6: Receptors Flashcards
(19 cards)
What charge is the inside of the receptor relative to the outside?
Negative
What is a generator potential?
Stimulus detected, cell membrane excited and becomes more permeable
The change in potential difference due to a stimulus
What is an action potential?
An electrical impulse along a neurone triggered when a generator potential reaches the threshold level
What are mechanoreceptors in the skin called?
Pacinian corpuscles
Structure of a Pacinian corpuscle?
Sensory nerve ending surrounded by lamellae (connective tissue)
How is a generator potential created in a Pacinian corpuscle?
Lamellae are deformed, press on the sensory nerve ending, sensory neurone’s cell membrane stretches, deforming the stretch-mediated sodium ion channels - sodium ions diffuse into the cell
What is the fovea?
An area of the retina that contains lots of photoreceptors (cones)
How do photoreceptors create a generator potential?
Light is absorbed by light-sensitive optical pigments, light bleaches the pigments, causing a chemical change and altering the membrane permeability to sodium ions
Where are nerve impulses sent from photoreceptors?
Bipolar neurone -> optic nerve -> brain
Where are rod cells found?
Peripheral parts of the retina
Where are cone cells found?
Fovea
Why do rod cells and cone cells give different information?
Contain different optical pigments so are sensitive to different wavelengths of light
What information do rod cells give?
Monochromatic vision - black and white
What information do cone cells give?
Colour - trichromatic vision
What are the three types of cone cell?
red-sensitive, green-sensitive, blue-sensitive
Rods sensitivity to light?
High as many rods join to one bipolar neurone so many weak generator potentials combine to reach threshold level
Cones sensitivity to light?
Low
Rods visual acuity?
Low as light from two different parts close together can’t be told apart due to multiple rods being joined to one bipolar neurone
Cones visual acuity?
High
