Aminoglycoside antibiotics : autotoxic, damages hair cells = hearing loss
Sensory Perception
Cochlear implant
Main somatosensory pathway Form of artificial stimulation if there are damaged hair cells but the cochlear
nerve is intact. 25 (ish) electrodes are placed on the ear and cochlear nerve
can be stimulated with electrodes instead of hair cells
Pressure on fingertip → receptor potential
1. Pressure on pacinian corpuscles (mechanoreceptors)
2. Cell membrane bends and opens Na+ VGCs by forcibly opening
channels and Na+ enters
3. Small depolarization occurs (ie. graded potential)
4. Multiple graded potentials can summate to cross the AP threshold to
trigger AP
5. -55mV (AP threshold) causes Na+ VGCs to open = Na+ influx =
depolarization
Types of thresholds
Sensory signals that get sent to subconscious: 1. AP threshold : membrane potential (-50mV) at which action
1. Movement : proprioception, vestibular system potentials are triggered.
2. Autonomic responses : olfactory = salivation 2. Activation threshold : minimum stimulus strength that will
3. Behavioral responses : olfactory = salivation = stomach rumbling depolarize the receptor enough to generate AP. Different activation
and hunger thresholds are to cover as much stimulus as possible (covering more
of electromagnetic spectrum)
Sensory signals to the arousal system 3. Perceptual threshold : minimum stimulus strength for us to
Sleep 0 senses perceive that something is happening. Easiest to clinically test (eg.
Snellen chart for eyes)
Focus attention eg. driving with 1 sense, suppress the others
a GPS and music but turn off Spatial resolution and perception
music to focus on GPS)
● Every nerve as a receptive field (ie. an area that can detect a
Switch attention eg. falling 1. Moving from stimuli to stimuli stimulus)
asleep on netflix but waking up 2. becoming aware of a known ● Size of receptive field varies depending on receptor and nerve type
after a loud noise stimulus again ● How sensitive the area is determines how many receptors in that
area converge onto the same neuron
● Can read braille with fingers but not forearm
Types of receptors ● More innervation to a specific area = larger area in cortex
All in one (eg. peripheral) Specialized (eg. photoreceptors,
inner hair cells)
Can regrow axon and myelin If damaged, there is no recovery
sheath after approx 18 months
, Fingertips Forearm
Small receptive fields Larger receptive fields
Each afferent send information Pressing on braille will activate
to cerebral cortex with a different branches of a single
distinguished pattern afferent and fine detail is lost
Temporal resolution and perception (not too important)
● If you tap the same afferent repeatedly, the afferent won’t respond
quick enough because there’s not a short enough refractory period
to fire again on the next tapping
● Result : neuron sends continuous APs (= not able to feel the
difference between quick and fast tapping vs pressing for a long
Dynamic Range
time)
● Consistent stimulation = adaptation and lateral inhibition = tells brain
● Every receptor has a different speed of reset to fire a new AP
to not waste energy on thinking about it
● Most perceptive = pacinian corpuscles in the hands for tactility
● This means we can increase the range of how receptors respond
Sensory System Adaptation eg. When we wear clothes, we aren’t aware
= adapt receptors back down = looking for stronger pressure
of fabric constantly against our skin
● Reduces the problem of saturation (can’t respond or any stronger
● If you repeatedly stimulate an afferent at the same rate, your afferent
because neurons are at their limit)
will reset its sensitivity (becomes our normal) = AP firing decreases
Why do you need to be aware of perceptual threshold and receptive
fields clinically?
Lateral inhibition : highlights the location where stimulus strength has
● damage/disease can differentially affect different types of receptors
changed
= determine which examination to do to figure out what the issue is
Consistent pressure (same Inconsistent pressure ● Neural damage = disrupt inhibitory system = hypersensitivity
pressure in all afferents) (increased pressure in one ● Epilepsy : wave of excitation that goes over the somatosensory
primary afferent) cortex/system (eg. olfactory area = smell of burning toast during
1. Stimulus is detected by primary afferent and sends AP to seizure)
secondary afferent ● Synesthesia : eg. misconnection between auditory and visual lobes
and anytime you hear an auditory stimulus, you get a visual stimuli
Secondary afferents send Secondary afferent with to appear (a person ‘sees’ sound as a color)
signals to inhibitory stronger pressure isn’t as ● Phantom limbs syndrome : lose the nerves in the amputated limb
interneurons to dampen down strongly inhibited and will inhibit so the brain reorganizes and reassigns new ‘jobs’ to the area. Not all
the weaker afferents so the of the brain is caught up with that so it can trigger the feeling in
the response to ‘not waste AP’
body is aware that at this exact
because all 3 afferents are the absent limb
point, pressure is slightly
same and there is nothing stronger than the others
drastic happening Neurogenic pain : Nociceptors can become active without obvious cause
Sensory Perception
Cochlear implant
Main somatosensory pathway Form of artificial stimulation if there are damaged hair cells but the cochlear
nerve is intact. 25 (ish) electrodes are placed on the ear and cochlear nerve
can be stimulated with electrodes instead of hair cells
Pressure on fingertip → receptor potential
1. Pressure on pacinian corpuscles (mechanoreceptors)
2. Cell membrane bends and opens Na+ VGCs by forcibly opening
channels and Na+ enters
3. Small depolarization occurs (ie. graded potential)
4. Multiple graded potentials can summate to cross the AP threshold to
trigger AP
5. -55mV (AP threshold) causes Na+ VGCs to open = Na+ influx =
depolarization
Types of thresholds
Sensory signals that get sent to subconscious: 1. AP threshold : membrane potential (-50mV) at which action
