NCERT Class 11 Biology Chapter 21 Notes Neural Control And Coordination- Download PDF Notes

The neural control and coordination is a very important chapter of the NCERT neural control and coordination from an exam point of view. The NCERT Class 11 Biology Chapter 21 notes give you a basic idea of the chapter neural control and coordination. The main topics covered in NCERT Class 11 Biology notes are definition, neural system, human neural system, neuron as structural and functional unit of neural system, central neural system, reflex action and reflex arc, sensory reception and processing. Download the CBSE Notes for Class 11 Biology, Chapter 21, PDF to use offline anywhere. Students must go through each topic in the anatomy of flowering plants in Class 11 Notes Biology in the easiest and most effective way possible with the help of NCERT Notes for Class 11.

Class 11 Biology chapter 21 notes also cover all the important concepts related to the structure and function of the human nervous system, which are useful in various competitive exams. Neural control and coordination NCERT Notes for Class 11 Biology help you revise these major concepts given in the NCERT Book in no time during the CBSE Board exam preparation. CBSE Class 11 Biology Chapter 21 notes will help you with quick revision. The Neural Control and Coordination chapter covers all headings of NCERT. CBSE Class 11 Biology chapter 21 notes also contain important examples that have been frequently asked in the various exams. Having revision notes and NCERT Solutions for Class 11 Biology Chapter 21 handy is beneficial to save you time. The NCERT Class 11 notes pdf can be downloaded through the link given below.

Also, students can refer to:

• NCERT Solutions for Class 11 Biology Chapter 21 Neural Control and Coordination.
• NCERT Exemplar for Class 11 Biology Chapter 21 Neural Control and Coordination.

NCERT Class 11 Chapter 21 Class Notes

Neural Control And Coordination

Neural System

• The neurological system in the human body offers an orderly network of point-to-point connections for immediate coordination.
• Coordination is the process through which two or more organs interact and coordinate/ complement the function of each other.
• The neural system is composed of neurons that detect, receive and transmit different kinds of stimuli.
• The neural system increases in complexity as we move from lower vertebrates (a very simple network of neurons) via insects (brain with a no. of ganglia and neural tissues) to vertebrates (well-developed neural system).

Human Neural System

• The central nervous system (CNS) and peripheral nervous system (PNS) make up the human neural system (PNS).
• The brain and spinal cord constitute the CNS, and this is where information is processed and controlled.
• PNS comprises all nerves associated with CNS, it has two types of nerve fibers; afferent (signal from tissue to CNS) and efferent (signals from CNS to tissue).
• The somatic nervous system and the autonomic neural system are two parts of the PNS.
• For voluntary muscles, the somatic neural system distributes impulses from the CNS to the skeletal muscles.
• The autonomic nervous system relays impulses from CNS to smooth involuntary muscles.
• The autonomous nervous system is further divided into the sympathetic and parasympathetic nervous systems.

Neuron as Structural And Functional Unit Of The Neural System

• The cell body, dendrites, and axon are the three distinct segments of the neuron cell, which is the structural and functional unit of the nervous system.
• The cell body contains cytoplasm, cell organelles, and granular bodies called Nissl’s granules.
• Nissl’s granules are absent in the axon.
• Dendrites are short fibres that branch repeatedly and project out of the cell body and also contain Nissl’s granules.
• Axon is a long fiber having a branched structure at the end that terminates into a knob-like structure called a synaptic knob.
• Neurons having one axon and 2 or more dendrites are called multipolar neurons, such neurons for example are found in the cerebral cortex.
• If a neuron has one axon and one dendrite, like those found in the retina of the eye, such neurons are termed bipolar.
• At the embryonic stage, neurons are unipolar, i.e., don’t have any dendrite, only the axon is present.

• Axons are of two types; myelinated and unmyelinated based on whether or not they have myelin sheath around them.
• Myelinated fibers are enveloped with Schwann cells to form the myelin sheath around the axon. The gap between two myelin sheaths is called the node of Ranvier. This type of neuron is found in the spinal cord and cranial nerves.
• Unmyelinated fibers are enclosed by Schwann cells that don’t form the myelin sheath around the axon. These are found in the autonomous and somatic neural systems.

Generation and Conduction of Nerve Impulse

The neural membrane has numerous ion channels which are selectively permeable to different ions.

Resting-state

• During the resting stage, the axonal membrane is more permeable to K+ ions but impermeable to Na+ ions.
• The sodium-potassium pump in the axonal membrane is responsible for the maintenance of this ionic gradient across the resting membrane.
• This will develop a positive charge outside the axonal membrane and a negative charge in the inner side.
• The electric potential difference across the resting membrane is called resting potential.

