Biology

Neural Control and Coordination

Question:

Briefly describe the structure of the following:
(a) Brain (b) Eye (c) Ear

Answer:

(a) Brain: The brain acts as control and command system of the body. It is protected by skull and is covered by three meninges. It is divisible into three main regions: forebrain, midbrain and hindbrain.
(i) Forebrain – It consists of three regions:
(a) Olfactory lobes: These are a pair of very small, solid club-shaped bodies which are widely separated from each
other. They are fully covered by cerebral hemispheres.
(b) Cerebrum – It is the largest and most complex of all the parts of human brain. A deep cleft divides the cerebrum into right and left cerebral hemispheres, connected by myelinated fibres, the corpus callosum.
(c) Diencephalon – It encloses a slit-like cavity, the third ventricle. The thin roof of this cavity is known as the epithalamus, the thick right and left sides as the thalami, and floor as the hypothalamus.
(ii) Midbrain – It is located between thalamus/ hypothalamus of forebrain and pons of hindbrain. Its upper surface has two pairs of rounded protrusious called corpora quadrigemina and two bundles of fibres called crura cerebri.
(iii) Hindbrain – It consists of:
(a) Cerebellum – The second largest part of the human brain is the cerebellum. It consists of two lateral cerebellar hemispheres and central worm-shaped part, the vermis. The cerebellum has its grey matter on the outside, comprising three layers of cells and fibres. It also has Golgi cells, basket cells and granule cells.
(b) Pons varolii – An oval mass, called the pons varolii, lies above the medulla oblongata. It consists mainly of nerve fibres which interconnect different regions of the brain.
(c) Medulla oblongata – It extends from the pons varolii above and is continuous with the spinal cord below. The mid brain, pons varolii and medulla oblongata are collectively called brain stem.

(b) Eye: Eye is a hollow spherical structure composed of three coats:
– Outer fibrous coat
– Middle vascular coat
– Inner nervous coat
(i) Fibrous coat: It is thick and protects the eyeball. It has two distinct regions – sclera and cornea. Sclera covers most of the eye ball. The sclera or white of the eye contains many collagen fibres. Cornea is a transparent portion that forms the anterior one – sixth of the eyeball. The cornea is avascular (i.e., lacks blood supply).
(ii)Vascular coat: It comprises of 3 regions : choroid, iris, ciliary body.
(a) Choroid : It lies adjacent to sclera and contains numerous blood vessels and pigmented cells.
(b) Iris: The iris is a circular muscular diaphragm containing the pigment giving eye its colour. It extends from the ciliary  body across the eyeball in front of the lens. It 2. has an opening in the centre called the pupil.
It contains two types of smooth muscles, circular muscles (sphincters) and radial muscles (dilators), of ectodermal origin.
(c) Ciliary body: Behind the peripheral margin of the iris, the vascular coat is thickened to form the ciliary body. It is composed of the ciliary muscles and the ciliary processes.
(iii) Nervous coat: It consists of retina which is neural and sensory layer of an eye ball.  It consists of three layers; ganglion cells, bipolar cells and photoreceptor cells (rods and cones).
Lens: It is a transparent, biconvex, elastic structure that bends light waves as they pass through its surface. It is composed of epithelial cells that have large amounts of clear cytoplasm in the form of fibres.
Chambers of eyeball: The lens, suspensory ligament and ciliary body divide the eye into an anterior aqueous chamber and a posterior vitreous chamber which are filled with aqueous humour and vitreous humour respectively.

(c) Ear: There are three portions in an ear:
(i) External ear: It further has 2 regions: pinna and external auditory canal or meatus.
(a) Pinna: The pinna is a projecting elastic cartilage covered with skin. Its most prominent outer ridge is called the helix. The lobule is the soft pliable part at its lower end composed of fibrous and adipose tissue richly supplied with blood capillaries. It is sensitive as well as effective in collecting sound waves.
(b) External auditory canal: It is an S-shaped tube leading inward from the pinna. It is a tubular passage supported by cartilage in its exterior part and by bone in its interior part.
(ii) Middle ear: It consists of 3 small bones called ear ossicles – malleus, incus and stapes, which are attached to one another and increase efficiency of transmission of sound waves to inner ear.
(iii) Internal ear: It consists of bony and

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Neural Control and Coordination

Q 1.

If someone receives a blow on the back of neck, what would be the effect on the person’s CNS?

Q 2.

Label the following parts in the given diagram using arrow.
(a) Aqueous chamber
(b) Cornea
(c) Lens
(d) Retina
(e) Vitreous chamber
(f) Blind spot
ncert-exemplar-class-11-biology-solutions-neural-control-and-coordination-6

Q 3.

