6A Receptors Flashcards
What happens when a receptor is in a resting state
there is a difference in charge between the inside and outside of the cell which means there is a voltage across the cell membrane
Define resting potential
the potential difference when a cell is at rest
What happens to the membrane when a stimulus is detected
it becomes more permeable allowing more ions to move in and out altering the potential difference
Define generator potential
The change in potential difference due to a stimulus
Define action potential
an electrical impulse across a neurone which is only triggered if a generator potential reaches a threshold
What is a mechanoreceptor
A receptor that detects mechanical stimuli
What are Pacinian corpuscles
pressure receptors on your skin
Pacinian corpuscles structure
contain the end of a sensory neurone called a sensory nerve ending wrapped in lamellae
What happens when a Pacinian corpuscle is stimulated
the lamellae are deformed pressing on the sensory nerve ending
This causes the sensory neurones cell membrane to stretch deforming the stretch mediated sodium ion channels
The chanells open and sodium ions diffuse in creating a generator potential
What are photoreceptors
Receptors that detect light
Where are photoreceptors located
on the fovea
What happens when light enters the eye
it hits the photoreceptors and is absorbed by light sensitive optical pigments light bleaches the pigments causing a chemical change and altering the membrane permeability to sodium ions a generator potential is created and if threshold is reached a nerve impulse is sent along a bipolar neurone
What do bipolar neurones connect photoreceptors to
the optic nerve
What are the two types of photoreceptors in the eye
rods and cones
Where are rods found
in the peripheral part of the retina
Where are cones found
in the fovea packed together
What do rods give information in
monochromatic
What do cones give information in
trichromatic
What are the different optical pigments
red sensitive, blue sensitive and green sensitive
How sensitive to light are rods
They are very sensitive to light because many rods join one neurone so many weak generator potentials combine to reach the threshold to trigger an action potential
How sensitive to light are cones
They are less sensitive to light because one cone joins one neurone so it takes more light to reach the threshold to trigger an action potential
Define visual acuity
the ability to tell two points apart that are close together
How much visual acuity do rods give
a low acuity because many rods join the same neurone which means light from two points close together can’t be told apart
How much visual acuity do cones give
a high acuity because cones are close together and one cone joins one neurone when light from two points hits two cones two action potentials go to the brain so you can distinguish two points that are close together as two separate pointsd