On stimulus

• The membrane becomes permeable to Na+ ions to create a negatively charged outer surface and the inner surface gets positively charged, this creates action potential or nerve impulse in the neuron.
• The nerve impulse from A moves to B on the inner surface and B to A on the outer surface and this process gets repeated several times to transmit the impulse.

Transmission of Impulses

• The synapse is a juncture where the nerve impulse is passed from one neuron to the next.
• Synapse junctions are formed by membranes of presynaptic neurons and postsynaptic neurons which can be separated by a gap called cleft.
• Synapses could be electrical synapses or chemical synapses.
• The membranes of the pre-and postsynaptic neurons are very proximal to each other in the electric synapse, and the current goes straight from one to the other. Transmission is very fast as compared to the chemical synapse.
• Chemical synapses use neurotransmitters for the transmission of the signal. The membrane of pre and postsynaptic neurons are separated by a synaptic cleft in the case of a chemical synapse and axon terminals contain vesicles filled with neurotransmitters.
• The role of chemical synapse starts when Impulse arrives at the axon terminal, this stimulates synaptic vesicles to move towards the plasma membrane and fuse with it.
• This releases neurotransmitters in the synaptic cleft which reach the postsynaptic membrane and bind them.
• This binding opens ion channels that generate a new potential (can have an excitatory or inhibitory effect) in the postsynaptic neuron.

Central Neural System

• The brain acts as a control and command center of the human body.
• The brain is protected inside the skull; it is covered by cranial meninges.
• Cranial meninges have 3 layers; dura mater, arachnoids, and pia mater.
• The brain has three broad divisions; forebrain, midbrain, and hindbrain.

Forebrain

• The cerebrum, thalamus, and hypothalamus make up the forebrain.
• The corpus callosum, which is a tract of nerve fibres, divides the cerebrum into left and right cerebral hemispheres.
• The cerebral cortex is the layer of cells that cover the cerebral hemisphere, it is called grey matter because of its greyish appearance due to the concentration of nerve fibres.
• Fibres have an opaque whitish appearance due to myelin sheath covering, hence they are called white matter.
• The cerebral cortex has a motor area, sensory area, and areas that have neither sensory nor motor functions. These regions are called association areas for memory, intersensory association, and communication.
• Thalamus is the coordination center for sensory signalling and motor signalling. The cerebrum is wrapped around the thalamus.
• Hypothalamus is situated at the base of the thalamus. It functions as a coordinating center for body temperature, hunger, and thirst.
• The limbic lobe is the sum of the cerebral hemisphere and a few deep structures like the amygdala and hippocampus; it controls sexual behaviours and emotional expressions.

Midbrain

• The midbrain is situated between the thalamus or hypothalamus of the forebrain and pons of the hindbrain.
• The cerebral aqueduct canal passes through the midbrain.
• The dorsal portion of the midbrain has 4 round swellings called corpora quadrigemina.

Hindbrain

• The hindbrain is composed of pons, cerebellum, and medulla.
• Pons has fiber tracts that interconnect different regions of the brain.
• The cerebellum is a convoluted surface; it provides additional space for many neurons.
• The medulla contains centers for cardiovascular reflexes, gastric secretion, and respiration, it is connected to the spinal cord.
• The brain stem (the connection between the brain and spinal cord) is formed by the midbrain, pons, and medulla oblongata.

Reflex Action And Reflex Arc

• A reflex action refers to the complete process of responding to peripheral nerve stimulation that occurs involuntarily and requires the involvement of a component of the central nervous system.
• The afferent neuron gets a signal from a sensory organ and sends the impulse into the CNS through a dorsal nerve root (at the level of the spinal cord).
• After that, the efferent neuron sends signals from the CNS to the effector.

Sensory Reception And Processing

Eye

Eyes are located in sockets of the skull called orbits

Parts of an eye

• The Wall of the eyeball has 3 layers: sclera, choroid, and retina.
• The sclera is made up of dense connective tissue and its anterior part is called the cornea.
• The choroid contains blood vessels, blue colour and thin in the posterior part and thick in the anterior part, this layer forms the ciliary body.
• This ciliary body forms the iris (visible coloured portion of the eye). The lens is attached to the ciliary body.
• The front of the lens has a pupil; it is surrounded by the iris and its diameter is regulated by the muscle fibres of the iris.

