Advanced Physiology Exam I Topic 4

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topic 4
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College: Fourth year
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physiology
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1

transduction

event that initiaties sensation (detects phsyical signal in the world and converts into neural signal

2

type 1 receptor

receptor cell triggers AP directly

3

type II receptor

forms a synapse on another cell, this second cell generates AP

4

photoreceptor (transduction of light)

doesnt make AP...synapses onto the bipolar cell (type II receptor)
bipolar cells then synapse onto ganglion cells, which generate AP

5

rhodopsin

key component of the transduction (photo) machinery...within rhodopsin is retinal (dark configuration vs. light configuration)...light config activates G protein causing alpha subunit to activate enzyme phosphdiesterase (PDE) which breaks down cGMP

6

rods

more sensative than cones...can detect light in low light but in daylight become saturated and can no longer respond to changes

7

3 reasons why rods are more sensative

1.larger outer segment...more chance to absorb light
2. long-lasting responses compared to cones (temporal summation)
3. rods converge on sigle ganlion cells...allows for tremndous spatial summation

8

cones

more spatially precise than rods...get greater visual acuity from cones than from rods

9

2 reasons why cones are more precise

1. rods have long-lasting responses...get smeared out as eye move
2. rods show tremendous convergenxe to ganglion cells...cant resolve where the signals come from on retina

10

cones responsible for colr vision

*S cones--short wavelengths
*M cones--medium wavelenths
*L cones--long wavelengths

11

fovea

region of the retina directly back from the pupil (where cones are mostly located)
high visual acuity, but low light sensitivity...only region with color vision

12

2 chemoreceptor systems

taste and smell (microvilli on taste cells, cilia on olfactory)

13

mechanoreceptors (3 possible theories to opening channels)

1. displacement distorts cell membrane
2. membrane-bound channel is pysically linked to extra/intr matrix
3. the activation of G protein

14

stereocilia (auditory system)

the surface wher the reularly arranged projections (hair cells) exist...is where transduction occurs.
have mechanically gated K channels that cause change (tip link of spring open channels...K flows through and changes Vm)

15

endolymph

solution that allows K to actually depolarize the channels in hari cells

16

basilar membrane

determines pitch (varies its width through the length of the cochlea to determine pitch)
CNS looks at different locations along the cochlea to deduce the frequency

17

THe cochlea conveys to the CNS

loudness of sound and frequency of sound

18

three principles of sensory coding

receptive fields
rate coding
labeled lines
**the brain knows whats in the world by 1. which neuron is responding (location) and 2. how rapidly the neuron is making APs

19

receptive field

range of stimuli that drive a sensory neuron
greater convergence...larger receptive fields...greater senstitivty, but less spatial acuity
less convergence...smaller receptive fields, but great spatial acuity (lower sensativity)

20

superior colliculus

command center for a voluntary eye meovement
(contains motor commands...responsible for firing a burst of AP...triggers the eye to rotate and stay

21

place code

eye movement is encoded by where on the SC the activity occurs
(SC produces burst...commands eye meovemet...command is then encoded by location on the SC)