PHYS Exam 4
Receptor potentials are _______. They increase in magnitude as a stimulus gets stronger.
graded
Receptor potentials of taste receptor cells are _______.
graded (either depolarize or hyperpolarize based upon chemical)
Both rods and cones produce what in response to retinal illumination?
graded hyperpolarizing potentials
Pitch gets encoded in the cochlea by....
hair cells (each of which has a best frequency)
What does the organ of corti contain?
hair cells with stereocilia
Which cutaneous receptors are unencapsulated?
hair follicles, merkel complex (specialized epithelial cell), free nerve endings
Name the reflex: compensates for head rotation, receives input from semicircular canals.... when the head moves rapidly in one direction the eyes move slowly in the opposite direction to maintain a clear and still image.
rotational vestibulo-ocular reflex
What type of coding is defined by each chemical having a preferred stimulus which has its own receptor and circuit?
labeled line coding (no crossing)
What does the superior olive help with?
localization of sound in the horizontal plane (has 3 neurons)
What are the sensory epithelia within the otolith organs called?
macula utriculi and macula sacculi
What kind of stimuli is the somatosensory system sensitive to?
many kinds - pressure, position of joints and muscles, temperature of limbs, pain
Define adaptation.
measure of how well a sensory receptor maintains its response to a constant stimulus
What are most of the sensory receptors in the skin?
mechanoreceptors (sensitive to physical stimuli like bending & stretching)
Which cutaneous receptors are encapsulated?
meissner corpuscle, pacinian corpuscle, ruffini corpuscle
What types of mechanoreceptors have a small receptive field?
sMall: - Meissner's corpuscle - Merkel's disk
The ______ is connected to the cochlea and senses head movement in the vertical plane.
saccule (ex: jumping up and down)
All the terminals of any one sensory unit have the....
same kind of receptor
What is the function of the supporting cells in the olfactory epithelium?
secrete mucus (odorants dissolve in mucus before reaching receptor cells)
Why is sound amplification needed through the ossicles?
sound amplification needed through ossicles (via mechanical energy) because sound displacement in liquid (high impedance) is lower than in air (low impedance)
How does sound travel to inner ear?
sound waves/energy enter external ear → tympanic membrane vibrations → mechanical energy in middle ear
What is wavelength dependent on?
source of the sound and the medium in which it travels
Where do hair cells synapse?
spiral ganglion cells within the modiolus
The otolithic membrane is split by a _______.
striola (all kinocilia are facing toward this striola --> can be depolarized or hyperpolarized upon movement)
What is our internal biological clock?
suprachiasmatic nucleus (SCN)
If taste is the modality, what are some sub-modalities?
sweet, sour, salty...etc
What is the kinocilium?
tallest stereocilia and causes depolarization and hyperpolarization
Which sense is the crudest of the 5 and gives us the least info about the world?
taste
What are the cues that account for taste perception?
taste, tactile, visual, auditory, and olfactory
What is the attenuation reflex?
tensor tympani & stapedius muscles contract in reflexive response to loud sounds → protect auditory apparatus (not protective against sudden loud sounds)
What muscles regulate the mechanical control of ear sensitivity?
tensor tympani and stapedius
What is the helicotrema?
the apex of the basilar membrane that connects the scala vestibuli and scala tympani
Where does sound processing begin at?
the cochlear nuclei
What is phase locking?
the consistent firing of a cell at the same phase of a sound wave
_______ is a photopigment in the membrane of rod outer segments that absorbs electromagnetic radiation in the form of light.
rhodopsin
Are there more rods or cones?
rods
What accounts for most of our peripheral vision and detects dim light (black and white)?
rods
Do rods or cones have a higher convergence?
rods (more rods giving signals to single bipolar cell)
positive chemotaxis:
used to find nutrients or locate a mate (ex: smells that are attracting (cookies) --> go toward stimulus)
The ______ is connected to all semicircular canals and senses head movement in the horizontal plane.
utricle (ex: walking)
The cilia of hair cells are embedded in the _______
cupula (within in the ampulla)
What do modality and sub-modality coding tell the body?
"what is present" (quality)
Describe what happens when sound is coming from our left side (in regard to the 3 neurons in superior olive).
- AP activity from axon of left cochlear nucleus traves from nuclei 1-3 (in olive) - interaural time delay is occurring at same time (sound reaches right ear a bit later) → AP travels along axon from right cochlear nucleus → impulses reach neuron 3 at same time (sound is from left)
Describe what happens when sound is coming from our right side (in regard to the 3 neurons in superior olive).
- AP activity from axon of right cochlear nucleus travels from nuclei 3-1 in olive - interaural time delay occurring at same time (sound reaches left ear a bit later) → AP travels along axon from left cochlear nucleus → impulses reach neuron 1 at same time (sound is from right)
What is the opponent color theory?
