Bio 225 - Exam 2 - Sensory Systems (incomplete)

Sensory systems do what (broad)

detect stimuli and send information to an integrating center

convert info abt stimulus into action potentials

What detects sensory stimuli

neurons (receptor protein in neuron) or accessory cells (receptor protein in epithelial censory cell) (in areas/tissues that need to be replaced a lot such as skin)

Sensory receptors what do they do

convert incoming stimuli into changes in membrane potential

sensory receptors can be classified by their…

stimulus modality

Sesnory receptor types

chemoreceptors - detect the presence of chemicals in the environment

mechanoreceptors - detect pressure and movement, including proprioception

photoreceptors - detect light

thermoreceptors - detect temperature

electroreceptors - detect electric fields (fish)

magnetoreceptors - detect magnetic fields (birds)

sensory receptors encode 4 important features

stimulus modality, location, intensity, and duration

labeled line theory

separate and dedicated sensory pathways encode different stimulus modalities (ex: taste, smell, and touch)

A _____ _____ neuron is associated with one type of ______

particular afferent; receptor

Each _____ _____ follows a particular ____ for ______

afferent neuron; pathway; integration

Polymodal receptors

are sensitive to multiple sensory modalities

Polymodal nocireceptors tranduce _____, ____, and _____ cues into ____ that are sensed as _____

thermal; mechanical; chemical; signals; pain

_____ of ____ ______ likely encodes ______ information from some polymodal receptors

pattern; action potentials; modality

Types of receptive fields

large receptive fields and small receptive fields

Overlapping receptive fields do what

improve ability to localize stimulus

Lateral inhibition function

improves acuity (defining exactly where touch is)

Action potential frequency encodes

stimulus strength

Receptor potential

a graded potential w/in the receptor

Sensory receptors encode a _____ range of stimulus ______

limited; intensities

Dynamic range

at what point does a receptor start sensing something and at what point does it reach saturation

Sensory discrimination improves by

distributing sensitivity amongst the receptor population

graph shows good sensitivity and large dynamic range

_______ _____ ___ __________ allows for a compromise b/w dynamic range and discriminaiton

logarithmic encoding of intensity

Tonic receptors

can encode stimulus duration

Phasic receptors

encode changes in stimulus

can do so in several ways

Types of chemoreceptors

exteroceptors:

interoceptors:

Exteroceptors

external to body (could be in the mouth/nasal passages)

• olfaction

• gustation

• nocioception

• ?pheromones?

Interoceptors

internal to body

• blood pH

• Chemosensors in stomach

• BP sensors

Odorant receptors neurons - receptor type and mechanism

express G-protein coupled receptors

Each afferent ORN expresses a

single odorant receptor

Combinatorial code for odors

odorant molecules binds G-protein receptor (can bind multiple different receptor types) —> tiggers combination of ORNs —> transmitted to brain for processing (diff. combinations = different smells)

Afferent ORNs w/ same GPCR connect to

the same region of the olfactory bulb (glomerulus) - the brain reads these combinations aas distinct patterns of activation in the olfactory bulbs - this is the combinatorial code for odors

5 tastes

sweet, bitter, salty, sour, umami

Gustatory receptors use

GPCRs to detect sweet and bitter tastes

Sweet Sensory Pathway

Bitter Sensory Pathway

Sour Sensory Pathway

Salty Sensory Pathway

Variations on mechanoreception

touch/pressure

proprioception

equilibrium/balance

hearing

baroreception (BP sensing)

What kind of receptors are widely disperesed in the skin

touch receptors

combination of tonic (Merkel’s disks - for light and fine touch) and phasic (Fuffini corpuscle - sense deep touch - have large receptive fields that don’t overlap as much) receptors which allows for dtection of both transient and sustained stimuli

Proprioceptors monitor

the position of the body in space - knowing where you are in space

vertigo: not knowing where you are in space

Muscle spindle fiber

senses stretch - causes contraction - incresaes contractile force

ex: stretching before box jump by bouncing/loading

lack of causes muscle discordination

Golgi tendon organ

senses overstretching of muscle - cause muscle relaxation

protection mechanism

Invertebrate ______ employ _____ for equilibrium

statocysts; mechanoreceptors

ciliated sensory neurons: the mechanoreceptors

helps signal which direction the lobster is moving in/oriented

The ____ cell is the _______ responsivle for hearing and ______ in vertebrates

hair; mechanoreceptor; balance

Hair cells general

are bathed in endolymph

maintain high external K+ relative to internal K+

hair cell is and main components

is an epithelial cell

kinocilium and stererocilia

tip links

mechanically-gated K+ (cation) channels (TRP) at stereocilia tips

voltage-gated Ca2+ channels at body of epithelial cells

Hair cells maintain ______ ____ on to _____ ____, even in the absence of ______

transmitter release; afferent neuron; delfection

Stereocilia ______ modulate _____ ________ and _______ _____ in hair cells

deflections; K+ conductance; transmitter release

movement to left - cilia move right: depolarization —> higher frequency of APs

movement to right - cilia move left: hyperpolarization —> lower frequency of APs

Where are the mechanreceptors necessary for hearing and balance located

inner ear - vestibular apparatus which includes utricle, saccule, and semicircular canals

Hair cells in _____ and _____ detect movements of _______ _____

utricle; saccule; otolithic membranes

x+y movement (front/back and up/down)

Macula of utricle

recognizes veritcal movement

macula of saccule

recognizes horizontal movement

hearing rocks

otoliths

Label ear (bottom clockwise)

tympanic membrane

ossicles (malleus, incus, stapes)

semicircular canals (balance)

utricle (balance)

saccule (balance)

vestibular apparatus (balance)

cochlea (hearing)

vestibular nerve (hearing)

oval window (hearing and balance)

round window (hearing)

Gelatinous layer

is a liquid (incompressible)

moves due to our movement or movement of oval window

Hair cells in ______ ____ deteect movements of the _____

semicircular canals; cupula

The middle ear

transforms sound waves into basilar membrane vibrations

The hair cells of the ____ amplify and transduce ____ _____ ____

cochlea (middle ear); basilar membrane movement/vibration

Label left to right row by row

malleus, incus, stapes, oval window

auditory canal, tympanic membrane, round window

vestibular duct, cochlear duct, organ of corti

basilar membrane, tectorial membrane, hair cells, tympanic duct

Organ of corti contains

outer and inner hair cells

hair cells are an example of

of mechanoreceptors and epithelial sensory receptor cells

inner and outer hair cells detect

basilar membrane movemements - down is inhibition and up is excitation

Outer hair cells

amplify sounds through “somatic electromotility” aka dancing

Inner hair cells

transduce basilar membrane vibrations into nerve impulses - sense frequency

How does the basilar membrane detect different sound frequencies

different regions of the basilar membrane resonate with different sound frequencies

Photoreceptors

convert light energy into changes in membrane potential