PSY1101 Chapter 5: Sensation & Perception

5.3 Hearing and Sound; 5.4 The Chemical Senses (Smell & Taste); 5.5 Skin and Body Senses; and 5.6 The Kinesthetic and Vestibular Senses

What are sound waves?

• The stimulus for hearing

• Characteristics:

  • Frequency: distance between peaks, measured in Hz, translates into pitch

  • Amplitude: height of wave, measured in DB, translates into volume/loudness

  • Complexity translates into timbre/uniqueness of sound

What is the mechanism of hearing/structure of the ear?

• Pinna funnels sound into the auditory canal until it reaches the eardrum (tympanic membrane) which vibrates

• Ossicles (3 tiniest bones in body) vibrate

• Oval window vibrates

• Cochlear fluid in the cochlea (shell shaped thing) forms waves and causes basilar membrane to vibrate

• Cilia/hair cells embedded in the basilar membrane activate auditory nerves and sends it to the thalamus and auditory cortex (temporal lobe)

What is tonotopic organization?

• Spatial organization of the basilar membrane/auditory system that is maintained

What is place theory (how do we perceive pitch)?

• Sound waves of different frequencies will activate different areas of the basilar membrane

• High frequency hits hair cells at the beginning

• Low frequency hits hair cells at the end

• Based on this, brain determines pitch

What is frequency theory (how do we perceive pitch)?

• Frequency of the sound wave affects the rate of firing

• 1 Hz = 1 action potential

• Based on this, brain determines pitch

How do we locate sound?

• Time of arrival (interaural time difference): the ear closer to the sound receives sound waves first

• Loudness (interaural level difference): the ear closer to the sound perceives sound as louder

• If sound hits both ears at the same time, we can turn/tilt our heads or use our vision

What are cutaneous senses?

• Variety of receptors that pick up different sensations in the skin

What are the top layers of the skin?

• Mechanoreceptors: receptors that sense different kinds of pressure

  • Merkel receptor: fine details

    • Fire continuously as long as the skin is making contact with the object

  • Meissner receptor: touch

    • Fires when the skin encounters the stimulus and when it is removed

• Both respond to pressure that is applied and then removed

What are the deeper layers of the skin?

• Ruffini cylinder — stretching of the skin

• Pacinian corpuscle — vibration, texture

What is the importance of touch?

• For physical and psychological well being

What are nociceptors?

• Detect, transduce, transmit information about pain

• Found all over the body and essential for survival

What is the gate-control theory?

• In the nervous system we have a neurological gate. Its state is linked and associated with whether we experience pain or not.

• Small nerve fibres carry pain information. When gate is opened, we feel pain.

• Large nerve fibres carry information not related to pain. When gate is closed, we feel little to no pain

• T-cells are found between the fibres and the gate. It must be activated for the gate to open.

What factors affect pain?

• Pain is complex — it’s not just determined by tissue damaged but also by:

  • Stimulation

  • Beliefs

  • Stress

  • Emotions

  • Self-confidence

  • Culture

How does smell work?

• Stimulation comes from odor molecules (chemical sense)

• Must reach olfactory receptors and our nasal cavity

• We have millions of olfactory receptors

  • Sorted into 300 types

  • We can sense 10000 odors, but detect 1 trillion odors

  • Different odor molecules activate different combos of receptors

• Olfactory receptors can regen. They can degenerate due to age, smoking, pollution

• Strong connection between smell and emotions/memories since information is sent to limbic system

How does taste work?

• Essential for survival

• Food molecules dissolve into saliva and come into contact with gustatory cells (sensory receptors of taste)

• Gustatory cells are found in the taste buds in the papillae (bumps on the tongue)

• Can regen, but we might not keep the same number of cells

What are the basic tastes?

1. Sweet

2. Sour

3. Salty

4. Bitter

5. Umami (savoury, high in protein)

6. Fat (maybe? more research needed)

What are bimodal neurons and where are they located?

• Neurons that respond to more than one sense

• Located in the orbitofrontal cortex (OFC)

What is kinesthesis?

• K sense

• Allows us to know where our body is, its position, and what our body is doing

  • Ex. you can move your feet without looking

What is the vestibular sense?

• Known as our sense of balance

• Located in the ear:

  • Semicircular canals: senses changes in acceleration and rotation of the head. Also has hair cells that respond to gravity

  • Vestibular sacs: responds to cues associated with balance and posture

• Connected to our sense of vision — David Lee’s test with moveable walls, people involuntarily stepped off a beam to keep from falling