- Color is processed in opponent pairs - 6 primary colors coupled in 3 pairs: red-green, yellow-blue, white-black - Any receptor turned off by one of these colors was excited by its coupled color - Perception of opponent colors due to presence of color-opponent cells in retina & brain
Explain the dark current pathway.
- Dark currents cause depolarization → increased levels of cGMP (second messenger) → continual Na+ influx via cGMP-gated channels → inhibitory signals sent to bipolar cells → no AP to the ganglionic cells
What is the filter, transducer, and encoder of a pacinian corpuscle (skin receptor)?
- Filter → connective tissue capsule - Transducer → unmyelinated free nerve ending → produces a receptor potential when deformed - Encoder → the trigger zone → first Node of Ranvier
Trace the pathway of visual signal from the retina to the lateral geniculate nuclei (LGN).
- Ganglions are excited within the retina → AP sent to optic nerve → optic chiasm → optic tracts → lateral geniculate nucleus (also to the superior colliculus and pretectal region) - At the optic chiasm: nasal hemiretina = crossing of stimulus to contralateral side of where it was received & temporal hemiretina = stimulus stays on the ipsilateral side
Where do ipsilateral and contralateral axons synapse in the LGN?
- Ipsilateral axons (info from temporal hemiretina) synapse in layers 2,3,5 - Contralateral axons (info from nasal hemiretina) synapse in layers 1,4,6
What types of mechanoreceptors are slow adapting?
- Merkel's disk - Ruffini's ending
Compare the two types of ganglion cells.
- P-type (parvo): small, majority of ganglions, small receptive field, slow APs - M-type (magno): large, only 10% of ganglions, large receptive fields, rapid APs
What are the five types of taste sensations?
- Sweet (stereochemical configuration of glucose) - salty (NaCl) - bitter (quinine, toxic plants) - sour (acids) - umami (glutamate)
How is the membrane potential generated?
- a change in the permeability of Na+ and K+
What else is taste influenced by?
- adaptation, memory, and conditioning - culture (taste is acquired)
What type of coding is the least measurable?
- affect coding - takes into account emotional content, learning, memory (depends on prior input)
What could be causes of an intracranial headache?
- alcohol --> toxicity irritates meninges - constipation
Explain the Young-Helmholtz trichromatic theory.
- any color can be created by combination of 3 primary colors - we perceive color by activating red, green, and blue cones
How is the pressure on the membrane increased?
- by increasing the force on the membrane (done by movement of ossicles on oval window) - reducing the surface area of the membrane (SA less on oval window compared to tympanic membrane.....smaller membrane receives greater pressure)
How is intensity (magnitude) coding determined?
- by the total number of impulses per second coming from the receptor population
Explain the steps of accommodation.
- ciliary muscle contracts - suspensory ligaments (zonules) relax - lens becomes thicker --> increases refractive power - objects up close come into focus
What are the three types of papillae (contain tastebuds)?
- circumvallate: posterior 1/3 of tongue - foliate: posterior and lateral surfaces of tongue - fungiform: top and sides of tongue
What is included in the inner ear?
- cochlea (contains organ of corti) - vestibular apparatus
Rinne test is?
- difference of loudness perceived by patient of tuning fork placed on mastoid process vs near ear (not on bone) - If louder touching mastoid process → conduction deafness - If same intensity → neurosensory deafness
What is the interaural time delay?
- difference of time between sound arriving at one ear vs the other - larger interaural time delay the more horizontally to one side the sound is coming from (0 msec delay from straight ahead)
direct vs consensual light reflex
- direct pupillary reflex is pupillary response to light that enters the ipsilateral (same) eye - consensual pupillary reflex is response of a pupil to light that enters the contralateral (opposite) eye
Filters can be ______. Transducers are ______.
- dispensable, indispensable - without transducer, no AP!!
What are the two parallel pathways of somatic sensation?
- dorsal column medial lemniscal pathway (A alpha, A beta, A delta) - spinothalamic pathway (A delta, C)
Why does the basilar membrane holding the hair cells vibrate easily at sound waves?
- due partly to coiling of cochlea - due mainly to how the structure of the membrane varies along its length (wider at apex than base and stiffness decreases from base to apex)
What happens after the membrane potential is formed?
- encoder - the receptor potential is converted into an AP
In the basic organization of the sensory system, what happens after sensory receptors sense the stimulus?
- filter - modify and limit the signal (eliminates unnecessary stimulus)
Where are the first, second, and third synapses regarding taste?
- first: taste bud - second: medulla - third: thalamus (signal then ends on the primary gustatory cortex)
Define rate.
- frequency of APs in individual sensory units - stronger stimulus = more APs sent up afferent fibers of sensory unit
List the different types of mechanoreceptors and their sensation plz
- hair receptor: touch, movement - pacinian corpuscle: touch, vibration - ruffini ending (corpuscle): touch, skin stretch - meissner corpuscle: touch, flutter, movement - merkel disk receptor (this one is the only type of sensory receptor in the somatosensory system): touch, pressure, form
In terms of types of color vision, what are dichromats?
