Sensory Systems Flashcards
What are the sensory systems?
Hearing, touch, vision, taste, smell, balance, thermoreception, nociception, proprioception
What types of energy can stimulate sensory systems?
Mechanical, chemical, light
What encodes the strength of a sensory stimulus?
Amplitude of generator potential and frequency of action potentials
What are the two ways a signal can be transmitted in response to a sensory stimulus?
Sensory neurones and epithelial receptors
What are the four extero-mechanoreceptors?
Merkel’s disc, Meissner’s corpuscle, Ruffini’s end organ, Pacinian corpuscle
Which extero-mechanoreceptors are deep?
Ruffini’s and Pacinian
Which extero-mechanoreceptors are superficial?
Merkel’s and Meissner’s
What are the three classes of special exteroreceptors?
Photoreceptors (rods and cones), mechanoreceptors (hair cells) and chemoreceptors (gustatory and olfactory)
What are the three classes of general exteroreceptors?
Mechanoreceptors, thermoreceptors, nociceptors
What are the general proprioceptors?
Mechanoreceptors: Golgi tendon organ, muscle spindle, joint capsule
What are the special proprioceptors?
Mechanoreceptors: Hair cells in otolith organs and semicircular canals
What are the ineroreceptors?
Baroceptors (mechanoreceptors), glucoreceptors and osmoreceptors (chemoreceptors)
What are the properties of tonic reception?
Slowly adapting, repeated membrane potential spikes throughout stimulus duration
What are the properties of phasic reception?
Rapidly adapting, membrane potential responses at the start and end of stimulus duration only
What determines the location of a shingles rash?
Which sensory nerve is infected by the virus
What is a receptive field?
Area of skin surface over which stimulation results in a change of action potentials
What effect does a high density of receptors have on the receptive field?
Smaller receptive fields of individual afferent fibres
What is 2-point discrimination a measure of?
Spatial acuity
Where on the body is the highest spatial acuity?
Fingertips
How do receptive fields and spatial acuity link?
Small receptive field -> high spatial acuity (and vice versa)
What is the dorsal column-medial lemniscal system?
Neurones transducing from the body to the somatosensory cortex
What is the trigeminothalamic system?
Neurones transducing from the face to the somatosensory cortex via the thalamus
What are the properties of the Pacinian corpuscle?
Sub-cutaneous, very large receptive field, very low spatial acuity, low density
What are the properties of Ruffini’s corpuscle?
Dermal, large receptive field, low spatial acuity, very low density
What are the properties of Merkel’s disc?
Dermal/epidermal, very small receptive field, very high spatial acuity, very high density
What are the properties of Meissner’s corpuscle?
Epidermal, small receptive field, high spatial acuity, high density
What generates sound?
Movement of air molecules
What is the hearing range of humans?
20 - 20,000 Hz
How are signals amplified in the middle ear?
Force of large tympanic membrane focused onto small oval window
What is the basilar membrane?
Tapered structure that undulates up and down according to frequency
What are hair cells bathed in?
High [K+] endolymph
What type of input do outer hair cells receive?
Efferent
What type of input do inner hair cells receive?
Afferent
What is the kinocilium?
The longest stereocilium of a hair cell
What do stereocilia contain?
Actin filaments and microtubules
What are tip links?
Connections of mechanically gated ion channels on stereocilia
How do de- and hyperpolarisation of hair cells differ to neurones?
Both are K+-dependent
What is the graded response of stereocilia movement?
Generator potential
What is the tonotopic organisation of the basilar membrane an example of?
Labelled line coding
What do outer hair cells do?
Amplify motion of basilar membrane and enhance responsiveness of inner hair cells by electromotility
What do cochlear amplifiers do?
Enhance amplitude and sharpness of sounds
What are the steps of auditory signal amplification?
Acoustic energy -> basilar membrane displacement -> modulation of current thorough OHCs and AP generation by IHCs -> mechanical transduction of OHCs -> acoustic energy
Where does information from each ear enter the auditory system?
Superior olive in mid-pons
What is described by the Jeffress model?
Sound localisation in the horizontal plane
What is theorised in the Jeffress model?
Neural circuits can encode short inter-aural time differences by acting as coincidence detectors for two or more signals
Where does sound localisation in the horizontal plane take place?
Medial superior olive
What is detected by proprioception?
Limb position
What is detected by the vestibular system?
Head position, self-motion and spatial awareness
What type of movement is detected by otolith organs?
Translational
What type of movement is detected by semi-circular canals?
Rotational
What are the otolith organs?
Utricle and saccule
Where in semi-circular canals are hair cells located?
Ampullae
Which movement plane is sensed by utricles?
Horizontal
Which movement plan is sensed by saccules?
Vertical
What is the macula?
Sensory epithelium of utricles and saccules
What is the otolithic membrane?
Gel layer with calcium carbonate crystals (otoconia)
Where is the reticular membrane?
Between hair cells and otolithic membrane
What is the striola?
Axis of symmetry for head position sensing, to which stereocilia are orientated towards
How many semi-circular canals are in each ear?
Three
How does transduction occur in vestibular hair cells?
Open K+ channels depolarise cells, triggering glutamate release
Where are vestibular signals integrated?
Brainstem
What does the vestibular-ocular reflex control?
Stabilising movement of eyes when the head moves
What is oscillopsia?
Damage to vestibular system causing bouncing vision
