1 BEYOND THE SENSES CONTENT. Photo receptors[rod, Cone] Optic nerve Auditory receptors Auditory nerve

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1 BEYOND THE SENSES CONTENT EYE Protection, Structure, Photo receptors, Image formation NEURON Structure, Transmission of impulse through synapse Brain structure, features and functions Mode of

1 1 BEYOND THE SENSES CONTENT EYE Protection, Structure, Photo receptors, Image formation NEURON Structure, Transmission of impulse through synapse Brain structure, features and functions Mode of vision EAR Structure, Mode of hearing, Equilibrium of body. Taste, Smell & senses through the Skin. Disorders of the Eye & Ear Sense Organs SKIN RECEPTORS SENSORY NERVES Photo receptors[rod, Cone] Optic nerve Auditory receptors Auditory nerve Olfactory receptors Olfactory nerve Taste receptors in taste buds Receptors for Touch,Heat, various sensory nerves Cold, Pressure & pain Central nerves 1. How are our eyes protected? * Eyes are situated in the eye-socket of the skull * Eyelids with eyelash protect from dust and other particles * Tears keep eyes wet, washes away the dust particles and prevent infection * The conjunctiva covers the front portion of the eye except cornea 2. 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. 3. The enzyme in tears? Lysozyme 4. The aperture at the centre of iris? Pupil 5. The fluids filled in the chambers of eye? * Aqueous humour A watery fluid seen in the aqueous chamber [between cornea and lens], oozes from theblood. This fluid supplies nutrients and oxygen to cornea and lens. * Vitreous humour - A jelly like fluid filled with in the vitreous chamber [between lens and retina], helps to maintain the shape of eyeball. 6. Redraw the following diagram. Find out and label the name of following parts. (a)-the transparent anterior (front) portion of outermost layer (b)- The transparent membrane that covers the anterior part except cornea (c)-the middle hole in the iris (d)-the white outermost layer that gives shape (e)-the middle layer for bringing nutrients and oxygen (f)- The fluid which supplies nutrients to the lens and iris (g)-the fluid that sustains the shape of eyeball (h)-the layer on which image forms b- conjunctiva a- cornea c- pupil (i)-the point of highest vision. f- (j)-a part of the innermost layer lacking vision aqueous (k)-the sensory nerve, starting from the retina humour (l)- Muscles and threads that change the curvature of lens Aqueous chamber Vitreous chamber l- ciliary muscle ligaments i- yellow spot j- blind spot d- sclera e- choroid h- retina g- vitreous humour k- optic nerve 7. Differentiate 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.

2 8. 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 lens so as to keep the ligaments tight. Therefore the curvature of lens decreases ligaments to fix the image on retina [figure-1]. ciliary 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]. 9. The charecteristics of images. Real, Small, Inverted and Accommodated. 10. When bright light falls, the pupil contracts. Why? When bright light falls, the circular muscles in the iris contract to constrict the pupil. 11. Compare and contrast the photo receptors. ROD CELLS * Receptor region is rod shaped * Receptor region is cone shaped * Contain the pigment rhodopsin * Contain the pigment photopsin * Stimulated by dim light * Stimulated by intense light * Help vision in dim light * Help for coloured vision Rod cells and Cone cells are modified nerve cells. Under dim light, rhodopsin dissociates to form retinal and opsin to produce impulses from rod cells. Under intense light, photopsin dissociates to form retinal and opsin to produce impulses fromcone cells. 12. Rod cells : Rhodopsin : Vision in dim light; Cone cells : : Vision in intense light. 13. Vitamin A help us for better vision. Give reason. Retinal,(found in rhodopsin and photopsin), is formed from vitamin A. 14. The condition by which certain colours cannot recognize : Colour blindness : Hereditary defect; Decreased vision in dimlight : : Deficiency disease. 15. The bird, owl has no vision in day time. Why? No cone cells in owl s retina. 16. Animals like cat and owl have more vision at night? Why? Cat and owl has more cone cells in their retina. 17. Vision is not possible at the blind spot of retina. Why? The photo receptors (rods and cones) are absent at blind spot. CONE CELLS റഷ ദ ഓടകല, ക ണ ട Experience of vision - Flow chart. Light rays from the object cornea Aqueous humour (pupil) lens vitreous humour image on retina stimulation in the photo receptors dissociation of rhodopsin/photopsin impulses optic nerve coordination of images by cerebrum[binocular vision] perfect vision 19. The structural and functional unit of the nervous system? Neuron (Nerve cell) 20. How does a nerve cell differ from an ordinary cell? Nerve cell never divides 21. Draw and label the following parts of a typical neuron. (a)- part, that carry impulses to the cell body (cyton) (b)- part, that carry impulses from the cell body (c)- the protective covering of elongated fibre (d)-the region, from which neurotransmitter secretes cyton a- dendron b- axon c- myelin sheath d- synaptic knobs 22. Define a nerve and ganglion. Nerve is a collection of enveloped nerve fibres / axons [even elongated dendrons are called as axons ]. Ganglion is the enveloped spherical collection of cytons of neurons.