- have 2 types of functioning cone cells - Protanopes → no red = red looks black - Deuteranopes → no green - Tritanopes → sensitivity to short wavelengths of light
What are some features of the magnocellular pathway?
- have binocular receptive fields, sense brightness but not color, have direction sensitivity to analyze object motion (direction of something) - the same stimulus on the same rod is read much better from one direction than the other (AP discharge varies)
What are some features of the parvocellular pathway?
- have binocular, rectangular receptive fields, are very sensitive to wavelength of light (red and green) and are sensitive to stimulus orientation which allows us to see object shapes - this is the pathway that is helpful to identify differences in facial features even if they are small differences
High frequency sound vs high intensity sound?
- high frequency is perceived as higher pitch - high intensity is perceived as louder
What is the tectorial membrane?
- holds the tips of the hairs - has flexible attachment but considerable mass - bends freely with slow movements but stiff with fast movements (sound frequencies)
What is the hypothalamus important for?
- important for responding to day length and regulating circadian and seasonal rhythms - synchronizes sleep and wakefulness with the daily dark-light cycle
Why don't we notice the blind spot?
- in binocular viewing, visual fields overlap and blind spot is overlayed - during monocular viewing, the blind spot is neurally filled in because the eye that sees the image can send that info to the brain
Describe what happens when the OPTIC nerve is damaged on the L side?
- ipsilateral direct reflex is lost (L eye stimulated --> neither pupil constricts) - ipsilateral consensual reflex is intact (light in R eye can still signal brain and CNIII causes constriction) - contralateral direct reflex is intact (light in R eye can still signal brain and CNIII causes constriction) - contralateral consensual reflex is lost (light shone into L eye cannot signal brain even though R eye CNIII is intact)
Describe what happens when the OCULOMOTOR nerve is damaged on the L side?
- ipsilateral direct reflex is lost (L eye stimulated --> only R pupil constricts) - ipsilateral consensual reflex is lost (R eye stimulated --> only R pupil constricts) - contralateral direct reflex is intact (light in both eyes can still signal brain and pupil on undamaged R side will constrict) - contralateral consensual reflex is intact (light shone into L eye can still signal brain via CN II and R eye will be able to constrict)
How is the somatosensory system different from other sensory systems?
- its receptors are distributed throughout the body rather than concentrated at small, specialized location - the somatosensory system is a group of at least 4 senses rather than one (tough, temp, body position, pain, and their subdivisions)
What are some features of magnocellular LGN neurons?
- large receptive fields - insensitive to wavelength differences - have features like M ganglion cells - are activated by only one eye (monocular) - respond to stimulation in receptive field with burst of APs
Explain the pretectum (light reflex).
- light in one eye dilates both pupils - reflex is mediated by retinal ganglion cells that project to the pretectum - may suspect damage to midbrain if this reflex is not working
What are the two roles of the filter?
- limits access - changes stimulus parameters
What type of coding is accomplished by an anatomical sorting or organization of the pathways and their central projections?
- location coding - example is the somatotopic organization of skin on cortex (homunculus)
How are different sound frequencies represented?
- low frequencies: phase locking used - intermediate frequencies: phase locking and tonotopy used - high frequencies: tonotopy used
What are the three pathways from the retina to the visual cortex?
- magnocellular pathway (rod cells) - parvocellular pathway (cone cells) - koniocellular pathway (blue light)
What is the function of aqueous humor?
- maintains stable pressure (too much = glaucoma) - feeds avascular tissue - maintains clear vision
What are the four categories of nociceptors (based on function)?
- mechanonociceptors: respond to intense mechanical stimulation (pinching, cutting, stretching) - thermal nociceptors: respond to burning heat (>45 deg C → tissue proteins become denatured & damage occurs) or extreme cold - chemically sensitive, mechanically insensitive nociceptors: respond to variety of agents (from environment or own tissue) --> ex: K+, pH extremes, neuroactive substances (histamine, bradykinin, etc.), various irritants - polymodal nociceptors: respond to high intensity stimuli that are a combination of mechanical, thermal & chemical stimuli (present in most body tissues EXCEPT brain)
What types of mechanoreceptors are fast adapting?
- meissner's CORPUSCLE - pacinian CORPUSCLE
In terms of types of color vision, what are trichromats?
- normal (can distinguish 150 hues) - Protanomalous → reduced red sensitivity (only see 5-25 hues) - Deuteranomalous → reduced green sensitivity (only see 5-25 hues)
Where are tonotopic maps found?
- on basilar membrane (base = higher frequencies, apex = lower frequencies) - auditory nerve (different afferent fibers for different frequencies) - cochlear nucleus (where afferent auditory nerve fibers synapse) - Also found in each auditory nerve relay nuclei, medial geniculate nucleus (MGN) & auditory cortex → certain areas of these organs for certain sound frequency information
What types of mechanoreceptors have a large receptive field?
