Call Now
1800-102-2727The process that assists in the interaction of two or more organs and through which complements each other's functions is called Coordination. It is the endocrine system and the neural system that jointly coordinate and integrate every activity of the organs inside the human body so that the organs keep working without any abnormalities. Thus, by now, students must have gotten the notion about the topics discussed in this chapter. Yes, it is the 'Neural Control and Coordination' that will be preached here.
Some of the topics discussed are the neural system of humans and neural coordination mechanisms, such as transfer of nerve impulse, physiology of reflex action, and impulse conduction beyond a synapse. Read the below explanations to understand better about the topics.
This second-last chapter of class 11 biology is all about the neural system that humans have inside their bodies. Through the topic 'Neural Coordination and Control', the human neural system has been extensively explained. The subtopics highlighted in the introductory portion above are the mechanisms of neural coordination.
This chapter is also a part of the fifth unit of class 11 Biology syllabus. The central nervous system (CNS) components, such as the forebrain, hindbrain, peripheral nervous system, midbrain, autonomic nervous system, spinal cord, and sense organs, i.e. the ears & eyes are also a part that has been explained under this chapter. The students would also get to know about the process of impulse conduction, vision, and hearing in a captivating manner.
a. Brain
Answer:
The brain is the main coordinating center of the body. It is a part of the nervous system that controls and monitors every organ of the body. It is well protected by cranial meninges that are made up of an outer layer called dura mater, a thin middle layer called arachnoid, and an inner layer called pia mater.
It is divided into three regions —
Forebrain:
It is the main thinking part of the brain. It consists of the cerebrum, thalamus, and hypothalamus.
Midbrain: It is located between the thalamus region of the forebrain and the pons region of the hindbrain. The dorsal surface of the midbrain consists of superior and inferior corpora bigemina and four round lobes called corpora quadrigemina.
Hindbrain: It consists of three regions - pons, cerebellum, and medulla oblongata.
- Pons is a band of nerve fibre that lies between the medulla oblongata and midbrain. It connects the lateral parts of the cerebellar hemisphere.
- The cerebellum is a large and well-developed part of the hindbrain. It is located below the posterior sides of the cerebral hemispheres and above the medulla oblongata. It is responsible for maintaining posture and equilibrium of the body.
-The medulla oblongata is the posterior and simplest part of the brain. It is located beneath the cerebellum. Its lower end extends in the form of the spinal cord and leaves the skull through the foramen magnum.
Q1. Briefly describe the structure of the following:
a. Eye
Answer:
Eye: We know that eyes are in spherical structures that consist of three layers.
1. The outer layer is composed of the sclera and cornea.
-The sclera is an opaque tissue that is usually known as white of the eye. It is composed of dense connective tissue.
- The cornea is a transparent anterior portion of the eye that lacks blood vessels and is nourished by lymph from the nearby area. It is slightly bulged forward and helps in focusing light rays with the help of the lens.
2. The middle layer of the eye is vascular and contains the choroid, ciliary body, and iris.
- The choroid lies next to the sclera and contains numerous blood vessels that provide nutrients and oxygen to the retina and other tissues.
- Ciliary body: The choroid layer is thin over the posterior region and gets thickened in the anterior portion to form the ciliary body. It contains blood vessels, ciliary muscles, and ciliary processes.
-Iris: At the junction of the sclera and cornea, the ciliary body continues forward to form a thin-colored partition called the iris. It is the visible colored portion of the eye. The eye contains a transparent, biconvex, and elastic structure just behind the iris. It is known as a lens. The lens is held in position by suspensory ligaments attached to the ciliary body. The lens divides the eyeball into two chambers — an anterior aqueous and a posterior vitreous chamber.
3. The innermost nervous coat of the eye contains the retina. The retina is the innermost layer. It contains three layers of cells — inner ganglion cells, middle bipolar cells, and outermost photoreceptor cells. The receptor cells present in the retina are of two types — rod cells and cone cells.
- Rod cells —The rods contain the rhodopsin pigment (visual purple) that is highly sensitive to dim light. It is responsible for twilight vision.