of both sensory and motor fibres] 24. The protective covering of nerve fibres (axons)? Mention its function. Myelin sheath.

3 23. Different kinds of nerves? * Sensory nerves [ carries impulses from sense organs to the brain and spinal cord] * Motor nerves [ carries impulses from brain and spinal cord to different organs] * Mixed nerves [nerves composed of both sensory and motor fibres] 24. The protective covering of nerve fibres (axons)? Mention its function. Myelin sheath. To provide nutrients, function as an insulator and protects the nerve fibre, increases the speed of impulse transmission and gives white appearance ('white matter'). 25. How is a myelinated neuron differ from non-myelinated neuron? 26. Give example for neurotransmitters. Acetyl choline, Dopamine 27. Define synapse. Synapse is the junction between neurons or between neuron and muscle cell. 28. The changes, that result the formation of impulses of reaction, are known as ? Stimuli [ Eg:- heat, cold, sound, light] 29. What is impulse? How are they form in nerve receptors? Impulses are electro-chemical messages flowing through nerves. An impulse is created by the variation in the electrical equilibrium existing on either side of the plasma membrane of the receptor cells, due to certain stimulus. 30. Synapse Observe the figure and draw a flowchart of transmission of impulse across the synapse. Impulse due to stimulus dendrites dendrons cyton axon axonites synaptic knob secretion of neurotransmitter to the synaptic cleft adjacent dendrites 31.Though two images form in both eyes, we can't see two objects. Why? The two images are coordinated to one perfect image by the centre of vision in the brain. 32. Define binocular vision. Binocular vision is the ability to focus our both eyes on objects at the same time. As a result, a three dimensional vision is possible. 33. The protective measures for human brain? Cranium (the bony covering), Three layered outer covering, known as meninges, that filled with CSF. 34. The outer covering of brain and spinal cord? Meninges. 35. The cavities inside the cerebrum? Cerebral ventricles. 36. What is CSF? How is it useful? Cerebro spinal fluid is a fluid formed from the blood and re absorbed to the blood. It provides nutrients and oxygen. It protects brain from external shocks. CSF seen in between the inner layers of meninges, in cerebral ventricles and in the central canal of spinal cord. 37. Draw human brain and label the name of following parts. 1- Cerebrum 1)- The part which controls voluntary movements and feeling of senses. 2)- The part that maintains the equilibrium of the body 4- Thalamus by coordinating muscular activities. 3)- The part which controls the heartbeat and breathing. 5- Hypothalamus 4)- The part which retransmit impulses to and fro cerebrum. 5)- The centre of homeostasis. 3- Medulla oblongata 2- Cerebellum 38. Differentiate between the grey matter and white matter. The part of nerve, made up of myelinated nerve fibres, is seen in white and is called as white matter. The part of nerve, made up of non-myelinated cytons, is grey coloured and called as grey matter. 39. There are many folds and grooves 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.