- pacinian corpuscle - ruffini's ending
What is the gate theory of pain?
- pain can be modified by non-painful sensory input via neural pathways in brain ---> pain sensation (from A delta and C) is reduced when other somatosensory signals are present (from A alpha and A beta)
What are the 3 layers of the tear film?
- posterior layer (rich in glycoproteins) - watery middle layer (secreted from lacrimal tissue) - anterior oily layer (produced by meibomian glands in eyelids)
Compare rapidly adapting mechanoreceptors to slowly adapting ones.
- rapidly adapting mechanoreceptors: respond quickly at first, then stop firing although stimulus continues - slowly adapting mechanoreceptors: generate more sustained response during long stimulus - best suited to represent static stimuli
What are the two interrelated ways sound intensity is coded?
- rate (as sound intensity increases, auditory nerve fiber fire APs faster) - recruitment (as sound intensity increases, additional receptors get recruited)
What are the 3 types of taste cells?
- receptor cells: modified epithelial cells: 50-150 per taste bud - supporting cells: develop into receptor cells - basal cells: develop into supporting cells
What comprises rhodopsin?
- receptor protein (opsin) - prebound chemical agonist (retinal)
What are some features of parvocellular LGN neurons?
- relatively small, circular receptive fields - very sensitive to wavelength differences - activated by only one eye - respond to stimulation from receptive field with sustained increase in frequency of APs - have features just like P ganglion cells
What happens when the eye returns to resting state?
- retinoid cycle - Transducin reassembles, PDE is inactivated, more cGMP, channels re-open allowing sodium to flow in
Where are the photoreceptors located?
- rods are spread over the entire retina except the fovea - cones are mainly located only in the fovea
What are the main functions of the sensory systems?
- sense environmental features - encode the features - transmit the info to the CNS for decoding - to allow the CNS to communicate with the outside world
List the three groups that sensory receptors are divided into.
- specialized receptor cells: most sensitive receptor type (ex: photoreceptor) - specialized endings on nerve fibers (ex: pacinian corpuscle) - free nerve endings: most common type; no anatomical specialization at receptor site (ex: nociceptor)
If touch was the modality, what would be an example of a sub modality and sub-sub modality?
- sub modality: itch, tickle, crude touch, discriminative touch - sub-sub modality: pressure, flutter, vibration
Can you guys explain the orientation of the semicircular canals?
- superior canals lie in the same plane as the posterior canals on the opposite side - the horizontal planes on both sides lie in the same planes - Horizontal → "across forehead" Superior → "like headphone" Posterior → "like mohawk"
sympathetic vs. parasympathetic innervation of the eye
- sympathetic (norepinephrine): pupil dilates ---> cocaine, paredrine, amphetamines - parasympathetic (acetylcholine): constricts pupil ---> pilocarpine, serine
What are some functions of the SCN?
- synchronizes sleep/wake cycles among other biological rhythms - adapts the timing cues to external environment (sunlight, noise, social interactions, alarm clocks)
Different patterns of firing may provide info about submodality. This defines ________ coding.
- temporal - receptors do not respond to constant stimuli but are more sensitive to stimulus change
What happens to the cupula when the head is stationary vs when it is bent?
- the cupula is not bent when head is stationary - the cupula is displaced by the flow of endolymph when the head moves
Total hearing loss in one ear corresponds to a loss of only...
3 Db (person may not even notice until they do a hearing test)
What is intensity?
- the difference in pressure between the compressed and rarefied patches of air (measured in decibels) - the amount of amplitude in the waves (determined by intensity)
What is a receptive field?
- the fraction of the total energy of a particular modality that initiates a response in a sensory receptor or sensory unit - sensory unit with the greatest number of sensory receptors has the largest receptive field
What happens after the stimulus is filtered and modified?
- transducer - everything is converted to membrane/receptor potential
What is the middle ear composed of?
- tympanic membrane: vibrates relative to frequency - ossicles: malleus, incus, stapes
When do warm receptors and cold receptors fire?
- warm: 30-45 deg C (fire faster during increases in temp) - cold: 30-10 deg C (fire faster during reductions in temp)
sensation allows us to understand....
- what, where, when, and how much - why and how are higher brain functions
How do outer hair cells respond to sound?
- with both receptor potential and a change in length - receptor potential generated by transducer: inner hair cells - change in length: motor proteins within outer hair cell bodies contract when cell is depolarized (via K+ influx); motor proteins expanded upon repolarization
Compare the refractive power of a young healthy lens, 40 year old lens, and 60 year old lens.
- young, healthy: 15 diopters - 40 year old: 8 diopters - 60 year old: 1 to 2 diopters
The lens is involved in formation of point images closer than about ____ meters.
9 (rays from objects at this distance or closer diverge and greater refractive power is required to bring them into focus on retina)
know that filter, transducer, and encoder chart
:P
What happens when sound waves are traveling through air and they hit the water?
