Sensation Flashcards
(50 cards)
what do our senses do?
our senses gather information about the outside world and translate it from physical energy into something the brain can use to produce an internal state called sensation in the form of brightness or loudness
what is sensation and perception?
sensation is the beginning stages
sensations are translated into perception
perception is the later, interpretation stages
conscious experiences about the world and yourself, prior knowledge, memory, current emotional state influence how sensations are translated into our knowledge of reality
stages of conversion from physical energy to neural energy
- accessory structures modify physical stimulus e.g. lens of the eye, outer ear modifies sound
- transduction is when physical energy is picked up by receptors and converted into neural energy e.g. cells in the retina respond to light energy (physical energy) and stimulates nerve (neural energy) - receptors respond best to changes in energy levels, otherwise adaptation occurs e.g. acclimatising after entering a cold pool
- sensory nerves send transduced neural energy to the brain - nerve signals first go to the thalamus (relay station) then onto different parts of the cortex for further processing e.g. visual or auditory cortex e.g. retina -> optic nerve -> thalamus -> visual cortex
- sensation is produced once message reaches brain - information is then interpretated in the context of the situation
how are senses and thresholds measured?
noise: random excitation or inhibition of neurons that either increases or decreases the sensed intensity of a physical stimulus
difficult to measure thresholds for individuals for light and sound
nervous system interprets information differently
nerve cells are active even when there is no stimulation coming from the outside world
that activity of nerve cells is called neural noise which can be excitatory or inhibitory
what does excitatory and inhibitory mean?
excitatory: cells ready to fire or fire - more active cell
inhibitory: cells don’t fire
excitatory and inhibitory stimuli change how intense the outside source is - same amount of energy - not directly linked to what is going on in your environment but is what is going on in your nervous system
implications of noise
- repeated presentations of the same physical level of intensity do not always produce the same internal sensation
- if a physical signal (e.g. sound units) is doubled that does not always produce a doubling of sensation (may not appear twice as loud)
- absolute threshold (lowest level of intensity at which a person detects stimulus) - defined as the physical intensity at which a person can detect the stimulus 50% of the time
threshold helps to determine if people have hearing loss or if senses are working or in music industry
explain Weber’s law
difference threshold is the smallest amount of change in the intensity of a stimulus before a change is detected
requires 2 stimuli to detect a difference
what is the smallest amount of change before a difference is detected? look at how much of the standard can change before you detect a difference
Weber fraction
difference threshold increases in proportion to the standard (stimulus with original intensity)
produces fraction:
change in intensity of stimulus / intensity of standard = C
∆I/I = C
what energy is involved in hearing?
physical energy –> sound waves
what is pitch?
frequency of the sound waves
measured in Hertz (Hz)
humans range from 20Hz to 20000Hz
dogs range up to 80000Hz
frequently = high pitch
infrequently = low pitch
what is volume?
amplitude of the sound waves
measured in decibels (dB)
higher wave = louder sound
lower wave = quieter sound
what is timbre?
‘nature’ of the sound e.g. instruments
‘simple’ wave - similar to sine graph
‘complex’ wave - similar to sine graph but zig-zag
how does sound work?
- Sound travels through pinna and ear canal into middle ear.
- Ear drum vibrates in response to sound waves.
- Small bones connected to the ear-drum (hammer, anvil, stirrup) vibrate in response to ear drum vibrates. Vibrates one after each other
- Stirrup vibrates against oval window and causes oval window to vibrate which causes waves within the fluid filled cochlea.
- Fluid in cochlea begins to move with the cilia.
- Fluid causes basal membrane to vibrate which stimulates hair cells or nerve cells to cause a sensation .
what is place theory?
different places on the basilar membrane vibrate more depending on pitch
low frequencies at apex, high frequencies at the base near oval window
research supports that artificially stimulate particular areas of the membrane, produces sensations of hearing different pitches
elderly and hearing
- Elderly who cannot hear certain high pitches show evidence that there is damage to the base of basilar membrane.
- Pitches are determined by where the hair cells on the basal membrane are being stimulated: if there is a high frequency then the base is stimulated, if there is a low frequency then the apex is stimulated
- may need cochlea implants
problems for place theory
Below 1000 Hz, no specific place on the membrane vibrates more than any other.
However, we can distinguish between tones that are below that frequency.
alternative to place theory
Frequency (temporal) Theory
Basilar membrane is like a guitar string. The higher the frequency of the sound, the faster it vibrates.
It is the rate that the hair cells are stimulated that matters, not which hair cells (place theory).
problem for frequency theory
Above 1000 Hz, cell cannot fire any faster (refractory period).
However, we can distinguish between tones that are above that frequency.
frequency and volley theory
There is alternation in the firing of hair cells (volleying).
Groups of hair cells fire in alternation, sending a higher frequency of signal to the brain.
problem for frequency and volley theory
Very high frequencies (e.g., 10,000 Hz) would need very complex teamwork
what energy is involved in vision?
physical energy –> light energy
how is light measured?
light is wavelike
measured in nanometers
1nm = 1 billionth of a meter
electromagnetic spectrum
x-rays (10-1 nm)
ultraviolet (101 nm) - visible light is in between
infrared (103 nm) - visible light is in between
radar (105 nm)
FM radio (109 nm)
TV (1011 nm)
am radio (1012 nm)
colours and wavelengths of light
- violet 400 nm
- blue 500 nm
- green 570 nm
- yellow 600 nm
- orange 650 nm
- red 700 nm
