Na⁺ influx → inside becomes positive
Membrane depolarized
3️⃣ Repolarization
K⁺ channels open → K⁺ efflux → negativity restored
Returns to resting state
💡 Impulse = wave of depolarization and repolarization
4️⃣ Conduction
Impulse travels along axon
In myelinated axons, jumps from node to node (saltatory conduction) → faster
🔄 Synapse
🧬 Junction between two neurons or neuron–effector.
Types:
1️⃣ Electrical synapse: direct ionic current; rare in humans
2️⃣ Chemical synapse: common; uses neurotransmitters (like acetylcholine)
🧠 Process:
Impulse → axon terminal → vesicle releases neurotransmitter → crosses synaptic cleft → binds receptor → new impulse in next neuron
✏️ Acetylcholinesterase destroys neurotransmitter to stop signal.
🧠 Central Nervous System (CNS)
🧩 1️⃣ Brain
📍 Located in cranial cavity, protected by cranium, meninges (dura, arachnoid, pia), and cerebrospinal fluid (CSF).
💡 Divided into three main regions:
🧠 (a) Forebrain
Includes:
Cerebrum: largest part; divided into two hemispheres connected by corpus callosum
Frontal lobe: reasoning, movement
Parietal lobe: sensory processing
Temporal lobe: hearing, memory
Occipital lobe: vision
Thalamus: relay center
Hypothalamus: controls hunger, thirst, temperature, and links with endocrine system (pituitary)
🧠 (b) Midbrain
Connects forebrain & hindbrain
Contains optic and auditory reflex centers
🧠 (c) Hindbrain
Cerebellum: balance, posture, coordination
Pons: bridges forebrain & medulla
Medulla oblongata: controls involuntary actions (breathing, heartbeat)
💡 Brainstem: midbrain + pons + medulla
🧬 2️⃣ Spinal Cord
📘 Cylindrical structure extending from medulla down vertebral canal
🧠 Functions:
Reflex actions
Relay between brain and body
⚙️ Protected by vertebral column and CSF
🧩 Peripheral Nervous System (PNS)
Consists of cranial (12 pairs) and spinal nerves (31 pairs).
📘 Functions:
Connects CNS to limbs and organs
Carries impulses to and from CNS
⚙️ Autonomic Nervous System (ANS)
Controls involuntary functions (heart rate, digestion).
🧠 Two divisions:
1️⃣ Sympathetic (“fight or flight”)
Increases heart rate, BP, respiration
Dilates pupils
2️⃣ Parasympathetic (“rest and digest”)
Decreases heart rate, conserves energy
💡 Work in antagonistic coordination.
⚡ Reflex Action
🧠 Reflex = involuntary, instantaneous response to a stimulus.
🌀 Pathway:
Stimulus → receptor → sensory neuron → spinal cord → motor neuron → effector → response
📘 Reflex arc is the structural and functional unit of reflexes.
💡 Spinal cord acts as integration center for reflexes (e.g., knee-jerk)
✏️ Examples: Withdrawal of hand from hot object, blinking.
🧠 Sense Organs (Brief Overview)
👁️ Eye
Sensory organ for vision
Composed of sclera, choroid, retina
Retina has rods (dim light) and cones (color)
Image formed is real, inverted
👂 Ear
Organ for hearing and balance
Outer ear → Middle ear → Inner ear
Cochlea = hearing
Semicircular canals = balance
💡 Converts sound waves to nerve impulses.
🌍 Coordination with Endocrine System
📘 Hypothalamus connects nervous and endocrine systems
🧠 Regulates pituitary gland through releasing hormones
⚙️ Ensures homeostasis
⚠️ Disorders of Nervous System
1️⃣ Epilepsy: recurrent seizures due to abnormal neural activity
2️⃣ Alzheimer’s disease: neurodegeneration → memory loss
3️⃣ Parkinson’s disease: dopamine deficiency → tremors
4️⃣ Stroke: brain damage due to disrupted blood supply
5️⃣ Depression: imbalance in neurotransmitters
💡 Healthy habits: balanced diet, rest, mental exercise.