-they get reflected (not much transmitted) - this is because their impedances don't match (water has high impedance and air has low impedance)
How often do receptor cells regenerate?
1 to 2 weeks (shortest-lived cells in the body)
1. loss of sense of taste: 2. diminished sense of taste: 3. persistent unpleasant taste:
1. ageusia 2. hypogeusia 3. dysgeusia
1. loss of sense of smell: 2. partial loss of smell: 3. perceiving a smell when no odor is present or perceiving familiar odors as smelling strange:
1. anosmia 2. hyposmia 3. parosmia
What frequency do we hear best at?
2,000 Hz
What type of primary afferent axon is the largest, fastest, contains proprioceptors of skeletal muscle, and is associated with group I muscle axons?
A alpha axons
What type of primary afferent axon is medium is size (6-12 um), fast (36-75 m/sec), contains mechanoreceptors of skin, and is associated with group II muscle axons?
A beta axons
Which primary afferent axons contain pain and temperature receptors?
A delta and C axons
Out of A delta and C axons which is faster?
A delta!! (C axons are unmyelinated and smaller)
treatment for Meniere's?
Can be treated with diuretics, sedatives, or steroids → more severe treatments include chemical labyrinthectomy (antibiotic that destroys hair cells so they can't be messed up), endolymphatic shunt, cut of vestibular nerve, or removal of labyrinth and CN VIII
What happens when we accommodate (when we constrict our pupils)?
F-number gets larger, the aperture gets smaller, and the depth of the field gets larger
What type of pain is characterized by pricking pain, transmitted by A delta fibers, well localized, and causes the body to want to immediately withdrawal upon stimulation?
FAST pain
_______ are third order neurons.
Ganglion cells
Does sound travel faster in water or air?
H2O
To summarize... what do photoreceptors do in response to light?
HYPERPOLARIZE
Explain phantom limb pain.
If large enough stimulus to face (or other adjacent body area in homunculus) → synapse on facial area on homunculus & also synapses on adjacent area corresponding to missing limb → stimulus perceived as sensation from phantom limb
How do you test color vision?
Ishihara plates (colorful circles with numbers of a different color)
endolymph is high in.....
K+
Endolymph is high in _____. Perilymph is high in _____.
K+, Na+
Explain what happens when light is absorbed.
Light stimulus (activation of rhodopsin = bleaching) → G-protein stimulation of transducin → activation of PDE (phosphodiesterase) → cGMP breakdown & closing of cGMP channels → hyperpolarization (inhibits the inhibitory responses --- there is no inhibitory NT going to bipolar cells which means APs can reach ganglion cells)
Edema in the inner ear of an unknown cause.....
Meniere's Disease
What kind of cells are olfactory receptors?
NEURONAL (they are both the transducer and the encoder --> it can make the AP on its own without ions)
What is it called when older people start to lose hearing at higher frequencies?
PRESBYCUSIS - they need higher intensity (loudness) to perceive sound
_________ is similar to CSF.
Perilymph
What type of pain is characterized by burning/soreness, transmitted by C fibers, poorly localized, and causes the body to want to immobilize to allow for healing?
SLOW pain
List the steps in transduction of hair cells.
Sound waves → endolymph movement → hair bending → mechanical opening of K+ channels → K+ influx (depolarization) → voltage-gated Ca2+ channel opening → Ca2+ influx from perilymph → NT release from hair cell → NT binding to receptors on spiral ganglion → AP generated down auditory nerve
Describe the pupillary reflex.
Stimulus in L eye → synapse on L optic nerve (CN II) → travels through optic chiasm to Edinger-Westphal nucleus → pathway sends signal via oculomotor nerve (CN III) to both eyes
What is the most important step in the organization of the sensory systems?
TRANSDUCER! (generates the membrane potential)
How is what we see of the visual world projected onto the retina?
The image of the target is reversed on the retina by the lens system
Describer the population coding in taste cells.
The submodalities have a preferred stimulus that they prefer (ex: salt) and can send the maximal amount of stimulus to the brain for.... this same submodality can also sense other stimuli (ex: bitter, sour) but not the best for sensing these stimuli
Explain the mechanism of taste transduction.
Two pathways: Ions → enter ion channel → depolarization of cell → Ca influx → vesicle of neurotransmitter sent to synaptic cleft → AP generated "complex stimuli" → stimulate ER to release Ca → vesicle of neurotransmitter sent to synaptic cleft → AP generated
What cranial nerves innervate the taste buds?
