Receptors Flashcards
What are the types of receptors?
- thermoreceptors
- pain receptors
- mechanoreceptors
- photoreceptors
- chemoreceptors
What are the roles of receptors?
- respond to a single specific stimulus at a certain intensity and act as transducers
What are transducers?
- convert a type of stimulus into an electrical signal (first a generator potential followed by an action potential in sensory neurone)
What are the stimuli for thermoreceptors?
- temperature change
What are the stimuli for pain receptors?
- tissue damage
What are the stimuli for mechanoreceptors?
- movement
- pressure
- tension
What are the stimuli for photoreceptors?
- light
What are the stimuli for chemoreceptors?
- chemicals
What are three examples of sensory receptors?
- Pacinian corpuscle
- Photoreceptors
- Chemo and pressure receptors
What does the pacinian corpuscle do?
- responds to mechanical pressure
What do photoreceptors (rods and cones) do and where are they located?
- respond to light in the retina
What do chemo and pressure receptors do?
- control heart rate
Where are thermoreceptors located?
- skin
- hypothalamus
Where are pain receptors located?
- all tissues and organs except brain
Where are mechanoreceptors located?
- skin
- ears
- muscles
Where are photoreceptors located?
- eyes
Where are chemoreceptors located?
- tongue
- nose
Where would you find pacinian corpuscles?
- deep in the skin: fingers, soles of feet, external genitalia, joints, ligaments and tendons
How does the pacinian corpuscle respond to stimulus?
- Ending of sensory neurone at centre of pacinian corpuscle has stretch mediated sodium ion channels in its plasma membrane
- In resting state, these stretch mediated channels are too narrow to allow sodium to pass through. Nerve has a resting potential
- When pressure is applied to the corpuscle it changes the sensory neurone membrane which changes the shape of the sodium ion channels (widen)
- Sodium channels open and sodium ions diffuse in cussing the neurone to become depolarised. Receptor generator potential is set up leading to all or nothing response (action potential) which passes along sensory neurone
Describe the structure of the pacinian corpuscle
- lamellae layers of membrane (connective tissues with viscous gel between)
- capsule
- myelinated sensory neurone
- blood vessel
- single nerve fibre
Comparison of rods and cones (photoreceptors)
- rods are rod shaped, cones are cone shaped
- rods are greater number than cones, cones are fewer number then rods,
- rods cannot distinguish between different wavelengths of light so produce black and white images, cones (3 types): each have peak light absorption at different wavelength (blue sensitive, green sensitive, red sensitive), many wavelengths absorbed by more than one type of cone cell so perceived colour depends on proportion of cones stimulated
- many rod cells attach to single bipolar cell (retinal convergence) so easier to exceed threshold value, cones often have their own separate bipolar cell connected to a sensory neurone so more difficult so exceed threshold value
- rods have poor visual acuity (stimulation of multiple rods still only produce single impulse and cannot distinguish between separate sources of light stimulating them), cones have good visual acuity (produces separate impulses as each one connected to single bipolar cell, can distinguish between separate sources of light stimulating them)
- rods contain rhodopsin pigment which must be broken down to create generator potential, low light intensity is sufficient to break this dow, cones contain iodopsin pigment which needs higher light intensity to break it down so explains why it cannot respond to low light intensity. Cannot combine stimulation of multiple cone cells to produce the generator potential as only one connected to each bipolar cell
Complete achromatopsia is a form of complete colour blindness. It is caused by having only rods and no functional cone cells. People with complete achromatopsia have difficulty in seeing detail. Explain why.
- no functional cones only rods
- cones are connected to a single neurone
- cones separate impulses to the brain
