Psychology Brain And Mind Week 5 - Sensation, Taste, Smell and Touch

Sensory Receptors

Specialised neurons that respond to specific types of stimuli

Ways Of Measuring Waves/Wavelengths

• Amplitude: Distance from the center line to the top of the crest or bottom of the trough

• Wavelength: Length of a wave from one peak to the next

• Frequency: Number of waves that pass at a given point or given time period and is often expressed in terms of Hertz

• Visible Spectrum: Portion of the larger electromagnetic spectrum that we can see

Light Waves

Associated with perception of colour

• Red are longer wavelengths

• Green’s are intermediate

• Blues/violets are shorter

Sound Waves - Decibels

Frequency of a sound saveis associated with our perception of that sounds pitch

• High frequency are higher pitched

• Low frequency are lower pitched

• Higher amplitude are louder

• Lower Amplitude are quiet

Sensation

Detection of physical stimuli and transmission of that information to the brain

• Can be light, sound, chemicals, pressure, temperature, acceleration

• Basic experience of stimuli with no interpretation

Perception

Brains further processing, organisation and interpretation of sensory information

• Results in conscious experience of the world

• Construct useful meaningful information

Bottom-Up Processing

Based off the physical features of a stimulus

• As each sensory aspect of a stimuli is processed, they build to form the perception of that stimulus

Top-Down Processing

How knowledge, expectations or past experience shape out interpretation of sensory experience

• Context affects perception, what we expect to see, influences what we perceive

Common Features Of Senses

• Discrimination

• Threshold

• Transduction

• Adaptation

Common Feature - Discrimination

The understanding that the nature of sensation depends on the neural pathways it activates

• Different sensory receptors for different sense, different neural pathways

• rods and cones for sight, taste receptors for taste, etc

Common Feature - Threshold (Of Activation)

Sensory items having a point or level at which they become active or “activate”

• Absolute threshold: Minimum intensity of a stimulus that you can detect

• Difference thresholds: The minimum amount of change in a stimulus that you can detect

Common Feature - Transduction

The detection and translation of physical energy into neural signals

• Sensory information converted into signal that the brain can understand

• Detection of energy starts at receptor cells

• Action potentials

Common Feature - Adaptation

The tendency of sensory receptors to respond preferentially to change

• Progressive loss of response to a maintained stimuli

• Tonic receptors: Firing all the time

• Phasic receptors: fire quickly when change occurs

Types Of Receptors

• Photoreceptors: Visible light

• Mechanoreceptors: Sound waves, movement, touch, pressure, stretching

• Chemoreceptors: Chemicals

• Thermoreceptors: Temperature

• Nociceptors: Pain

• Electroreceptors: Natural electrical stimuli

Chemical Sensations

Taste and smell

Taste (Gustation)

Molecules of food/beverages dissolve in our saliva and interact woth taste receptor on tounge (papilla), in our mouth and in our throat.

• Contain one or more taste buds

• Sweet, salty, sour, bitter, unami and potentially fatty

Taste Cells

Each receptor cell senses one of the 5 basic tastes

Taste Buds

Formed by groupings of taste receptor cells with hair-like extensions that protruude into central pore of taste bud

• life cycle of 10-14 days

• 50-150 taste receptor cells

• Not all signal taste, but some signal pain or touch

How Taste Works

1. Taste molecules bind to receptors on taste buds

2. chemical changes occur depending on receptor location

3. Neural impulses transmitted to brain via different nerves

Where is Taste Information Transported to

• Medulla

• Thalamus

• Limbic system

• Gustatory cortex

Smell Criteria

• Chemical stimulus must be volatile

• Molecules must have left the object that is being smelled

• Must be water and lipid soluble

• Tend to be organic rather than organic

• Tend to be complex compounds

Olfactory Epithelium

Small, thin sheet of cells high up in the nasal cavity

• 4-8 week cycle

• Olfactory receptor cells are located on mucous membrane at the top of the nose

Olfactory Receptors

Small hair like extensions from said receptors are seats for odot molecules dissolved in mucus to interact with chemical receptors on the extensions

• Once odor molecule binds, chemical changes in the cell result in signals being sent to olfactory bulb

Where is Olfactory Information Sent

• Limbic system

• Primary olfactory cortex

Phermonal Communication

Involves providing information about a reproductive status of a potential mate

Somatosensation (Touch)

Involves pressure, texture, temperature, limb position and pain

• All sensations work together to give information about sensory environments

Three Skin Layers

• Epidermis: Outermost layer which is the thinnest

• Dermis: Middle layer, containing connective tissue and blood vessels

• Hypodermis: Innermost layer, which anchors muscles and helps shape the body. Contains loose connective tissue and fat

Receptors Involved In Skin To Respond To touch-Related Stimuli

• Meissners Corpuscles

• Pacinian Corpuscles

• Merkels Disks

• Ruffini Corpuscles

Meissners Corpuscles

Respond to pressure and lower frequency vibrations

• touch, fast adapting

Pacinian Corpuscles

Detect transient pressure and higher frequency vibrations

• Vibration, fast-adapting

Merkels Disks

Respond to light pressure

• edges, slow-adapting

Ruffini Corpuscles

Detect stretch

• stretch, slow-adapting

Nerve Endings

Serve sensory functions and repsond to:

• Thermoception

• Nonciception

Importance Of Pain Perception

Makes us less likely to suffer additional injurty due to gentler action with injured body parts

Inflammatory Pain

Pain that signals some type of tissue damage is known as

Neuropathic Pain

Sometimes, pain results from damage to neurons of PNS or CNS, resulting in exaggerated pain

Vestibular Sense

Contributes to our ability to maintain balance and body posture

• These organs are fluid filled and have hair cells, which respond to movement of head and gravitational forces

Proprioception

Perception of the body

Kinesthesia

Perception of the body’s movement through space

• Both systems interact with information provided by vestibular system

Somatosensory Cortex

Primary somatosensory cortex is in pstcentral gyrus

• recives touch information from opposite side of the body

• cells in somatosensory cortex are arranged in accordance to plan on bod’s surface

Secondary Somatosensory Cortex Performs higher order functions including:

• Sensorimotor intergration

• intergartion of ifnromation from two halves

• attention

• learning

• memory