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Biological Psychology > Sensory Systems > Flashcards

Sensory Systems Flashcards

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1
Q

SENSE ORGANS & BODY SYSTEMS

A
  • structures w/receptors/interneurons specialised for detecting/processing particular stimuli types
  • sensory organs = eye/ear
  • body systems = touch
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2
Q

MECHANICAL SENSORY SYSTEM

A

MODALITIES & ADEQUATE STIMULI

  • touch = contact w/ or deformation of body surface
  • pain = tissue damage
  • hearing = sound vibrations in air/water
  • vestibular = head movement/orientation
  • joint = position/movement
  • muscle = tension
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3
Q

VISUAL SENSORY SYSTEM

A

MODALITIES & ADEQUATE STIMULI

- seeing = visible radiant energy

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4
Q

THERMAL SENSORY SYSTEM

A

MODALITIES & ADEQUATE STIMULI

  • cold = skin temp decrease
  • warmth = skin temp increase
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5
Q

CHEMICAL SENSORY SYSTEM

A

MODALITIES & ADEQUATE STIMULI

  • smell = odorous substances dissolved in air/water in nasal cavity
  • taste = substances in contact w/tongue
  • common chemical = changes in CO2/pH/osmotic pressure
  • vomeronasal = pheromones in air/water
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6
Q

ELECTRICAL SENSORY SYSTEM

A

MODALITIES & ADEQUATE STIMULI

- electroreception = difs in electrical current density

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7
Q

SENSORY RECEPTOR NEURONS

A
  • specialised neurons detect internal/external stimuli of particular sensory modality
  • input zone gen contains accessory structures/receptor molecules/specialised ion channels instead of dendrites
  • transduction = transforming stimulus energy into neural signals transmitted to sensory interneurons
  • filtering stimulus energy as have defined affinity/sensitivity range
  • either spiked/non-spiking neurons
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8
Q

PHOTORECEPTORS

A
  • axon terminals
  • axon
  • cell body w/nucleus w/DNA
  • accessory structure = light-sensitive receptor molecules in membrane
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9
Q

MECHANORECEPTORS

A
  • accessory structure = stereocilia w/ion-channels in membrane
  • no axon/axon terminals
  • input zone = axon/tissue layers (accessory structure) around unmyelinated end w/membrane ion channels
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10
Q

SIGNAL TRANSDUCTION IN RECEPTOR CELLS

A

MECHANORECEPTORS
- mechanical stimulus energy/perceived = pressure/vibration/stretch/sound
PHOTORECEPTORS
- electromagnetic stimulus energy/perceived = light
THERMORECEPTORS
- heat stimulus energy/received = temp (warm/cold)
CHEMORECEPTORS
- chemical stimulus energy = airborne/surface molecules
- stimulus perceived = odour/taste (sweet/bitter/umami/salty/sour)
NOCICEPTORS
- mechanical/thermal/chemical stimulus energy (uni/polymodal)
- stimulus perceived = pain

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11
Q

SIGNAL TRANSMISSION IN SENSORY SYSTEMS

A 
TONGUE
- taste receptors/sensory interneurons
EYE
- photoreceptor/sensory interneurons
EAR
- hair cells/sensory interneurons
SKIN
- pacinian corpuscle
NOSE
- olfactory receptor
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12
Q

REFLEX ARCS = BASIC NEURAL CIRCUITS

A
  • reflex arcs synapse in spinal cord
  • knee-jerk reflex = v fast (40ms latency) connecting sensory (receptor) neuron directly to motor neuron (monosynaptic = w/o interneurons)
  • reflex arcs often more complex (polysynaptic = w/several interneurons)
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13
Q

SENSORY NEURONS CONNECT TO 1+ CIRCUITS

A
  • sensory neurons (receptor neuron/interneuron) = afferent neurons
  • motoneurons = efferent neurons innervating effector muscle
  • spinal interneurons = mono/disynaptic somatic reflex arcs from muscle spindle -> motorneuron/other somatic reflex arcs from skin mechanoreceptors -> same motorneuron
  • sensory neuron A = first order interneuron in disynaptic arc BUT also second/third order in other arcs
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14
Q

