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Flashcards · Biology

The Nervous System

112 cards from 7 lessons

  1. What is a stimulus?

    A change in the environment that can be detected by a receptor.

  2. What does a sensory receptor do?

    It detects a stimulus and converts it into an electrical impulse.

  3. Which two organs make up the central nervous system?

    The brain and the spinal cord.

  4. Name the two types of effector.

    Muscles and glands.

  5. What does a muscle do when it receives an impulse?

    It contracts.

  6. What does a gland do when it receives an impulse?

    It secretes a substance, such as a hormone.

  7. Which type of neurone carries impulses to the CNS?

    Sensory neurones.

  8. Which type of neurone carries impulses away from the CNS?

    Motor neurones.

  9. Where are relay neurones found?

    Inside the central nervous system, in the brain or spinal cord.

  10. What is the job of a relay neurone?

    To pass impulses from sensory neurones to motor neurones.

  11. What is the function of the myelin sheath?

    It insulates the neurone and makes the impulse travel faster.

  12. What is the dendron of a sensory neurone?

    A long extension that carries the impulse towards the cell body.

  13. What is the axon of a neurone?

    The extension that carries the impulse away from the cell body.

  14. Why do neurones have branched ends?

    To connect with many other neurones and share information.

  15. Which type of receptor is found in the retina?

    Light receptors (rod and cone cells).

  16. What happens to impulses when myelin is damaged?

    They travel more slowly or are lost, as in multiple sclerosis.

  17. Why is a neurone called a specialised cell?

    It has a long, insulated, branched structure that suits it to carrying electrical impulses.

  18. A pain receptor in the skin is triggered by a pin. Which neurone carries the impulse next?

    A sensory neurone.

  19. What is a synapse?

    The junction between two neurones, with a tiny gap between them.

  20. Can an electrical impulse cross a synaptic gap?

    No. The signal changes into a chemical one, a neurotransmitter, to cross the gap.

  21. What is a neurotransmitter?

    A chemical released by a neurone that carries the signal across the synapse.

  22. Where are neurotransmitters stored before they are released?

    In vesicles in the end of the first neurone.

  23. How does a neurotransmitter cross the synaptic gap?

    By diffusion.

  24. What do neurotransmitter molecules bind to?

    Receptor molecules on the membrane of the next neurone.

  25. What happens when the neurotransmitter binds to the receptor?

    A new electrical impulse starts in the next neurone.

  26. Why can impulses travel in one direction only across a synapse?

    Vesicles are only on one side and receptors only on the other.

  27. Why does the first neurone's ending contain lots of mitochondria?

    They release energy for making and releasing the neurotransmitter.

  28. What happens to a neurotransmitter after it has done its job?

    It is broken down or taken back up, which stops the signal.

  29. Why does a synapse slightly delay an impulse?

    Diffusion across the gap takes a short time.

  30. A motor neurone is 0.8 m long and an impulse takes 0.008 s to travel along it. What is its speed?

    \(0.8 \div 0.008 = 100\) m/s.

  31. Which neurotransmitter works at the synapse between a motor neurone and a muscle?

    Acetylcholine.

  32. Why must a receptor have a specific shape?

    Only the matching neurotransmitter can fit into it and trigger an impulse.

  33. What is the usual mistake when describing a synapse?

    Saying that the electrical impulse jumps across the gap. A chemical crosses it.

  34. What is a reflex action?

    A fast, automatic response to a stimulus that does not involve conscious thought.

  35. What is a reflex arc?

    The pathway of neurones that carries an impulse in a reflex, from receptor to effector.

  36. Name the parts of a reflex arc in order.

    Receptor, sensory neurone, relay neurone, motor neurone, effector.

  37. Where is the relay neurone in a spinal reflex?

    In the spinal cord, in the central nervous system.

  38. How many synapses are in a simple reflex arc?

    Two: one between the sensory and relay neurone, and one between the relay and motor neurone.

  39. Why are reflexes quick?

    Short pathway, few synapses and no conscious thought.

  40. Why are reflexes protective?

    They move the body away from danger before damage is done.

  41. Give an example of a reflex action.

    Pulling the hand away from a hot object, blinking or the pupil getting smaller in bright light.

  42. What is a voluntary action?

    An action that is controlled by conscious thought.

  43. Which part of the brain is used in voluntary actions?

    The cerebral hemispheres.

  44. What is reaction time?

    The time between a stimulus and a response.

  45. In the ruler drop test, what does a longer distance mean?

    A slower reaction time.

  46. Why should the ruler drop test be repeated?

    To calculate a mean and reduce the effect of random errors.

  47. Name two variables to control in a reaction time test.

    The same person and hand, and the same starting position of the ruler.

  48. Why might a person's reaction time get faster with repeated tries?

    Practice improves the reaction, so results change for a reason other than the variable being tested.

  49. True or false: a person decides to pull away from a hot plate.

    False. It is a reflex, and the impulse passes through the spinal cord without conscious thought.

  50. What are the three main regions of the brain you need to know?

    The cerebral hemispheres, the cerebellum and the medulla oblongata.

  51. What do the cerebral hemispheres control?

    Consciousness, intelligence, memory, language and voluntary movement.

  52. Why is the cerebral cortex folded?

    To give a bigger surface area, so more neurones fit in the skull.

  53. What does the cerebellum control?

    Balance and the coordination of movement.

