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August 14, 2018 by 

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Ayisha Nafiya
class: VI
Dahwath English Medium School
Othukkungal, Malappuram

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Chapter 2 Windows of knowledge

August 08, 2018 by 


Contents


• Vision - The protective measures of eyes.
- Structure of human eye, Working of eye lens,
- Photo receptors in the retina, Sense of vision.
- Disorders & diseases of eyes, Hygiene of our eyes.
• Hearing- Structure of human ear, Auditory receptors,
- Sense of hearing, Body balancing.
• Tasting - Taste receptors in the tongue, sense of tasting.
• Smelling - Olfactory receptors in the nose, sense of smelling.
• Different senses in the skin
• Sensory receptors in certain other organisms

Questions and answers

1. How is the feeling of senses made possible ?
Sense is possible only when impulses from sense organs reach at the brain through the sensory nerves.
The ends of sensory nerve from the brain act as the receptors inside the sense organs.
2. How are our eyes protected?
- Bony eye socket (orbit) - protects eye.
- External eye muscles – fixes the eye ball in the orbit.
- Eyelids - protect from dust and other particles.
- Eyelashes - protect from dust with out obstructing vision.
- Eyebrow – prevents perspiration or water reaching in to the eyes.
- Tears - clean and lubricate the anterior part, washes away the dust particles and destroys germs.
- Conjunctiva – secretes mucus to prevent the eye from being dry.
3. The enzyme contained in tears ? 
 Lysozyme.
4. Which are the 3 layers of human eye ?
. Sclera –The outermost, strong layer, that gives shape. Its transparent anterior portion is the cornea.
.Choroid- Middle layer of blood capillaries, which supply nutrients and oxygen.
Its anterior dark screen with pupil is the iris. A convex lens is placed behind the iris.
. Retina- The innermost layer on which, the image forms. The optic nerve starts from the retina.
5. The fluids filled in the chambers of eye , position and function ?
* Aqueous humor – A watery fluid seen in the aqueous chamber [between cornea and lens] , oozes from the blood. This fluid supplies nutrients and oxygen to cornea and lens.
* Vitreous humor - A jelly like fluid filled with in the vitreous chamber [between lens and retina], helps to maintain the shape of eyeball.

 6. Slightly projected transparent anterior part of the sclera ? Ans: Cornea.
7. The transparent membrane which protects the sclera, except the cornea ? Ans: Conjunctiva.
8. The dark coloured anterior part of choroid is --------, which contains the pigment melanin. Ans: Iris.
9. The aperture at the centre of iris ? Ans : Pupil.
10. The antagonistic muscles in the iris that regulate the size of eye pupil ?
Radial muscles (pupillary dilator) and Circular muscles (pupillary constrictor).
11. When bright light falls, the eye pupil --------- ?
- Constricts [due to the contraction of the circular muscles]
12. The muscles, which adjust the curvature of eye lense, seen behind the iris ?
Ciliary muscles.
13. Define the power of accommodation of the eye.
The capacity of the eye to change the curvature of lens depending up on the distance between the the eye and the object by adjusting the focal length is called the power of accommodation of the eye.
14. How can our lens adjust its focal length according to the distance from objects?
[ How is power of accommodation possible?]
When we look at a distant object, the ciliary muscles are in a relaxed position so as to keep the ligaments tight. Therefore the curvature of lens decreases to fix the image on retina [figure-1].
When we look at a near object, the ciliary muscles contract to loosen the ligaments. When ligaments relax, the curvature of lens increases naturally ,to focus the image on retina. [figure-2].
15. The characteristics of images formed on retina ?.
Real, Small, Inverted and Accommodated.
16. Compare and contrast between the photo receptors seen on the retina.

 Receptor region of the rod cells is rod shaped and contain the pigment rhodopsin, which will be stimulated under dim light. Receptor region of the cone cells is cone shaped and contain the pigment photopsin (iodopsin) which will be stimulated under intense light.
Under dim light, rhodopsin dissociates to form retinal and opsin to produce impulses from rod cells.
Under intense light, photopsin (iodopsin) dissociates to form retinal and opsin to produce impulses from cone cells. The three types of cone cells (red, green & blue) provide us with colour vision.

