Sensory systems

Question 1

Visual art and storytelling

Answer 1

1. emerges and develops as behavioural activity in different evolutionary and historical contexts
2. costly as time, effort and resources required
3. it is more than just intuitive or purely aesthetic use of lines, colours and dots, inherent reflection of cultural and social norms, use of symbols and colours for visual storytelling

Question 2

communication to reflect subjective sensations

Answer 2

1. art goes back extremely far
2. can look back to psychology in the past

Question 3

how can we explore and measure sensations

Answer 3

1. stimulus detection experiment
2. stimulus discrimination - which one is larger
3. stimulus magnitude estimation - how much larger
4. stimulus matching - which is similar in size to the sample
5. 2 alternative forced choice, response is either correct or incorrect

Question 4

Weber’s law - discrimination thresholds

Answer 4

1. to be just noticeable different, any stimulus must differ from another by a constant proportion not a constant amount
2. stimulus dimensions - intensity
3. observer dimensions - sensitivity, speed, accuracy, internal representations, adaptation state
4. threshold - difference between stimuli that observer discriminates correctly

Question 5

noise in stimuli, background and neurons

Answer 5

1. depends on adaptation state of receptors and neurons
2. background noise from varying loud traffic sounds makes it difficult to hear even if you’ve adapted to higher stimulus intensities
3. stimulus detection is impaired if background noise is high relative to strength of stimulus
4. Signal to noise ratio is a measure of the fidelity of signal transmission and detection by neurons and synapses. SNR also a metric to characterise activity of neural networks

Question 6

psychology as an experimental science

Answer 6

1. interest in understanding behaviour of human beings and animals and their minds in ancient civilisations
2. psychphysics - origins of psychology as an experimental science
3. first quantitative studies that presented systematic approaches to experimenting with sensory stimuli and mathematically describe the relationship between sensations and behavioural response
4. Weber and Fechner asked how fo we detect a sensory stimulus
5. Weber’s law - described just noticeable differences
6. Fechner’s law - intensity of a sensation increases as the logarithm of an increase in energy
7. Steven’s law - perceptual intensity increases as the nth power of stimulus intensity

Question 7

sensory systems - sense organs and pathways

Answer 7

1. sensory systems are structures containing receptor neurons, their specialised sensory interneurons and other projection layers of neurons that are specialised for detecting and processing particular types of sensory stimuli
2. these can include sensory organs or sensory body systems

Question 8

signal transduction in receptor cells

Answer 8

1. transduction - receptor cell transforms stimulus energy into neural signal

Question 9

sensory receptors specialised structures

Answer 9

1. sensory receptor neurons are specialised neurons that detect internal and external stimuli of a particular sensory modality
2. the receptor neuron’s input zone usually contains accessory structures, receptor molecules and/or specialised ion channels instead of dendrites
3. they transform stimulus energy into neural signals that are transmitted to sensory interneurons
4. they filter stimulus energy because they have a defined affinity and sensitivity range
5. receptors are either spiking or nonspiking neurons

Question 10

Enteric nervous system and sensory functions of the vagus nerve

Answer 10

1. gut brain axis - bidirectional communication via the vagus and spinal nerves, not only to maintain gut homeostasis but also regulating brain functions
2. sensory functions of the vagus nerve - critical for conscious perceptions and for monitoring visceral functions in the cardio-pulmonary and gastrointestinal systems
3. ENS - mesh like system of neurons that governs the functioning of the gut, gut microbiota, ENS supports local muscle reflexes for gut motility, vagus nerve projects to enteric neurons

Question 11

sensing external stimuli with our sensory organs

Answer 11

1. taste receptors and sensory interneurons in the surface of the tongue
2. photoreceptors and sensory interneurons in the retina of the eye
3. hair cells and sensory neurons in the inner ear
4. pacinian corpuscles in the skin
5. olfactory receptors in the olfactory epithelium of the nose

Question 12

sensory projections to brain areas are segregated

Answer 12

brain discriminates between different information encoded in sensations by processing them in different neural pathways and networks

Question 13

mechanoreceptors

Answer 13

1. touch and pain - diverse receptors in skin and body
2. posture control - proprioceptors in the body
3. hearing - hair cells in the inner ear
4. balance control - vestibular recptors in the vestibular apparatus
5. each type of mechanoreceptor has a distinct pathway to the brain
6. different qualities of skin stimulation are communicated to distinct brain areas

