Important Questions Class 11 Biology Chapter 18 Neural Control and Coordination
Important Questions Class 11 Biology Chapter 18 Neural Control and Coordination
Neural Control and Coordination is Chapter 18 of Class 11 Biology. The neural system controls and coordinates the activities of all the organs of the body with the help of nerve cells called neurons. The chapter covers the structure of a neuron, how a nerve impulse is generated and conducted, the synapse and the parts of the human brain.
This page gives 12 important questions from Neural Control and Coordination with clear answers prepared by Extramarks experts. The questions cover the generation and conduction of a nerve impulse, myelinated and non-myelinated axons, afferent and efferent neurons, the reflex pathway, and the structure and working of the human eye. Students can use them for school tests and CBSE (Central Board of Secondary Education) exam revision, and teachers and parents can use them for quick practice.
Q1. Describe the functioning of the human eye.
Answer: The light enters the eye through pupil onto the lens which forms a real and inverted image of the object on the retina. The photopigments rhodospin and iodospin in the retinal cells composed of opsin and retinal. As the image is focused on the retina, the dissociation of the retinal from the opsin takes place which causes the structural changes in the opsin. This leads to the generation of the action potential which is transmitted to the visual cortex area of the brain by optic nerve. The impulses are then processed by the brain to recognize the image.
Q2. Explain the pathway taken for the involuntary responses.
Answer: The process of involuntary responses to the peripheral nervous stimulation is called Reflex action. The path taken by an impulse in the reflex action is called Reflex arc. Steps involved in a reflex path are as follows:
a) Stimulus is received by the receptor, i.e., sense organ.
b) Afferent nerve receives signal from the sensory organ and transmits the impulse to the spinal cord.
c) The spinal cord transforms the sensory impulse to the motor impulse.
d) The efferent nerve carries the signal from the spinal cord to the effector organ that may be a muscle which moves in response to the stimulus or a gland which secretes chemicals in response.
Q3. Describe the structure of an eye.
Answer: The human eye is a spherical structure whose wall is made of three concentric layers:
Sclera: It is the outermost, opaque layer of the eye composed of dense fibrous connective tissue. Anteriorly it forms a transparent layer called cornea.
Choroid: It is the middle vascular layer composed of blood vessels and abundant pigment. It thickens anteriorly to form ciliary body. The ciliary body continues forward as a thin, pigmented, muscular structure called iris which gives eye its colour. An aperture called pupil, lies in the centre of the iris. A transparent, crystalline lens lies behind the iris. It is held in place by the ligaments attached to the ciliary body.
Retina: It is the innermost layer of the eye composed of layers of the cells- ganglion cells, bipolar nerve cells and photoreceptor cells. The photoreceptor cells found are rods and cones. The optic nerve leaves the eye and blood vessels enter the eye from its posterior through a point called blind spot in the retina. Blind spot is devoid of any photoreceptor cells. A point called Fovea where only densely packed cones are found lies inside yellow spot, found lateral to the blind spot The space between cornea and lens and is called the aqueous chamber and the space between the lens and the retina is called vitreous chamber. Aqueous chamber is filled with fluid called aqueous humor and the vitreous is filled with the vitreous humor.
Q4. Draw the structure of human eye and label the part where –
(i) Maximum refraction occurs
(ii) Sharpest image formation takes place
(iii) Curvature of lens is altered
(iv) Focuses light rays
(v) Optic nerve emerges
Answer: (i) Maximum refraction occurs – Cornea
(ii) Sharpest image formation takes place – Fovea
(iii) Curvature of lens is altered – Ciliary body
(iv) Focuses light rays – Lens
(v) Optic nerve emerges – Blind spot
Q5. Draw a schematic digram to show the spinal reflex arc. Label the components of the pathway.
Answer:
| Receptor Sensory neuron (dorsal root) Dorsal root ganglion Interneuron in spinal cord Motor neuron (ventral root) Effector (skeletal muscle) |
|---|
Q6. Give the location and function in the human eye, of the following: 3
a) Cornea
b) Iris
c) Vitreous humor
Answer: Step 1: Location of the Cornea. The cornea is the transparent, dome-shaped frontmost layer of the eye that covers the iris, pupil and anterior chamber.
Step 2: Function of the Cornea. It refracts (bends) incoming light rays to help focus them onto the retina and acts as a protective barrier against dust, germs and other harmful matter.
Step 3: Location of the Iris. The iris is the coloured, ring-shaped membrane situated immediately behind the cornea and in front of the lens; its central opening forms the pupil.
Step 4: Function of the Iris. It regulates the amount of light entering the eye by adjusting the diameter of the pupil (contraction in bright light and dilation in dim light).
Step 5: Location of the Vitreous Humour. The vitreous humour is the clear, jelly-like substance that fills the space between the lens and the retina in the posterior segment of the eyeball.
Step 6: Function of the Vitreous Humour. It helps maintain the shape of the eyeball, provides internal support for the retina, and allows light to pass through to the retina unobstructed.
