3.6.1.2 Receptors Flashcards
What is a cholinergic synapse?
A synapse with the neurotransmitter acetylcholine
What is acetylcholine composed of?
Acetyl and choline
What are receptors?
Cells or proteins which detect stimuli (energy)
Can only detect a specific stimulus e.g. light
Can create generator potentials in sensory neurones
Can act as transducers which convert one form of energy to another
What is the Pacinian corpuscle?
Receptor which can detect mechanical stimuli
The corpuscles wrap around the sensory nerve ending in layers of connective tissue called lamellae
What does compression of the lamellae cause?
A sodium influx (due to stretch-mediated Na+ channels) which causes an action potential
Where are Pacinian corpuscles found?
Abundant in the hands and feet
Also found in ligaments and tendons to determine which joints are changing direction
What are the steps of the compression of the Pacinian corpuscle?
Shape of the corpuscle changed
Stretch-mediated Na+ channels open
Na+ diffuses into the neurone
The membrane is depolarised
A generator potential is produced
The greater the pressure, the greater the generator potential
The action potential develops if the threshold is reached
What is the process of photoreceptors?
Light enters the eye through the pupil
The amount of light entering is controlled by the muscles in the iris
The lens focuses the light rays onto the retina
The retina contains the photoreceptor cells
What is the forea?
An area of the retina with loads of receptors
How do nerve impulses from the photoreceptor cells get to the brain?
They are carried from the retina to the brain via the optic nerve (a bundle of nerves)
What is the blindspot caused by?
The spot where the optic nerve leaves the eye
What is the process of information from the eyes reaching the brain?
Light sensitive optical pigments absorb light and chemically breakdown
Na+ permeability changes in the photoreceptor (Na+ channels close) and neurotransmitter release stops
A generator potential can be created in the bipolar neurone
A signal is transmitted to the brain
What do rod and cone cells act as?
Transducers by conserving light energy into the electrical energy of a nerve impulse
What are rod cells?
Lead to black and white imagery
More numerous than cone cells
Many connected to a single sensory neurone
Certain threshold has to be exceeded before a generator potential is created
Three connected to one bipolar cell which creates a greater chance of exceeding the threshold due to summation
Pigment must be broken down to create a generator potential
Give low visual acuity
Found in higher concentrations further away from the fovea
What are cone cells?
Three types each responding to a different range of wavelength of light
The proportion of each causes images to be in full colour
One cone cell connects to one bipolar cell
Only respond to high light intensity due to no summation
Requires a higher light intensity to break down the pigment
High visual acuity
Found at the forea
