Perception

Question 1

Papillae

Answer 1

Gives the tongue its bumpy appearance

Question 2

What are the four types of papillae?

Answer 2

1. Filiform – no taste function, located at the anterior portion of tongue (tip). Different shapes in different species (e.g., cats). Draws in food and acts as an abrasive (most numerous)
2. Fungiform – (resemble tiny mushrooms), visible to eye on anterior portion of tongue. Huge variation between people.
3. Foliate – sides of the tongue; look like folds, taste buds buried in the folds
4. (Circum)vallate – large visible structures like an inverted V on back of
   tongue. Look like islands surrounded by moats

Question 3

What are the biological functions of taste sensations:

• sweet
• umami (savoury)
• salty
• sour
• bitter

Answer 3

• sweet (identify energy rich nutrients)
• umami (savoury) - detection of amino acids (MSG and aspartate)
• salty - maintain electrolyte balance
• sour – acidity (dangerous at high levels)
• bitter (potential poison - huge class)

Question 4

Why is there an innate preference for sweetness?

Answer 4

To get enough energy to grow a body.

Taste discrimination does not change much with age but preferences do.

Question 5

What tastes are we most sensitive to?

Answer 5

1. Sweetness
2. Saltiness
3. Sourness
4. Bitterness

Question 6

What are super-tasters?

Answer 6

People who are genetically more prone to have more fungiform taste receptors around the tip and sides of their tongue

Question 7

What is olfaction?

Answer 7

Smell

Question 8

__ + __ + __ = Flavour

Answer 8

Tempature, smell, taste

Question 9

What are pheromones?

Answer 9

Many mammals use a separate set of sensory receptor cells in their nose to receive social and sexual information from members of their speciies.

Question 10

What is sensation and perception?

Answer 10

Sensation refers to how your senses transform physical properties of the environment and body into electrical signals relayed to the brain

Perception is the active process of organizing, selecting, and interpreting information into meaningful (useful) representations of the world

Question 11

What are the 6 senses for humans?

Answer 11

• Vision - receptors in eyes respond to light
• Hearing - receptors in ears respond to sound and vibrations
• Somatosensation - the awareness of the body
• Taste - receptors on tongue respond to chemicals
• Smell (Olfaction) - receptors in the nose respond to chemicals
• Vestibular - inner ear senses gravity and movement

Question 12

What are micro-saccades?

Answer 12

Fixational eye movement. Small jerk-like involuntary eye movements –– cause for a lot of illusions.

Question 13

Why are illusions important?

Answer 13

• Illusions indicate we don’t know exactly how things are structured in the world around us
• They provide insight into how perceptual systems break down
• Reveal the kinds of assumptions or general rules we are using to make guesses (or inferences) about the physical world

Question 14

What is scotopic vision?

Answer 14

A class of photosensitive receptors that operate in low-light levels. Rod dominated (more of them, just more sensitive). Night vision - no colour.

Question 15

What is photopic vision?

Answer 15

A class of photosensitive receptors that operate in high-light levels, cone dominated. Daylight vision. Cones responsible for our experience of colour.

Question 16

Four types of photoreceptors?

Answer 16

one rod, three cones

Question 17

What are the two mechanisms of light adaption?

Answer 17

• pupil dilation/contraction –to control amount of light entering eye
• isomerisation of the photopigments (can’t absorb photons when it has the shape on the right)

Question 18

What is trichromacy?

Answer 18

Colour is closely related to the proportions of responses of the three different types of cone receptors.

Trichromatic theory of colour vision
– millions of different perceived colours can be explained in terms of the responses of the three cone types.

Question 19

Why do objects appear coloured?

Answer 19

Short and medium wavelengths

When light strikes an object, the white light (natural daylight) mostly reflect in the longer wavelength, so it becomes red. They all fire equally. It predominantly reflects the long wavelength, some of the medium and very little short.

(Short = blue; medium - green; long = red)

Question 20

What is opponent processes theory?

Answer 20

Colour perception depends on six psychological primaries that are arranged in pairs.

Evidence for opponent processes theory: reddish greens; bluish yellows. They steal each other’s hues.

Colour aftereffects

Question 21

What is the receptive field?

Answer 21

The receptive field of a visual cell is the retinal area that, when stiumulated, can affect the firing of that cell.

Centre-Surround opponency observed in ganglion cells.

Question 22

What are the three types of colour-vision deficiencies?

Answer 22

red-green, blue-yellow, complete

Question 23

What causes colour-vision deficiency (anamolous trichromats)?

Answer 23

Three cone types but the L and M overlap more than they should.

Question 24

Which visual field goes to which hemisphere?

