A+ BLOG-SSLC-BIOLOGY-CHAPTER-2-WINDOWS OF KNOWLEDGE-EM-PDF NOTES.pdf

LIFE SSLC BIOLOGY NOTES 2. Windows of knowledge Sensory organs are the windows to get information from the surroundings to our sense. Our brain analyses the information given by the sensory organs and helps to communicate, to search food, to hear...

LIFE SSLC BIOLOGY NOTES 2. Windows of knowledge Sensory organs are the windows to get information from the surroundings to our sense. Our brain analyses the information given by the sensory organs and helps to communicate, to search food, to hear the sound, etc. I. Eye  Sensory organ for vision. Protection a) Eye fixed within the eye socket with the help of 3 pair external eye muscle – protection from injury. b) Eye brow, eye lashes, eye lid – protection from dust, sweat. c) Conjuctiva - secretes mucus which protects the anterior portion of the eye ball from being dry. d) Tears –  lubricate the anterior part of the eyeball  Wipes out the dust  Lysozyme – destroys the germs that enter the eye. Structure and function Part Peculiarity Function The white outer layer made up of I Sclera Gives firmness to the eye connective tissue Transparent and projected anterior a) Cornea Refracts light to focus onthe retina part Layer which covers the front part of b) Conjuctiva Protection sclera except cornea II Choroid Middle layer with blood vessels Provide nutrition and O2 to the eye The dark colored (due to the a) Iris presence of melanin) part seen behind the cornea. Regulates the entry of light - Circular muscles of iris The aperture seen at the centre of Pupil contract in intense light iris and size of pupil decreases - Radial muscles of iris LIFE SSLC Biology Notes Mohammed Rasheed www.apluseducare.blogspot.com KP #9747394788 or Watsapp 9072708051 Page 1  LIFE SSLC BIOLOGY NOTES contract in dim light and size of pupil increases Elastic transparent convex lens, Helps to focus light rays on the b) Lens connected to ciliary muscles by retina by adjusting focal length ligaments Impulses are generated according to III Retina The inner layer with photoreceptors the image s formed a) Yellow spot Plenty of photoreceptors are present Point of maximum visual clarity b) Blind spot Photoreceptors are absent No vision Carries impulses from photo recep c) Optic nerve Starts from blind spot tors to the brain Is filled with aqueous humor which provides nutrition and O2 to the ⦁ Aqueous chamber Chamber between cornea and lens cornea and lens. This fluid formed from blood and reabsorbed to the blood. Is filled with jelly type vitreous ⦁ Vitreous chamber Chamber between lens and retina humor, which helps in maintain the shape of the eye. Vision - phases (Step 1) Regulation of focal length The ability of the eye to adjust the focal length of the lens by changing its curvature in accordance to the distance of the object from the eye and form the image on the retina is called the power of accommodation of eye. While viewing distant object Ciliary muscles relax Ligaments stretch Focal length increases Curvature of lens decreases While viewing nearby objects Ciliary muscles contract Ligaments relax Focal length decreases Curvature of lens increases LIFE SSLC Biology Notes Mohammed Rasheed www.apluseducare.blogspot.com KP #9747394788 or Watsapp 9072708051 Page 2  LIFE SSLC BIOLOGY NOTES (Step 2) Images on retina Image Object Flow chart of light rays coming from the object Light Cornea Aqueous humor Pupil Lens Vitreous humor Retina Peculiarities of image  Real  Small  Inverted (Step 3) Structure of retina and changes due to the formation of images Rod cell Cone cell ⧳ The basis of vision is that the dissociation of visual pigments, rhodopsin and photopsin/iodopsin present in rod and cone cells respectively. The visual pigments are formed from opsin (protein) and retinal, derivative of Vit.A. Vit.A Rhodopsin / Photopsin Retinal + Opsin These chemical changes generates impulses.  Rod cells (12 lakh) – Activated in dim light. It enables black&white vision. Rhodopsin dissociated into retinal and opsin. These fuses in the absence of light.  Cone cells (6 lakh) – Stimulated in bright light. These cells have an ability to detect colour (because of the dissociation of photopsin/iodopsin only in bright light).  The human eye have 3 types of cone cells, which are stimulated by the red, green and blue light rays. This diversity is due to the difference in the amino acids in the opsin molecule. (Step 4) Impulses to the brain – sense of sight Retina Impulses Optic nerve Cerebrum sense of sight LIFE SSLC Biology Notes Mohammed Rasheed www.apluseducare.blogspot.com KP #9747394788 or Watsapp 9072708051 Page 3  LIFE SSLC BIOLOGY NOTES i. Photoreceptors are stimulated when the light (image) falls on retina ii. Impulses are generated iii. Impulses reach the cerebrum through optic nerve iv. Cerebrum enables three dimensional image by combining 2 images of same object from both eyes. This is called binocular vision. Defects and diseases of eye Defect / Disease Causes Symptom Remedy Myopia(short Concave lens sightedness) Hypermetropia(Long Convex lens sightedness) Can’t see near object Presbiopia Loss of elasticity of lens Convex lens clearly Astigmatism Cylindrical lens Deficiency of Vit.A results in low production of retinal, Can’t