VII, IX, X
What is Hertz?
cycles per second (how frequency is measured)
What is a complex sound?
a spectrum of pure tones each of different frequencies
What is the superior colliculus?
a structure in the brainstem that is involved in orienting the eye toward a stimulus that initially appears in the peripheral field of vision
What does it mean when we say the ossicles of the ear act as a matching device?
allows sound waves to be transmitted from air to water (middle to inner ear)
The difference between wave trough and peak...
amplitude
The swelling on each semicircular canal is an _______
ampulla (these contain sensory epithelia known as the ampullary crest)
Where is the aqueous humor located?
anterior segment of the eye
Define saturation.
as intensity increases, eventually nerve fiber reaches limit for carrying impulses - further stimuli do not produce corresponding increase
Afferents from the spiral ganglion enter the brainstem in the....
auditory nerve
Why is speed not as important for C axons?
because they carry info about chronic pain --> not something that needs immediate attention (like stepping on a nail)
What kind of light has high energy content (high frequency, short wavelength)?
blue light (gamma radiation, x-rays)
How are ganglion cell receptive fields organized?
center-surround organization
An auditory neuron is most responsive to sound at one frequency. This is called its....
characteristic frequency
_____________ are among the oldest and most influential of all sensory mechanisms.
chemosensations
What at happens at ~45 degrees C?
cold receptors activated more than warm receptors → person may sense cold even though temp is high
Hearing interference due to middle ear conduction or dysfunction commonly caused by wax build up (otosclerosis).
conduction deafness
Do rods or cones have higher visual acuity?
cones
What accounts for most of our central vision and detects color and bright lights?
cones
Which responds faster... rods or cones?
cones (rods have a slow response time which is why it takes a minute to adjust to the dark)
What else does the superior colliculus help with?
controls automatic saccades that keep a steady image on the fovea of the retina
The ________ is part of the outer layer of the eye which also includes the sclera.
cornea (protects internal eye structures)
When fluid is moving toward the utricle, what happens?
depolarization and AP occur (the opposite side will have fluid moving away from utricle and no AP)
In complete darkness, what is the membrane potential of the outer segment (of the rod)?
depolarized
Explain the concept of blind sight and the superior colliculus?
detection of stimulus and movement even when visual perception is lost because the visual pathway passes through the superior colliculus
What is the dorsal visual pathway used for?
determining object position in space (ex: know where coffee mug is positioned to be able to reach for it)
Neuronal damage due to diabetes... patient may be unaware they have injury on distal portion of limbs.
diabetic neuropathy
what can Meniere's disease cause
dizziness, tinnitus (ringing in the ears), and distorted hearing usually affecting middle-aged individuals
ding
dong?
The ____ converts the magnitude of a receptor potential into a frequency code that is carried by actions potentials along the axon.
encoder (trigger zone)
When the head moves right, how does the cupula move?
endolymph moves to the left which displaces the cupula to the left
The _____ is an organ specialized for the detection, localization, and analysis of light.
eye
Are hair follicles fast or slow adapting?
fast
The ____ is the first component of the sensory receptor. It conditions the stimulus making the receptor function with relative specificity for one modality.
filter
The energy content of electromagnetic radiation is proportional to its _________.
frequency
The number of waves per second...
frequency
The number of compressed or rarefied patches of molecules that pass by our ears each sound is.....
frequency (frequency is fixed for each person)
negative chemotaxis:
helps to avoid noxious agents such as rotten smells and food
What is the main feature of the koniocellular pathway?
helps us to analyze the color blue
What may be a cause of a deficit in the sensation of pain?
higher endorphin activity than usual (natural pain killer) or lack of C fibers
What is the ventral visual pathway used for?
identifying objects (ex: seeing a coffee mug)
How does sound travel?
in longitudinal WAVES
What happens when there is a greater contrast between the ganglion cell receptive field and surrounding area?
increased AP frequency --> greater visual acuity
If the horizontal canal on the right side is excited, what happens to the horizontal canal on the other?
inhibited
Out of the special sensory cells, which ones are lowest in number?
inner and outer hair cells (no regeneration)
How is sound located when a continuous sound is emitted?
interaural intensity difference
The _______ functions like the diaphragm in a camera to increase or decrease the amount of light entering the eye.
iris
What is the function of the pinna?
it acts as a funnel to magnify pressure
What can happen when the ganglion cell contrast is enhanced?
it can cause a distortion of the perception of light and dark (boxes with different contrasts and center looks different)
What is the purpose of pain?
it is a protective mechanism for the body
Are free nerve endings fast or slow adapting?
it just depends...
How is the olfactory system similar to gustation?
it uses simultaneous responses of a large population of receptors to be ablet to encode a specific stimulus
How does phototransduction differ in cones?
it's the same except a different type of opsin (receptor protein) is used in the outer segments
What is the function of the tear film?
keeps the cornea moisturized so it can function
At the LGN, are inputs from both eyes combine or kept separate?
kept separate
Define threshold.
minimum value of intensity needed to cause an AP
List the five attributes of sensory coding.
modality, location, intensity, temporal, affect
Why is the gustatory pathway distinct?
most of its fibers are uncrossed
Explain the path of sound in cochlea.