SENSORY SYSTEMS

A

receptors -> thalamic nuclei -> PSC (primary sensory cortex) -> SSC (secondary sensory cortex) -> association cortex

  • good egs demonstrating main principles of how brain is organised/works
  • many connect to brain
  • sensory signals typically transmitted in processing step hierarchy
  • info filtered/combined/enhanced as passes from 1 layer -> next in serial fashion
  • each layer has networks composed of input/output neurons & as many interneurons
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15
Q

BRAIN CONNECTIVITY

A
  • identified anatomically/functionally
  • anatomical connection descriptions give v limited insight to functional hierarchies/info flow
    SERIAL CONNECTIONS
  • bottom-up processing (ie. sensory organ -> primary cortex); top-down control (ie. modulation/inhibition/synchronisation)
    PARALLEL STREAMS
  • (ie. signals diverge to dif networks)
    CROSS-CONNECTIONS
  • (ie. modulation/inhibition/synchronisation)
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16
Q

MECHANORECEPTORS

A
  • each (stretch/vibration/pain/touch) has distinct path to brain so dif skin stimulation qualities communicated to distinct brain areas
    TOUCH/PAIN
  • diverse receptors in skin/body
    POSTURE CONTROL
  • propioreceptors in body (muscles/joints)
    HEARING
  • inner ear hair cells
    BALANCE CONTROL
  • vestibular receptors in vestibular apparatus
17
Q

SKIN SENSITIVITY TO MECHANICAL STIMULATION

A
  • several somatosensory systems
  • encapsulated nerve endings; long/myelinated axons
  • soma located in dorsal root (spinal) ganglia of spinal cord
18
Q

SMALL/LARGE NEURON RECEPTIVE FIELDS

A

SMALL RECEPTIVE FIELDS
- in touch-sensitive receptors
- free nerve endings
- Merkel’s disc/Meissner’s corpuscle sense innervates skin surface; sensitive to stimuli in small skin areas
WIDE/LARGE RECEPTIVE FIELDS
- Pacinian corpuscles/Ruffini’s endings innervate deeper skin layers; sensitive to stimuli over large areas

19
Q

RECEPTORS TRANSMIT SIGNALS FROM SKIN -> SPINAL CORD

A
  • pacinian corpuscle (skin/muscles detect vibration/pressure) = unipolar cell extending one axon branch to skin; other to spinal cord
  • afferent projections form dorsal root (spinal) nerve; cell bodies part of dorsal root ganglion
20
Q

MECHANICALLY-GATED ION CHANNELS

A
  • vibration/pressure on skin deforms corpuscle; stretches axon tip opening mechanically-gated ion channels
  • concentric tissue layers around axon tip amplify signal
21
Q

SENSORY SIGNAL TRANSMISSION IN SPIKING RECEPTOR NEURON

A
  • similar to postsynaptic neuron dendrites; receptors respond to stimulation w/graded/receptor potential
  • spiking receptor neurons convert graded receptor potential -> action potentials for fast/long-distance transmission along axon
22
Q

RECEPTOR NEURON RESPONSE THRESHOLDS

A
  • receptors respond to stimulus in limited stimulus intensities range
  • when sensing 2 dif low-intensity stimuli:
    1. Merkel’s disc = 2 dif spike rates
    2. Pacinian corpuscle = no spikes
  • when sensing 2 dif high-intensity stimuli:
    1. Merkel’s disc = max spike rates
    2. Pacinian corpuscle = 2 dif spike rates
23
Q

COMBINING RECEPTOR NEURONS W/DIF SENSITIVITIES

A
  • sensory systems can combine receptor neurons w/dif sensitivities (dif thresholds)
  • useful for extending intensities range (ie. gentle touch -> strong pressure)
  • graphs refer to receptor signals summation to measure intensity over large range BUT sensory systems oft also compare dif receptor signals (signal subtraction) to differentiate between stimuli
24
Q