see clearly in dim Vit.A contained Night blindness this prevents resynthesis of light diet rhodopsin Prolonged deficiency of Cornea and conjuctive Vit.A contained Xerophthalmia Vit.A become dry and opaque diet Cannot distinguish red and Colour blindness Defect of cone cells No remedy green colours Reabsorption of aqueous Pressure inside the eye Glaucoma Laser surgery humor does not occur increases Lens replacement Cataract Lens become opaque Leads to blindness surgery Infection of conjuctiva by Conjuctivitis Self hygiene bacteria, virus etc. II. Ear  The sensory organ for hearing  Also, ear helps to maintain body balance. LIFE SSLC Biology Notes Mohammed Rasheed www.apluseducare.blogspot.com KP #9747394788 or Watsapp 9072708051 Page 4  LIFE SSLC BIOLOGY NOTES Structure of ear Semi circular canals Pinna Vestibule Vestibular nerve Auditory canal Auditory nerve Malleus Stapes Incus Cochlea Tympanum Eustachian tube Ear ossicles Part I External ear a) Pinna Carries sound waves to auditory canal Small hairs and wax are helps to prevent b) Auditory canal Carries sound waves to tympanum dust and foreign particles Circular membrane that separates It vibrates resonance with sound c) Tympanum middle ear from external ear waves Chamber between external ear and II Middle ear internal ear The chain of malleus, incus and stapes Amplify and transmit vibration of d) Ear ossicles connects tympanum to the internal ear tympanum to the oval window through oval window Eustachian Regulates pressure on both sides of e) Connects middle ear and pharynx tube tympanum The parts seen inside the bony labyrinth III Internal ear of brain Oval widow Spreads the vibration of stapes into the f) The holes covered by membranes in the (above) inner ear wall that separate middle ear and Round window Helps in the movement of fluid inside g) internal ear (below) cochlea The fluid filled between membraneous ⦁ Perilymph and bony labyrinth The fluid filled in the memraneous ⦁ Endolymph labyrinth The snail shell like tube has 3 chambers. The upper and lower chambers filled h) Cochlea with perilymph and middle chamber is Helps in the hearing filled with endolymph. The auditory receptors seen in basilar membrane LIFE SSLC Biology Notes Mohammed Rasheed www.apluseducare.blogspot.com KP #9747394788 or Watsapp 9072708051 Page 5  LIFE SSLC BIOLOGY NOTES (organ of corti) that separate middle and lower chambers is Carries impulses from the organ of i) Auditory nerve Starts from cochlea corti to the cerebrum Semi circular Endolymph is filled in the semi circular Impulses formed due to the j) canals canals that are perpendicular to each movements of hair cells by the Chambers of vestibule is filled with movement of endolymph according to k) Vestibule endolymph the body movement. Vestibular It starts from vestibule and semi circular Carries impulses from vestibule and l) nerve canals semi circular canals to the cerebellum Sense of hearing Sound waves Pinna Auditory canal Tympanum Ear ossicles Oval window Cochlea Perilymph endolymph Organ of corti Impulse Auditory nerve Cerebrum Sense of hearing Body balancing  The 3 semi circular canals and vestibule are helps to maintain body balancing. The movement of head accordance with body movement Semi circular canals Vestibule Receptors – hair cells Movement of endolymph Impulses formed by the stimulation Vestibular nerve Cerebellum Coordinates muscular activities and maintain body balance III. Tongue  The taste buds seen in tongue and cheek are helps in the detection of taste  There are different types of taste buds to detect different tastes like sweet, sour, bitter, salt and umami LIFE SSLC Biology Notes Mohammed Rasheed www.apluseducare.blogspot.com KP #9747394788 or Watsapp 9072708051 Page 6  LIFE SSLC BIOLOGY NOTES Structure Sense of taste  Substances responsible for taste dissolved in saliva  Chemo receptors in taste buds are stimulated  Impulses generated  Through nerve  Reach the site of taste in cerebrum  Sense of taste IV. Nose Structure Sense of smell  Aromatic particles diffuse in the air and enter the nostrils  These particles dissolve in mucus and reach the olfactory receptorts  Olfactory receptors are stimulated and impulses generated  Impulses reach the site of smell in the cerebrum  Sense of smell V. Skin  Temperature, pressure, pain, touch, cold receptors get stimulated  Impulses generated  Impulses reach the cerebrum through related nerves  Experiences different sensations LIFE SSLC Biology Notes Mohammed Rasheed www.apluseducare.blogspot.com KP #9747394788 or Watsapp 9072708051 Page 7  LIFE SSLC BIOLOGY NOTES Receptors in various organisms Organism Receptors Peculiarity Planaria Eye spot Reacts with the variation of light Impulses from thousands of ommatidia reach the Insect (House fly) Ommatidia brain. Brain enables vision by the fusion of images. The aromatic particles stick on the tongue reach the Snake Jacobson’s organ Jacobson’s organ seen on the roof of mouth cavity. Then the receptors get stimulated. Lateral line Help to detect the change in body balance Shark Highly sensitive olfactory Help to detect smell receptors Eye spot Ommatidia Jacobson’s organ Lateral line LIFE SSLC Biology Notes Mohammed Rasheed www.apluseducare.blogspot.com KP #9747394788 or Watsapp 9072708051 Page 8