17. Vitamin A help us for better vision. Give reason.
Retinal, the visual pigment found in the photoreceptors, is formed from vitamin A.
18. Compare between Blind spot and Yellow spot
Blind spot is a part of retina from where the optic nerve begins. No photoreceptors at this spot, hence no vision. Yellow spot is the point of highest vision in the retina, where more cone cells seen. Images form in and around the yellow spot.
19. Point on retina lacking vision : Blind spot ; Point of highest vision in retina:--------?
Yellow spot
20. The bird, owl has no vision in day time. Why?
Owl’s retina is devoid of cone cells and hence no vision in day time.
21. Animals like cat and owl have more vision at night. Why ?
Cat and owl has more rod cells in their retina, so that they have more vision at night.
22. A kite can locate its prey even from high altitude. How is this possible ?
The eyes of kite are closer to each other and contain a large number of cone cells. Hence it has high power of vision.
23. Flowchart of image formation in retina.
Light rays from the object→ Cornea→  Aqueous humor / Pupil→  Lens→  Vitreous humor→ 
Image on retina
24. What are the changes occur in retina when images focus on it ? (Describe that how vision is possible.)
When light rays from the object passes through cornea and pupil fall on the lens, a small, real inverted image forms on the retina. When the image is formed under dim light, rhodopsin in the rod cells dissociate to produce impulses and when the image is formed under intense light, photopsin in the cone cells dissociate to produce impulses. These impulses are transmitted through the optic nerve. The brain coordinates the images from both eyes to feel perfect vision.
25.Experience of vision - Flowchart.
Image on retina → stimulation in the photo receptors → dissociation of rhodopsin / photopsin→  impulses→  optic nerve→  coordination of images by cerebrum→  perfect vision.
26. Though images of object are formed in both eyes, we can see only one object. Give reason.
Cerebrum coordinates the two images and hence get a three dimensional view of the object.
27. Define binocular vision.
The ability of both the eyes to focus on the same object is known as binocular vision.
Binocular vision help us to get a three dimensional image of the object. This help us to calculate the correct distance, depth, height and width of the object.
28. What is the need of closing one eye while shooting an object ?
Binocular vision help us to get a three dimensional image of the object and to calculate the correct distance, depth, height and width of the object. But in the case of aiming an object, we need to get correct line instead of common focus through binocular vision.
29. The condition by which certain colours cannot recognize : Colour blindness ;
Decreased vision in dim light : ------------------- ? Ans: Night blindness.
30 .------------ and ------------- are the two conditions of eye due to the deficiency of vitamin A.
Night blindness and Xerophthalmia (dry conjunctiva and cornea)
31. A few points related with the health of our eyes.
• Avoid falling of bright source of light directly to the eyes. Don't look at the sun.
• Avoid reading under dim light.
• Do not watch TV or other screens continuously.
• Frequently wash our eyes.
• Include vitamin A contained items in our daily food.
32.Table which shows reason of various disorders and diseases that affect on our eyes.
33.The functions of human ear ? Ans: Hearing, body balance.

34. What are the main parts of human ear ?

External Ear 
1. Ear pinna 
2. Ear canal 
3. Ear drum / Tympanum
 Middle Ear
4. Malleus
5. Incus
6. Stapes
7. Eustachian tube
Internal Ear
8. Cochlea
9. Vestibule [Sacule, Utricle]
10. Semicircular canal
11. Auditory nerve
12. Vestibular nerve