🌍 Importance of Neural Control
🧠 Enables rapid communication across body
⚙️ Maintains coordination and reflexes
🌿 Integrates sensory input and motor output
💡 Essential for learning, memory, emotions
🌍 Why This Lesson Matters
💡 Provides foundation for understanding brain functions
🧠 Crucial for medicine, psychology, neuroscience
⚙️ Explains how body reacts and adapts
🌍 Helps understand disorders and mental health
📝 Quick Recap
🧠 Neuron = structural unit
⚡ Impulse = depolarization + repolarization
🔄 Synapse = chemical or electrical junction
🧬 Brain: forebrain, midbrain, hindbrain
🧩 Spinal cord = reflex center
⚙️ PNS: cranial + spinal nerves
🌀 ANS: sympathetic & parasympathetic
🧠 Reflex arc = receptor → effector
⚠️ Disorders: epilepsy, Parkinson’s, Alzheimer’s
📘 Summary
The nervous system regulates body functions via electrical impulses transmitted by neurons. Impulses travel through axons and synapses to coordinate actions. The CNS (brain and spinal cord) integrates information, while the PNS links the CNS to the body. The ANS controls involuntary processes through sympathetic and parasympathetic divisions. Reflex actions ensure rapid responses. Disorders like Alzheimer’s and Parkinson’s highlight its complexity. Neural control ensures coordination, perception, reaction, and adaptation — vital for survival.
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QUESTIONS FROM TEXTBOOK
🔵 Question 1. Briefly describe the structure of the Brain.
🟢 Answer:
🧠 The human brain is divided into three main parts:
🌿 Forebrain:
Cerebrum: Largest part; divided into two hemispheres; controls intelligence, will, memory, voluntary actions.
Thalamus: Relay centre for sensory impulses.
Hypothalamus: Maintains homeostasis; regulates hunger, thirst, temperature, endocrine functions.
🌸 Midbrain:
Connects forebrain with hindbrain.
Contains corpora quadrigemina; controls reflexes of vision and hearing.
🌿 Hindbrain:
Cerebellum: Coordinates muscular activities and balance.
Pons: Connects parts of brain; helps in respiration.
Medulla oblongata: Controls involuntary actions like heartbeat, breathing, swallowing.
✔️ Protected by skull, meninges, and cerebrospinal fluid (CSF).
🔵 Question 2. Compare the following:
🟢 (a) Central Neural System (CNS) and Peripheral Neural System (PNS)
Feature CNS PNS
Components Brain and spinal cord Cranial and spinal nerves
Function Integration and control Transmission of impulses
Protection Protected by skull & vertebral column Not protected
🟢 (b) Resting potential and Action potential
Feature Resting Potential Action Potential
State Membrane at rest During impulse
Potential –70 mV +30 mV
Ion condition Na⁺ outside, K⁺ inside Na⁺ moves in, K⁺ out
Function Maintains polarity Generates impulse
🔵 Question 3. Explain the following processes:
🟢 (a) Polarisation of the membrane of a nerve fibre:
At rest, membrane is polarised:
Na⁺ outside, K⁺ inside, large negatively charged proteins inside.
Potential difference ≈ –70 mV (resting potential).
🟢 (b) Depolarisation of the membrane of a nerve fibre:
When stimulated, Na⁺ channels open → Na⁺ influx → inside becomes positive (+30 mV).
Depolarised state initiates action potential.
🟢 (c) Transmission of a nerve impulse across a chemical synapse:
Impulse reaches axon terminal.
Ca²⁺ enters → synaptic vesicles release neurotransmitter (acetylcholine).
Neurotransmitter binds to receptors on postsynaptic membrane.
Opens Na⁺ channels → new impulse.
Neurotransmitter degraded by enzyme (acetylcholinesterase).
✔️ Ensures one-way transmission.
🔵 Question 4. Draw labelled diagrams of the following:
🟢 (a) Neuron – Showing dendrites, cell body, axon, myelin sheath, nodes of Ranvier.
🟢 (b) Brain – Showing forebrain, midbrain, hindbrain, cerebrum, cerebellum, medulla oblongata.
✏️ (Draw in notebook with clear labels as per NCERT diagram)
🔵 Question 5. Write short notes on the following:
🧠 (a) Neural coordination:
Integration of sensory input and motor output through neurons, brain, and spinal cord.
🌿 (b) Forebrain:
Cerebrum, thalamus, hypothalamus; responsible for intelligence, emotions, and sensory perception.
🌸 (c) Midbrain:
Connects forebrain and hindbrain; controls visual and auditory reflexes.
🌿 (d) Hindbrain:
Includes cerebellum, pons, medulla; regulates balance, posture, and involuntary actions.
⚡ (e) Synapse:
Junction between two neurons; transmits impulses via neurotransmitters.
🔵 Question 6. Give a brief account of the mechanism of synaptic transmission.
🟢 Answer:
Impulse reaches axon terminal.
Ca²⁺ influx causes neurotransmitter release.
Neurotransmitter diffuses across synaptic cleft.
Binds to receptors on postsynaptic membrane.