movement of basilar membrane via sound waves through liquid → movement of fixed tectorial membrane (bending of stereocilia of outer hair cells/filters) → increased pressure stereocilia of inner hair cells → signals transduced to spiral ganglion (encoder) deep to basilar membrane → APs sent to auditory nerve
What could be causes of an extracranial headache?
muscle spasms, sinus headaches, eye disorders
Hearing deficit due to damage to cochlea or central auditory neurons commonly caused by loud sounds or tumors.
neuronal deafness
Are the axons that travel from the nasal cavity to the olfactory bulb myelinated?
no (very slow APs)
Is the relationship between the receptor potential and stimulus strength linear?
nooo (eventually saturation occurs and receptor potential flattens out)
Does most of our perception of taste come from taste itself?
nope (taste buds only identify 5 flavors... our nose does the rest by identifying "odor molecules" from food)
Define recruitment.
number of units activated by stimulus increases with stimulus intensity
Name the refelx: compensates for head tilt in the vertical plane, receives input from otoliths...when something tilts out of vertical position, otoliths estimate the deviation and initiate counter rolling of eyes to compensate
ocular counter-rolling response (otolith reflex)
Summarize the olfactory transduction pathway.
odorant molecule absorbed in mucus → binds receptor → stimulation of AC and upregulate cAMP → channel opens to influx Ca2+ in → activation of Cl- out → depolarization = receptor potential and potentially an AP
If a person is colorblind, they are missing....
one or more of the cone photopigment types (R, G, or B)
Where do all ascending pathways converge?
onto the inferior colliculus
The ________ is the joining of the optic nerves of each eye just above the pituitary gland.
optic chiasm (axons cross which allows us to see in 3D)
The _____ exits the left and right eyes at the optic disks and passes through the holes in the floor of the skull.
optic nerve
The LGN cells project the primary visual cortex (striate cortex) through the __________.
optic radiation
The ______ are the axons projecting from the optic chiasm toward specific regions of the brain.
optic tracts
The ________ supplements the vestibulo-ocular reflexes. It allows the eye to follow objects in motion when the head remains stationary.
optokinetic system
The otolithic membrane is a gelatinous mass containing ______, stones of calcium crystals (calcite).
otoconia (ear stones that sit on top of otolithic membrane; provide more gravitational force than just a membranous gel would and creates more accuracy with awareness of movements)
What window do ossicles amplify sound force at?
oval window
What are some chemosenses of the internal environment?
pCO2, pO2, and osmolarity
What is referred pain?
pain referred from the area of damage to another area (ex: kidney pain felt in lower back)
Explain the gate theory of pain pathway.
pain stimulus: nociceptor senses pain via C fiber stimulation → inhibitory interneuron inhibited (stopped) → maximal excitation of projection neuron in CNS → pain signal sent up ST tract mechanical stimulus: mechanoreceptor senses stimulation via A𝞫 fiber → inhibitory interneuron excited (activated) → reduced excitation of projection neuron in CNS → decreased pain signal sent up ST tract
The semicircular canals are surrounded by ______ and contain the fluid, ______.
perilymph, endolymph
The ______ is the time duration of one cycle of vibration in seconds. It is the inverse of frequency.
period
What is the main issue when hearing is lost in one ear?
person can't localize sounds
Pain of a missing limb?
phantom pain (same pathway that would have been activated for missing limb pain, activated by another stimulus??)
What are examples of first order neurons?
photoreceptors (rods and cones)
Explain the pathway for processing light.
photoreceptors (transducers) → synapse with bipolar neurons (second order neurons) → synapse with ganglionic cells (third order neurons & encoders) → send AP through optic nerve
_____ respond to 2 or more forms of stimuli (such as mechanical and thermal)
poly-modal receptors
What type of coding is defined by receptors and circuits being not being ultimately selective and the CNS analyzing all the chemical responses to pinpoint the stimulus?
population coding (pattern coding)
What is the monocular zone?
portion of the visual field associated with only one eye
taste and smell involve both...
positive and negative chemotaxis
What is pressure equal to?
pressure = force/surface area
Does the pressure at the oval window need to be greater or less than the pressure at the tympanic membrane in order for the sound waves to travel through air to pass into the fluid of the cochlea?
pressure needs to be GREATER at oval window
How is the bending of the stereocilia produced?
produced by the upward motion of the basilar membrane
what's a vestibular nystagmus?
rapid movement of eyes after sustained rotation of head
What are the basic mechanisms of intensity coding?
rate, recruitment, adaptation, threshold, saturation
The _________ of a cell in the visual system is the area of retina that, when stimulated by light, changes the cell's membrane potential.
receptive field
What kind of light has low energy content (low frequency, longer wavelength)?
red light (radar, radio waves)
What is localization of sound in the vertical planed based on?
reflection from the pinna
chemoreceptors...
sense chemical stimuli (taste, smell)
photoreceptors...
sense light stimuli (sight)
Mechanoreceptors....
sense mechanical stimuli (touch, sound)
nociceptors
sense pain stimuli
osmoreceptors...
