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A Sensory Phys > Exam 1 > Flashcards

Exam 1 Flashcards

(49 cards)

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1
Q

bacterial chemotaxis

A

directed movement towards more favorable chemical environment or away from an unfavorable environment

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2
Q

temporal sensing

A

constantly comparing current conditions with those a few seconds/minutes ago

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3
Q

repellents

A

active RT proteins

CheA phosphorylated

CHeY phosphorylated

motor turns clockwise

tumblign

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4
Q

attractant

A

inhibit RT proteins

CheA dephosphorylated

CheY dephosphorylated

motor turns counter clockwise

running

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5
Q

3 components to bacterial chemoreception

A

sensitive response

precise adaptation

large dynamic range

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6
Q

sensitive response:adaptation

A

receptors from higher order arrays; large arrays act cooperatively (amplify signal)

when one receptor changes conformation, it can induce change in many of its neighbors

1% cange in receptor occupancy can lead to 50% change in rotational bias of flagellum

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7
Q

amplification at individual receptor level

A

one activated receptor can lead to phosphorylation of multiple CheY proteins

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8
Q

precise adaptation

A

tumble rate tends to go back to immediate state

allows bacteria to monitor temporal changes in concentration gradient (form of memory)

negative feedback loop

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9
Q

what is beneficial about bacteria’s tend to go back to intermediate state of tumbling?

A

allows bacteria to change tumble rate to any decreases or increases in chemical concentrations

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10
Q

why is it important for bacteria to monitor temporal changes in concentration gradient?

A

memory

overcomes inability to sense gradients spatially

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11
Q

how does adaptation occur

A

through methylation of 4-6 sites on receptor

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12
Q

methylation of 4-6 sites

A

increases receptor activity (tumbling) even if attractant is bound

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13
Q

CheR

A

methylates (constitutively active)

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14
Q

CheB

A

demethylates (active when phosphorylated by CheA)

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15
Q

negative feedback loop of adaptation

conc. inc.

A

more receptors bind attractant

more receptor inactivated

CheA kinase inactive

tumble suppressed

CheR methylase active / CheB demethylase inactive

receptor methylated

receptor activity increases even though attractant is still bound — more tumbling

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16
Q

negative feedback loop of adaptation

conc. dec.

A

fewer receptors bind attractant

more receptors in activated conformation

CheA kinase active

tumbles increased

CheR methylase active / CheB demethylase active

receptor demethylated

receptor activity decreases even through little attractant bound == less tumbling

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17
Q

tumble rate reflects…

A

the change in attractant concentration over time

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18
Q

large dynamic range

A

diff. between the largest and smallest stimuli which can be reliably reported/detected

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19
Q

bacteria sensory transduction & modality

A

doesn’t discriminate well between chemical stimuli since they all use same downstream effector (motor)

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20
Q

bacteria intensity

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A

greater instantaneous tumbling rate changes for greater concentration changes

21
Q

bacteria adaptation

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A

precise and robust adaptation allows for system to detect a large dynamic range and temporal sensing

22
Q

internal chemoreceptors

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A

PaO2/PaCO2

ECF pH

blood glucose levels

23
Q

internal receptors

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A

temp, osmotic pressure, body posture

24
Q

central chemoreceptors

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A

medulla

stim:

inc. PaCO2
dec. pH

25
peripheral chemoreceptors
carotid and aortic bodies stim. by inc. PaCO2 dec pH dec PaO2
26
patch clamp technique
record to measure change in membrane potential TTX: prevent communication with other cells allows observation of circuit effect not just sole effect
27
chemoreceptor cell for blood gases
respond directly to changes in CO2 or O2 connected directly or indirectly to respiratory circuit manipulations of chemoreceptor cell should affect breathing at whole animal level
28
test: direct/indirect connection to respiratory circuit
microscopy: look to see cells/neurons that make contact w chemoreceptor anterograde tracer: soma to terminal retrograde: terminals to soma transsynaptic viral: cross one or multiple synapses; entirety of circuit
29
test chemoreceptor affects breathing at whole animal level
ablation of cell or axon measure air pressure with plethysmography
30
PaO2 sensed by
carotid body
31
PaCO2 sensed by
peripheral central
32
medullar respiratory neurons
integrate info to regulate respiration vol. control over breathing rate emotional stimuli through hypothalamus stretch receptors in lungs irritant receptors receptors in muscles and joints
33
central chemoreceptors in brainstem
in RTN and NST integrates from multiple sensory systems
34
prebotzinger nucleus
initiating breathing and maintenance of rhythm
35
how is breathing regulated?
by brainstem output to phrenic motor neurons to control breathing muscles
36
central chemoreceptors respond to pH drop
induced by hypercapnia determine 70% of response changes has greater effect on CSF pH than blood pH due to weaker H+ buffering system
37
carotid bodies negative feedback loops: PaCO2 increase
chemoreceptors active inc. respiration rate and inhalation volume lowers PaCO2
38
features of carotid bodies
firing rate is typically low; dec. in CO2 or inc. in O2 can’t decrease firing rate much peripheral chemoreceptors are sensitive to small changes in particular directions sensitive to hypercapnia because CO2 levels vary more than O2 levels do
39
high altitude adaptations
hypoxia: lower air pressure, less O2 carotid body can grow
40
biochemical steps in carotid body inc. PaCO2
inc. CO2 — increased H+ and dec. pH H+ enter and close TASK K+ channels depolarization of cell Na+ outflux coupled to Ca2+ influx vesicles release catecholamines, NT, ACh, ATP inc. frequency in sensory nerves
41
doxapram
respiratory stimulant stimulates carotid body by inhibiting TASK channels
42
oxygen sensing
haem protein is associated w K+ channels and senses O2 K+ channels inhibited by reduced ATP due to impaired mito respiration
43
reduced ATP
carotid mito are more sensitive to hypoxia than other tissues mito respiration inhibitors activate type 1 cells hypoxia inhibits ETC less ATP
44
sensory sensilla
have 1 or more sensory neurons within a cuticular housing
45
sensory sensilla anatomy
uniporous 2-4 GRNs GRNs surrounded by 3-4 accessory cells multimodal
46
gustatory sensillum biophysics
tastants open receptors in tips of dendrites on GRNs receptors respond at high tastant concentrations receptor opening = depolarization dendritic sheath aids in conduction inc. concentration of tastant = inc. AP frequency
47
GRs
sugar bitter CO2
48
iR
low salt acid AA
49
labellar gustatory sensilla
each Gr receptor binds particular category of tastants most receptors can bind more than one tastant within a category diff. receptors respond to diff combinations most tastants are detected by many Gr family members each sweet and bitter GRN express multiple members of Gr fam strict segregation of sugar/bitter receptors in each GRN

A Sensory Phys (1 decks)

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