RECEPTOR ADAPTATION

A
  • thresholds adapted over time
  • receptor neuron responds to stimulus in limited stimulus intensities range; shifts threshold in limited range to code for prevailing stimulus intensities range (sensory adaptation)
  • maximises coding efficiency when exposed to continuous/unchanging stimuli
  • stimuli intensities range oft varies over time
25
Q

STIMULATION ADAPTATION

A
  • tonic receptors = receptor neurons showing slow response loss
  • phasic receptors = receptor neurons showing fast response loss shortly after stimulation onset
26
Q

RECEPTOR RESPONSE PROPERTY DIVERSITY

A 
SMALL FIELD X TONIC
- Merkel's disc (sensing texture)
SMALL FIELD X PHASIC
- Meissner's corpuscle (vibration)
LARGE FIELD X TONIC
- Ruffini's ending (sustained contact)
LARGE FIELD X PHASIC
- Pacinian corpuscle (initial contact)
27
Q

RECEPTOR POTENTIAL -> SENSORY INFO

A 
- ie. holding coffee cup
PACINIAN CORPUSCLE (VIBRATION)
= initial contact w/cup ->
MEISSNER'S CORPUSCLE (TOUCH)
= detects if cup slips ->
MERKEL'S DISCS (TOUCH)
= detects texture of cup ->
RUFFINI'S ENDING (STRETCH)
= hand in contact w/cup
28
Q

SOMATOSENSORY PATHWAY

A
  • segregated projections to dif brainstem/thalamus/cortex (labelled-line principle) areas
  • where possible spatial stimuli location info preserved by separating projections coming from receptors in dif locations
  • important to know where stimulation occurred in body (ie. if hand/back touched)/relative to body (ie. if wind blows into face/neck)
29
Q

RECEPTIVE NEURON FIELDS

A
  • receptive fields can be mapped for neurons in sensory pathway
30
Q

CORTICAL ENCODING VIA SOMATOTOPIC MAPS

A
  • primary somatosensory cortex located in postcentral gyrus in parietal lobe of brain (Brodmann areas 1/2/3a/3b)
  • adjacent body regions generally encoded in adjacent cortex regions
  • cortical somatotopic mao sensory segregation = fast adapting signals (from Meissner’s/Pacinian’s) & slow adapting signals (Merkel’s/Ruffini’s) remain segregated in cortex
31
Q

VERTEBRATE/INVERTEBRATE SENSORY MAPS

A
  • somatosensory map in cortex of star-nosed mole for dif tips of nose (touch organ)
32
Q

EXPERIENCE DEPENDENT CORTICAL MAPS PLASTIC REORGANISATION

A
  • cortical representations can change w/use
  • owl monkey trained for several months at task w/2-4 fingers
    ELBERT et al (1995)
  • investigated dipole strength in string players
    YANG et al (1994)
  • region formerly stimulated by receptors in hand now responds to face/arm touch post somatosensory cortex reorganisation
33
Q

STOPPING/SUPPRESSING SENSORY INPUT

A
  • nerve cells require inhibition; receptors/conveyed signals require “switch off” times
  • suppression oft involves accessory organs; structures reduce intensity/alter stimulus before it reaches receptor (ie. eyelids/ear muscles)
  • can be via top-down processes (ie. brain stem sends messages to receptor cells in ear to selectively dampen sounds)
34
Q

SUMMARY

A
  • receptor neurons specialised to detect stimuli of particular sensory modalities/filter stimulus info/transform stimulus energy -> neural signals
  • serial processing of receptor input = sensory processing that isn’t exclusively serial/hierarchical
  • mechanoreceptors (ie. Pacinian corpuscle) transmit signals skin -> spinal cord
  • info filtering/coding = receptor neurons can have dif receptive fields/response thresholds
  • receptors adapt threshold over time to optimise stimuli coding; can be fast (phasic)/slow (tonic)
  • sensory paths = dif receptor project to dif areas of brainstem/thalamus/cortex
  • somatotropic maps = adjacent regions on body gen encoded in adjacent

Biological Psychology (21 decks)

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