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other senses
- vision, smell, touch, hearing, taste
- vibration, pain, acceleration, head position, motion
- also internal senses
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primary sensory cortex
- each sense has one
- primary sensory cortices contain "maps", hierarchy leads to abstract processing
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hearing
- sound is a vibration carried through a conductive medium
- sound travels through the air as pressure waves. Increases and decreases in pressure at regular intervals
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frequency
- the number of high/low-pressure cycles per second (Hz)
- pitch
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amplitude
- the size of the pressure change (from peak to trough)
- loudness
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outer ear parts
- captures sound waves
- pinna: selectively amplifies certain frequencies of sound
- tympanic membrane: vibrates to the sound waves, enabling their transmission
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middle ear
- receives the vibrations of the eardrum
- 3 ossicles: malleus, incus, and stapes
- transfers energy from tympanic membrane to oval window
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inner ear
- contains the cochlea which has basilar membrane, triggered by vibrations of the oval window
- organ of corti contains inner hair cells run along edge of the basilar membrane, transduce sound into electrical signals
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tonotopic map
- basal end vibrates to high frequencies,
- the apical end vibrates to low frequencies,
- intermediate positions vibrate to intermediate frequencies
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cochlea to brain
each fiber from the cochlea to the brainstem (in the auditory nerve) receives information from only one inner hair cell
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labeled-line coding:
each neuron carries only one specific type of sensory information
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somatosensory
the ability to detect sensory information from the body
includes: nociception, proprioception, interoception
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touch receptors
- mechanoreceptors (detect changes in pressure/vibrations)
- thermoreceptors (detect changes of temp to point then paint receptor), warm and cold
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somatosensory receptive field
area of the skin that, when touched, activates the sensory receptor
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congenital analgesia
inability to feel pain
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nociception
pain
- types
- mechanical: physical damage caused by pressure
- thermal: extreme heat or extreme cold
- chemical: toxins, spices, poisonous gases
- polymodal: respond to combinations of noxious stimuli
*not on brain
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proprioception
body position and movement
- muscle spindles: receptors in the body of muscles; senses the length of muscles and speed of stretching (prevents overstretching)
- Golgi tendon organs: receptors in tendons (prevents over contractions)
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interoception
- feeling of internal bodily state e.g hunger, thirst, gut movement
- stretch receptors: sensitive to muscle and organ distention (e.g. when you've eaten too much it signals the feeling of fullness)
- chemoreceptors: monitor chemical levels throughout the body (e.g. CO2 to signal suffocation)
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somatosensory pathway
- signals from the face travel to brain via trigeminal pathway
- signals from the body travel to brain via the spinal cord
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dermatomes
areas of the skin that are the receptive fields of somatosensory neurons in each dorsal root ganglion
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somatotopic map
- density of somatosensory receptors
- relative importance of sensation in different
- parts of the body
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chemical senses
- taste and smell
- depend on the binding of molecules to receptors
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tastant
- chemicals that can depolarize taste cells
- taste receptors can depolarize via ionotropic or metabotropic routes
- depend on population code
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gustatory pathway (slide 33/34)
- taste receptors on the tongue, palate, pharynx, epiglottis, and the upper half of the esophagus
- receptor categories: 50 types into sweet, salty, bitter, sour, umami
- *have preference but can do others, encoded by pattern of activity
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taste
action potentials from taste cells cause release of neurotransmitters --> affect primary gustatory afferent neurons--> brainstem --> thalamus --> primary gustatory cortex --> then to higher-order gustatory cortices
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smell
- odorant --> nose/mouth ---> olfactory epithelium (nasal cavity) --> olfactory receptor --> olfactory neuron
- receptor to neuron is 1-1 but receptor can react to many odorants if similar
population coding (pattern of activity across primary olfactory neurons)
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anosagnosia
a condition in which an individual lacks awareness about their own physical impairments
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