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Did you know that humans have a complex nervous system that controls all body actions and responses? The NCERT Notes for Class 11 Biology Chapter 18 are written in clear language for better understanding. It includes well-labeled diagrams which make learning more effective. This chapter gives an idea of the human nervous system and how it plays an important role in coordinating body functions. These NCERT notes help in building a strong foundation for board and entrance exams like NEET.
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The NCERT Notes for Class 11 Biology are useful for clear revision before exams and saves a lot of time. The chapter include the definition of the neural system, a summary of the human neural system, and the neuron as the structural and functional unit. In addition, Neural Control and Coordination chapter also deals with the central nervous system (CNS), reflex action and reception and processing of sense. The NCERT Notes for Class 11 help students understand complex topics in a simple way and improves exam performance.
Also, students can refer to:
Students preparing for school exams and for NEET can download the PDF notes for quick revision of important concepts. The notes explain the structure and functions of the nervous system in a simple and clear way. Diagrams and key points are included to make learning easier. This PDF can be accessed both online and offline to do study at anytime.
The notes given below are a helpful resource for easy and quick revision. The Neural Control and Coordination chapter includes topics like the structure of neurons, reflex action, and coordination through the nervous system. It also explains the brain and sense organs in a clear and simple way.
The neural system gives an organized network for the rapid coordination of body functions.
Coordination: Coordination among organs to support each other's functions.
Made up of neurons that perceive, receive, and conduct stimuli.
Complexity grows:
Lower vertebrates: Uncomplicated neuron network.
Insects: Brain with ganglia and neural tissues.
Vertebrates: Advanced neural system.
The human nervous system is divided into two parts:
System | Components |
The brain and spinal cord processes and controls information. | |
Nerves are connected to the CNS. Includes afferent (to CNS) and efferent (from CNS) nerve fibers. |
Somatic Nervous System: Regulates voluntary muscles (e.g., skeletal muscles).
Autonomic Nervous System (ANS): Regulates involuntary muscles (e.g., smooth muscles).
Sympathetic Nervous System: "Fight or flight" response.
Parasympathetic Nervous System: "Rest and digest" response.
Diagram: Structure of the Human Neural System
A neuron consists of three parts:
Part | Description |
Cell Body | Contains cytoplasm, organelles, and Nissl’s granules (absent in axons). |
Dendrites | Short fibers branching from the cell body; contain Nissl’s granules. |
Axon | Long fiber ending in synaptic knobs; may be myelinated or unmyelinated. |
The types of neurons based o structure are give below:
Multipolar: One axon, multiple dendrites (e.g., cerebral cortex).
Bipolar: One axon, one dendrite (e.g., retina).
Unipolar: Only axon present (found in embryos).
The types of axons are:
Myelinated Axons:
Covered with a myelin sheath formed by Schwann cells.
Found in the spinal cord and cranial nerves.
Gaps between myelin sheaths are called Nodes of Ranvier.
Unmyelinated Axons:
No myelin sheath; found in autonomic and somatic systems.
Diagram: Structure of a Neuron
Generation and Conduction of Nerve Impulse
The stage and process of nerve impulse can be discussed In the table given below:
Stage | Process |
Resting State | - Membrane permeable to K+ but impermeable to Na+ |
- Sodium-potassium pump maintains ionic gradient (++ outside, −−inside). | |
- The potential difference across the membrane is called the resting potential. | |
Stimulus Response | - Membrane becomes permeable to Na+, reversing charges (−−outside, ++ inside). |
- This creates an action potential or nerve impulse. | |
- Impulse travels through repeated depolarization/repolarization cycles along the neuron. |
Diagram: Generation of Nerve Impulse
The CNS includes the brain and spinal cord.
Protected by the skull and covered by three layers called cranial meninges:
Dura mater
Arachnoid
Pia mater
The divisions of the brain are as follows
Diagram: Divisions of the Brain
Includes cerebrum, thalamus, and hypothalamus.
Functions:
Cerebrum: Memory, sensory processing.
Thalamus: Sensory relay center.
Hypothalamus: Regulates temperature, hunger, and thirst.
Structure of Forebrain:
Connects forebrain to hindbrain.
Midbrain contains corpora quadrigemina for visual/auditory reflexes.
Structure of Midbrain:
Hindbrain includes pons, cerebellum, and medulla oblongata.
Functions:
Pons: Relays signals between brain regions.
Cerebellum: Maintains posture/balance.
Medulla oblongata: Controls heart rate, breathing.
Structure of Hindbrain:
Reflex action is an involuntary response to a stimulus.
Components of a reflex arc:
Receptor
Sensory neuron
CNS (spinal cord)
Motor neuron
Effector
Diagram: Reflex Arc
Also, Read
Some previous year questions given below help students get familiar with the exam format and test their level of preparation.
Question 1: Which of the following is not involved in the Knee reflex?
Option 1. Muscle spindle
Option 2. Motor neuron
Option 3. Brain
Option 4. Inter neurons
Answer:
An automatic response channel that does not directly engage the brain is known as the reflex arc. It consists of parts including motor neurons, which send signals to muscles for contraction, interneurons, which let sensory and motor neurons in the spinal cord communicate, and muscle spindles, which sense changes in muscle length.
Hence the correct answer is Option (3) Brain
Question 2: Resting membrane potential is maintained by
Option 1. Hormones
Option 2. Neurotransmitters
Option 3. Ion pumps
Option 4. None of the above
Answer:
The sodium-potassium pump and leak channels are examples of ion pumps and channels that preserve a cell's resting membrane potential:
Potassium-sodium pump
For every ATP molecule, this pump transports two potassium ions into the cell and three sodium ions out of it. The potassium ion concentration gradient produced by this action adds to the resting membrane potential.
Hence, The correct answer is option (3) Ion pumps.
Question 3: Potential difference across the resting membrane is negatively charged. This is due to differential distribution of the following ions
Option 1. Na+ and K+ ions
Option 2. CO3++ and Cl- ions
Option 3. Ca++ and Mg++ ions
Option 4. Ca4+ and Cl- ions
Answer:
The potential difference across the resting membrane is negatively charged. This is due to the differential distribution of Na+ and K+ ions. The electrical charge differential across a cell membrane caused by the combined forces of ions and their permeability is known as the membrane potential. It is essential for both cellular communication and general bodily processes.
Hence, the correct answer is Option (1) Na+ and K+ ions.
Also Read:
The chapter-wise notes are given below by which students can easily access all the chapter and start practicing to score well in the exam.
Neural control refers to the nervous system’s regulation of body activities through electrical impulses, while coordination ensures organs work together harmoniously. For example, withdrawing a hand from fire involves rapid neural signaling
The components are the Central Nervous System (CNS) and Peripheral Nervous System (PNS). CNS includes the brain and spinal cord, while PNS consists of nerves connecting CNS to organs.
CNS processes information (brain/spinal cord), while PNS transmits signals between CNS and body parts via afferent (to CNS) and efferent (from CNS) nerves.
Neurons transmit electrical signals (action potentials) via depolarization. At synapses, neurotransmitters carry signals to the next neuron.
The brain processes sensory input, controls voluntary movements and homeostasis, and regulates emotions, memory, and endocrine functions.
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