Q7. A person spontaneously removes his hand after touching a hot plate. Draw a schematic pathway involved in this response. What is such a response called?
Answer: Reflex action.
Q8. Give the location and function of the following in the human eye:
Cornea (ii) Iris (iii) Vitreous humor
Answer: (i) CORNEA: It is transparent, curved, anterior most part of the eye.
Its main function is refraction of light towards the retina.
(ii) IRIS: It extends in front of the lens from the ciliary body of the choroid.
It controls the amount of light entering the eye by dilating or constricting the pupil.
(iii) VITREOUS HUMOR: The chamber behind the eye is filled with a viscous fluid called vitreous humor.
It supports the eye ball.
Q9. 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.
Answer: (a) The sodium (Na+) ion plays an important role in generating and maintaining the potential difference necessary for the conduction of nerve impulse. When the outer side of the membrane of the nerve fibre is positively charged and the inner side is negatively charged, it is in resting state. At this state, there is a high concentration of sodium ions at the outer side of the membrane of nerve fibres. To generate an action potential, polarity should be reversed i.e. outer side should be negative and inner side of the membrane should be positive. When a neuron gets a nerve impulse, sodium ions cross the membrane of nerve fibres through sodium ion channels. This reverses the charge distribution across the membrane. The outer side of membrane becomes negatively charged, while the inner side becomes positively charged. Potential difference generated by this charge redistribution is called an action potential.
(b) Photoreceptor cells contain light-sensitive photo-pigments that are composed of opsin (a protein) and retinal (an aldehyde of vitamin A). As the light falls on retina passing through the pupil, it causes dissociation of retinal from opsin. It changes the conformation of opsin that results in change in membrane permeability of photoreceptor cells and generates an action potential. These impulses are transmitted by the optic nerves to the visual cortex area of the brain, where the neural impulses are analyzed and the image formed on retina is perceived.
(c) The external ear receives sound waves and transfers them to the tympanic membrane (eardrum). Sound waves generate vibrations in the tympanic membrane which are transferred to the oval window of the internal ear through ear ossicles (malleus, incus and stapes). Vibrations are then passed on to cochlea where they generate waves in the lymph. The waves in the lymph induce a ripple in the basilar membrane. It causes the hair cells to bend and presses them against the tectorial membrane. As a result, nerve impulses are generated in the associated afferent neuron that is transmitted via auditory nerves to the temporal lobe of the cerebral cortex of the brain, where the impulses are analysed and the sound is recognised.
Q10. Differentiate between:
(a) Myelinated and non-myelinated axons
(b) Dendrites and axons
(c) Rods and cones
(d) Thalamus and Hypothalamus
(e) Cerebrum and Cerebellum
Answer: (a)
| Myelinated axons | Non-myelinated axons |
|---|---|
| These are covered with a myelin sheath. | These are not covered with a myelin sheath. |
| Schwan cells are present in the myelin sheath. | Schwan cells are absent. |
| Node of Ranvier is present. | Node of Ranvier is absent. |
| Conduction of nerve impulse is faster. | Conduction of nerve impulse is slower. |
| Chances of loss of impulse during conduction are less. | Chances of loss of impulse during conduction are high. |
(b)
| Dendrites | Axons |
|---|---|
| Dendrites may be branched or unbranched. | Axons are branched structures. |
| They carry impulse towards the cell body (neuron). | They carry impulse away from the cell body. |
| Myelin sheath is absent. | They may or may not have a myelin sheath. |
| Dendrites are small. | They are long and big. |
| Nissl’s granules are present. | They are absent in axons. |
(c)
| Rods | Cones |
|---|---|
| Rods help to see in dim light. | They help to see in bright light. |
| They are not involved in visualisation of a colour. | They help in visualisation of colours. |
| They contain purple photo-pigment called rhodopsin. | They have violet photo-pigment called iodopsin. |
(d)
| Thalamus | Hypothalamus |
|---|---|
| Thalamus is the part of forebrain. It is a major coordination centre for sensory and motor signalling. | Hypothalamus is the part of forebrain that controls body temperature and urge for eating and drinking. |
(e)
| Cerebrum | Cerebellum |
|---|---|
| It is part of the forebrain. | It is part of hindbrain. |
| It is the centre for controlling activities like intelligence, communication, memory, movement, etc. | It controls involuntary activities like balance, body equilibrium, fine movement coordination, sneezing, coughing, etc. |
| It is located in the anterior portion of the forebrain. | It is located just above the brain stem. |
| It is the largest part of the brain. | It is the second-largest part of the brain. |
Q11. Answer the following:
(a) Which part of the ear determines the pitch of a 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?
Answer: (a) Cochlea determines the pitch of sound.
(b) Forebrain is the most developed part of brain.
(c) Hypothalamus acts as a master clock of body.
