animal sensory

Question 1

what is the general pathway for sensing a stimuli?

Answer 1

stimulus –> change in AP frequency –> CNS –> response

Question 2

what do each of these receptors detect?
1) mechanoreceptors
2) chemoreceptors
3) photoreceptors
4) thermoreceptors
5) nocireceptors
6) electroreceptors
7) magnetoreceptors

Answer 2

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

Question 3

what are the two signal transduction pathways for a stimulus?

Answer 3

specialized sensory neuron –> CNS
specialized sensory receptor –> neuron
–> CNS

Question 4

what happens in the outer ear?

Answer 4

• 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)

Question 5

what happens in the middle ear?

Answer 5

• stapes vibrates against oval window
• oval window oscillates and creates waves in fluid inside cochlea

Question 6

what happens in the inner ear?

Answer 6

• hair cells (mechanoreceptors) in cochlea pick up vibrations and transduce them into neuron signals
• neurons pass action potentials to CNS for sound interpretation

Question 7

what is the overall pathway through the ear?

Answer 7

ear canal –> eardrum –> stapes –> oval window –> cochlea

Question 8

what are stereocilia?

Answer 8

microvili reinforced with actin found on hair cells, opens and closes ion channels

Question 9

what happens when stereocilia bend towards the kinocilium?

Answer 9

• 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

Question 10

what happens when stereocilia bend away from the kinocilium?

Answer 10

• membrane hyperpolarizes
• ion channels close
• APs are inhibited

Question 11

what part of the eye is the sclera?

Answer 11

tough, white outermost layer

Question 12

what part of the eye is the cornea?

Answer 12

thin connective tissue at the front of the sclera, has the pupil which lets light in

Question 13

what does the iris do?

Answer 13

muscle that controls the amount of light entering

Question 14

what is the retina? what are in different layers?

Answer 14

innermost layer with concentrations of photoreceptors and neurons
epithelium: photoreceptors
intermediate: connecting neurons
innermost: ganglion cells

Question 15

what do rods detect? what do cones detect?

Answer 15

rods: dim light
cones: wavelengths of light

Question 16

describe the sensory pathway for an odorant

Answer 16

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

Question 17

which direction do sensory action potentials travel (towards/away from cell)?

Answer 17

towards the cell body (different than in other neurons)

Question 18

what are the different effects caused by photoreception and olfaction?

Answer 18

photoreception = hyperpolarization
olfaction = depolarization

Question 19

what are the second messengers for photoreception and olfaction?

Answer 19

photoreception = cGMP
olfaction = cAMP

Question 20

where are the receptors for photoreception and olfaction?

Answer 20

photoreception = epithelial cells
olfaction = receptor neurons

Question 21

describe the pathway taken when glucose levels are too high

Answer 21

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

Question 22

what are the components of rods and cones?

Answer 22

• opsin (transmembrane protein)
• retinal (pigment)
• together = rhodopsin (rod cells)

Question 23

how does retinal react when it detects light?

Answer 23

• 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

Question 24

what are the steps for rods detecting light?

Answer 24

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

Question 25

what are the three opsins and their colours?

Answer 25

S opsin (short) = blue light
M opsin (medium) = green light
L opsin (long) = red light