35. The safety measures to prevent dust and other particles from entering the ear are, ------------
Hairs and ear wax.
36. When sound waves enter to the ear, ............. starts to vibrate. Ans: Ear drum (tympanum)
37. The smallest bone in the human body ? Ans: Stapes
38. Name the bones of ear ossicles. Ans: Malleus, Incus, Stapes.
They amplify sound waves 22 times and pass the vibrations from the ear drum to the oval window.
39. The tube that connects the middle ear to the pharynx ? What is its function ?
Eustachian tube. It helps to regulate the pressure inside the middle ear.
40. The structure of internal ear.
The internal ear, seen inside the bony labyrinth, as membraneous labyrinth. A coiled
tube like cochlea and the vestibular apparatus (vestibule & three semicircular canals)
are the parts of inner ear. The membraneous labyrinth is filled with a fluid, named
endolymph and the space between the bony and membraneous labyrinths is filled with
another fluid, named perilymph. Cochlea of the internal ear functions in hearing, while the vestibular apparatus helps to maintain body balance through transmitting impulses to the cerebellum.
41. What are the different receptors seen inside the vestibular apparatus ?
The cluster of receptors (hair cells) seen inside the utricle and sacule of the vestibule are immersed in a jelly substance and the sensory hair cells in the ampulla of the semicircular canals are also immersed in a jelly substance. All these receptors (hair cells) are stimulated according to the movement of head.
42. Cochlea : Hearing ; ------------ :Equilibrium of the body.
Vestibular apparatus (Vestibule and semicircular canals)
43. The swollen end of semicircular canals. Ans: Ampulla.
44. Cochlea : Auditory nerve : Cerebrum; Vestibular apparatus : Vestibular nerve : ................. ?  
Ans: Cerebellum.
45. Hearing. Flowchart.
Sound waves→ ear pinna →ear canal→ ear drum (tympanum) vibrates →ear ossicles
oval window→ cochlear perilymph→ endolymph →stimulation in auditory receptors of the
basilar membrane→ impulse transmitted through auditory nerve →auditory centre of the brain→ hearing.
46. What is the role of ear in maintaining the equilibrium of the body ? How is it possible ?
Receptors (hair cells) seen inside the ampulla of semicircular canals, sacule and utricle are stimulated according to the movement of head. The impulses formed thus will be transmitted to the cerebellum through the vestibular nerve. Cerebellum functions so as to maintain the equilibrium of body.
47. Why giddiness is felt when you turn round and round ?
When we turn round continuously, the endolymph inside the semicircular canals and vestibule also moves and there will be continuous stimulation of the receptors and passing of impulses to the cerebellum. Hence cerebellum can not coordinates the muscular activities properly and we feel giddiness.
48. How do we sense taste ?
Chemoreceptors seen inside the mouth and tongue help us to detect taste. The chemoreceptors seen inside the papillae of the tongue are called as taste buds. Smell also influences taste.
49. The different taste buds of the tongue. 
Ans: Sweet, salt, sour and bitter. Other tastes are created by the
brain from the primary tastes.
50. The projected structures seen on the tongue surface are known as ----------?
Ans: Papillae.

51. Make a flowchart of sensing taste.
52. Recognize the figure A and B.

 Ans: A. Taste bud     B. Olfactory receptors.
53. How can we feel smell ?
When particles enter to the nose and disperse in the mucus, the olfactory receptors in the mucus membrane get stimulate and the impulses reach the brain through the olfactory nerve.
54. The ability of shark to sense smell is sharp. Why?
Shark has highly sensitive olfactory receptors.
55. The largest sense organ ? Ans: Skin.
56. The stimuli that can be received by our skin ? Ans: Heat, Touch, Pain, Cold and Pressure
57. How skin perform as a sense organ ?
Heat, cold, touch, pressure and pain are felt by our skin. When these receptors
are stimulated, impulses form and reach in the cerebrum for its perception.
58. The eyes of an insect consist of a cluster of photoreceptors called --------- ?
Ommatidia.
59. Housefly : Ommatidia Planaria : ---------- ? Ans: Eye spot.
60. The special olfactory organ seen in the mouth of snake ? Ans: Jacobson's organ.
61. How is the lateral lines important to the shark ?

The receptors in the lateral lines help to detect the change in the balance the body.

