2Human sensory receptors receptors detects the changes in both internal and external environmentthey transform the stimuli energy into a nerve impulse that can be sent to the central nervous system (CNS) which in turn coordinates an appropriate response.receptors are located in the sense organs such as the eye, ear, skin, tongue etc.
3Human sensory receptors & stimuli that can detect Type of receptorStimulus detectedExample of receptorsmechanoreceptorspressure, soundhair cells in the earchemoreceptorschemical substancestaste buds on the tongue & olfactory cells along the nosethermoreceptorstemperaturenerve endings in the skin & hypothalamus of the brainphotoreceptorslightrods and cone in the retinas of the eyehydroreceptorshumidity?nocireceptorspainsensory nerve ending in the skin
7StructureFunction(s)Scleratough outer layer of the eye which overs and protect eyeball.Choroidprevents internal reflection of light and nourish retina.Retinacontains rods and cones which convert light into nerve impulses.Ciliary Bodya ring of muscle controlling the shape and curvature of the lens.Iriscontrols the pupil size thus controls entry of light.Pupila hole in the iris that lets light into the back of the eye.Lensaccommodation & focusing of light onto the retina.Corneabends incoming light focusing it on the retina.Foveaa tiny area of densely packed cones for detailed and coloured vision.exit point of the optic nerve cutting through the retina so no rods or conesBlind SpotOptic Nervecarries the impulses from the rods and cones to the visual center of the brain.
9Annotate the diagram of the retina below Axon of the ganglion celldirection of light movementGanglion cellBipolar cellSynapseRodConePigmentSclera
10Compare rod and cone cells Rod CellsCone Cellsrod cells more effective in low light intensitycone cells more effective in high light intensityrod cells detect a broad range of colours (wavelength)cone cells are sensitive to a specific colours (wavelength)groups of rod cells pass impulses to a single nerve fibrea single cone cell passes impulses to a single nerve fibrerod cells more sensitive to movementcone cells give higher visual acuity (sharpness )rod cells respond more slowly to lightcone cells respond more rapidly to lightrod cells spread through retinacone cells concentrated in centre of retina (at fovea )rod cells contains one type of pigment (rhodopsin)cone cells contains three types of pigment (iodopsin)rod and cone cells are both are photosensitive
11Compare rod and cone cells Rod Cellsrod cells more effective in low light intensityrod cells detect a broad range of colours (wavelength)groups of rod cells pass impulses to a single nerve fibrerod cells more sensitive to movementrod cells respond more slowly to lightrod cells spread through retinarod cells contains one type of pigment (rhodopsin)cone cells more effective in high light intensitycone cells are sensitive to a specific colours (wavelength)a single cone cell passes impulses to a single nerve fibrecone cells give higher visual acuity (sharpness )cone cells respond more rapidly to lightcone cells concentrated in centre of retina (at fovea )cone cells contains three types of pigment (iodopsin)rod and cone cells are both are photosensitive
12Contralateral processing of visual stimuli rod & cone cells in the retina convert light into nerve impulsesimpulses pass to bipolar cellsbipolar cells pass impulses to sensory neurons of the optic nerveat the optic chiasma, impulses cross over to the opposite optic nerveimpulses continue to the thalamus where optical information is processedimages form in the visual cortex of the brain
13Edge enhancementedge enhancement is a ‘pre- central nervous system ‘processing of information on the retinait enhances contrast at the edges (boundaries of different objects) and provides more detail to the visual system of the environmentin certain regions of the retina, single ganglion cell receives information form a number of rods and cones, such a region is called receptive fieldthe fewer the rods and cones that supply a single ganglion the smaller the receptive field & the higher visual acuity i.e. the detailed information one sees
14Label the diagram of the ear below Middle ear bonesSemi circular canalsOval WindowAuditory NerveRound windowCochleaEustachian tubeEardrumAuditory canalPinna
17How sound is perceived by the ear sound waves reaching eardrum cause it to vibratevibrations are passed to bones of middle ear which amplify themthe bones pushes the oval window which cause a pressure wave in the fluid-filled cochleaAs the oval window moves in, the round window moves out, this allows the fluid in the cochlea to move freely backward & forwardthe vibrations caused by fluid movement pushes the membrane on which the hair cells (mechanoreceptors) sits, triggering nerve impulses in the auditory nervesthe nerve impulse is carried to the auditory cortex in brain through auditory nerve for interpretation