full transcript

From the Ted Talk by Rose Eveleth: How do we smell?

Unscramble the Blue Letters

It's the first sense you use when you're born. One out of every fifty of your genes is dedicated to it. It must be important, right? Okay, take a deep breath through your nose. It's your ssene of smell, and it's breathtakingly powerful. As an adult, you can distinguish about 10,000 different smells. Here's how your nose does it. Smell starts when you sniff molecules from the air into your nostrils. 95% of your naasl cvaity is used just to filter that air before it hits your lungs. But at the very back of your nose is a region called the olfactory epithelium, a little patch of skin that's key to everything you smell. The olfactory epithelium has a layer of olfactory rpeotecr cells, special neurons that sense smells, like the taste buds of your nose. When odor molecules hit the back of your nose, they get sctuk in a layer of muucs covering the olfactory epithelium. As they dissolve, they bind to the olfactory receptor clels, which fire and send signals through the olfactory tract up to your brain. As a side note, you can tell a lot about how good an animal's sense of smell is by the size of its olfactory epithelium. A dog's olfactory epeihtiulm is 20 times bigger than your puny human one. But there's still a lot we don't know about this little patch of cells, too. For example, our olfactory epithelium is pigmented, and scientists don't really know why. But how do you actually tell the dfrcfnieee between sellms? It turns out that your brain has 40 million different olfactory receptor neurons, so odor A might trigger neurons 3, 427, and 988, and odor B might trigger neurons 8, 76, and 2,496,678. All of these different combinations let you deectt a staggeringly broad array of smells. Olfactory neurons are always fresh and ready for action. They're the only neuron in the body that gets rcaelepd regularly, every four to eight weeks. Once they are triggered, the signal travels through a bundle called the otforalcy tract to dtsinotneias all over your brian, making stops in the aydlgama, the thalamus, and the nocroteex. This is different from how sight and sound are processed. Each of those signals goes first to a relay center in the middle of the cerebral hemisphere and then out to other reoings of the brain. But smell, because it evolved before most of your other senses, takes a direct route to these different regions of the brain, where it can trigger your fight-or-flight response, help you recall memories, or make your mouth wtaer. But even though we've all got the same physiological set-up, two nostrils and millions of olfactory nurneos, not everybody smells the same things. One of the most famous examples of this is the ability to smell so-called "asparagus pee." For about a quarter of the population, uitiannrg after eating asparagus means smelling a distinct odor. The other 75% of us don't ncitoe. And this isn't the only case of smells differing from nose to nose. For some pelpoe, the cmaciehl androstenone smells like vanilla; to others, it smells like setawy unire, which is unfortunate because androstenone is commonly found in tasty things like pork. So with the sweaty urine smellers in mind, pork producers will castrate male pigs to stop them from making anetondosrne. The inability to smell a scent is cllaed anosmia, and there are about 100 known elmxapes. People with alilcin anosmia can't smell grialc. Those with eugenol anosmia can't selml cloves. And some people can't smell anything at all. This kind of full anosmia could have several causes. Some people are born without a sense of smell. Others lose it after an acneicdt or during an illesns. If the olfactory epithelium gets swollen or infected, it can hpemar your sense of smell, something you might have experienced when you were sick. Not being able to smell anything can mess with your other sneses, too. Many people who can't smell at all also can't really taste the same way the rest of us do. It turns out that how something tastes is closely related to how it smells. As you chew your food, air is pushed up your nasal pgaasse, carrying with it the smell of your food. Those sectns hit your olfactory epithelium and tell your brain a lot about what you're eating. Without the ability to smell, you lose the ability to tsate anything more complicated than the five tastes your taste buds can detect: seewt, salty, bitter, sour, and savory. So, the next time you smell exhaust fumes, salty sea air, or rsoat chicken, you'll know exactly how you've done it and, perhaps, be a little more thankful that you can.