 Prepared by Rasheed Odakkal, 9846626323, GVHSS Kondotty
source: Spandanamnews blogspot

Structure and working of eye



Working of eye



Human ear



Tongue

Chapter 1 Sensations and responses

August 08, 2018 by 
Simplified note

Contents

• External and internal stimuli
• Neuron -structure, Impulse generation and transmission.
• Types of nerve.
• Central nervous system
- Brain & Spinal cord – structure and functions.
- Reflex actions
• Peripheral nervous system
- Sympathetic and parasympathetic nerves
• Disorders of nervous system
- Alzheime'rs, Parkinsons & Epilepsy.
Questions and answers

1. Define stimulus.
 The senses that evoke responses in organisms are called stimuli. These are two types,
External stimuli :- Sound, touch, heat, chemicals, pressure, cold, radiations.

Internal stimuli :- Hunger, touch, infection, pressure variation, thirst, exhaust.

2. What is the function of nervous system ?

To generate and coordinate responses according to external and internal changes.

3. Name the parts included in our nervous system.

Brain, spinal cord, nerves and receptors.

4.The structural and functional units of the nervous system ?
Neurons (nerve cells).
5. Structure of a model neuron.
A neuron has mainly the following parts; a cyton (cell body), impulse receiving dendrons (branches are known as dendrites), impulse transmitting axon (branches are axonites) and synaptic knobs for secreting neurotransmitter.
In certain neurons, the nerve fibres are covered by myelin sheath, made up of white shining Schwann cells.
6. The protective covering of nerve fibres (axons) ? Mention its function.
Myelin sheath.
• Provide nutrients and oxygen to the axon.
• Accelerate impulses.
• Act as an electric insulator.
• Protects the axon from external shocks.
• Gives white appearance ('white matter') to the neural parts.

7. Differentiate between white matter and grey matter.
The part of nerve, where myelinated neurons are present in abundance,is called as the white matter.
The part of nerve where the cell bodies and nonmyelinated neurons are present, is called as the grey matter.
8. Table showing the function of different parts of nerve cell.
9. Name the swollen ends of axon . How is it important in the transmission of impulse ?
Synaptic knobs, from which neurotransmitter secretes. The impulses are transmitted across the synaptic cleft only through a chemical (neurotransmitter), secreted from the synaptic knobs.
10. Give example for neurotransmitter.
Acetyl choline (Dopamine is another example)
11. Define synapse.
The junction between neurons or between neurons and muscles or glands is known as the synapse.
It helps to regulate the speed and direction of impulses. The impulses are transmitted across the synaptic cleft only through a chemical (neurotransmitter), secreted from the synaptic knobs.
12. The electrical messages conducted through nerves ?
Impulses
13.How is an impulse generated ?
The difference in the distribution of ions maintains positive charge on the outer surface and negative charge inside the plasma membrane of the receptor part of neuron. When stimulated, this ionic equilibrium (polarity) changes there and the outer surface becomes negatively charged and inner become positively charged. As a result, impulse generated. This charge difference stimulates its adjacent parts and similar changes occur there too. Thus a continuous flow of the impulse becomes possible.
14. How is the impulses transmits through the neurons ?
Impulse due to stimulus →dendrites→ dendrons →cyton→ axon →axonites→
synaptic knob→ secretion of neurotransmitter to the synaptic cleft →Stimulation in the adjacent dendrites →Impulse forms.
When impulses reach at the synaptic knobs, a chemical substance, known as neurotransmitter, released in the synaptic cleft. This chemical stimulates the adjacent dendrites to form new electric impulses.
15. Name the two types of neurons ?
Sensory neurons – (carry impulses from different body parts to the brain and spinal cord)
Motor neurons - ( carry impulses from the brain and spinal cord to various parts of body)
16. Define a nerve ?
A nerve is a group of axons or nerve fibres, covered by connective tissue.
17. Show different kinds of nerves with their functions in a table.