Comment upon the role of ear in maintaining the balance of the body and posture.

Q 4.

Which cells of the retina enable us to see coloured objects around us?

Q 5.

Answer the following.
(a) Which part of the ear determines the pitch ofa sound?
(b) Which part of the human brain is the most developed?
(c) Which part of our central neural system acts as a master clock?

Q 6.

Complete the statement by choosing appropriate match among the following.
ncert-exemplar-class-11-biology-solutions-neural-control-and-coordination-4

Q 7.

The major parts of the human neural system is depicted below. Fill in the empty boxes with appropriate words.
ncert-exemplar-class-11-biology-solutions-neural-control-and-coordination-2

Q 8.

Neural system and computers share certain common features. Comment in five lines. (Hint: CPU, input-output devices).

Q 9.

Name the structures involved in the protection of the brain.

Q 10.

Name the parts of human forebrain indicating their respective functions.

Q 11.

Rearrange the following in the correct order of involvement in electrical impulse movement- Synaptic knob. Dendrites, Cell body. Axon terminal. Axon.

Q 12.

Explain the following.
(a) Role of Na+ in the generation of action potential.
(b) Mechanism of generation of light-induced impulse in the retina.
(c) Mechanism through which a sound produces a nerve impulse in the inner ear.

Q 13.

What do grey and white matter in the brain represent?

Q 14.

6. Give a brief account of
(a) Mechanism of synaptic transmission.
(b) Mechanism of vision.
(c) Mechanism of hearing.

Q 15.

Arrange the following in the order of reception and transmission of sound wave from the ear drum:
Cochlear nerve.External auditoru canal, Ear drum, Stapes, Incus, Malleus, Cochlea.

Q 16.

While travelling at a higher altitude, a person complains of dizziness and vomiting sensation. Which part of the inner ear is disturbed during the journey?

Q 17.

Explain the following.
(a) Role of Na+ in the generation of action potential.
(b) Mechanism of generation of light-induced impulse in the retina.
(c) Mechanism through which a sound produces a nerve impulse in the inner ear.

Q 18.

What is the function ascribed to Eustachian tube?

Q 19.

Which sensory organ is involved in vertigo (sensation of oneself or objects spinning around)?

Q 20.

The region of the vertebrate eye, where the optic nerve passes out of the retina, is called the
(a) fovea (b) iris
(c) blind spot (d) optic chiasma
 

Q 21.

Our reactions like aggressive behaviour, use of abusive words, restlessness etc. are regulated by brain, name the parts involved.

Q 22.

Briefly describe the structure of the following:
(a) Brain (b) Eye (c) Ear

Q 23.

Write short notes on the following:
(a) Neural coordination (b) Forebrain
(c) Midbrain                       (d) Hindbrain
(e) Retina                             (f) Ear ossicles
(g) Cochlea                          (h) Organ of Corti
(i) Synapse

Q 24.

Compare the following:
(a) Central neural system (CNS) and Peripheral neural system (PNS).
(b) Resting potential and action potential.
(c) Choroid and retina.

Q 25.

Where is the hunger centre located in human brain?

Q 26.

Answer briefly.
(a) How do you perceive the colour of an object?
(b) Which part of our body helps us in maintaining the body balance?
(c) How does the eye regulate the amount of light that falls on the retina?

Q 27.

Explain the following processes:
(a) Polarisation of the membrane of a nerve fibre.
(b) Depolarisation of the membrane of a nerve fibre.
(c) Conduction of a nerve impulse along a nerve fibre.
(d) Transmission of a nerve impulse across a chemical synapse.

Q 28.

Explain the structure of middle and internal ear with the help of diagram.

Q 29.

Explain the process of the transport and release of crneurotransmitter with the help of a labelled diagram showing a complete neuron, axon terminal and synapse.

Q 30.

Distinguish between
(a) Afferent neurons and efferent neurons
(b) Impulse conduction in myelinated nerve fibre and unmyelinated nerve fibre
(c) Aqueous humour and vitreous humour
(d) Blind spot and yellow spot
(e) Cranial nerves and spinal nerves

Q 31.

During resting potential, the axonal membrane is polarised, indicate the movefnent of +ve and -ve ions leading to polarisation diagrammatically.

Q 32.

Draw labelled diagrams of the following:
(a) Neuron (b) Brain
(c) Eye (d) Ear

Q 33.

What is the difference between electrical transmission and chemical transmission?

Q 34.

Differentiate between
(a) Myelinated and non-myelinated axons
(b) Dendrites and axons
(c) Rods and cones
(d) Thalamus and Hypothalamus
(e) Cerebrum and Cerebellum