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Phsyiology 210 B > Special Senses 1 > Flashcards

Special Senses 1 Flashcards

1
Q

Afferent neurons are

A

Sensory axons, that enter via dorsal root

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2
Q

Efferent neurons are

A

Motor neurons that are located in ventral horn and exit via ventral root.

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3
Q

Motor endplate

A

Efferent axon contact with several skeletal muscle fibres at peripheral synapse = motor endplate

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4
Q

Motor axons release ACh =

A

excitatory endplate potential (EEP)=Na+ AP

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5
Q

Mixed peripheral nerve

A

Bundles of sensory fibres and motor fibres (both sensory (afferent) and motor (efferent))

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6
Q

Fibres

A

Axons and neurons that propagate information via AP

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7
Q

DRG: dorsal root ganglion

A

Cell bodies (somata) of neurons forming the sensory axon located just before the ventral and dorsal roots

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8
Q

Where does info go from the spinal cord (which cortex)

A

The sematosensory cortex

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9
Q

DRG neurons are

A

somatic sensors (i.e. their dendritic nerve endings are sensitive To either mechano, pain or temperature stimuli)

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10
Q

What produced a receptor potential

A

Dendritic nerve ending

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11
Q

At the first node of ranvier, a receptor potential is

A

Transformed into action potentials, then goes to higher brain regions

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12
Q

Where dendritic nerve ending located

A

Within skin

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13
Q

AP travel across axons via

A

Salutary conduction made by Schwann cells (myelinated glial cells)

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14
Q

• White matter in CNS has axons and

A

oligodendrocytes (glial cell) around axon.

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15
Q

• Grey matter contains

A

sonata and dendrites of CNS neurons, next to astrocyte glial cells.

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16
Q

The axon for dendrites nerve endings are

A

“functional axons” that produce AP

  • there’s 2, pre and postsynaptic terminal found before the DRG cell
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17
Q
  • The axon of the DRG are

- DRG functions as a

A
  • Axons that produce AP

- dendrite, receives info from both proximal and distal processes, DRG sends info to spinal cord

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18
Q

What are the two pathways for afferent nerve fibre to send info to brain

A

1) afferent -> DRG enters dorsal root -> synapses with excitatory inter neuron of dorsal horn (grey matter) —> inter neuron leaves via white matter -> somatosensory cortex
2) afferent -> DRG enters enters dorsal root and exited via (white matter) -> somatosensory cortex

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19
Q

mechano-, temperature- and pain- sensitive distal processes of the DRG neurons express each a specific type of

A

ion channel that responds optimally to the specific stimulus.

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20
Q

Types of mechanoreceptors

A

A - Meissner corpuscle
B – Merkel disk receptor
C - Pacinian corpuscle
D - Ruffini ending

  • non-neuronal tissues surrounds free nerve endings to mediate responses
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21
Q

Nociceptors (pain) Thermoreceptors

A

Free nerve ending

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22
Q

Meissner corpuscle

A
  • located in pouches enfolded b/w epidermis

- coiled up free nerve ending embedded in homologous layer of connective tissue

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23
Q

Merkel disk receptor

A

Have nerve endings with multiple cup like connective sheaths

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24
Q

Pacinian corpsule

A

Deep in dermis, each free nerve ending wrapped with connective tissue (onion like layers)

  • most complex
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25
Q

Riffing endings

A
  • Inside dermis, but close with epidermis

- free nerve endings are coiled up inside spindle shaped connective tissue

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26
Q

Nociceptors (pain) Thermoreceptors:

Free nerve endings

A
  • response to pain and temp

- plots dismally and therefore called collaterals = “ receptor field “

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27
Q

What do collaterals give

A

Receptive field

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28
Q

(Sub) Cutaneous mechanoreceptors

A

1) Meissner corpuscle - Stroking, fluttering
2) Merkel disk receptor - Pressure, texture
3) Pacinian corpusle - Deep pressure
4) Ruffini ending - Skin stretch, gravity

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29
Q

Muscle and skeletal mechanoreceptors

A

1) Muscle spindle - Muscle length and speed

2) Golgi tendon organ - Muscle contraction/tension

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30
Q

Nociceptors

A

1) Mechanical - Sharp, pricking pain
2) Thermal-mechanical - Burning pain
3) Polymodal - Slow, burning pain

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31
Q

Thermal receptors

A

Cool receptors - skin cooling

Warm receptors - skin warming

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32
Q

‘adaptation’

A

Despite the constant stimulus amplitude, the initial depolarization recovered for each receptor potential slightly towards resting Vm.