sense pressure stimuli
thermoreceptors...
sense temperature stimuli
Outline the path of the AP once it reaches the CNS.
sensory systems --> association systems --> effector (motor) systems --> effectors --> response
sensory receptors are connected to...
sensory units
Does receptor potential travel short or long distances?
short
How are vestibular hair cells similar and different to cochlear hair cells?
similar because they both contain stereocilia on the apical surface but different because vestibular hair cells have a kinocilium
When the stereocilia are bent toward the kinocilium, what happens?
the hair cell is depolarized and more NT is released
What happens when the stereocilia are bent away from the kinocilium?
the hair cell is hyperpolarized and less NT is released
How does interaural intensity difference work?
the head casts a sound shadow causing a more intense sound in one ear than the other
the larger the receptor potential....
the higher the frequency of action potentials
What are the four dorsal layers of the LGN know as?
the parvocellular LGN layers (contain smaller cells and P-type ganglion cells project here)
What helps to sharpen the responsiveness of the hair cells?
the vibration pattern of the basilar membrane and the tonotopic arrangement of hair cells along the membrane
What is located at the encoder?
the voltage gated Na+ and K+ channels that produce the AP
What is the F-number of the eye? (f-stop)
the ratio of the focal length of the eye (from cornea to retina) and physical aperture (pupil opening) F-number = focal length (fixed #)/aperture diameter
What happens when complex sounds have no dominant rhythm?
the sound gets perceived as noise, hisses, or scratches
What is pure tone?
the sound made from only one single frequency
What does visual acuity depend on?
the spacing of the photoreceptors in the retina
What happens when high sound frequencies come in contact with basilar membrane?
the stiffer base of the membrane will vibrate and the pressure wave will not propagate to the apex
Where is the medial geniculate nucleus?
the thalamus (MGN)
What does it mean when we say modality coding is done by "labeled lines"?
there is an anatomical grouping of receptors and pathways devoted to particular modality (aka Place Theory - specific pathways for particular modalities!)
What is special about the two ventral layers of the LGN?
these are the magnocellular layers (contain large neurons and M-type retinal ganglion project here)
What is the function of ganglion cells?
they are the encoders.... generate axons that travel through the optic nerve to the brain
Olfactory neurons are special because....
they are the only neurons that undergo constant renewal (rapid turnover every 4-8 weeks from basal cells to receptor cells)
When there is a greater amount of the tastant, what happens to the firing rate of afferent fibers?
they fire faster
What is the function of the basal cells (stem cells) in the olfactory epithelium?
they turn into mature receptor cells
Why do receptor cells need innervation?
they will degenerate without
What does it mean when we say submodality coding is done by "pattern codes"?
this is the pattern of activity within the system of labeled lines (ex: color vision uses 3 cone types - red, green, blue --> red goes through red pathway)
What are the koniocellular layers?
tiny neurons that lie just ventral to each layer (their ganglion cannot be classified as P or M cells)
What is the function of the lens?
to focus light on the retina
Where does output from the superior colliculus go?
to motor centers responsible for orienting behaviors (quick responses)
What is the main function of the cornea?
to refract (bend) light
The systematic organization within an auditory structure based on characteristic frequency is...
tonotopy (certain frequencies go to certain places within auditory organ (ex: cochlea))
In terms of types of color vision, what are monochromats?
totally color blind --> the world is gray :,(
What is the role of the vestibular sensory organs?
transduce the forces associated with head acceleration and gravity into a biological signal
The second component of the sensory receptor, ______ , creates the receptor potential.
transducer
The taste receptors are the ______ and the afferent fibers are the ______.
transducers, encoders
Name the reflex: compensates for linear head movement, receives input from otoliths...modification of eyes moving while something near or far is also moving
translational vestibulo-ocular reflex (otolith reflex)
Name the reflex: important in maintaining vertical posture....when the head moves the vestibular system responds much faster than the visual system and provides an early warning for derangements of posture (signals from vestibular nuclei to spinal cord).
vestibulospinal reflex
What are Pacinian corpuscles sensitive to?
vibrating, high-frequency stimuli (this is because of their surrounding capsule - great at sensing changing stimuli, but unresponsive to steady pressure)
The ________ is the ability of the eye to distinguish between two nearby points.
visual acuity
The __________ is the total amount of space that can be viewed by the retina when the eye is fixated straight ahead.
visual field
The _______ is the spacing between cycles, in meters.
wavelength
The distance between successive waves is....
wavelength
When is an AP generated at the encoder?
when the receptor potential entering the trigger zone is above the threshold
What is the binocular zone?
where left and right visual fields overlap (both eyes see image)
In the otolithic organs, can the hair cell stereocilia be bent even when the head is stationary?
yep
Can one receptor cell respond to more than one basic category of taste?
yes but it has a preferred taste at threshold levels
What temperature can someone not tell if it is cold or warm?
~35 deg C (this is bc warm and cold receptors are equally activated)
