6.1.2 Receptors Flashcards
What is a stimulus?
A detectable change in an organism’s environment.
What detects a stimulus?
Receptors.
Each receptor responds only to a _______ stimuli.
Specific.
What does the stimulation of a receptor lead to?
The establishment of a receptor potential.
What are rods and cones and where are they found?
Photoreceptors, found in the retina.
Can rods distinguish between different wavelengths of light?
No.
Do rods process images in black and white or colour?
Black and white.
Do rods detect light of a low or high intensity?
Low.
What is retinal convergence?
Many rod cells connect to one sensory neuron.
What must happen in rod cells to create a generator potential?
The pigment of rod cells (rhodopsin) must be broken down by light energy.
Why can the threshold be reached even in low light energy?
Because many rod cells are connected to a single bipolar cell - summation.
Why do rod cells give low visual acuity?
- Retinal convergence means the brain cannot distinguish between the separate sources of light that stimulated it.
- The 2 light sources close together cannot be seen as separate.
How many types of cone cells are there?
3.
What do the different cone cells do?
- Different types of iodopsin pigment.
- Which all absorb different wavelengths of light.
Why do cone cells need a high light intensity to generate an action potential?
Iodopsin is only broken down if there is a high light intensity.
Does spatial summation occur in cone cells?
No - only one cone cell connects to a bipolar cell.
Do cone cells give a high visual acuity?
Yes - because only one cone cell is connected to one bipolar cell.
Is there an even or uneven distribution of rods & cone cells in the retina?
Uneven.
How is light focused by the eye?
- By the lens on the part of the retina opposite the pupil (fovea).
- Which will receive the highest intensity of light.
Where are most cone cells located?
Near the fovea - as they only respond to high light intensities.
Where are rod cells located?
Further away from the fovea, as they can respond to lower light intensities.
What is the nervous system made up of?
Peripheral nervous system and central nervous system.
What is the peripheral nervous system?
The sensory and motor neurons that connect the CNS to the rest of the body.
What is the central nervous system?
Brain and spinal cord.
What is the pacinian corpuscle?
A receptor.
What does the pacinian corpuscle respond to?
Pressure changes.
What does the pacinian corpuscle consist of?
Single sensory neurone wrapped with layers of tissue separated by gel.
How does the pacinian corpuscle work?
- When pressure is applied, it deforms the neuron plasma membrane.
- Stretching the Na+ channels, so sodium ions diffuse in.
- Causing a generator potential.
Explain how the fovea enables an eagle to see its prey in detail.
- High visual acuity.
- Each cone is connected to a single neurone.
- Cones send separate impulses to brain.
Explain how the high density of rod cells in an owl’s retina enables it to hunt at night.
- High visual sensitivity.
- Several rods connected to a single neurone.
- Spatial summation to overcome threshold.
Explain how applying pressure to the Pacinian corpuscle produces changes in membrane potential.
- Pressure causes membrane to become stretched.
- Sodium ion channels in membrane open and sodium ions move in.
- Greater pressure more channels open / sodium ions enter.