  54. What does the medulla oblongata control?

    Unconscious activities such as heart rate and breathing rate.

  55. Where is the cerebellum?

    At the back of the brain, below the cerebral hemispheres.

  56. Which part of the brain joins to the spinal cord?

    The medulla oblongata.

  57. Which part of the brain is used for learning a language?

    The cerebral hemispheres.

  58. What happens to the heart rate when you start to exercise, and which region controls it?

    It increases, and the medulla oblongata controls it.

  59. Why is damage to the medulla oblongata so dangerous?

    It controls breathing and heart rate, and these may stop.

  60. A person has poor balance after a head injury. Which region may be damaged?

    The cerebellum.

  61. A person has trouble speaking after a stroke. Which region may be damaged?

    The cerebral hemispheres.

  62. What protects the brain?

    The skull, the meninges and a layer of fluid.

  63. What did the case of Phineas Gage suggest?

    That different parts of the brain have different functions.

  64. What is a stroke?

    Damage to the brain caused by a blocked or burst blood vessel.

  65. Why is "the cerebellum is for thinking" a common mistake?

    Thinking is controlled by the cerebral hemispheres. The cerebellum coordinates movement and balance.

  66. Why is it difficult to study the brain directly?

    It is protected by the skull and made of delicate tissue that is easily damaged.

  67. What does a CT scan use?

    X-rays taken from many angles, combined by a computer.

  68. What does a CT scan show?

    The structure of the brain, such as tumours, bleeds and damage.

  69. What does a PET scan use?

    A radioactive tracer, usually a form of glucose.

  70. What does a PET scan show?

    The function of the brain: which areas are active.

  71. Why does a PET scan use glucose?

    Active neurones use more glucose, so the tracer collects in the busiest areas.

  72. Which scan would show a tumour in the brain?

    A CT scan (a PET scan can also show a fast-growing one).

  73. Which scan would show which area is used for speaking?

    A PET scan.

  74. Give one limitation of a CT scan.

    It exposes the patient to X-rays, and it only shows structure, not activity.

  75. Give one limitation of a PET scan.

    It uses a radioactive tracer, it is expensive and it is less detailed.

  76. Why do neurones in the brain make it hard to treat damage?

    They do not regenerate well, so damage is usually permanent.

  77. What is the effect of a severe spinal injury?

    Paralysis and loss of feeling below the injury, because impulses cannot pass.

  78. Why is it hard to remove a brain tumour?

    The tissue is delicate, and a tumour can be near vital areas, so healthy tissue can be damaged.

  79. Why can many drugs not be used to treat the brain?

    A barrier between the blood and the brain stops many chemicals reaching it.

  80. Why are CT and PET scans often used together?

    A CT scan shows the structure and a PET scan shows the activity, so together they give more information.

  81. What is the function of the cornea?

    To refract (bend) light as it enters the eye.

  82. What is the function of the lens?

    To focus light onto the retina.

  83. What does the iris do?

    It controls the size of the pupil, and so the amount of light entering the eye.

  84. What is the pupil?

    The hole in the middle of the iris through which light enters.

  85. What is the retina?

    The layer at the back of the eye that contains the light receptors.

  86. What does the optic nerve do?

    Carries impulses from the retina to the brain.

  87. What happens to the pupil in bright light?

    It gets smaller.

  88. What happens to the pupil in dim light?

    It gets larger.

  89. Which iris muscles contract in bright light?

    The circular muscles.

  90. Why does the pupil get smaller in bright light?

    To stop too much light damaging the retina.

  91. Which cells work in dim light?

    Rod cells.

  92. Which cells detect colour?

    Cone cells.

  93. Where are most cone cells found?

    In the fovea, at the centre of the retina.

  94. How many types of cone cell are there and what colours do they detect?

    Three: red, green and blue.

  95. What happens to the lens when looking at a near object?

    It becomes thicker and more curved.

  96. Why can you not see colours well at night?

    Only the rod cells work in very dim light, and they cannot detect colour.

  97. What is short-sightedness?

    A defect where distant objects look blurred, because light focuses in front of the retina.

  98. What is long-sightedness?

    A defect where near objects look blurred, because light would focus behind the retina.

  99. What causes short sight?

    An eyeball that is too long, or a lens that bends light too much.

  100. What causes long sight?

    An eyeball that is too short, or a lens that bends light too little.

  101. Which lens corrects short sight?

    A concave lens.

  102. Which lens corrects long sight?

    A convex lens.

  103. What does a concave lens do to light rays?

    It spreads them out (diverges them).

  104. What does a convex lens do to light rays?

    It brings them together (converges them).

  105. What is a cataract?

    A cloudy area in the lens, which makes vision misty or blurred.

  106. How is a cataract treated?

    The cloudy lens is replaced with a clear artificial lens by surgery.

  107. What causes colour blindness?

    Missing or faulty cone cells for one or more of the colours.

  108. Why is colour blindness more common in men?

    The genes for the cone cells are on the X chromosome, and men have only one.

  109. Can colour blindness be cured?

    No. It is inherited, though tinted lenses can help some people.

  110. Name one other way to correct short sight apart from glasses.

    Contact lenses or laser eye surgery.

  111. Why do many people become long-sighted as they get older?

    The lens becomes stiffer and cannot get thick enough to focus on near objects.

  112. Which common mistake do students make about the retina?

    Saying the light is focused "on the cornea". It must be focused on the retina.