Sensory Receptors Flashcards
What is the function of sensory receptors?
They inform your brain about external and internal environment.
What do sensory receptors turn stimuli into?
The frequency of action potentials.
Name three tyes of sensory receptor.
Mechanoreceptors, proprioceptors and nociceptors.
Describe mechanoreceptors.
Stimulated by mechanical stimuli - pressure, stretch, deformation - give us skin sensations of touch and pressure
What are proprioceptors?
Mechanoreceptors in joints and muscles. They signal information about body or limb position
Describe nociceptors.
Respond to painful stimuli
What receptors are found in the nose and tongue?
Chemical receptors.
What receptors are found in the ears?
Sound and position receptors
What receptors are found in the eyes?
Light receptors
What receptors are found in the skin?
Touch, pain, temperature and pressure receptors.
What is sensory modality?
The stimulus type that activates a particular receptor: eg. touch, pressure, joint angle, pain
What is an adequate stimulus?
The form of energy to which a receptor normally responds.
Minimum amount of energy required.
What does sensory receptor transduction involve?
The opening and closing of ion channels.
What is receptor potential/ generator potential?
When an adequate stimulus causes a graded membrane potential change (only a few mV) –
What is the adequate stimulus in cutaneous mechanoreceptors and proprioceptors?
Membrane deformation.
What does membrane deformation activate?
Activates stretch-sensitive ion channels – so ions flow across the membrane and change the membrane potential locally.
When do action potentials start firing?
When depolarisation reaches the area with voltage-gated ion channels (the first node of Ranvier)
How does stimulus intensity impact the production of action potentials?
Lowest stimuli intensity=no action potentials
Highest stimuli intensity= most action potentials
In a sensory nerve, a larger stimulus…?
Causes a larger receptor potential and a higher frequency of action potentials (frequency coding of stimulus intensity).
The info from the receptors on the skin depends on what?
The properties of nerve endings and of accessory, non-neuronal structures
Why do nociceptors not adapt?
As they detect pain due to the free nerve endings, it is important not to ignore pain generated.
Describe the Pacinian corpuscle.
Mechanoreceptor
It comprises a myelinated nerve with a naked nerve ending
enclosed by a connective tissue capsule of layered membrane lamellae
each layer is separated by fluid : (a bit like a spongy onion)
How does the Pacinian corpuscle respond?
- A mechanical stimulus deforms the capsule and the nerve ending
- This stretches the nerve ending and opens ion channels
- Na+ influx causes local depolarisation - a receptor/generator potential
- APs are generated and fire where myelination begins (because regenerative Na+ channels cluster at nodes of Ranvier)
What component of sensory receptors mean that you can feel an itch?
Receptive fields
->a somatic sensory neuron is activated by stimuli in a specific area called the receptive field
A touch-sensitive neuron in the skin responds to pressure within a defined receptive field (area of skin)