1. Movement : proprioception, vestibular system potentials are triggered.
2. Autonomic responses : olfactory = salivation 2. Activation threshold : minimum stimulus strength that will
3. Behavioral responses : olfactory = salivation = stomach rumbling depolarize the receptor enough to generate AP. Different activation
and hunger thresholds are to cover as much stimulus as possible (covering more
of electromagnetic spectrum)
Sensory signals to the arousal system 3. Perceptual threshold : minimum stimulus strength for us to
Sleep 0 senses perceive that something is happening. Easiest to clinically test (eg.
Snellen chart for eyes)
Focus attention eg. driving with 1 sense, suppress the others
a GPS and music but turn off Spatial resolution and perception
music to focus on GPS)
● Every nerve as a receptive field (ie. an area that can detect a
Switch attention eg. falling 1. Moving from stimuli to stimuli stimulus)
asleep on netflix but waking up 2. becoming aware of a known ● Size of receptive field varies depending on receptor and nerve type
after a loud noise stimulus again ● How sensitive the area is determines how many receptors in that
area converge onto the same neuron
● Can read braille with fingers but not forearm
Types of receptors ● More innervation to a specific area = larger area in cortex
All in one (eg. peripheral) Specialized (eg. photoreceptors,
inner hair cells)
Can regrow axon and myelin If damaged, there is no recovery
sheath after approx 18 months
, Fingertips Forearm
Small receptive fields Larger receptive fields
Each afferent send information Pressing on braille will activate
to cerebral cortex with a different branches of a single
distinguished pattern afferent and fine detail is lost
Temporal resolution and perception (not too important)
● If you tap the same afferent repeatedly, the afferent won’t respond
quick enough because there’s not a short enough refractory period
to fire again on the next tapping
● Result : neuron sends continuous APs (= not able to feel the
difference between quick and fast tapping vs pressing for a long
Dynamic Range
time)
● Consistent stimulation = adaptation and lateral inhibition = tells brain
● Every receptor has a different speed of reset to fire a new AP
to not waste energy on thinking about it
● Most perceptive = pacinian corpuscles in the hands for tactility
● This means we can increase the range of how receptors respond
Sensory System Adaptation eg. When we wear clothes, we aren’t aware
= adapt receptors back down = looking for stronger pressure
of fabric constantly against our skin
● Reduces the problem of saturation (can’t respond or any stronger
● If you repeatedly stimulate an afferent at the same rate, your afferent
because neurons are at their limit)
will reset its sensitivity (becomes our normal) = AP firing decreases
Why do you need to be aware of perceptual threshold and receptive
fields clinically?
Lateral inhibition : highlights the location where stimulus strength has
● damage/disease can differentially affect different types of receptors
changed
= determine which examination to do to figure out what the issue is
Consistent pressure (same Inconsistent pressure ● Neural damage = disrupt inhibitory system = hypersensitivity
pressure in all afferents) (increased pressure in one ● Epilepsy : wave of excitation that goes over the somatosensory
primary afferent) cortex/system (eg. olfactory area = smell of burning toast during
1. Stimulus is detected by primary afferent and sends AP to seizure)
secondary afferent ● Synesthesia : eg. misconnection between auditory and visual lobes
and anytime you hear an auditory stimulus, you get a visual stimuli
Secondary afferents send Secondary afferent with to appear (a person ‘sees’ sound as a color)
signals to inhibitory stronger pressure isn’t as ● Phantom limbs syndrome : lose the nerves in the amputated limb
interneurons to dampen down strongly inhibited and will inhibit so the brain reorganizes and reassigns new ‘jobs’ to the area. Not all
the weaker afferents so the of the brain is caught up with that so it can trigger the feeling in
the response to ‘not waste AP’
body is aware that at this exact
because all 3 afferents are the absent limb
point, pressure is slightly
same and there is nothing stronger than the others
drastic happening Neurogenic pain : Nociceptors can become active without obvious cause
