1. PERCEPTION OF STIMULI

2. Sensory Receptors & diversity of Stimuli Sensory receptors for pleasure Sensory receptors elicit emotion Sensory receptors elicit memory

3. We see, smell, taste & feel with…

4. E.2.1 Outline the diversity of stimuli that can be detected by human sensory receptors, including mechanoreceptors, chemoreceptors, thermoreceptors and photoreceptors.

5. Mechanoreceptors Mechanical force or pressure Skin Arteries Lung inflation Proprioceptors Maintain posture and position Pressure receptors sensitive to waves of fluid = equilibrium

6. Chemoreceptors Respond to chemical substances External Taste and smell Internal pH – adjust breathing rate Pain receptors Respond to chemicals released by damaged tissue

7. Thermoreceptors Change in temperature

8. Photoreceptors Respond to light energy Found in the eyes Rod cells respond to dim light = black & white vision Cone cells respond to bright light = colour vision

9. E.2.2 Label a diagram of the structure of the human eye

10. Posterior chamber filled with vitreous humour Ciliary muscle Anterior chamber with aqueous humour

11. PartFunction IrisRegulates the size of the pupil PupilAdmits light RetinaContains receptors for vision Aqueous humourTransmits light rays and supports the eyeball Vitreous humourTransmits light rays and supports the eyeball RodsAllow black and white vision in dim lighjt ConesAllow colour vision in bright light FoveaAn area of densely packed cone cells where vision is most acute LensFocuses the light rays ScleraProtects and supports the eyeball CorneaFocusing begins here ChoroidAbsorbs stray light ConjunctivaCovers the sclera & cornea & keeps eye moist Optic nerveTransmits impulses to the brain Eye lidProtects the eye

12. EYE Lecture

13. E.2.3 Annotate a diagram of the retina to show the cell types and the direction in which the light moves

14. The Retina – photoreceptor cells

15. The Retina The retina is the only part of the CNS which is directly observable Light is coming through the eye from the right There are 3 layers of neurons shown, photoreceptors, bipolar & ganglion cells (reflect the order of activity) The ganglion cells and bipolar cells are transparent & don’t significantly reduce the intensity of light passing to the photoreceptor video

16. The photoreceptor absorbs the light which changes the rate of neurotransmitter produces at the first synapse (S1) The head of the photoreceptor cell contains the light sensitive pigments The Bipolar cell (named after its 2 processes at either side of the cell body) responds by changing rate of neurotransmitter released to the Ganglion cell The ganglion cell generates the impulse which will travel along the axon of the ganglion to the brain. Notice that these axons are grouped together to form the optic nerve. Also, note that the cell body of the ganglion is in the retina.

17. (a) Bipolar cell forming synapses with more than one photoreceptor. (b) Bipolar cells connecting together rods and cones (c) Ganglion cell collecting input from a group of photoreceptors (receptive field) (d) Axon of the ganglion cell forming the optic nerve at (i) (e) Summation of rod photoreceptors gives low visual acuity (resolution) Non-fovea arrangement (f) Another form of summation (g) The arrangement of cones in the fovea provides a high level of visual acuity (resolution).

18. E.2.4. Compare rod and cone cells

19. RodsCones These cells are more sensitive to light and function well in dim light. These cells are less sensitive to light and function well in bright light Only one type of rod is found in the retina. It can absorb all wavelengths of visible light. Three types of cone are found in the retina. One type is sensitive to red light, one type to blue light and one type to green light. The impulses from a group of rod cells pass to a single nerve fibre in the optic nerve. The impulse from a single cone cell passes to a single nerve fibre in the optic nerve.

20. E.2.5 Explain the processing of visual stimuli, including edge enhancement and contralateral processing

21. Processing of Visual Stimuli Light passes through the pupil Light is focused by the cornea, lens & the humours Image on retina is upside down and reversed Photoreceptors stimulated Optic nerve carries message to cerebral cortex of the brain Brain corrects the position of the image (right side up & not reversed) Coordinates images coming from left & right Watch 5:35 – 8:20

22. Edge Enhancement Optical illusions – Hermann grid Watch 1 st 1:25 minutes

23. Edge Enhancement Why did you see the grey blobs? Theory Areas where you see grey are in your peripheral vision Fewer light-sensitive cells than in the center of your retina (fovea) Some cells present may even be turned off This sends message of grey instead of white

24. Edge Enhancement Now look at the “grey” area

25. Edge Enhancement Eye is fooled because of extreme contrast between black & white Special mechanism for seeing edges “light-sensitive receptors switch off their neighbouring receptors” Makes edges look more distinct

26. Contralateral processing Due to the optic chiasma

28. Contralateral processing Nerve fibres bringing information from the right half of each visual field converge at the optic chiasma & pass to the left side of the brain Nerve fibres bringing information from the left half of each visual field converge at the optic chiasma & pass to the right side of the brain Information ends up in the visual cortex of the brain Must share information to make a complete image

29. Contralateral processing The cerebral cortex rebuilds all the parts into a visual image This process can be illustrated by looking at patients with brain lesions (injuries) We look at a and we see a Lesion to right side of brain do not recognize this. They will DENY it is a bucket Lesion to left side of brain can tell you the function but cannot name “bucket” Both sides must work together Video 

30. E.2.6 Label a diagram of the ear

31. The ear

33. E.2.7 Explain how sound is perceived by the ear, including the roles of the eardrum, bones of the middle ear, oval and round windows and the hair cells of the cochlea

34. How sound is perceived Outer ear catches sound waves Vibrates air Down the auditory canal Tympanic membrane (eardrum) vibrates Bones of ear receive vibrations & multiply them 20 times Stapes strikes the oval window – vibrates Vibrations pass to fluid in cochlea Hair cells vibrate Release a chemical message to sensory neuron To auditory nerve  brain

36. Sounds Loud noises = high degree of vibration Hair cells bend greatly High volume Pitch = function of sound wave frequency Short, high-frequency = high pitch Long, low-frequency = low pitch

37. The Bozeman Start at 8:22