animal sensory Flashcards
what is the general pathway for sensing a stimuli?
stimulus –> change in AP frequency –> CNS –> response
what do each of these receptors detect?
1) mechanoreceptors
2) chemoreceptors
3) photoreceptors
4) thermoreceptors
5) nocireceptors
6) electroreceptors
7) magnetoreceptors
1) detects changes in pressure
2) detects specific chemical molecules
3) detects different wavelengths
4) detects changes in temperature
5) detects harmful stimuli/damage
6) detects electrical fields
7) detects magnetic fields
what are the two signal transduction pathways for a stimulus?
specialized sensory neuron –> CNS
specialized sensory receptor –> neuron
–> CNS
what happens in the outer ear?
- sound waves are funneled into ear
- sound waves hit tympanic membrane (eardrum)
- ear drum vibrates at same pitch as stimulus
- vibrations are passed to the stapes bone (middle ear)
what happens in the middle ear?
- stapes vibrates against oval window
- oval window oscillates and creates waves in fluid inside cochlea
what happens in the inner ear?
- hair cells (mechanoreceptors) in cochlea pick up vibrations and transduce them into neuron signals
- neurons pass action potentials to CNS for sound interpretation
what is the overall pathway through the ear?
ear canal –> eardrum –> stapes –> oval window –> cochlea
what are stereocilia?
microvili reinforced with actin found on hair cells, opens and closes ion channels
what happens when stereocilia bend towards the kinocilium?
- K channels open, ions flow in
- membrane depolarizes (endolymph contains excess K)
- Ca ions flow in
- NT get released into the synaptic cleft into the afferent neuron creating APs
what happens when stereocilia bend away from the kinocilium?
- membrane hyperpolarizes
- ion channels close
- APs are inhibited
what part of the eye is the sclera?
tough, white outermost layer
what part of the eye is the cornea?
thin connective tissue at the front of the sclera, has the pupil which lets light in
what does the iris do?
muscle that controls the amount of light entering
what is the retina? what are in different layers?
innermost layer with concentrations of photoreceptors and neurons
epithelium: photoreceptors
intermediate: connecting neurons
innermost: ganglion cells
what do rods detect? what do cones detect?
rods: dim light
cones: wavelengths of light
describe the sensory pathway for an odorant
1) odorant enters nose, diffuses through the mucus layer
2) binds to and conforms the shape of olfactory receptory neurons
3) G-proteins are activated and triggers activation of adenylyl cyclase
4) adenylyl cyclase converts ATP into cAMP
5) cAMP opens gated Na and Ca ion channels, which depolarize the membrane
6) Ca influx opens gated Cl ion channels which flows out and further depolarizes membrane
7) ion flows opens voltage gated Na channels, creating an AP
8) AP is sent by neuron axons through olfactory bulb to CNS
which direction do sensory action potentials travel (towards/away from cell)?
towards the cell body (different than in other neurons)
what are the different effects caused by photoreception and olfaction?
photoreception = hyperpolarization
olfaction = depolarization
what are the second messengers for photoreception and olfaction?
photoreception = cGMP
olfaction = cAMP
where are the receptors for photoreception and olfaction?
photoreception = epithelial cells
olfaction = receptor neurons
describe the pathway taken when glucose levels are too high
1) glucose enters pancreatic cell
2) glucose powers ATP production in mitochondria
3) ATP blocks K-ATP channels, depolarizing membrane
4) voltage gated Ca channels open, bringing in Ca ions
5) presense of Ca ions causes secretion of insulin
6) insulin stimulates liver cells to store excess glucose as glycogen
what are the components of rods and cones?
- opsin (transmembrane protein)
- retinal (pigment)
- together = rhodopsin (rod cells)
how does retinal react when it detects light?
- cis to trans conformation
- “light switch”
- changes shape when interacting with photons, which causes opsin to morph
- Na channels close, membrane hyperpolarizes and decreases NT released
what are the steps for rods detecting light?
1) light activated retinol conformation activates rhodopsin
2) rhodopsin activates the protein transducin which activates the enzyme PDE
3) PDE converts cGMP into GMP
4) drop in cGMP closes cGMP-gated Na channels
5) membrane hyperpolarizes
6) amount of neurotransmitters released decreases which signals to bipolar cells that rod detected light
what are the three opsins and their colours?
S opsin (short) = blue light
M opsin (medium) = green light
L opsin (long) = red light
