3.6.1.2 Receptor

Question 1

sensory reception feature

Answer 1

• Stimuli are detected (recognised) through receptor cells
• Each receptor responds to a single specific stimulus
• Receptors are found at the end of sensory neurones
• They act as transducers - they convert a type of stimulus into an electrical signal (first a generator potential, followed by an action potential in the sensory neurone)

Question 2

Pacinian Corpuscle
(structure)

Answer 2

Lamellae
core
nerve ending
node of ranvier
myelin
nerve fiber

Question 3

why pacinian corpuscle doesn’t works without pressure

Answer 3

Normally at rest, the stretch-mediated Na+ channels, located on the nerve ending membrane, are too narrow to allow Na+ ions through
However, when pressure is applied to the skin, this deforms the layers of connective tissue on the pacinian corpuscle and the sensory neurone membrane, opening the stretch-mediated Na+ channels
Na+ surrounding the neurone diffuse in and causes depolarisation, producing a generator potential

Question 4

how pacinian works

Answer 4

• pressure from stimulus
• stretch- mediated Na+ channel open
• Na+ diffuse in
• depolarisation
• generator potential produce (graded response)
  -The generator potential sets up local currents that trigger an Action Potential if the stimulus is big enough.
  This AP is propagated

Question 5

receptor in retina

Answer 5

photoreceptor

Question 6

rod and cone cell

• more or less
• color vs bw

Answer 6

• Rods more numerous than cone cells
• Only one type of rod cell - cannot distinguish between different wavelengths of light - so images seen in black and white
• 3 different types of cone cell - sensitive to different wavelengths of light (green, red and blue) causing images to be seen in colour

Question 7

Pigment in Rod cell and Cone cell

Answer 7

Rhodopsin (one type)
High sensitivity to light
Pigment easily broken down

Iodopsin (3 types - each sensitive to a different wavelength of light)
(B, G, R)
Low sensitivity to light

Question 8

How pigment works

Answer 8

Light stimulate the pigment
broken down pigment
trigger a change in membrane potential - trigger AP
resynthesis into pigment to absorb more light

Question 9

Rod cell

light intensity
single / multiple
visual acuity

Answer 9

• Used to see in low light intensities (the receptors have high light sensitivity)
• Multiple rod cells synapse with a single sensory neurone - uses summation
• Low visual acuity - a bit blurry (not as clear as in high light intensities)

Question 10

Cone cell

light intensity
single / multiple
visual acuity

Answer 10

• Only responds to high light intensity (the receptors have low sensitivity to light)
• Each cone cell synapses with a its own separate (single) sensory neurone - no summation
• Good visual acuity - accurate /detailed vision