33
Q

Adaptation is due to the fact that after initial stretching of the membrane, the tension in the tether molecule strands

A

decreases. Consequently, the pore in each activated channel gets smaller and thus the influx of depolarizing positive charge is attenuated

34
Q

Mechanoreceptor cation channel

When there’s no skin indentation,

A

The tethered molecules b/w the extracellular matrix and the gate proteins have no tension = closed

35
Q

Mechanoreceptor cation channel

When there IS skin indentation,

A

The tethered molecules b/w the extracellular matrix and the gate proteins have tension = open

36
Q

Receptor potential amplitude is proportional to

A

(stretch) mechano stimulus amplitude

37
Q

Adaptation due to:

A

inactivation of ion channel and/or filter properties of non-neuronal structure, e.g. corpuscle

38
Q

the amplitude of a mechanostimulus is transduced into a

A

receptor potential of a certain amplitude.

39
Q

If the receptor potential depolarization is above the threshold,

A

action potentials are evoked at a rate that is proportional to the amplitude of the receptor potential and NT is released, proportional to stimulus strength.

40
Q

Adaptation:

A

attenuation of action potential frequency or receptor potential amplitude during a constant stimulus

41
Q

During receptor potentials, does attenuation occur, and if so what is it?

A

YES, is is how Receptor potentials decrease in amplitude over distance, while action potentials are all or nothing and so remain the same distance for each AP.

42
Q

In the AP, why does the frequency decrease over distance for a middle sized stimulus for both in the node and ranvier and presyanpatic terminal DRG?

A

Rate of spiking decreases over distance because of adaption, less ions released over time.

43
Q

Mechanorecptors with corpsule and without composure difference

A

With corpsule: FAST adaptation, only Rec Pot. When stimulus starts and ends, not during constant.

Without corpsule: SLOW adaptation, RP when stim. Starts and then attenuation occurs (decreases slowly overt distance stim is present) then ends when stim removed.

44
Q

Properties of meissner corpsule

A
  • receptive field size: small
  • receptors location: shallow
  • adaptation: FAST
45
Q

properties of Pacinian corpsule

A
  • receptive field size: large
  • receptors location: deep
  • adaptation: FAST
46
Q

Properties of Merkel disk

A
  • receptive field size: small
  • receptors location: shallow
  • adaptation: SLOW
47
Q

Properties of riffing endings

A
  • receptive field size: Large
  • receptors location: deep
  • adaptation: SLOW
48
Q

At the distal end of each collateral, the axon contains the same type of Meissner corpuscles that respond to the same type of stroking or fluttering mechanical stimulus. This means that the DRG neuron which ultimately sends out this process,

A

expresses only this type of mechanoreceptor

49
Q

Meissner corpuscle mechanoreceptors have what kind of pattern of receptive furies on the hands, and what do they mean?

A

Multiple spots = afferent axon splits into branches called collaterals

50
Q

Pacinian corpuscle mechanoreceptors have what kind of pattern of receptive furies on the hands, and what do they mean?

A

large area indicates that the DRG neuron process branches out quite a bit = fewer collaterals

51
Q

Separate spots indicate number of

A

major collaterals of one sensory dendrite (= functional axon)

52
Q

Precise cognitive localization possible

of one

A

sensory dendrite (= functional axon) due to overlap of receptive fields

53
Q

Smaller receptive fields have

A

limited branching = smaller area = better spatial resolution of location of stimulus site

54
Q

Larger respective fields have

A

More branching = larger area = more info of that large area

55
Q

Without overlap, why doesn’t the CNS recognize where the stimulus occurred?

A

Cuz similar train of AP released to the CNS regardless of where the stim occurred

  • overlapping = precise localization
56
Q

When a stimulus hits a particular sensor, information of neighboring receptive fields is ultimately

A

transmitted to neighboring areas on the somatosensory cortex. This enables the cortex to get an idea where exactly the stimulus was located.

57
Q

Lateral inhibition enhances localization how??