4 40. Compare cerebrum, cerebellum and medulla oblongata. CEREBRUM CEREBELLUM MEDULLA OBLONGATA * Many folds and grooves * Folds and grooves * No folds or grooves * The largest part of brain * The second largest * stem-like bottom part * Outer grey matter, inner white * Outer grey matter * Outer white matter, inner grey * Centre of voluntary movements, * Centre of equilibrium of body * Centre of involuntary actions like sense organs, special qualities by muscular coordination. heartbeat and breathing 41. Any mild injury to the medulla oblongata may lead to sudden death. Why? The injury to medulla oblongata results stoping of breathing and heartbeat. 42. The functions of human ear? Hearing, body balance. 43. Three areas of ear? EXTERNAL EAR MIDDLE EAR INTERNAL EAR 1-ear pinna 4- malleus 8-cochlea 2- ear canal 5-incus 9-vestibule [sacule, utricle] 3- ear drum / tympanum 6-stapes 10- semicircular canals 7-eustachian tube 11-auditory nerve 44. 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. 45. Name the swollen end of semicircular canals. Ampulla. 46. The auditory receptors are seen in the of cochlea. Organ of Corti. 47. Internal ear : Cochlea : Hearing ; Internal ear : -----, :Equilibrium of the body. [ vestibule, semicircular canals ] 48. Structure of internal ear. Internal ear constitutes 3 regions. COCHLEA (looks like a snail shell), VESTIBULE having sacule (lower sac) and utricle (upper sac) and three SEMICIRCULAR CANALS with swollen end,-ampulla. These are filled with a fluid, endolymph and receptors are seen immersed in it. All receptors are connected with the brain by the AUDITORY NERVE. Cochlea has 3 chambers, of which, only the middle chamber is filled with endolymph and contain the Organ of Corti with auditory receptors. The outer chambers are filled with perilymph. Receptors seen inside the ampullaof semicircular canals and vestibule are stimulated according to the movement of head. But the impulses thus created reach in the cerebellum, to maintain the equilibrium. 49. Hearing. Flowchart. Sound waves ear pinna ear canal ear drum (tympanum) vibrates malleus, incus and stapes (ear oscicles) oval window cochlear perilymph endolymph stimulation in auditory receptors of th Organ of Corti impulse transmitted through auditory nerve auditory centre of the brain hearing 50. What is the role of ear in maintaining the equilibrium of the body? How is it possible? Any change in the position of our head causes movements in the endolymph and there by stimulation of receptors, (seen inside the vestibule and ampulla of semicircular canals). The impulses are transmitted to the the cerebellum through the auditory nerve. Cerebellum functions so as to maintain the equilibrium of body. odakkalrasheedkondotty@gmail.co.in

5 51. The distribution of taste buds in the tongue. sweet salt swore bitter 52. How do we sense taste and smell? The receptors in the taste buds get stimulated when the food particles dissolve in the saliva. The impulses thus formed are carried through the nerve to the centre of taste in the brain, which helps in the perception of taste. The olfactory receptors seen in the mucus membrane of the nasal cavity get stimulated when particles enter the nose along with air. The impulses thus formed are carried through the olfactory nerve to the centre of smell in the brain, which helps in the perception of smell. 53. How do we recognize different taste? There are 4 types of taste buds to recognize primary tastes sweetness, saltness, sourness and bitterness. Other tastes are created by the brain from the primary tastes. 54. The largest sense organ? Skin 55. The stimuli that can be received by our skin? Heat Cold Pain Touch Pressure 56. Table showing various disorders and diseases that affect on our eyes. Disorder/Disease Reason or Symptom Remedy Hypermetropia (long sight) Due to shortened eyeball images form behind retina. Cannot see nearby objects clearly Convex lens Myopia (short sight) Due to elongated eyeball images form in front of retina. Cannot see distant objects clearly Concave lens Presbyopia Due to the loss of elasticity of lens, nearby objects are not clearly seen Convex lens Cataract Gradual decrease in the power of lens due to decreas ing of transparency of lens Surgical replacement of lens Glaucoma Defective vision due to incresed pressure when the reabsorption of aqueous humour obstructed Early treatment Squint Both eyes are not able to focus on the same object Surgery

1. BEYOND THE SENSES. SKIN Various reetor

1. BEYOND THE SENSES. SKIN Various reetor 1. BEYOND THE SENSES Major Idea Sense is possible only when impulses from sense organs [eye, ear, nose, tongue and skin] reach at the brain through the sensory nerves. Photoreceptors Audtory receptors