Neuro Ch 6

• vision, smell, touch, hearing, taste
• vibration, pain, acceleration, head position, motion
• also internal senses

• each sense has one
• primary sensory cortices contain "maps", hierarchy leads to abstract processing

• 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

• the number of high/low-pressure cycles per second (Hz)
• pitch

• the size of the pressure change (from peak to trough)
• loudness

• captures sound waves
• pinna: selectively amplifies certain frequencies of sound 
• tympanic membrane: vibrates to the sound waves, enabling their transmission

• receives the vibrations of the eardrum
• 3 ossicles: malleus, incus, and stapes
• transfers energy from tympanic membrane to oval window

• 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

• basal end vibrates to high frequencies,
• the apical end vibrates to low frequencies,
• intermediate positions vibrate to intermediate frequencies

each fiber from the cochlea to the brainstem (in the auditory nerve) receives information from only one inner hair cell

each neuron carries only one specific type of sensory information

the ability to detect sensory information from the body

includes: nociception, proprioception, interoception

• mechanoreceptors (detect changes in pressure/vibrations)
• thermoreceptors (detect changes of temp to point then paint receptor), warm and cold

area of the skin that, when touched, activates the sensory receptor

inability to feel pain

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

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)

• 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)

• signals from the face travel to brain via trigeminal pathway
• signals from the body travel to brain via the spinal cord

areas of the skin that are the receptive fields of somatosensory neurons in each dorsal root ganglion

• density of somatosensory receptors
• relative importance of sensation in different
• parts of the body

• taste and smell
• depend on the binding of molecules to receptors

• chemicals that can depolarize taste cells
• taste receptors can depolarize via ionotropic or metabotropic routes
• depend on population code

• 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

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

• 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)

a condition in which an individual lacks awareness about their own physical impairments