Opens ion channels → new action potential generated.
✔️ Unidirectional transmission; neurotransmitter degraded thereafter.
🔵 Question 7. Explain the role of Na⁺ in the generation of action potential.
🟢 Answer:
Na⁺ influx causes depolarisation.
Rapid entry of Na⁺ reverses polarity (inside positive).
Triggers action potential.
Later, Na⁺/K⁺ pump restores resting potential.
✔️ Na⁺ essential for impulse initiation.
🔵 Question 8. Differentiate between:
(a) Myelinated Axons Non-myelinated Axons
Covering Myelin sheath No sheath
Conduction Saltatory, faster Continuous, slow
Location White matter Grey matter
(b) Dendrites Axons
Function Receive impulses Transmit impulses
Number Many One
Direction Towards cell body Away from cell body
(c) Thalamus Hypothalamus
Function Relay sensory impulses Regulates homeostasis
Position Above midbrain Below thalamus
(d) Cerebrum Cerebellum
Function Intelligence, thinking Balance, coordination
Structure Largest part Smaller, posterior
🔵 Question 9. Answer the following:
(a) 🌿 Which part of the human brain is the most developed?
➡️ Cerebrum – controls intelligence, memory, emotions.
(b) 🌸 Which part of our central neural system acts as a master clock?
➡️ Hypothalamus – regulates circadian rhythm and endocrine control.
🔵 Question 10. Distinguish between:
(a) Afferent Neurons Efferent Neurons
Function Carry impulses to CNS Carry impulses from CNS
Type Sensory Motor
(b) Myelinated vs Unmyelinated conduction
Myelinated: Saltatory (nodes of Ranvier), faster
Unmyelinated: Continuous, slower
(c) Cranial Nerves Spinal Nerves
Origin Brain Spinal cord
Number 12 pairs 31 pairs
Function Sensory, motor, mixed Sensory and motor
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OTHER IMPORTANT QUESTIONS FOR EXAMS
(CBSE MODEL QUESTIONS PAPER)
ESPECIALLY MADE FROM THIS LESSON ONLY
🔴 Question 1:
Structural and functional unit of the nervous system is —
🔴1️⃣ Brain
🟢2️⃣ Neuron
🟡3️⃣ Spinal cord
🔵4️⃣ Nerve
🟢 Answer: 2️⃣ Neuron
🔴 Question 2:
Which part of the neuron receives impulses?
🔴1️⃣ Axon
🟢2️⃣ Dendrites
🟡3️⃣ Synapse
🔵4️⃣ Node of Ranvier
🟢 Answer: 2️⃣ Dendrites
🔴 Question 3:
Which division of the nervous system controls involuntary actions?
🔴1️⃣ Somatic
🟢2️⃣ Autonomic
🟡3️⃣ Central
🔵4️⃣ Peripheral
🟢 Answer: 2️⃣ Autonomic
🔴 Question 4:
Which part of the brain controls posture and balance?
🔴1️⃣ Cerebrum
🟢2️⃣ Cerebellum
🟡3️⃣ Medulla oblongata
🔵4️⃣ Pons
🟢 Answer: 2️⃣ Cerebellum
🔴 Question 5:
Which type of neuron carries impulses from sense organs to CNS?
🔴1️⃣ Motor neuron
🟢2️⃣ Sensory neuron
🟡3️⃣ Interneuron
🔵4️⃣ Mixed neuron
🟢 Answer: 2️⃣ Sensory neuron
🔴 Question 6:
Node of Ranvier is found in —
🔴1️⃣ Non-myelinated neurons
🟢2️⃣ Myelinated neurons
🟡3️⃣ Sensory neurons only
🔵4️⃣ Spinal nerves only
🟢 Answer: 2️⃣ Myelinated neurons
🔴 Question 7:
Which part of the brain controls respiration and heartbeat?
🔴1️⃣ Cerebrum
🟢2️⃣ Medulla oblongata
🟡3️⃣ Cerebellum
🔵4️⃣ Hypothalamus
🟢 Answer: 2️⃣ Medulla oblongata
🔴 Question 8:
The junction between two neurons is called —
🔴1️⃣ Axon terminal
🟢2️⃣ Synapse
🟡3️⃣ Dendrite
🔵4️⃣ Node
🟢 Answer: 2️⃣ Synapse
🔴 Question 9:
Which part of the brain is known as the “seat of intelligence”?
