Receptors

  • Created by: Ribenas1
  • Created on: 04-03-17 14:21

How many stimuli do receptors detect + why?

One - they're specific

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What + where are receptors?

1) Proteins 

2) On cell surface membrane 

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How do receptors communicate?

  • Via Nervous System

1) Resting state : difference in charge inside + outside = meaning there is a voltage across membrane (potential difference) 

2) At rest called resting potential 

3) Cell membrane excited by stimulus = becomes permeable 

4) Ions in + out alter potential difference

5) Generator potential: changes in potential difference

6) Big enough G.P triggers A.P if exceeds threshold 

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Explain Pacinian Corpuscles

  • It's a pressure receptor in skin

1) When stimulated lamelle deforms + press on sensory nerve ending

2) Causing stretch-mediated sodium ion channels to open + ions to diffuse = G.P 

3) G.P reaches threshold = triggers A.P 

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Explain/Define Photoreceptor, Iris and Lens

Photoreceptor - Light receptor in eye 

Iris - controls amount of light that enters 

Lens - Focuses rays onto retina 

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Explain/Define Retina and Blind Spot

Retina - contains loads of photoreceptors in fovea 

  • Nerve impulses carried from retina to brain by optic nerve, a bundle of neurones

Blind spot - NO photoreceptors = not sensitive to light 

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Explain how photoreceptors convert light into impu

  • Light hits photo.rec + absorbed by light sensitive optical pigment 
  • Causing chemical change - alterning membrane permability to sod ions 
  • G.P reaches threshold + nerve impulse sent along bipolar neurone 
  • This N connects photoreceptors to optical nerve - takes impulses to brain
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Name types of photoreceptors

1) Rod 

2) Cone 

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Where is the rod + cone found?

Rod - Peripheral part, Retina 

Cone - Fovea 

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How do rods + cones give information?

Rods - Black + White 

Cones - Coloured 

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What types of cones are there?

Red, blue + green sensitive 

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Sensitivity - Rod

Very - work in dim light - bc many rods join to one N = weak G.P combines 

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Sensitivity - Cone

Low - only fires A.P in bright light - one cone to one N = more needed to reach threshold

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Acuity - Rod

Low - many rods join to one N - meaning light from two points cannot be told apart 

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Acuity - Rod

High - cones are close together + one cone joins to one N - when light from two points hit two cones two A.P = so can distinguish between two points 

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