3.6.1.2 - Receptors Flashcards
Where does the central nervous system receive information from it external and internal environment?
receptors
What is the pacinian corpuscle?
- a receptor that responds to changes in mechanical pressure
What are features of all receptors (demonstrated by pacinian corpuscle?
- Only respond to a specific type of stimulus
( pacinian corpuscle only responds to mechanical pressure. ) - Stimulation of a receptor leads to the establishment of a generator potential
> by acting as a transducer - convert the change in form of energy by the stimulus into a nerve impulse/ generator potential
what is the function of the pacinian corpuscle?
- transduces the mechanical energy of the stimulus (eg: pressure) into a generator potential
where is the pacinian corpuscle found?
- occur deep in the skin
- most abundant on fingers, soles of feet, external genetalia
- also occur in joints/ligaments/tendons
describe the basic structure of a pacinian corpuscle
- sensory neurone ( axon to ending
- surrounded by layers of connective tissue - viscous gel between
- surrounded by blood capillary
- surrounded by capsule
What is the type of sodium channel in the plasma membrane of the sensory neurone at the centre of the pacinian corpuscle?
- stretch - mediated sodium channel
> permeability to sodium changes when they are deformed (eg: by stretching)
Describe how the pacinian corpuscle functions…
- in its resting state, the stretch-mediated sodium channels of the plasma membrane around the neurone of a pacinian corpuscle are too narrow to allow sodium ions to pass along them
> pacinian corpuscle is at resting potential - when pressure is applied to pacinian corpuscle it is deformed and the plasma membrane around its neurone becomes stretched
- stretching widens stretch-mediated sodium channels on plasma membrane allowing sodium ions to diffuse into the neurone (greater pressure causes more sodium channels to open - more sodiums ions enter)
- influx of sodium ions changes the potential of the plasma membrane and it becomes depolarised
> produces a generator potential - if generator potential reaches threshold it creates an action potential (nerve impulse) that passes along the neurone, via other neurones to central nervous system.
where are light receptor cells of the mammalian eye found?
retina (the inner most layer of eye)
What are the two main types of light receptor cells?
- rod cells
- cone cells
How do light receptors act as transducers?
- convert light energy into the electrical energy of a nerve impulse
Explain what the Pacinian corpuscle illustrates
● Receptors respond only to specific stimuli
○ Pacinian corpuscle only responds to mechanical pressure
● Stimulation of a receptor leads to the establishment of a generator potential
○ When threshold is reached, action potential sent (all-or-nothing principle)
Explain the differences in sensitivity to light for rods & cones in the retina
> Rods are more sensitive to light
● Several rods connected to a single neurone
● Spatial summation to reach / overcome threshold (as enough
neurotransmitter released) to generate an action potential
> Cones are less sensitive to light
● Each cone connected to a
single neurone
● No spatial summation
Explain the differences in visual acuity for rods & cones in the retina
> Rods give lower visual acuity
● Several rods connected to a single neurone
● So several rods send a single set of impulses
to brain (so can’t distinguish between
separate sources of light)
> Cones give higher visual acuity
● Each cone connected to a single neurone
● Cones send separate (sets of) impulses to brain
(so can distinguish between 2 separate sources
of light)
Explain the differences in sensitivity to colour for rods & cones in the retina
> Rods allow
monochromatic vision
● 1 type of rod / 1
pigment
> Cones allow colour vision
● 3 types of cones - red-, green- and blue-sensitive
● With different optical pigments → absorb different wavelengths
● Stimulating different combinations of cones gives range of colour perception