• The retina is made up of 3 layers; ganglion cells, bipolar cells, and photoreceptor cells.
• Photoreceptor cells are of two categories; rods and cones, which contain photopigments.
• Rods have rhodopsin (derivative of vitamin A) protein, these cells assist night vision.
• Cones are stimulated by bright coloured light, these cells help in colour vision as they are stimulated by red, green, and blue light (if all are stimulated together, white light is perceived).
• A blind spot refers to the point where no photoreceptor cells are present. Pole lateral to blind spot is called Macula lutea (yellowish pigment spot) with a central pit called the fovea; this region has the highest resolution as cones are densely packed.
• Each eye has 2 chambers: An aqueous chamber and a vitreous chamber.
• The aqueous chamber is the space between cornea and lens, it is filled with fluid termed aqueous humour.
• The vitreous chamber forms the space between lens and retina, it is filled with vitreous humour fluid.

Mechanism of Vision

• Light entering the eye is focused only on the retina via cornea and lens.
• Photopigments present in retina cells (rods and cones) are made up of opsin protein and retinal (aldehyde form of vitamin A).
• Changes in opsin structure change the membrane permeability.
• Potential difference is generated in rods and cones, this produces an action potential.
• This action potential is transmitted to ganglion cells through bipolar cells.
• This signal is transmitted through the optic nerve to the visual cortex in the brain.
• The visual cortex recognizes the image based on early memory and experience.

The Ear

• The ear can be divided into three parts; outer, middle, and inner ear.
• Pinna on the outer ear collects sound vibration from outside.
• The outer ear has an external auditory meatus (ear canal) that passes sound to the tympanic membrane.

Middle Ear

• The middle ear has malleus bone attached to the tympanic membrane.
• Malleus collects sound vibration from the eardrum and passes to incus bone which then passes to stapes bone.
• The eustachian tube connects the middle ear to the pharynx, it helps in equalizing pressure on either side of the eardrum.
• Stapes are connected to the oval window of the cochlea.

Inner Ear

• The inner ear has a bony and membranous labyrinth.
• Bony labyrinth has a series of channels, inside these channels, there is a membranous labyrinth which is surrounded by perilymph.
• Perilymph is the fluid of the bony labyrinth; endolymph is the fluid of the membranous labyrinth.
• The coiled portion of the labyrinth is called the cochlea.
• The bony labyrinth is divided into upper scala vestibuli and lower scala tympani by Ressner’s membrane and basilar membrane.
• Space within the cochlea is called scala media, it is filled with endolymph.
• The organ of Corti is located on the basilar membrane and contains auditory receptors in the form of hair cells arranged in rows on the interior side of the organ of Corti. The hair cell's basal end is in close proximity to afferent nerve fibres.
• The inner ear has vestibular apparatus located above the cochlea, it is composed of 3 semi-circular canals (having a membrane suspended in perilymph) and an otolith organ (made of saccule and utricle, they contain macule).
• The base of the canals is swollen and is called the ampulla, which contains a projecting ridge called crista ampullaris which has hair cells.
• The vestibular apparatus's specialized receptors, the crista and macula, are important for maintaining body balance and posture.

Mechanism of hearing

• Sound collected by the external ear reaches the eardrum and so is passed on to ear ossicles that act as an amplifier to increase the efficiency of vibration.
• Sound vibrations then reach the oval window of the cochlea which is filled with fluid of labyrinth.
• This induces ripple in the basilar membrane and makes hair cells bend against the tectorial membrane, this action generates an impulse in the afferent neuron.
• The auditory nerve carries the signal to the auditory cortex in the brain which analyses and recognizes the sound.

Chapter-Wise NCERT Class 11 Notes Biology

Significance of NCERT Notes for Class 11 Biology Chapter 21

Neural control and coordination Class 11 notes will help students revise the chapter and have a better understanding of the major concepts addressed. The NCERT Class 11 chapter 21 notes are a part of NCERT Class 11 unit 5 Human physiology. Some of the topics covered in neural control and coordination Class 11 notes are the human neural system, impulse transmission, reflex action, sensory mechanism of the eye and ear. This NCERT Class 11 Biology chapter 21 notes can also be used to cover the important concepts of the CBSE Biology Syllabus in Class 11 as well as for competitive examinations such as the NEET, AIIMS, etc,.

Subject Wise NCERT Exemplar Solutions

• NCERT Exemplar Class 11 Solutions
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• NCERT Exemplar Class 11 Physics
• NCERT Exemplar Class 11 Chemistry
• NCERT Exemplar Class 11 Biology

Subject Wise NCERT Solutions

• NCERT Solutions for Class 11 Mathematics
• NCERT Solutions for Class 11 Chemistry
• NCERT Solutions for Class 11 Physics

• NCERT Solutions for Class 11 Biology