 18. How is human nervous system classified ?
Central Nervous System  
- Brain                                  
- Spinal cord                       
Peripheral Nervous System
- Cranial nerves (12 pairs)
- Spinal nerves (31 pairs)
19. The protective measures for human brain ?
The brain is protected inside a hard skull and is covered by a three layered membrane, called the meninges.
Cerebrospinal fluid,a fluid formed inside the meninges, also protects the brain.
20. The outer covering of brain and spinal cord ?
Meninges.
21. The fluid which provides nutrients and oxygen to brain tissues ?
Cerebrospinal fluid (CSF).
22. How is the CSF form? Give its function ?
Cerebrospinal fluid is a fluid formed from the blood inside the meninges and eventually reabsorbed to the blood. Functions of CSF are,
• CSF provides nutrients and oxygen to brain tissues.
• Regulates the pressure inside the brain.
• Protects brain from injuries.
23. Name the functional parts of human brain.
Human brain has outer cerebrum, cerebellum and medulla oblongata and inner thalamus and hypothalamus.

24. Table showing different parts of brain, peculiar feature and functions of each.
25. The largest part of human brain ?
Cerebrum.
26. The peripheral part of brain is the ----------- .
Cerebral cortex.
27. There are many fissures and folds in the cerebral cortex. What is the advantage of this ?
This is an adaptation to include more number of neurons and there by increase the efficiency of cerebrum.
28. Any mild injury to the medulla oblongata may lead to sudden death. Why?
Medulla oblongata controls involuntary actions like heart beat and breathing. Any mild injury to medulla oblongata results malfunctioning of breathing and heartbeat and this may lead to death.
29. A person could not walk easily after drinking alcoholic beverage. Can you say which part of his brain is affected ?
Cerebellum, which maintains equilibrium of the body through muscular coordination.
30. After a road accident, a person lost his memory for a few days. In which part of his brain got injured ?
Cerebrum.
31. The central nerve, seen as the continuation of medulla oblongata ?
Spinal cord.
32. How is our spinal cord protected ?
Spinal cord is protected inside the vertebral column and is covered by the meninges.
33. The ------------- of the spinal cord is filled with cerebrospinal fluid.
Central canal.
34. Describe the structure of our spinal cord.
Spinal cord, which is the continuation of medulla oblongata, is situated with in the vertebral column and is covered by a three layered membrane, called meninges. The outer part of spinal cord is white matter and inner is grey matter. The central canal at its centre is filled with CSF.

Spinal nerves originate from the spinal cord as dorsal root (sensory) and ventral root(motor).
35. Spinal cord : Sensory impulse : Dorsal root;
Spinal cord : Motor impulse : ...................
Ventral root.
36. Mention the functions of spinal cord.
• Transmitting impulses from different parts of our body to and fro the brain.
• Coordinates the rapid and repeated movements during walking, running etc.
• Effects certain reflex actions.
37. What do you mean by reflex action ?
Reflex actions are the accidental and involuntary responses of the body, in response to a stimulus.
These are two types,
1. Cerebral reflexes (Eg:-Blinking of eyes, sudden fright when hearing a loud noise or seeing a snake, sneezing)
2. Spinal reflexes (Eg :- On touching hot object, the hand is withdrawn, withdrawal of the leg when a spine pierce in to the feet)

38.The pathway of impulses in a reflex action. Reflex arc.
39. What are the parts that involve in a reflex arc ?
a. stimulus receiving receptor
b. sensory neuron
c. inter neuron
d. motor neuron
e. effecting muscles.
40. The central neuron, which converts sensory impulse in to motor impulse, is usually known as an --------
Inter neuron.
41. A few nerves in the peripheral nervous system that function automatically and involuntarily, is known as ------------ ?
Autonomous nervous system.
It includes sympathetic and parasympathetic nerves.
42. How the contrasting actions of Sympathetic and Parasympathetic nervous systems help to maintain the normalcy of the physiological activities ?
Sympathetic and parasympathetics nervous system activate with or with out the endocrine gland system involuntarily. The contrasting actions of both systems help to maintain the normalcy of the physiological activities.
43. List out the physiological changes that may occur when a boy facing the audience during a competition.
(see the activities of the sympathetic nerves)
44. The table showing neural disorders, reason and symptoms.

45. Name a neurotransmitter, which is secreted in the brain. What will happen when the production of this hormone cease in a person ?
Dopamine.
The deficiency of dopamine may result a disease called parkinsons.

 Prepared by RASHEED ODAKKAL, 9846626323, GVHSS Kondotty, for www.mathematicschool.blogspot.in
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