Sensory Nerves/body sensation Flashcards
What is sensory modality?
That different type of stimulus are picked up by specialised receptors
What are mechanoreceptors?
Sensory receptors that are stimulated by mechanical stimuli - touch stretch, pressure, deformation.
Detect many stimuli, balance hearing
What are proprioceptors?
Mechanoreceptors in joints and muscles that signal information information related to body or limb position.
What are nociceptors?
Respond to painful stimuli
What is a graded membrane potential change called in a sensory nerve?
Receptor potential or a generator potential
Transduction always results in the opening or closing of ion channels
When do you get a higher frequency of action potentials?
When there is a larger stimulus since this causes a larger receptor potential, can also activate more receptors too
What is meant by adaptation of a mechanoreceptor?
When the mechanoreceptor stops producing action potentials to a maintained stimulus and only activates on a change or a novel event
Give an example of a sensory receptor that does not adapt?
Nociceptor, because it is important not o ignore a painful stimuli.
What is a pacinian corpsucle responsive to?
Vibration and pressure
Describe the structure of a pacinian corpsucle
Myelinated nerve, naked nerve ending. The nerve ending is enclosed in a connective tissue capsule. This capsule contains layered membrane lamellae separated by fluid.
How are action potentials generated from a pacinian corpsucle
Mechanical stimuli deforms the capsule and nerve ending, causing ion channels to open, - generator potential and then action potential.
How is the pacinian corpsucle capable of rapid adaptation?
Fluid redistribution of corpsucle rapidly dissipates stimulus, nerve ending no longer stretched
What happens to the pacinian corpsucle when the stimulus is withdrawn?
Capsule springs back - more action potentials
What type of structure is the pacinian corpsucle?
Specialised Non-neural accessory structure
What is the receptive field?
The area that a stimuli will activate a sensory neurone
What does the ability to tell apart two points on the skin depend on?
The size of the receptive field and neuronal convergence
What is meant by convergence?
When multiple presynaptic neurones synapse with fewer post synaptic neurones
What does convergence allow?
Allows sub threshold stimuli to sum at the secondary neurone forming and initiating action potentials
How can we locate a stimulus so precisely?
Lateral inhibition of sensory neurones that are at the edge of the stimulus and those which are close to each other but have different strength of APs (Find exact location of pin prick)
What must depolarisation reach in sensory neuron to cause an action potential?
Voltage-gated sodium channels in first node of Ranvier
Does all adaptation occur at the same speed?
No, some receptors and fast/moderately adapting or slow adapting
Why do some receptors adapt?
Not all information is relevant, constant light pressure of back is not as important to be aware of as gaining or losing that pressure
What is the acuity of the back and hands?
Back - low acuity (fails two point discrimination test due to convergence and larger receptive field
Hand - high acuity (low convergence and small receptive fields, accurate two point discrimination)
How does sensory receptor information travel through the CNS?
Afferent nerve fibre synapses with interneuron which carries information up spinal cord to thalamus and somatosensory cortex
What is the relationship between sensitivity of body area and size of somatosensory cortex section used for that area?
The larger the area of somatosensory cortex dedicated to that area the more sensitive it is to stimuli (more discriminatory too)