🔴1️⃣ Cerebellum
🟢2️⃣ Cerebrum
🟡3️⃣ Medulla
🔵4️⃣ Thalamus
🟢 Answer: 2️⃣ Cerebrum
🔴 Question 10:
Impulse transmission is fastest in —
🔴1️⃣ Non-myelinated neuron
🟢2️⃣ Myelinated neuron
🟡3️⃣ Synapse
🔵4️⃣ Spinal cord
🟢 Answer: 2️⃣ Myelinated neuron
🔴 Question 11:
Define a synapse.
🟢 Answer:
A synapse is the functional junction between two neurons or between a neuron and an effector where nerve impulses are transmitted via neurotransmitters.
🔴 Question 12:
Name the three main parts of the human brain.
🟢 Answer:
1️⃣ Forebrain (cerebrum, thalamus, hypothalamus)
2️⃣ Midbrain
3️⃣ Hindbrain (pons, cerebellum, medulla)
🔴 Question 13:
Describe the structure of a neuron.
🟢 Answer:
Cell body (Soma): Contains nucleus and cytoplasm with Nissl’s granules.
Dendrites: Short, branched processes that receive impulses.
Axon: Long fibre conducting impulses away from cell body; may be myelinated (with Schwann cells) or non-myelinated.
💡 Function: Neuron is the structural and functional unit of the nervous system.
🔴 Question 14:
Differentiate between myelinated and non-myelinated neurons.
🟢 Answer:
Feature Myelinated Neuron Non-Myelinated Neuron
Sheath Present Absent
Conduction Fast (saltatory) Slow
Nodes of Ranvier Present Absent
Location White matter, peripheral nerves Grey matter, ANS
💡 Myelin sheath insulates axon and increases speed.
🔴 Question 15:
Explain the generation and conduction of nerve impulse.
🟢 Answer:
1️⃣ Resting potential: Outer side +ve (Na⁺), inner side –ve (K⁺).
2️⃣ Depolarization: Stimulus → Na⁺ enters → inside becomes +ve.
3️⃣ Action potential: Electrical impulse generated.
4️⃣ Repolarization: K⁺ moves out → potential restored.
💡 Impulse travels unidirectionally along axon.
🔴 Question 16:
Describe the structure and function of synapse.
🟢 Answer:
Structure: Presynaptic membrane, synaptic cleft, postsynaptic membrane.
Process:
1️⃣ Impulse reaches axon terminal.
2️⃣ Vesicles release neurotransmitters (e.g., acetylcholine).
3️⃣ Neurotransmitters bind receptors → new impulse in next neuron.
💡 Allows one-way conduction of impulses.
🔴 Question 17:
Write short notes on reflex action and reflex arc.
🟢 Answer:
Reflex action: Automatic, involuntary response to stimulus.
Reflex arc: Pathway of reflex:
Receptor → Sensory neuron → Interneuron → Motor neuron → Effector
Example: Withdrawal of hand from hot object 🔥.
💡 Ensures quick protection from harmful stimuli.
🔴 Question 18:
Explain the parts of human central nervous system.
🟢 Answer:
1️⃣ Brain: Control centre with cerebrum, cerebellum, medulla.
2️⃣ Spinal cord: Extends from medulla; conducts impulses between brain and body; reflex centre.
💡 Protected by cranium and vertebral column; covered by meninges.
🔴 Question 19:
Describe the three meninges covering the brain.
🟢 Answer:
1️⃣ Dura mater: Outermost, tough fibrous layer.
2️⃣ Arachnoid: Middle delicate layer.
3️⃣ Pia mater: Innermost vascular layer; nourishes brain.
💡 Between arachnoid & pia = subarachnoid space filled with CSF.
🔴 Question 20:
Write the functions of cerebrospinal fluid (CSF).
🟢 Answer:
1️⃣ Acts as shock absorber.
2️⃣ Maintains constant pressure.
3️⃣ Provides nutrients and removes wastes.
4️⃣ Helps in exchange of materials between brain & blood.
💡 Present in ventricles, central canal, subarachnoid space.
🔴 Question 21:
Explain the structure and function of spinal cord.
🟢 Answer:
Structure: Cylindrical cord; grey matter inside, white matter outside.
Protected by: Vertebral column, meninges, CSF.
Functions:
1️⃣ Transmits impulses to/from brain.
2️⃣ Controls reflexes through reflex arcs.
💡 Extends from medulla to lumbar region.
🔴 Question 22:
Differentiate between sympathetic and parasympathetic nervous system.
🟢 Answer:
Feature Sympathetic Parasympathetic
Function Fight/flight Rest/digest
Effect on heart Increases rate ❤️ Decreases rate 💓
Effect on pupil Dilates 👁️ Constricts 👁️
Neurotransmitter Noradrenaline Acetylcholine
💡 Both form autonomic nervous system maintaining internal balance.