- Cone cells —The cones contain the iodopsin pigment (visual violet) and are highly sensitive to high-intensity light. They are responsible for daylight and color vision. The innermost ganglionic cells give rise to optic nerve fibre that forms the optic nerve in each eye and is connected with the brain.
Q1. Briefly describe the structure of the following:
d. Ear
Answer:
Ear: The ear is the sense organ for hearing and equilibrium. It consists of three portions external ear, middle ear, and internal ear.
External ear: It consists of the pinna, external auditory meatus, and a tympanic membrane. Pinna is a sensitive structure that collects and directs the vibrations into the ear to produce sound. The external auditory meatus is a tubular passage supported by cartilage in the external ear. The tympanic membrane is a thin membrane that lies close to the auditory canal. It separates the middle ear from the external ear.
Middle ear: It is an air-filled tympanic cavity that is connected with the pharynx through the eustachian tube. The eustachian tube helps to equalize the air pressure on both sides of the tympanic membrane. The middle ear contains a flexible chain of three middle bonescalled ear ossicles. The three ear ossicles are malleus, incus, and stapes that are attached.
Internal ear: It is also known as the labyrinth. The labyrinth is divided into the bony labyrinth and a membranous labyrinth. The bony labyrinth is filled with perilymph while a membranous labyrinth is filled with endolymph.
The membranous labyrinth is divided into 2 parts.
Q2. Compare the following:
a. Central neural system (CNS) and Peripheral neural system (PNS)
Answer:
|
|
|
|
|
|
|
|
|
|
|
|
Q2. Compare the following:
a. Resting potential and action potential
Answer:
|
|
|
|
|
|
|
|
|
|
Q2. Compare the following:
c. Choroid and retina
Answer:
|
|
|
|
|
|
|
|
|
|
Q3. Explain the following processes:
a. Polarisation of the membrane of a nerve fiber
Answer:
Polarisation of the membrane of a nerve fiber:
- When the nerve fiber is at the resting phase, it is said to be in the polarised state.
- In a polarised state, the membrane of the nerve fiber experiences resting potential.
- The following steps take place during the process of polarization of the membrane of a nerve fiber:
- When a depolarised region of a nerve fiber starts becoming polarised initially, there are more K +ions outside the nerve fiber and the axon membrane contains a large amount of Na + ions.
- As the region of the membrane starts attaining the polarised state, the membrane becomes more permeable to K + ions and impermeable to Na + ions and negatively charged proteins.
- 3 Na + ions are sent outside the axon and 2 K + ions are sent into the axon by a sodium-potassium pump by active transport.
- The inner side of the membrane becomes electronegative (negatively charged) and the outer side becomes electropositive (positively charged) because of the movement of sodium and potassium ions. This makes the nerve fibre polarised.
Q3. Explain the following processes:
b. Depolarisation of the membrane of a nerve fibre
Answer:
Q3. Explain the following processes:
c. Conduction of a nerve impulse along with a nerve fiber
Answer:
- A nerve impulse is conducted across the length of a nerve fibre in an organized manner.
- On the nerve fibre during the conduction of an impulse, a region is always depolarised and a region next to it will be polarised. To send the impulse forward, the depolarised region repolarizes and the polarised region depolarises. This is repeated across the length of the nerve fibre which helps in the conduction of impulse.
- It occurs in the following steps:
- At a depolarised region, consider site A, there will be a positive charge on the inner surface of the membrane and a negative charge on the outer surface of the membrane.
- The region next to it which is polarised, consider site B, there will be a B positive charge on the outer surface of the membrane and a negative charge on the inner surface of the membrane.
- Hence, at site A, the current will flow on the inner surface of the membrane from A to B, and at site B, the current will flow on the outer surface from B to A. This will complete the circuit of the current flow.
- This will help site B to depolarise so that the impulse is conducted to site B.
- As soon as the impulse is conducted to site B, site A will get depolarised.
- When site B will be in the depolarised state, the region next to it, consider site C, will be polarised.
