3.6.1.2 Receptors (C14) Flashcards
Give the location of osmoreceptors in the body of a mammal
hypothalamus
When a person is dehydrated the water volume of an osmoreceptor falls - why?
- Water potential of blood will decrease;
- Water moves from osmoreceptor into blood by osmosis;
What is the function of a receptor cell?
To detect stimuli
The pressure receptors found in the skin are called…
Pacinian Corpuscles
Pacinian corpuscles respond to which type of stimuli?
Mechanical pressure.
Receptors cells are transducers. What is a transducer?
Something that converts one form of energy (e.g. light) into a form that can be understood by the body (e.g. an electrical impulse).
In order to create an electrical impulse a receptor cell creates a…
generator potential.
Where are pacinian corpuscles abundantly found?
In the skin of the fingers, genitals, hands, feet, ligaments and tendons.
The cell membrane at the end of the sensory neurone found inside a pacinian corpuscle contains…
Stretch-mediated sodium ion channels
What is a stretch-mediated sodium channel?
A sodium channel protein whose permeability to sodium ions increases when they are deformed.
Describe how a generator potential is created by a pacinian corpuscle.
- When pacinian corpuscle is stimulated, lamellae (connective tissue that wrapped around sensory nerve) are deformed + press on sensory nerve ending
- Causes sensory neurone’s cell membrane to stretch
- Which deforms stretch-mediated sodium ion channels
- Causes channels to open & Na+ can diffuse into cell
- Creates a generator potential
- If GP reaches threshold it triggers action potential
In which part of the eye are light receptor cells found?
The retina
The 2 types of light receptor cells are called…
rod cells
cone cells
Rod and cone cells are transducers. Explain.
They convert light energy into an electrical impulse.
Rod cells are responsible for ____________ vision
black and white
Why can rod cells only lead to images seen in black and white?
They cannot distinguish between different wavelengths of light.
Does the eye contain more rod cells or cone cells?
Rod cells
Rod cells are sensitive to _____ intensity light, cone cells are sensitive to _________ intensity light.
Rod cells are sensitive to LOW intensity light, cone cells are sensitive to HIGH intensity light.
Why are many rod cells connected to a single sensory neurone?
- To allow retinal convergence to occur.
- The is a greater chance of the threshold value being exceeded to allow an action potential to occur along the sensory neurone. (note: you will need to study next topic to fully understand this).
Which pigment, that breaks down in low intensity light, is found inside rod cells?
Rhodopsin
Because each rod cell connects to multiple single sensory neurones the light from each neurone is not individually distinguishable. This means that rod cells can only produce…
LOW VISUAL ACUITY (low resolution)
How many types of cone cell are there?
3
Each of the three types of cone cell contain a specific group of pigments called…
iodopsins
Does iodopsin break down in the presence of low or high intensity light?
high intensity
Cone cells are connected to their own individual sensory neurone. True or False?
TRUE
Because each cone cell connects to a single sensory neuron the light from each neurone is individually distinguishable. This means that cone cells can produce…
HIGH VISUAL ACUITY (high resolution)
The lens of the eye focuses light at a central point in the retina called the…
fovea
The outer periphery of the retina (not the fovea) contains _________ cells
Rod cells
The fovea is where ________ cells are found because it receives the highest intensity of light.
Cone cells
Describe how a pacinian corpuscle works
- Pressure is applied and the lamella is deformed
- Stretch mediated sodium ion channels open
- Na+ diffuse into axon
- Leading to depolarisation and action potential if threshold is exceeded
Describe convergence in rod cells
- Rods are found around the outside of the retina, away from the fovea
- Light stimulus triggers depolarisation in the rod cells
- Many rods converge and are connected to a single sensory neurone
- Depolarisation undergoes (spatial) summation to trigger an action potential
- In low light there is enough light to lead to action potential
- However, this reduces visual acuity
Describe acuity in cone cells
- Cone cells are located in the fovea (behind the retina to maximise light stimulus)
- Every cone cell is connected to a single sensory neurone (no convergence)
- Each cone sends a single impulse to the brain
- With high visual acuity
- Three types of cones detect three different wavelengths of light