Open Cloze

It's the first sense you use when you're born. One out of every fifty of your genes is dedicated to it. It must be important, right? Okay, take a deep breath through your nose. It's your _____ of smell, and it's breathtakingly powerful. As an adult, you can distinguish about 10,000 different smells. Here's how your nose does it. Smell starts when you sniff molecules from the air into your nostrils. 95% of your _____ ______ is used just to filter that air before it hits your lungs. But at the very back of your nose is a region called the olfactory epithelium, a little patch of skin that's key to everything you smell. The olfactory epithelium has a layer of olfactory ________ cells, special neurons that sense smells, like the taste buds of your nose. When odor molecules hit the back of your nose, they get _____ in a layer of _____ covering the olfactory epithelium. As they dissolve, they bind to the olfactory receptor _____, which fire and send signals through the olfactory tract up to your brain. As a side note, you can tell a lot about how good an animal's sense of smell is by the size of its olfactory epithelium. A dog's olfactory __________ is 20 times bigger than your puny human one. But there's still a lot we don't know about this little patch of cells, too. For example, our olfactory epithelium is pigmented, and scientists don't really know why. But how do you actually tell the __________ between ______? It turns out that your brain has 40 million different olfactory receptor neurons, so odor A might trigger neurons 3, 427, and 988, and odor B might trigger neurons 8, 76, and 2,496,678. All of these different combinations let you ______ a staggeringly broad array of smells. Olfactory neurons are always fresh and ready for action. They're the only neuron in the body that gets ________ regularly, every four to eight weeks. Once they are triggered, the signal travels through a bundle called the _________ tract to ____________ all over your _____, making stops in the ________, the thalamus, and the _________. This is different from how sight and sound are processed. Each of those signals goes first to a relay center in the middle of the cerebral hemisphere and then out to other _______ of the brain. But smell, because it evolved before most of your other senses, takes a direct route to these different regions of the brain, where it can trigger your fight-or-flight response, help you recall memories, or make your mouth _____. But even though we've all got the same physiological set-up, two nostrils and millions of olfactory _______, not everybody smells the same things. One of the most famous examples of this is the ability to smell so-called "asparagus pee." For about a quarter of the population, _________ after eating asparagus means smelling a distinct odor. The other 75% of us don't ______. And this isn't the only case of smells differing from nose to nose. For some ______, the ________ androstenone smells like vanilla; to others, it smells like ______ _____, which is unfortunate because androstenone is commonly found in tasty things like pork. So with the sweaty urine smellers in mind, pork producers will castrate male pigs to stop them from making ____________. The inability to smell a scent is ______ anosmia, and there are about 100 known ________. People with _______ anosmia can't smell ______. Those with eugenol anosmia can't _____ cloves. And some people can't smell anything at all. This kind of full anosmia could have several causes. Some people are born without a sense of smell. Others lose it after an ________ or during an _______. If the olfactory epithelium gets swollen or infected, it can ______ your sense of smell, something you might have experienced when you were sick. Not being able to smell anything can mess with your other ______, too. Many people who can't smell at all also can't really taste the same way the rest of us do. It turns out that how something tastes is closely related to how it smells. As you chew your food, air is pushed up your nasal _______, carrying with it the smell of your food. Those ______ hit your olfactory epithelium and tell your brain a lot about what you're eating. Without the ability to smell, you lose the ability to _____ anything more complicated than the five tastes your taste buds can detect: _____, salty, bitter, sour, and savory. So, the next time you smell exhaust fumes, salty sea air, or _____ chicken, you'll know exactly how you've done it and, perhaps, be a little more thankful that you can.

Solution

  1. sweaty
  2. garlic
  3. chemical
  4. receptor
  5. roast
  6. urinating
  7. scents
  8. neurons
  9. neocortex
  10. cells
  11. sense
  12. called
  13. passage
  14. stuck
  15. nasal
  16. amygdala
  17. urine
  18. notice
  19. brain
  20. epithelium
  21. accident
  22. difference
  23. destinations
  24. smell
  25. detect
  26. mucus
  27. allicin
  28. illness
  29. taste
  30. water
  31. regions
  32. smells
  33. people
  34. senses
  35. cavity
  36. androstenone
  37. olfactory
  38. sweet
  39. hamper
  40. examples
  41. replaced