✅ End of Response 2 (Q13–Q22)
Proceed to Response 3 for Q23–Q30 (4-mark long answers).
all questions and answers belongs to this lesson……..only and all answers are rechecked and found correct.
📘 Lesson: Neural Control and Coordination — Code 3 — Response 3
(Class 11 Biology · NCERT 2025–26 Edition · Board-Style Paper Q23–Q30 · 4 Marks Each)
🔴 Question 23:
Explain the structure of the human brain.
🟢 Answer:
Main Parts:
1️⃣ Forebrain:
– Cerebrum: Largest part; controls intelligence, memory, reasoning.
– Thalamus: Relay centre for sensory impulses.
– Hypothalamus: Regulates hunger, thirst, temperature, endocrine control.
2️⃣ Midbrain: Connects forebrain and hindbrain; controls reflexes of eyes and ears.
3️⃣ Hindbrain:
– Cerebellum: Maintains posture and balance.
– Pons: Relays signals between cerebrum and cerebellum.
– Medulla oblongata: Controls heartbeat, respiration.
💡 Protected by cranium, meninges, and CSF.
🔴 Question 24:
Describe the parts and functions of the forebrain.
🟢 Answer:
1️⃣ Cerebrum:
– Two hemispheres, four lobes.
– Controls voluntary actions, intelligence, emotions, memory.
2️⃣ Thalamus:
– Relay centre for sensory impulses to cerebrum.
3️⃣ Hypothalamus:
– Maintains homeostasis (temperature, hunger, thirst).
– Controls pituitary gland; regulates sleep-wake cycle.
💡 Forebrain = seat of intelligence and sensory integration.
🔴 Question 25:
Explain the role of cerebellum and medulla oblongata.
🟢 Answer:
Cerebellum:
– Coordinates muscular movements.
– Maintains posture, equilibrium, balance.
– Ensures smooth voluntary movements.
Medulla oblongata:
– Controls involuntary activities: respiration, heartbeat, blood pressure.
– Reflex centres for coughing, sneezing, swallowing.
💡 Both belong to hindbrain, vital for survival.
🔴 Question 26:
Describe the transmission of nerve impulse across a synapse.
🟢 Answer:
1️⃣ Impulse reaches axon terminal of presynaptic neuron.
2️⃣ Synaptic vesicles release neurotransmitter (e.g., acetylcholine).
3️⃣ Neurotransmitter diffuses across synaptic cleft.
4️⃣ Binds to receptors on postsynaptic membrane, generating new impulse.
5️⃣ Neurotransmitter is degraded by enzyme (acetylcholinesterase).
💡 Ensures unidirectional transmission.
🔴 Question 27:
Explain the pathway of reflex action with an example.
🟢 Answer:
Reflex Arc Pathway:
Stimulus → Receptor → Sensory neuron → Interneuron (spinal cord) → Motor neuron → Effector
Example: Touching a hot object 🔥 → withdrawal of hand.
💡 Provides quick response to protect body without involving brain.
🔴 Question 28:
Differentiate between central and peripheral nervous system.
🟢 Answer:
Feature Central Nervous System (CNS) Peripheral Nervous System (PNS)
Components Brain & spinal cord Cranial & spinal nerves
Function Integration, control Transmission of impulses
Protection Cranium & vertebral column Not protected by bone
Example Brain 12 cranial nerves
💡 CNS = control centre; PNS = communication network.
🔴 Question 29:
Describe the autonomic nervous system and its divisions.
🟢 Answer:
Autonomic Nervous System (ANS): Controls involuntary actions of internal organs.
Divisions:
1️⃣ Sympathetic:
– Prepares body for emergency (“fight or flight”).
– Increases heart rate, dilates pupil, decreases digestion.
2️⃣ Parasympathetic:
– Restores normal state (“rest and digest”).
– Decreases heart rate, constricts pupil, promotes digestion.
💡 Both maintain homeostasis.
🔴 Question 30:
Write short notes on sense organs of humans.
🟢 Answer:
1️⃣ Eyes: Visual organ; image formed on retina; rods & cones for light and colour vision.
2️⃣ Ears: Hearing and balance; cochlea for sound, semicircular canals for equilibrium.
3️⃣ Nose: Olfactory receptors detect smell.
4️⃣ Tongue: Taste buds for sweet, sour, salty, bitter.
5️⃣ Skin: Receptors for touch, pain, temperature.
💡 Sense organs are receptors linking body with environment.
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