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AQA A-Level Biology > Receptors > Flashcards

Flashcards in Receptors Deck (10)
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1
Q

Explain why it takes time for the rod cells to recover their sensitivity to light after moving into the darkness (2)

A

Rhodopsin is bleached

2
Q

Explain why the membrane potential was the same whether medium or heavy pressure was applied to the finger tip. Explain why (2)

A
  • The threshold has been reached
  • All-or-nothing principle (If that stimulus exceeds the threshold potential, the nerve or muscle fibre will give a complete response; otherwise, there is no response.)
3
Q

Explain why vision using the fovea has high visual acuity (1)

A
  • Each receptor in the fovea is connected to a separate neurone
4
Q

Explain why the resting potential of -70mV is maintained in the sensory neurone when no pressure is applied (2)

A
  • membrane is more permeable to potassium ions and less permeable to sodium ions
  • sodium ions are actively transported out and potassium ions in
5
Q

Describe how the number and distribution of rods and cones across the retina would differ in a nocturnal mammal from a human (3)

A
  • more rods in nocturnal mammals
  • rods have high sensitivity
  • rhodopsin bleached at low light intensities
6
Q

When the image is focused on the fovea, the person sees the object in colour. Explain why (3)

A
  • colour is detected by cone cells
  • fovea contains mainly cone cells
  • three types of cone cells that are each sensitive to different wavelengths
7
Q

Explain why vision using other parts of the retina has high sensitivity to light (3)

A
  • many rods in other parts of the retina
  • rhodopsin (pigment in rod cells) are sensitive to light
  • receptors are connected in groups to neurone
  • summation
8
Q

Describe how a Pacinian corpuscle produces a generator potential when stimulated (3)

A
  • increased pressure deforms the stretch-mediated sodium ion channel
  • sodium channels open and sodium ions flow in
  • depolarisation leads to a generator potential
9
Q

Give one similarity and one difference between a taxis and tropism (2)

A
  • similarity = directional response to a stimulus
  • difference:
    taxis = whole organism moves
    tropism = growth response
10
Q

Explain the importance of reflex actions (3)

A
  • reflex actions are involuntary
  • reduce damage to tissues
  • escape from predators
  • find food