Original Text

It's the first sense you use when you're born. One out of every fifty of your genes is dedicated to it. It must be important, right? Okay, take a deep breath through your nose. It's your sense of smell, and it's breathtakingly powerful. As an adult, you can distinguish about 10,000 different smells. Here's how your nose does it. Smell starts when you sniff molecules from the air into your nostrils. 95% of your nasal cavity is used just to filter that air before it hits your lungs. But at the very back of your nose is a region called the olfactory epithelium, a little patch of skin that's key to everything you smell. The olfactory epithelium has a layer of olfactory receptor cells, special neurons that sense smells, like the taste buds of your nose. When odor molecules hit the back of your nose, they get stuck in a layer of mucus covering the olfactory epithelium. As they dissolve, they bind to the olfactory receptor cells, which fire and send signals through the olfactory tract up to your brain. As a side note, you can tell a lot about how good an animal's sense of smell is by the size of its olfactory epithelium. A dog's olfactory epithelium is 20 times bigger than your puny human one. But there's still a lot we don't know about this little patch of cells, too. For example, our olfactory epithelium is pigmented, and scientists don't really know why. But how do you actually tell the difference between smells? It turns out that your brain has 40 million different olfactory receptor neurons, so odor A might trigger neurons 3, 427, and 988, and odor B might trigger neurons 8, 76, and 2,496,678. All of these different combinations let you detect a staggeringly broad array of smells. Olfactory neurons are always fresh and ready for action. They're the only neuron in the body that gets replaced regularly, every four to eight weeks. Once they are triggered, the signal travels through a bundle called the olfactory tract to destinations all over your brain, making stops in the amygdala, the thalamus, and the neocortex. This is different from how sight and sound are processed. Each of those signals goes first to a relay center in the middle of the cerebral hemisphere and then out to other regions of the brain. But smell, because it evolved before most of your other senses, takes a direct route to these different regions of the brain, where it can trigger your fight-or-flight response, help you recall memories, or make your mouth water. But even though we've all got the same physiological set-up, two nostrils and millions of olfactory neurons, not everybody smells the same things. One of the most famous examples of this is the ability to smell so-called "asparagus pee." For about a quarter of the population, urinating after eating asparagus means smelling a distinct odor. The other 75% of us don't notice. And this isn't the only case of smells differing from nose to nose. For some people, the chemical androstenone smells like vanilla; to others, it smells like sweaty urine, which is unfortunate because androstenone is commonly found in tasty things like pork. So with the sweaty urine smellers in mind, pork producers will castrate male pigs to stop them from making androstenone. The inability to smell a scent is called anosmia, and there are about 100 known examples. People with allicin anosmia can't smell garlic. Those with eugenol anosmia can't smell cloves. And some people can't smell anything at all. This kind of full anosmia could have several causes. Some people are born without a sense of smell. Others lose it after an accident or during an illness. If the olfactory epithelium gets swollen or infected, it can hamper your sense of smell, something you might have experienced when you were sick. Not being able to smell anything can mess with your other senses, too. Many people who can't smell at all also can't really taste the same way the rest of us do. It turns out that how something tastes is closely related to how it smells. As you chew your food, air is pushed up your nasal passage, carrying with it the smell of your food. Those scents hit your olfactory epithelium and tell your brain a lot about what you're eating. Without the ability to smell, you lose the ability to taste anything more complicated than the five tastes your taste buds can detect: sweet, salty, bitter, sour, and savory. So, the next time you smell exhaust fumes, salty sea air, or roast chicken, you'll know exactly how you've done it and, perhaps, be a little more thankful that you can.

Frequently Occurring Word Combinations

ngrams of length 2

collocation frequency
olfactory epithelium 7
olfactory receptor 3
taste buds 2
olfactory tract 2
trigger neurons 2

Important Words

  1. ability
  2. accident
  3. action
  4. adult
  5. air
  6. allicin
  7. amygdala
  8. androstenone
  9. anosmia
  10. array
  11. asparagus
  12. bigger
  13. bind
  14. bitter
  15. body
  16. born
  17. brain
  18. breath
  19. breathtakingly
  20. broad
  21. buds
  22. bundle
  23. called
  24. carrying
  25. case
  26. castrate
  27. cavity
  28. cells
  29. center
  30. cerebral
  31. chemical
  32. chew
  33. chicken
  34. closely
  35. cloves
  36. combinations
  37. commonly
  38. complicated
  39. covering
  40. dedicated
  41. deep
  42. destinations
  43. detect
  44. difference
  45. differing
  46. direct
  47. dissolve
  48. distinct
  49. distinguish
  50. eating
  51. epithelium
  52. eugenol
  53. evolved
  54. examples
  55. exhaust
  56. experienced
  57. famous
  58. fifty
  59. filter
  60. fire
  61. food
  62. fresh
  63. full
  64. fumes
  65. garlic
  66. genes
  67. good
  68. hamper
  69. hemisphere
  70. hit
  71. hits
  72. human
  73. illness
  74. important
  75. inability
  76. infected
  77. key
  78. kind
  79. layer
  80. lose
  81. lot
  82. lungs
  83. making
  84. male
  85. means
  86. memories
  87. mess
  88. middle
  89. million
  90. millions
  91. mind
  92. molecules
  93. mouth
  94. mucus
  95. nasal
  96. neocortex
  97. neuron
  98. neurons
  99. nose
  100. nostrils
  101. note
  102. notice
  103. odor
  104. olfactory
  105. passage
  106. patch
  107. pee
  108. people
  109. physiological
  110. pigmented
  111. pigs
  112. population
  113. pork
  114. powerful
  115. processed
  116. producers
  117. puny
  118. pushed
  119. quarter
  120. ready
  121. recall
  122. receptor
  123. region
  124. regions
  125. regularly
  126. related
  127. relay
  128. replaced
  129. response
  130. rest
  131. roast
  132. route
  133. salty
  134. savory
  135. scent
  136. scents
  137. scientists
  138. sea
  139. send
  140. sense
  141. senses
  142. sick
  143. side
  144. sight
  145. signal
  146. signals
  147. size
  148. skin
  149. smell
  150. smellers
  151. smelling
  152. smells
  153. sniff
  154. sound
  155. sour
  156. special
  157. staggeringly
  158. starts
  159. stop
  160. stops
  161. stuck
  162. sweaty
  163. sweet
  164. swollen
  165. takes
  166. taste
  167. tastes
  168. tasty
  169. thalamus
  170. thankful
  171. time
  172. times
  173. tract
  174. travels
  175. trigger
  176. triggered
  177. turns
  178. unfortunate
  179. urinating
  180. urine
  181. water
  182. weeks