Stimulus Flashcards Preview

Biology Unit 5 > Stimulus > Flashcards

Flashcards in Stimulus Deck (14)
Loading flashcards...
1

Importance of reflex

  • avoids damage to tissues;
  • escape from predators;
  • plays a role in homeostasis

2

How does a pacinian corpuscle produce a generator potential in response to a stimulus 

  • when pressure is applied, it stretches membrane, causing the PC to change shape
  • stretch-mediated sodium ion channels  open
  • this causes sodium ions to enter,
  • this results in depolarisation
  • a generator potential is formed

3

Why can rod cells allow us to see in dim light

  • several rods are connected to 1 bipolar neurone
  • many generator potential combine (spatial summation)
  • this can then exceed threshold for an action potential;
  • individual generator potentials won't  exceed threshold;
  •  

4

Benefits of having a large fovea

  • High cone cell density on Fovea 
  • Enables high visual acuity
  • As one cone linked to one bipolar neurone;
  • Wider area of clear vision;

5

Explain the high visual acuity of cone cells

  • Each cone cell connects to 1 bipolar neurone
  • The brain recieves impulse  from each cone cell individually

6

Define visual acuity

Resolving power, the ability to distinguish close objects

7

How do plants shoot respond to illumination and explain the benefit of this

  • IAA moves to the shaded area
  • Causes this side to grow faster, leading to positive phototropism 
  • This causes the shoot to bend towards the light source
  • Light is needed for photosynthesis 

8

How do plants roots respond to gravity?

  • Gravity causes IAA to accumulate at bottom of root, leading to high conc of IAA
  • This inhibits cell elongation on the lower side 
  • Less inhibition on upper side so it grows more
  • This causes the root to bend downwards

9

Kinesis definition

  • A non-directional response to a stimulus;
  • Results in an increased speed of movement and repeated change in direction
  • Organism keeps until it is in a more favourable environment;

10

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

  • rhodopsin broken down by light;
  • takes time to resynthesis it;

11

Similarity/Difference between taxis and tropism

1. Similarity – directional response to a stimulus

2. Difference –Taxis occurs in animals organisms and tropism occurs in plants

12

Explain the poor visual acuity of rod cells

  • Spatial Summation of rod cells
  • the brain cannot distinguish between impulse from different rod cells 

13

Benefits of kinesis

  • stays longer stays in favourable conditions ;
  • remains near food source 

14

Explain trichromatic vision

  • three types of cones cells
  •  each sensitive to different wavelength of light