Senses Worksheet Week 8

TOPIC 7: Senses Worksheet Week 8 Task 1 (LO 1, 2, 3) Vision  Label the diagram.  Answer the questions. 1. What is the blind spot and why is it blind? The blind spot of the eye is the optic disc. This is the part of the retina where the optic nerve (cranial nerve II) exits, so there are no photoreceptors. The brain fills in those blanks. 2. On the drawing below, add an arrow showing the path that light takes to the photoreceptors. Add another arrow to indicate the path that the information takes to the brain. What are c, d and e? What layer comes after e? The next layer would be the choroid which contains many blood vessels. 1 3. Fill in the table. Rods Type of vision Sensitivity Acuity Location Non-colour vision in dim light Very sensitive, i.e. require not much light Low, i.e. images appear blurred and fuzzy as many rods converge to one axon Mostly in the peripheral retina, more numerous than cones Cones Colour vision in bright light Low, require bright light High, only one axon (in fovea) or only a few cones converge Central retina 4. Define glaucoma and cataract. Glaucoma: A problem with the drainage of the aqueous humour (= fluid in the anterior segment of the eye) increases the amount of this fluid and therefore the pressure in the whole eye (normal = 16mmHg). This compresses the retina and optic nerve which can eventually lead to blindness. Cataract: A clouding of the lens, mostly due to age-related thickening and hardening. It leads to blurred vision. Risk factors are smoking and diabetes. Need to know: All of the above, apart from cell types in the retina (only rods and cones). Task 2 (LO 4, 5) Taste and smell  Answer the questions. 5. Where do you find taste buds? On all parts of the tongue and some on the palate, cheeks, epiglottis and pharynx. 2 6. Name some characteristics of olfactory receptor cells. They are chemoreceptors, are bipolar neurons, have cilia, have a short life-span (30-60 days) and get replaced. 7. Name the five taste modalities and examples of chemicals that trigger them.      Sweet: sugars, alcohol, amino acids Sour: acids, H+ ions Salty: metal ions, salt Bitter: alkaloids, e.g. caffeine Umami: glutamate 8. Why can smell trigger an emotional response? Explain this by listing the sequence of the olfactory pathway from receptor to the brain. Olfactory receptors → olfactory bulb → olfactory tracts → cranial nerve I (olfactory) → primary olfactory cortex (temporal lobe) → two pathways: 1) to the frontal lobe for further interpretation and 2) to the limbic system, which is the emotional centre of the brain. Dangerous smells can trigger a flight and fight response, appetising smells activate the digestive system via the ANS. However, many smells just elicit emotional responses and/or memories. Need to know: All of the above. Task 3 (LO 6, 7) Hearing and balance  Label the diagrams. 3  Answer the questions: 9. Define transduction using the example of hearing. Transduction = the stimulus energy gets converted into a graded potential. In the case of the receptor being a separate cell (so not the peripheral axon of a sensory unipolar neuron), this is called a receptor potential. The receptor potential leads to the release of neurotransmitters from the receptor cell. In the case of the ear, sound waves make the basilar membrane vibrate, which stimulates the cochlear hair cells and their stereocilia as they move and pivot with that vibration. This opens ion channels causing a graded receptor potential in the cochlear hair cells. 10. How do we hear sound? Describe the structures involved from sound waves to brain. Sound waves travel through the external meatus, hit the tympanic membrane and make it vibrate → auditory ossicles pick up, amplify and transfer the vibration to the oval window → triggers movement of perilymph and endolymph in the cochlea → the spiral organs in the cochlea contain cochlear hair cells (see Q 10) → cochlear nerve → cranial nerve VIII (vestibulocochlear) → midbrain → thalamus → primary auditory cortex (temporal lobe) 11. How are sound waves characterised and how does that relate to sound interpretation? Name the units that are used for measuring the two characteristics. Frequency = pitch, measured in Hertz (Hz) Amplitude = loudness, measured in decibels (dB) 4