Q12. Distinguish between:
(a) Afferent neurons and efferent neurons
(b) Impulse conduction in a myelinated nerve fibre and unmyelinated nerve fibre
(c) Aqueous humor and vitreous humor
(d) Blind spot and yellow spot
(e) Cranial nerves and spinal nerves
Answer: (a)
| Afferent neurons | Efferent neurons |
|---|---|
| Afferent neurons transmit nerve impulse towards brain or spinal cord. | Efferent neurons transmit nerve impulse from brain to effector organs. |
(b)
| Impulse conduction in a myelinated nerve fibre | Impulse conduction in an unmyelinated nerve fibre |
|---|---|
| In myelinated nerve fibres, Schwann cells form the myelin sheath around the axon. The gaps between two adjacent myelin sheaths are called nodes of Ranvier. | In unmyelinated nerve fibres, a single Schwann cell encloses the axon and there is no myelin sheath. |
| The nerve impulse is transmitted from one node to another. This type of impulse transmission is fast. | The nerve impulse is transmitted in a continuous manner along the entire length of the nerve fibre. This type of impulse transmission is slow. |
(c)
| Aqueous humor | Vitreous humor |
|---|---|
| It is a thin and watery fluid that is present between cornea and lens. | It is a transparent gel that is present between the lens and retina. |
(d)
| Blind spot | Yellow spot |
|---|---|
| Blind spot is the region of retina where optic nerves pass. | It is small area on retina that is present at the posterior pole of the eye. |
| Photoreceptors are absent in this region. | Cone cells are present. |
| It does not sense light due to the absence of photoreceptors. | It perceives bright light. |
(e)
| Cranial nerves | Spinal nerves |
|---|---|
| Nerves arising from brain are called as cranial nerves. There are 12 pairs of cranial nerves. | Nerves arising from spinal cord are called as spinal nerves. There are 31 pairs of spinal nerves. |
Related Study Material on Extramarks
- Important Questions for Class 11 Biology Chapter 1 The Living World
- Important Questions for Class 11 Biology Chapter 2 Biological Classification
- Important Questions for Class 11 Biology Chapter 3 Plant Kingdom
- Important Questions for Class 11 Biology Chapter 4 Animal Kingdom
- Important Questions for Class 11 Biology Chapter 5 Morphology of Flowering Plants
- Important Questions for Class 11 Biology Chapter 6 Anatomy of Flowering Plants
- Important Questions for Class 11 Biology Chapter 7 Structural Organisation in Animals
- Important Questions for Class 11 Biology Chapter 8 Cell: The Unit of Life
- Important Questions for Class 11 Biology Chapter 9 Biomolecules
- Important Questions for Class 11 Biology Chapter 10 Cell Cycle and Cell Division
- Important Questions for Class 11 Biology Chapter 11 Photosynthesis in Higher Plants
- Important Questions for Class 11 Biology Chapter 12 Respiration in Plants
- Important Questions for Class 11 Biology Chapter 13 Plant Growth and Development
- Important Questions for Class 11 Biology Chapter 14 Breathing and Exchange of Gases
- Important Questions for Class 11 Biology Chapter 15 Body Fluids and Circulation
- Important Questions for Class 11 Biology Chapter 16 Excretory Products and their Elimination
- Important Questions for Class 11 Biology Chapter 17 Locomotion and Movement
- Important Questions for Class 11 Biology Chapter 19 Chemical Coordination and Integration
Q.1 Observe the given image, the labelled part of mammalian heart receives blood from
Marks:1
Ans
The superior vena cava is a large vein that carries deoxygenated blood from the upper half of the body to the heart’s right atrium. The inferior vena cava (or IVC) is the large vein that carries de-oxygenated blood from the lower half of the body into the right atrium of the heart.
Q.2 Identify the correct sequence of the chambers of the heart in order of thinnest to thickest walls.
Marks:1
Ans
Atria-Right ventricle-Left ventricle
The walls of the atria are thin because they only need enough pressure to move the blood into the ventricles. The ventricles possess thicker walls as compared to auricles. The left ventricle is with thickest walls because it has to pump blood throughout the body.
Q.3 If you have low level of red blood cells in your blood then you would have
Marks:1
Ans
Red blood cells transport oxygen to all body tissues. If our body will not produce red blood cells then we will feel fatigue due to lack of oxygen.
Q.4 Which of the following statements are true?
i. Pulse rate is not the same as the rate of the heartbeat.
ii. Wall of the left ventricle is thicker than the right one.
iii. Valves guard the opening between auricles and ventricles.
iv. Blood within the pulmonary vein returns to the right auricle.
Marks:1
Ans
Pulse rate is the same as the rate of the heartbeat. Blood within the pulmonary vein returns to the left auricle.
Q.5 Which of the following guards the left atrio-ventricular aperture in the human heart?
Marks:1
Ans
Bicuspid valve is one of the four valves of the heart. This valve is situated between the left atrium and the left ventricle. It permits blood to flow in one way only, from the left atrium into the left ventricle.
