Sensory Receptors Flashcards
What are sensory receptors?
Sensory receptors are nerve endings which are often specialised with some non-neural structures. They transduce and convert energy into action potentials.
What do sensory receptors do?
Convert sensory information / energy into action potentials.
What are the 3 types of sensory receptor?
Mechanoreceptors
Proprioceptors
Nociceptors
What do mechanoreceptors do?
Stimulated by mechanical stimuli (pressure/stretch/deformation/touch/pressure).
What do proprioceptors do?
Mechanoreceptors in the joints and muscle (signal info about body and limb position).
What do nociceptors do?
Respond to painful stimuli, tissue damage and heat.
What sensory receptors are stimulated by mechanical stimuli?
Mechanoreceptors.
Where do proprioceptors exist?
Joints and muscles.
What type of sensory receptor responds to pain?
Nociceptor.
What are cutaneous mechanoreceptors and proprioceptors a good example of?
Peripheral sensory processing and ion channel transduction.
What does an adequate stimulus cause?
Graded potential membrane change.
What is the graded potential membrane change called in sensory receptors?
Receptor potential or generator potential.
What does membrane deformation lead to?
Activates stretch-sensitive ion channels so ions flow across the membrane and change the membrane potential locally.
What is generator potential graded to?
Stimulus intensity.
What does generator potential trigger?
Triggers ions to flow through the membrane locally and when depolarisation reaches the VG-ion channel area, action potentials start firing.
When do action potentials start firing?
When depolarisation reaches the VG-ion channel area.
What is frequency coding?
In a sensory nerve, a larger stimulus causes a larger receptor potential and a larger frequency of action potentials.
What is the link between larger generator potential and larger frequency of action potentials called?
Frequency coding.
What is the skin packed with?
Sensory receptors for touch.
What does the information of skin touch receptors depend on?
Properties of nerve endings and of accessory, non-neural structures.
What is adaptation?
Adaptation occurs when mechanoreceptors only respond to a change or novel event.
Do different receptors show the same level fo adaptation?
No- they all show different levels.
How are adapting receptors characterised?
Rapid/moderately adapting receptors
Slow adapting receptors
Do nociceptors adapt?
No.
Why do nociceptors not adapt?
To prevent painful stimuli from being ignored.
What is the best understood mechanoreceptor?
Pacinian corpsicule.
What is the Pacinian corpsicule?
Best understood mechanoreceptor.
How is the Pacinian corpsicule structured?
It comprises a myelinated nerve with a naked nerve ending enclosed by a connective tissue capsule of layered membrane lamellae with each layer separated by fluid.
What is each layer of membrane lamellae separated by in the Pacinian corpsicule?
Fluid.
What happens in the Pacinian corpsicule after a stimulus is detected?
A mechanical stimulus deforms the capsule and nerve ending. This stretches the nerve ending and opens ion channels. Na+ influx causes local depolarisation (generator potential)- APs are generated and fire where myelination begins.
What causes the opening of ion channels in the Pacinian corpsicule?
Stretching of nerve ending.
What causes the local depolarisation in the Pacinian corpsicule.
Na+ influx causes local depolarisation resulting in a generator potential.
Does the Pacinian corpsicule show adaptation?
Shows rapid adaptation through fluid distribution.
What does rapid fluid distribution cause in the Pacinican corpsicule?
Rapid adaptation.
What happens to Pacinian corpsicule adaptation of lamellae are lost?
Adaptation is lost.
What happens do Pacinian corpsicule if the capsule is intact?
On/off function remains intact.
What happens to Pacinian corpsicule if the capsule is damaged?
Bare nerve ending loses adaptation because a continuous generator potential is upheld.
What is the function of the Pacinian corpsicule dependent on?
Accessory non-neural capsule structure.
What does the capsule non-neural accessory structure do in the Pacinian corpsicule?
Enhances sensory function.
What are receptive fields?
Specific areas where somatic sensory nerves are stimulated.
In what areas are somatic sensory nerves stimulated?
Receptive fields.
What is the name of a test that measures our ability to determine 2 points on the skin?
2 point discrimination test.
What is our ability to determine 2 points dependent on?
Receptive field size
Neuronal convergence
What is neuronal convergence?
When multiple presynaptic neurons input on a smaller number of post-synaptic neurons.
What neurones exhibit neuronal convergence?
Neurones with neighbouring receptive fields.
What might neurones with neighbouring receptive fields exhibit?
Neuronal convergence.
What does convergence allow?
Summation of sub-threshold stimuli.
What do lots of convergence and a large receptive field indicate?
Low sensitivity.
What areas of the body are sensitive?
Fingers/lips are more sensitive than limbs/back.
What is acuity?
Acuity is the ability to locate a stimulus on the skin and differentiate it from another close by.
What is low acuity caused by?
Low acuity = high levels of convergence.
What is lateral inhibition?
Lateral inhibition is when the surrounding lateral areas around a sensory area are inhibited in order to sharpen the contrast between relevant and irrelevant information.