Q3. Explain the following processes:
d.Transmission of a nerve impulse across a chemical synapse
Answer:
Q4. Draw labeled diagrams of the following:
a.Neuron
Answer: Neuron-
Q4. Draw labeled diagrams of the following:
b. Brain
Answer: Brain-
Q4. Draw labeled diagrams of the following:
(c) Eye
Answer: Eye-
Q13. Draw labeled in diagrams of the following:
(d) Ear
Answer: Ear-
Q5. Write short notes on the following:
a. Neural coordination
Answer:
Q5. Write short notes on the following:
b. Forebrain
Answer:
The forebrain consists of these three: Cerebrum, Thalamus, and Hypothalamus
Cerebrum:
Thalamus:
Hypothalamus:
Q5. Write short notes on the following:
c. Midbrain
Answer: The midbrain consists of cerebral peduncles and corpora quadrigemina.
Cerebral Peduncles:
Corpora quadrigemina:
Q5. Write short notes on the following:
d. Hindbrain
Answer: The hindbrain consists of the cerebellum, pons Varolii, and medulla oblongata:
Cerebellum:
Pons Varolii:
Medulla oblongata:
Q5. Write short notes on the following:
e.Retina
Answer:
The retina is the innermost, neurosensory, thin layer of the eyeball. The external surface of the retina is in contact with the choroid and its inner surface is in contact with the vitreous humor. The retina is the site of image formation.
Rods:
Cones:
Macula lutea:
Q5. Write short notes on the following:
f. Ear ossicles
Answer:
Q5. Write short notes on the following:
(g) cochlea:
Answer:
Q5. Write short notes on the following:
h. Organ of Corti
Answer:
- It is the organ of hearing. It is located on the basilar membrane of the inner ear.
-It contains hair cells which are auditory receptor cells.
-These cells are present in rows on the internal side of the organ.
-The apical ends of the hair cells have processes called stereocilia.
-The basal parts of the hair cells have synaptic contacts with the afferent nerve fibers.
-Above the rows of hair cells is a smooth gelatinous layer called the tectorial membrane.
Q5. Write short notes on the following:
i. Synapse
Answer:
Synapse:
-A synapse is formed by the membranes of the pre-synaptic neuron and the postsynaptic neuron.
-A synapse may or may not be separated by a gap which is called the synaptic cleft.
-There are two kinds of synapses-electrical synapse and chemical synapse.
Q6. Give a brief account of:
a. Mechanism of synaptic transmission
Answer:
-The mechanism of synaptic transmission at the electrical synapse:
- In this case, the pre-synaptic and post-synaptic membranes are in proximity.
- Impulse in the form of electric current directly flows from the pre-synaptic neuron to the post-synaptic neuron.
- Transmission is faster than the chemical synapse. four-fifths labeled in fibers the mechanism of synaptic transmission at the chemical synapse:
- The pre-synaptic and post-synaptic neurons are separated by the synaptic cleft.
- When an impulse arrives at the axon terminal, the calcium ions present in the synaptic cleft enter the synaptic knobs present at the axon terminals of the pre-synaptic neuron.
- The synaptic vesicles present in the synaptic knobs present in the pre-synaptic neuron move towards the plasma membrane and fuse with it.
- The vesicles release the neurotransmitter acetylcholine in the synaptic cleft. (Empty synaptic vesicles return to the cytoplasm of the pre-synaptic neuron where they are refilled.)
- The molecules of acetylcholine bind to the protein receptors present on the plasma membrane of the post-synaptic neurons.
- This binding opens the channels, and sodium ions enter the post-synaptic neuron, while potassium ions leave the post-synaptic membrane.
-This generates an action potential in the membrane of the post-synaptic neuron, and hence, the impulse is transmitted to the post-synaptic neuron.
Q6. Give a brief account of:
a. Mechanism of vision
Answer:
Q6. Give a brief account of:
b. Mechanism of hearing
Answer:
Mechanism of hearing is given below:
Q7. Answer briefly:
a. How do you perceive the color of an object?
