receptors Flashcards

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1
Q

Describe the basic structure of a Pacinian corpuscle

A

lamellae
sensory neurone ending
sensory neurone axon
myelin sheath
stretch mediated ion channel
gel

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2
Q

Describe how a generator potential is established in a Pacinian corpuscle

A
  1. Mechanical stimulus eg. pressure deforms
    lamellae and stretch- mediated sodium ion
    (Na+) channels
  2. So Na+ channels in membrane open and Na+
    diffuse into sensory neurone
    ○ Greater pressure causes more Na+channels to open and more Na+ to enter
  3. This causes depolarisation, leading to a
    generator potential
    ○ If generator potential reaches threshold
    it triggers an action potential
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3
Q

Explain what the Pacinian corpuscle illustrates

A

● Receptors respond only to specific stimuli
○ Pacinian corpuscle only responds to mechanical pressure
● Stimulation of a receptor leads to the establishment of a generator potential
○ When threshold is reached, action potential sent (all-or-nothing principle)

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4
Q

Explain the differences in sensitivity to light for rods & cones in the retina

A

Rods are more sensitive to light
● Several rods connected to a single neurone
● Spatial summation to reach / overcome threshold (as enough
neurotransmitter released) to generate an action potential

Cones are less sensitive to light
● Each cone connected to a
single neurone
● No spatial summation

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5
Q

Explain the differences in visual acuity for rods & cones in the retina

A

Rods give lower visual acuity
● Several rods connected to a single neurone
● So several rods send a single set of impulses
to brain (so can’t distinguish between
separate sources of light)

Cones give higher visual acuity
● Each cone connected to a single neurone
● Cones send separate (sets of) impulses to brain
(so can distinguish between 2 separate sources
of light)

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6
Q

Explain the differences in sensitivity to colour for rods & cones in the retina

A

Rods allow
monochromatic vision
● 1 type of rod / 1
pigment

Cones allow colour vision
● 3 types of cones - red-, green- and blue-sensitive
● With different optical pigments → absorb different wavelengths
● Stimulating different combinations of cones gives range of colour perception

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