A

Inhibitory interneurons inhibit neighbouring sensory axons on both sides of the axon where excitation will occur = reduction in AP = inhibitory interneurons can inhibit the central axon less = increased AP spike frequency of central = better info of location for the brain

58
Q

contrast for the localization of a stimulus site can be further enhanced within the CNS via a

A

neuronal network wiring that provides lateral inhibition

59
Q

The 2 Afferent Pathways of Somatosensory System

A

1) Afferent neuron form pain or temp receptor

2) receptors for body movement, limb positions, fine touch discrimination, and pressure

60
Q

1) Afferent neuron form pain or temp receptor

A

Afferent enter dorsal horn, SYNAPSE 1 w interneuron = crosses anterlateral column of and exits spinal cord = up brianstem = some collaterals synapse with reticular formation activation system (ARAS) = SYNAPSE 2 w thalamus = SYNAPSE 3 with cortical neuron in sematosensory cortex through diffuse projection (divergence)

61
Q

2) receptors for body movement, limb positions, fine touch discrimination, and pressure

A

Receptors enter dorsal root, exit spinal cord via dorsal column = SYNAPSE 1 w brainstem nucleus (either nucleus cuneatus or nucleus gracilus) = some collaterals w ARAS = SYNAPSE 2 w thalamus - SYNAPSE 3 w cortical neuron in sematosensory cortex via sematosensory projection

62
Q

Nucleus cuneatus and nucleus gracilus in brainstem functions

A
  • Nucleus cuneatus: received info form upper body

- nucleus gracilus: receive info from lower body

63
Q

Somatosensory Cortical Projection - Somatotopy

A

Somatosensory cortex and primary motor cortex separated by central sulcus.

  • Homunculus: somatotopic representation of body surface on somatosensory cortex
    Larger area = more activation in somatosensory cortex for that portion of body
64
Q

MRI distrusted what kind of ions

A

H+ ions

65
Q

Two-point discrimination is the ability to

A

discern that two nearby objects touching the skin are truly two distinct points, not one.

66
Q

experiment to determine the density of mechanoreceptor innervation in different areas of the skin.

A

• If areas of the back of the body are simultaneously touched by 2 sharp-tipped objects, the sensation of a dual stimulation only becomes conscious when the distance of the stimulating tips is 42 mm or larger.

67
Q

Higher frequency and higher intesity meaning

A

Higher frequency = more cycles

Higher intensity = higher amplitude (more loud)

68
Q

Outer ear contains

A
  • pinna: shapes for INC sensitivity to 200-600Hz
  • auditory canal
  • tympanic membrane:
69
Q

Middle ear contains

A
  • ossicles: (malleus, incus, stapes) connect tympanic membrane with oval window
  • oval window: separates middle ear form fluid filled inner ear.
70
Q

Function of occicles

A

Amplify vibration of frequency before it gets to oval window.

  • no ossicles = moderate-severe hearing loss
71
Q

Inner ear contains

A
  • semicircular canals
  • vestibule: sensation, posture, gravity
  • cochlea: contains hair cells
  • auditory neuron
72
Q

What do the little muscles connected to the ossicles do?

A

When contracted to loud noise = inhibiting vibrations to malleus, incus, stapes = DEC intensity of sounds to inner ear

73
Q

Cochlear structure

A

3 Scala:

  • scala vestibuli
  • scala media
  • scala tympani
  • reissners membrane bw vestibuli and media
  • basilar membrane bw media and tympani
74
Q

What does the scala media contain

A
  • tectorial membrane
  • stria vascularis: specialized endothelium secreting K+ into scala media
  • organ of corti
75
Q

Organ of corti structure

A
  • 3 rows of outer hair cells: fine tuning of inner hair cell responce, have steriocilia on top
  • steriocilia: makes contact with gelaton layer and techorial membrane
  • techorial membrane
  • epithelium and glial cells
  • inner hair cells
76
Q

Epithelial and glial cells in organ of corti

A

Mechanically stabilize organ of corti and interact with hair cells and iNC their functions

77
Q

Inner hair cells axons

A

Synapse with afferent nerve fibres (spiral ganglion) to form auditory nerve

  • therefore inner hair cells - auditory receptors
78
Q

Structure of basilar membrane

A

Vibrations enter the oval window (w stapes) and run across scala vestibuli (from base to apex) = reaches helicotrema (connecting scala vestibuli and tympani) = runs back towards round window via scala tympani

Phsyiology 210 B (24 decks)

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