Answer:
Cone cells present in the retina of the eye are responsible for color vision. Three kinds of cone cells respond to red, green, and blue light. Different cone cells get stimulated at different wavelengths of light. The other colors are detected by the simultaneous stimulation of more than one kind of cone cells. When all three types of cells are stimulated simultaneously, a sensation of white light is produced.
Q7. Answer briefly:
b. Which part of our body helps us in maintaining body balance?
Answer:
Crista ampullary present in the three semicircular canals, the macula utriculi present in the utricle, and the macula sacculi present in the saccule of the inner ear help us in maintaining body balance.
Q7. Answer briefly:
c. How does the eye regulate the amount of light that falls on the retina?
Answer:
Light enters the eye through the pupil, an aperture present in the center of the iris. The iris has two types of muscles-circular smooth muscles and radial smooth muscles-which regulate the amount of light that falls on the retina.
The smooth circular muscles contract in bright light which makes the pupil smaller in size; hence, the lesser amount of light falls on the retina. In the dim light, the pupil is widened by the contraction of radial smooth muscles so that a sufficient amount of light falls on the retina.
Q8. Explain the following:
(a) Role of Na+ in the generation of the action potential.
Answer: Sodium ions diffuse from the outside to the intracellular fluid because of the electrochemical gradient. The potassium ions move out, and the membrane becomes negatively charged from outside and positively charged from inside. This sudden change in the membrane potential is called the action potential, and the membrane is said to be depolarised.
Q8. Explain the following:
( b) Mechanism of generation of light-induced impulse in the retina.
Answer: The photosensitive compounds (photopigments) in the human eye are composed of opsin and retinal. Light induces dissociation of retinal and opsin which changes the structure of opsin. It generates an action potential in the bipolar neurons. These impulses/action potentials are transmitted by the optic nerves to the visual cortex of the brain where the neural impulses are analyzed and the erect image is recognized.
Q8. Explain the following:
(c) Mechanism through which a sound produces a nerve impulse in the inner ear.
Answer: From the perilymph, the vibrations are transferred to the scala vestibuli of the cochlea and then to the scala media through Reissner's membrane and stimulate the sensory hair of the organ of Corti. The impulses thus received by the hair cells are carried to the brain through the auditory nerve where the sensation of hearing is felt.
Q9. Differentiate between: (a) Myelinated and non-myelinated axons
Answer:
|
|
|
|
|
|
|
|
|
|
|
|
Q9. Differentiate between: (b) Dendrites and axons
Answer:
|
|
|
|
|
|
|
|
|
|
Q9. Differentiate between:
c. Rods and cone
Answer:
|
|
|
|
|
|
|
|
|
|
Q9. Differentiate between:
d. Thalamus and Hypothalamus
Answer:
|
|
|
|
|
|
|
|
|
|
Q9. Differentiate between:
e. Cerebrum and Cerebellum
Answer:
|
|
|
|
|
|
|
|
|
|
Q10. Answer the following:
a. Which part of the ear determines the pitch of a sound?
Answer: The cochlea determines the pitch of a sound.
Q10. Answer the following:
b. Which part of the human brain is the most developed?
Answer: The cerebrum is the most developed.
Q10. Answer the following:
c.Which part of our central neural system acts as a master clock?
Answer: The hypothalamus of the central neural system acts as a master clock.
Q11. The region of the vertebrate eye, where the optic nerve passes out of the retina, is called
a) fovea b) iris c) blind spot d) optic chaisma
Answer:
c) Blind spot
The region of the vertebrate eye, where the optic nerve passes out of the retina, is called the blind spot. Photoreceptors are absent in this region.
Q12. Distinguish between:
a. afferent neurons and efferent neurons
Answer:
|
|
|
|
|
|
|
|
Q12. Distinguish between:
b. impulse conduction in a myelinated nerve fibre and unmyelinated nerve fibre
Answer:
|
|
|
|
|
|
|
|
Q12. Distinguish between:
c. aqueous humor and vitreous humor
Answer:
|
|
|
|
|
|
|
|
|
|
Q12. Distinguish between:
d. blind spot and yellow spot
Answer:
|
|
|
|
|
|
|
|
|
|
Talk to Our Expert