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Phsyiology 210 B > Special Senses 2 > Flashcards

Special Senses 2 Flashcards

1
Q

Travelling wave

A

A vibration on the basilar membrane

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2
Q

Strucure of basilar membrane

A

Narrow and stiff as the base - 16 Hz

Wide and floppy as the apex - 0.5 Hz (max amplitude)

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3
Q

How are frequencies on certain spot of the basilar membrane?

A

Each frequency of sounds has maximum movement on a certain spot on the basilar membrane, and the hair cells on that spot will be stimulated

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4
Q

A proof for the traveling wave concept is the fact that exposure to a loud noise of a certain frequency

A

destroys hair cells at a specific spot of the basilar membrane

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5
Q

Frequencies at the apex vs at the base

A

Apex: high frequency
Base: low frequency

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6
Q

Bending of stereocilia

A
  • Compression: basilar membrane deflected downwards

- rarefaction: basilar membrane bends upwards

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7
Q

A rarefraction ( bending upwards) causes

A

Steriocilia being to the left in responce to adequately stimuli = release K+ ions = receptor potential

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8
Q

A bending of the cilia to the left side vs right side evokes a

A

hyperpolarization of their resting Vm by <1 mV while bending to the right side evokes a depolarization of ~3 mV.

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9
Q

sinusoid wave of a single frequency that the time course of the receptor potential (shown in the lower traces) follows exactly that of the sound pressure changes (shown in the upper trace). The receptor potential can precisely follow back and forward stereocilia movements even when they occur at a rate of >10 kHz. This indicates that the

A

hair cell mechanoreceptor channels can open and close very rapidly.

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10
Q

Receptor potential and hair cell bending have a

A

close relation even at >10Hz

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11
Q

Do hair cells have dendrites

A

No, instead they got mechanosensitve steriocilia which transmit info via neurite from follow neuron form postsynaptic neuron to send AP to auditory cortex

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12
Q

Follow neuron located in

A

Spiral ganglion

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13
Q

When hair cells bend to the right, influx of K+ =

A

Depolarization = activation of cytosolic Ca2+ = NT release (glutamate)

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14
Q

Where’s glutamate store in hair cells

A

In vesicles at the base of the hair cells

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15
Q

What connected the hair cells together

A

Tip links (Cadherines)

  • relaxed (left bend) = channel closed
  • no stimulus = partly open
  • bending to right = channel activated = depol
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16
Q

Stria vascularis secreted what into the scala media

A

K+ ions, causing the K+ level in the scala vestibuli and scala tympani to be low

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17
Q

What kind of interstitial fluid found in all three scala in the cochlea

A
  • Perilymph (3 K+, 150 Na+) in scala vestibuli and tympani

- endolymph (150 K+, 15 Na+) in scala media

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18
Q

In the endolymph, the K+ ions follow their

A

conc gradient, going form high to low conc = into the steriocilia = releasing glutamate

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19
Q

2 pathways for afferent auditory pathway

First

A

Afferent neuron (spiral ganglion) receive info from HC = excited = glutamate release into axons of vestibulocochlear nerve, AP sent to medulla, excited = neuron activated in superior Oliver’s nucleus (in pons), get excited, AP transmitted via lateral meniscus axon tracts to neuron in inferior follicular (in midbrain), excited = activate neurons in medial geniculate nucleus (in thalamus), excited = activate neurons in auditory cortex.

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20
Q

2 pathways for afferent auditory pathway

Second

A

second pathway is activated in parallel on the contralateral side. The crossing occurs already (via collaterals) in the nuclei of the medulla oblongata. From there, the action potentials propagate in similar fashion as on the ipsilateral side except, that some axons pass by the superior olivary nucleus in the pons without synapsing onto them.

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21
Q

conjunctiva is a mucous membrane which comprises the

A

inner surface of the eyelids and covers the forepart of the sclera. The conjunctiva helps to lubricate the eye by producing mucus and tears, although a smaller volume of tears than the lacrimal gland

22
Q

sclera is the

A

hard connective tissue that forms the major portion of the almost round eyeball. Located in the middle of the eye is the pupil

23
Q

pupil is not a structure, but rather a

A

hole that is covered by a transparent layer through which the light enters the eye

24
Q

round iris muscle surrounds the pupil and its diameter can be adjusted via the pupil reflex. The pupil reflex makes sure that the

A

diameter of the pupil is reduced during exposure of the eye to high intensity light signals to protect the photoreceptive structures and the other cells within the retina.