Answer 24

Left vision field (from both eyes) goes to right hemisphere. Right field (from both eyes) goes to left hemisphere.

Question 25

What are the two major subsystems of the 'body senses'?

Answer 25

- somasensatory system: touch and proprioception | - interoception: the sense of the physiological condition of the body

Question 26

What is tactile afterimage?

Answer 26

Opponent-like after-effects: texture contrast after-effects (after touching something rough, a medium rough surface feels smoother); can be observed for temperature as well.

Question 27

What is tactile adaption?

Answer 27

Importance of movement in perceiving spatial patterns in the skin; stabilized (i.e., non-moving) objects on the skin are less salient than when the skin is first perturbed

Question 28

What are the two major subsystems of the somatic sensory system?

Answer 28

- Detection of mechanical stimuli (light touch, vibration, pressure, and cutaneous tension): identify shapes and texture of objects, to monitor the internal and external forces acting on the body at any moment - Detection of pain and temperature: detect potentially harmful circumstances

Question 29

What are proprioceptors?

Answer 29

receptors located in muscles, joints, and other deep structures monitor mechanical forces generated by the musculoskeletal system "receptors for self"

Question 30

What is sensory transduction?

Answer 30

When stimuli applied to the skin deform or otherwise change the nerve endings, which in turn affects the ionic permeability of the receptor cell membrane. This induces a depolarizing current in the nerve ending, which triggers action potentials

Question 31

Three function-based groups of receptors?

Answer 31

* Mechanoreceptors (touch) * Nociceptors (pain) * Thermoceptors (temperature)

Question 32

What does a rapidly adapting touch fibre do? Name two examples.

Answer 32

Rapidly adapting: provide info about change or dynamical quality (what + where) of stimuli. Meissner corpuscles: - Generate rapidly adapting action potentials following minimal skin depression - Found under epidermis of fingers, palms, and soles (glabrous skin - smooth/hairless); - Respond best in the range of low-frequency vibrations (30- 50 Hz) - Pacinian corpuscles: - Acts like a filter that allows only transient, high-frequency disturbances (250-350 Hz) to active the nerve endings - Stimulation introduces a sense of vibration and/or tickle.

Question 33

What is a slowly adapting touch fibre do? Name two examples.

Answer 33

Slowly adapting: provide info about shape, edges, rough texture, persisting features. Merkel disks: - Stimulation induces sense of light pressure - Fingertips, lips and external genitalia Ruffini organ: - Deep in skin + ligaments and tendons - Don't elicit any feeling when stimulated

Question 34

What does local anaesthesia do?

Answer 34

The absence of the sensation is attributed to the world not the body

Question 35

What are nociceptors?

Answer 35

Terminate in unspecialized free endings, so two axons associated with them: Aδ: myelinated axons, conduct at 20 m/s - faster, first pain / sharp pain C fibers: unmyelinated axons, which conduct at 2 m/s - slower, dull pain; diffuse type pain

Question 36

What are the three classes of nociceptors in the skin?

Answer 36

- Aδ mechanosensitive nociceptors - Aδ mechanothermal nociceptors - polymodal nociceptors (C fibers, quite slow)

Question 37

What is Capsaicin?

Answer 37

- Principle ingredient responsible for the pungency of hot peppers - Activates a subset of C-fibers, the polymodal fibers Birds don't have receptors for capsaicin

Question 38

What is Hyperalgesia?

Answer 38

Where pain is the only sense that exhibits an enhanced sensitivity to stimuli over time; all other senses exhibit adaptation (decreased sensitivity) to the same stimulation.

Question 39

How is visceral pain transmitted?

Answer 39

Receptors conveyed centrally via neurons also coding for cutaneous pain and through a dorsal column pathway. The former leads to a type of referred pain.

Question 40

What do thermoreceptors do?

Answer 40

Skin works to maintain a constant internal body temperature, sensation of warmth or cold are generally caused by departures from a reference skin temperature called physiological zero.

Question 41

Name three examples of proprioceptors.

Answer 41

– Muscle spindles – provide info on muscle length – Golgi tendon organ – muscle tension – Joint receptors – provide info on position / tension of joints

Question 42

What is the two-point thresholds?

Answer 42

Ability to discern that two nearby objects touching the skin are truly two distinct points, not one. Provides information about the size of the receptive fields. Smaller receptive fields in fingertips, larger in arm.

Question 43

Somasensatory and the homunculi ("little man")?

Answer 43

Representation of the body along the cortex, where adjacent areas of the body have adjacent representations in the cortex. Certain body locations have a disproportionate amount of cortical area because of the increased sensitivity needed (tongue, fingers...)