Question 14

skin is sensitive to mechanical stimulation

Answer 14

1. several somatosensory systems encode touch via arcs and somatosensory pathways
2. morphological details - encapsulated nerve endings, long and myelinated axons
3. soma of skin receptors are located in the dorsal root ganglia of the spinal cords

Question 15

small and large receptive field of neurons

Answer 15

1. small receptive fields in touchsensitive receptors - free nerve endings, merkel’s disc and meissner’s corpuscle sense innervate the surface of the skin and are sensitive to stimuli in small areas of the skin
2. wide or large receptive fields - pascinian corpuscles and ruffini’s endings innervate deeper layers of the skin and are sensitive to stimuli over larger areas of the skin

Question 16

receptors that transmit skin to spinal cord

Answer 16

1. pacinian corpuscle is a unipolar cell that extends one brain of its axon to skin and another to spinal cord
2. afferent projections form the dorsal root nerve and the cell bodies are part of the dorsal root ganglion
3. vibration or pressure on skin deforms the corpuscle and stretches the tip of the axon opening mechanically-gated ion channels

Question 17

transmission of a sensory signal in a spiking receptor neuron

Answer 17

1. similar to the dendrites of a postsynaptic neuron, receptors respond to stimulation with a graded potential, the receptor potential
2. a spiking receptor neurons converts the graded receptor potential into action potentials for fast and long distance transmission along the axon

Question 18

response of receptors is long lasting or transient

Answer 18

1. receptor neurons that show a slow loss of response are termed tonic receptors
2. receptor neurons that show fast loss of response shortly after onset of stimulation are termed phasic receptors

Question 19

response thresholds can differ in receptor neurons

Answer 19

receptors respond to a stimulus within a limited range of stimulus intensities
2. receptor response curve describes the sensitivity range of a receptor
3. absolute threshold - lowest possible stimulus intensity detected or highest stimulus intensity that can be discriminated
4. experimental threshold measurements - methods of constant stimuli in which stimuli of different intensities are presented in random order
5. when sensing two different low intensity stimuli, low threshold neuron responds with two different spike rates, high threshold neuron does not respond
6. when sensing two different high intensity stimuli - low threshold neuron gives the same maximal spike rates for both stimuli, high threshold neuron can respond with two different spike rates to the stimuli

Question 20

connecting receptors, brain and body

Answer 20

1. sensory systems and pathways are good examples to demonstrate the main principles of how the brain and central nervous system works
2. sensory pathways project to both subcortical and cortical brain areas and often have parallel streams
3. sensory signals are typically transmitted within a sensory pathway in a hierarchy of processing - information is filtered, combined or enhanced as it passes from one layer to the next which are connected in serial order, as bottom up projections
4. each layer has networks that are composed of input and output neurons

Question 21

mapping receptive fields of brain neurons

Answer 21

1. receptive fields can be mapped for neurons in different layers of a sensory pathway
2. recording from a neuron in the primary somatosensory cortex whilst touching a specific area on the body surface maps the size of the receptive field, its shape and sensitivity within the receptive field
3. RF of neuron B is larger in size than neuron A

Question 22

somatosensory pathway

Answer 22

1. segregated projections to different areas of brainstem, thalamus and cortex
2. where possible, information about the spatial location of stimuli is preserved by separating projections that come from receptors in different locations
3. it is important to know where stimulation occurred in the body
4. connectivity - there are many top down projections that modulate signal transmission via bottom up connections between layers and also the activity within layers

Question 23

cortical encoding in form of somatotopic maps

Answer 23

1. primary somatosensory cortex is located in the post central gyrus in the parietal lobe of the human brain
2. adjacent regions on body are generally encoding in adjacent regions in cortex

Question 24

sensory segregation in cortical somatotopic maps

Answer 24

1. fast adapting signals and slow adapting signals remain segregated in cortex
2. somatosensory map in the cortex of the mole for the different tips of their noses

Question 25

stopping and suppressing sensory input

Answer 25

1. just as nerve cells need to be inhibited, receptors and the signals they convey also need to be 'switched off' at times 2. often suppression involves accessory organs, such structures reduce the intensity or alter the stimulus before it reaches the receptor 3. or it can be via neural top down processes