25
Q

transparent cornea protects the

A

front portion of the eye. It also contributes to a major portion to focusing the light via refraction onto the retina.

26
Q

extraocular muscles are attached to the middle of the eyeball pointing backwards. Their contraction enables the

A

movement of the eye towards objects in case the head can not be turned for this purpose.

27
Q

light passes the outer eye chamber that is filled with

A

aqueous humor fluid.

28
Q

Light passes through the transparent lens that is attached via the so- called

A

zonular fibers comprising connective tissue to the ciliary muscle.

29
Q

ciliary muscle serves to make the lens

A

more round when looking at near objects

30
Q

main inner space of the eyeball that is filled with

A

vitreous humor

31
Q

point of sharpest vision, called the

A

Fovea (centralis), only cones

32
Q

The optic nerve is also the

A

Afferent axon

33
Q

Greatest amount of Refraction occurs where

Refraction def?

A

At the cornea, minority at the lens.

Light bent opposite direction = mirror image on retina (fixed by CNS)

34
Q

Myopia

A

Eyeballs to long = nearsighted (only see close things) = corrected with CONCAVE lense so that light touches the cornea and actually reaches retina

35
Q

Hyperopia

A

Eyeballs to short = farsighted (only see far thing) = corrected with CONVEX lense so that light touches cornea correctly and doesn’t pass the retina

36
Q

Later eyes surgery does what to lense

A

Reshapes the lense

37
Q

Accommodation

A

Increasing lens curvature for near vision

38
Q

Accommodation how?

A

Zonular fibres
- stretched = tension when ciliary muscle relaxed = pulls lens = less curved

  • relaxed = no tension when ciliary muscle contracted = curved lense = rounded lense = accomodation cuz light now focused on retina
39
Q

Light pathway through the retina

A

Goes through ganglion cells (form optic nerve) -> bipolar cells -> horizontal cells -> cones / rods -> pigment epithelium (reflects incoming light so photons detected by photoreceptors) -> choroid

40
Q

Rods vs cones

A

Rods:

  • dim light = grey light
  • longer outer segment = more photopigment

Cones:

  • daylight = color vision
  • shorter outer segment - less photopigment
41
Q

Fovea centralis

A
  • Sharpest image represnetion

- ganglion and bipolar cells pushed to the sides, photons more directly on the cones only

42
Q

Number of photoreceptors

A
  • 30 degrees: little cones, lots of rods
  • 60 degrees: little cons, lots but decreasing # of rods
  • 0 degree: 0 rods, LOTS of cones
43
Q

Different extent of convergence

A
  • Temporal retina : many rods, bipolar cells. One cone and follower neuron and optic neuron
  • nasal retina: many rods, bipolar cells. One cone and follower neuron and optic neuron
  • central retina: one cone, bipolar cell, ganglion/follower, optic nerve
44
Q

Central retina is what

A

Center of fovea, this is why it has lowest convergence - best temporal resolution

45
Q

Phototransduction

A

In dark: channels kept open by high concentration of the second messenger cGMP. Light strike the retina of the ops in photo pigment, changes conformation, dissociates from opsin = cGMP phosphodiester are in the disc membrane stimulated via action of protein transductin. Activated cGMP phophso. Changes into GMP = decreases the conc. Of cGMP in cytosol and the channels have closed = hyperpolarization cuz influx of Na through open pores = depolarization

46
Q

Receptive fields in the retina

A
  • Receptive field center: 10-20 photoreceptors
  • receptive field surround: peripheral photoreceptors

All connected horizontal cell and one bipolar cell

47
Q

Direct and indirect pathway of light in receptive field center vs light in reactive field surround

A
  • Light in receptive field center (Direct pathway): photoreceptors hyperpolarized = bipolar depolarizer
  • light in receptive field surround (indirect pathway): photoreceptors hyperpolarized = horizontal cells hyperpolarized = bipolar cells hyperpolarized
48
Q

Stereoscopic vision (depthperception):

A

only possible in binocular zone: overlapping area of visual field

49
Q

Visual fields

A

Left visual field collect info form left eye, projects it onto right side of retina = mirror image

Right visual field collect info form right eye, projects it onto left side of retina = mirror image

50
Q

Optic chiasm

A

The crossing of the axons in the brain when the visual fields are crossing pathways between optic nerves (right) and lateral geniculate nucleus (left) , as those two tracts seperate and meet up in the back of the head in the visual cortex of the occipital lobe

Phsyiology 210 B (24 decks)

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