Sensation

Question 1

what do our senses do?

Answer 1

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

Question 2

what is sensation and perception?

Answer 2

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

Question 3

stages of conversion from physical energy to neural energy

Answer 3

1. accessory structures modify physical stimulus e.g. lens of the eye, outer ear modifies sound
2. 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
3. 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
4. sensation is produced once message reaches brain - information is then interpretated in the context of the situation

Question 4

how are senses and thresholds measured?

Answer 4

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

Question 5

what does excitatory and inhibitory mean?

Answer 5

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

Question 6

implications of noise

Answer 6

1. repeated presentations of the same physical level of intensity do not always produce the same internal sensation
2. 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)
3. 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

Question 7

explain Weber’s law

Answer 7

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

Question 8

Weber fraction

Answer 8

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

Question 9

what energy is involved in hearing?

Answer 9

physical energy –> sound waves

Question 10

what is pitch?

Answer 10

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

Question 11

what is volume?

Answer 11

amplitude of the sound waves
measured in decibels (dB)
higher wave = louder sound
lower wave = quieter sound

Question 12

what is timbre?

Answer 12

‘nature’ of the sound e.g. instruments
‘simple’ wave - similar to sine graph
‘complex’ wave - similar to sine graph but zig-zag

Question 13

how does sound work?

Answer 13

1. Sound travels through pinna and ear canal into middle ear.
2. Ear drum vibrates in response to sound waves.
3. Small bones connected to the ear-drum (hammer, anvil, stirrup) vibrate in response to ear drum vibrates. Vibrates one after each other
4. Stirrup vibrates against oval window and causes oval window to vibrate which causes waves within the fluid filled cochlea.
5. Fluid in cochlea begins to move with the cilia.
6. Fluid causes basal membrane to vibrate which stimulates hair cells or nerve cells to cause a sensation .

Question 14

what is place theory?

Answer 14

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