Sensory Receptors 1 Flashcards
What is a transducer
Something that converts various forms of energy to into Action Potentials. With energy stength represented by AP frequency
Define sensory modality:
The type of stimulus activating a specific receptor
Define adequate stimulus:
The type of energy a receptor normally responds to. can also respons to extremes of other energies (i.e. the eye normally repsons to light but youll see stars if someone pokes you in the eye)
What do mechanoreceptors detect?
Pressure, touch, hearing, balance, blood pressure
What do proprioceptors detect?
Postion of limbs or body parts from the joints and muscles
What receptors detect painful stimuli?
Nociceptors.
What type of graded membrane potential change is produced by an adequate potential?
A generator potential or receptor potential
What is the adequate stimulus in cutaneous mechanoreceptors and how does it trigger a generator potential?
Membrane deformation from pressure and activates stretch-sensitive ion channels in the membrane.
What effect does increasing the stimulus intensity have on APs?
It increases the number (or frequency) of APs.
lager stimulus = larger receptor (generator) potential = higher frequency of APs
What does the number of receptors activated refelct?
Stimulus intensity.
What do merkel receptors detect?
Steady pressure & texture
What receptors detects flutter or stroking movements?
Meissners corpuscles
What part of a nociceptor detects noxious stimuli?
Free nerve endings
What do ruffini corpuscles respond to?
SKin stretch
How is vibration detected in the skin?
By pacinian corpuscles
How is har movement detected?
By free nerve endings in the root.
What does adaptation mean in reference to mechanoreceptors?
Some mechanoreceptors only respond to changes in stimuli, i.e. they adapt to a maintained stimulus. i.e. the feel of putting clothes on stops until we take them off again (changes in the stimuli)
What is the diffence between rapidly and slowly adapting receptors?
rapidly adapting stop sendin APs very quickly then send them again briefly when the stimulus drops off again.
Slowly adapting send many fewer APs but dont stop completely and dont increase aain when the stimulus ends.
Name two types of rapidly adapting receptors?
Pacinian corpuscles and meissners corpuscles.
Name two types of slowly adapting corpuscles:
Merkels discs and ruffini endings.
Why dont Nociceptors adapt?
Because its important not to ignore painful stimuli
Explain the structure of a pacinian corpuscle:
Onion like. A conncetive tissue capsule made from layers of membrane lamellae seperated by fluid.
Contains a naked nerve ending attaching to a myelinated nerve.
How does a pacinian corpuscle detect vibration?
Stimulus deforms the capsule and nerve ending
Stretchin nerve ending opens stretch-sensitive ion channels
Allows influx of Na+ which causes local depolarisation. (generator potential)
APs fire at myelinated nerve
How do pacinian corpuscles adapt?
Fluid redistribution quickly removes the mechanical stretch on the nerve ending, essentially dissipating the stimulus.
When the stimulus withdraws the capsule springs back and APs fire again.
What happens if the connective tissue capsule is removed from a pacinian corpuscle?
Then it loses the ability to adapt and continues to produces generator potentials.
What non-neural accessory structure is cirtical to a pacinian corpuscle?
The connective tissue capsule (membrane lamellae seperated by fluid)
What is a receptive field?
A receptive field is the area of receptors in which a stimuli will acitvate a specific somatic sensory neuron.
What determines our ability to tell between feelingon two points of our skin?
Receptive field size for each neuron and neuronal convergance.
Why is converance of senseory neurons useful?
Allows simultaneous sub-threshhold stimuli from multiple nearby sensory neurons to sum at the secondary sensory neuron and trigger an AP. (i.e. forms a large secondary receptive field.)
A relatively insensitive area (e.g. back) has what qualities?
Convergance of sensory neurons and a large secondary receptive field.
Define acuity:
The ability to locate a stimulus on the skin and differentiate from another close by
What is lateral inhibition?
Sensory receptors at the edge of stimuli are heavily inhibited compared with those at the centre.
Why is lateral inhibition useful?
It enhances the contrast between relavent and irrelevant info. making the stimulus more obvious.
How does lateral inhibition occur?
The secondary neuron of the pathway closest to the stimulus inhibits its neighbours.
Where does sensory information go?
To the brain to be relayed through the thalamus to the somatosensory cortex
Why is our cortical body map distorted?
The most sensitive areas occupy the bigest cortical space
