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MHD2 > Block 8 (Neuro) - Sensory 1-4 > Flashcards

Block 8 (Neuro) - Sensory 1-4 Flashcards

1
Q

What are the three common steps to coding and processing of all sensory information?

A
  1. A physical stimulus is present
  2. That stimulus is transduced into a message of electrical signals
  3. There is typically a response to that message by the CNS.
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2
Q

True or false - all colors, tones, smells, sounds, and tastes are not real outside the CNS.

A

True

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3
Q

What is the accurate organization of the essential properties of an object/stimulus that allows us to interpret and manage/manipulate it successfully?

A

Perception

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4
Q

What are the three main functions of receptors?

A
  1. Sensation
  2. Control and coordination of movements
  3. Arousal
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5
Q

What are the 4 elementary attributes of a stimulus?

A
  1. Modality (one of the 5 senses)
  2. Intensity (strength of stimulus)
  3. Duration (perceived time a stimulus is present)
  4. Location (homunculus)
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6
Q

Every stimulus has a sensory threshold - how is this threshold defined?

A

Lowest detectable intensity which can be perceived at least 50% of the time

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7
Q

True or false - threshold is due to changes in the receptor of changes in the receptor’s threshold.

A

False - it is not due to the receptor; changes occur in the CNS.

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8
Q

What is the capacity to process a certain type of signal that must be present for that stimulus to be perceived?

A

Detectability

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9
Q

What is an attitude or bias towards certain sensations that allows us to tolerate certain stimuli and prevent false alarms?

A

Criterion

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10
Q

The perceived duration of a stimulus is a function of the ___ and NOT of the ___.

A

CNS; receptor

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11
Q

Duration is the relationship between the ___ intensity and the ___ intensity.

A

Stimulus; perceived

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12
Q

___ occurs in most stimulus pathways, resulting in a decrease of the perceived intensity of a stimulus during long-term stimulation.

A

Adaptation

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13
Q

Where is perception of stimuli greatest/sharpest?

A

At regions of greatest contrast

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14
Q

What is the basic outline for all sensory modalities, beginning with receptors?

A
  1. Receptors (transduction)
  2. 2nd order neurons (transmission)
  3. 3rd order neurons (thalamus - modulation)
  4. Cortex
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15
Q

Where does perception occur?

A

Cortex

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16
Q

What is the conversion of a particular form of energy into an electrochemical signal by a receptor?

A

Signal transducton

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17
Q

What is the process of relaying a signal to the next neuron in the pathway via a series of APs?

A

Neural encoding

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18
Q

True or false - signal transduction is always excitatory.

A

True

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19
Q

What are the two ways of encoding intensity?

A
  1. Frequency coding - stronger stimuli evoke a greater number of AP’s from a single receptor (frequency increases)
  2. Population coding - stronger stimuli excite a greater number of receptors (population increases)
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20
Q

What is the area innervated by a single receptor?

A

Receptive field

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21
Q

What are the two types of receptors related to duration?

A
  1. Rapidly adapting (fire AP’s only at on/off of stimulus)

2. Slowly adapting (AP’s throughout stimulus duration)

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22
Q

What determines the modality of a receptor?

A

Labeled line code - the specific type of receptor and its transducing abilities

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23
Q

Most sensory inputs to the CNS follow a pattern of extensive ___ or ___.

A

Convergence; divergence

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24
Q

What are the three types of inhibition?

A
  1. Feed-forward: allows the primary incoming input to inhibit the input of surrounding neurons, resulting in one response over all others
  2. Feed-back: allows the most active output cell from a nucleus to inhibit or suppress the less active cells of that nucleus (less robust than feed-forward)
  3. Distal: allows for resetting of the gain of selected synapses by the cortex directly
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25
Q

What does it mean to increase contrast?

A

Inhibition of surrounding areas enhances the perception of the stimulus

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26
Q

Where does adaptation occur in the pathway?

A

In the spinal cord, NOT in the receptor or its afferent fibers

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27
Q

At the most sensitive areas, the number of receptors per unit area of skin is ___, while the size of the receptive field of each receptor is proportionally ___.

A

Large; small

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28
Q

As the size of the receptor field gets larger, what happens to the number of receptors?

A

Decreases

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29
Q

Receptor output is greatest when a stimulus is applied at the ___ of the receptive field.

A

Center

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30
Q

The cortex is arranged in ___.

A

Columns

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31
Q

What is the primary receptor on hairy skin?

A

Hair follicle receptor (also has deep receptors and Merkel’s)

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32
Q

What are the receptors on glaborous (hairless) skin?

A

Superficial: Merkel’s (slowly adapting), Meissner’s (rapidly adapting) - small receptive fields, very sensitive

Deep: Pacinian’s (rapidly adapting), Ruffini (slowly adapting) - large receptive fields

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33
Q

What are the three types of nociceptors?

A
  1. Mechanical
  2. Thermal (hot >45 C, cold <15 C)
  3. Polymodal (chemical and mechanical)
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34
Q

What size/type of fibers are the fastest and what type of information do they carry?

A

Large, myelinated fibers; proprioceptive information

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35
Q

What types of information do small, thinly myelinated fibers carry?

A

Sensory information

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36
Q

What type of information do the smallest myelinated and unmyelinated fibers carry?

A

Pain and temperature

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37
Q

What are the three types of proprioceptors involved in proprioception?

A
  1. Muscle spindle receptors within the muscle tissue (primary position sensor)
  2. Mechanoreceptors in joint capsules and tendons
  3. Mechanoreceptors in the skin
38
Q

What are the two types of muscle receptors?

A
  1. Muscle spindle

2. Golgi tendon organ (GTO)

39
Q

Force and change in length of muscles are dependent on what three factors?

A
  1. Initial length
  2. Velocity of length change
  3. External loads (tension) opposing movement
40
Q

Where are muscle spindles found?

A

Within the extrafusal muscle fibers in parallel with the muscle

41
Q

What innervates muscle spindles?

A

Group 1a and 2 axons (large and medium myelinated axons)

42
Q

What are muscle spindles composed of?

A

Intrafusal muscle fibers (contractile), sensory axons (afferents), and motor axons (efferents which regulate sensitivity)

43
Q

Each muscle spindle has three types of intrafusal fibers - what are they?

A
  1. Nuclear chain fibers
  2. Nuclear bag fibers
    a. Dynamic
    b. Static
44
Q

What are nuclear chain fibers?

A

Thin fibers with nuclei arranged in a single file; afferents include groups 1a and 2

45
Q

What are nuclear bag fibers?

A

Thicker fibers with nuclei grouped in the central region

46
Q

What are the two subtypes of nuclear bag fibers and how do they differ?

A
  1. Dynamic: sensitive to rate of change (rapidly adapting); afferents include group 1a only
  2. Static: slowly adapting stretch receptors; afferents include both group 1a and2
47
Q

What happens when a muscle is loaded (stretched)?

A

Intrafusal fibers are stretched, leading to an increase in the number of AP’s sent to the CNS

48
Q

Motor axons are called ___ motor neurons and innervate only the ___ regions of the intrafusal muscle fibers. This is known as the ___ system.

A

Gamma; polar; fusimotor

49
Q

Where are GTOs found?

A

At the junction of the muscle fibers and the tendon (in series with muscle)

50
Q

What innervates GTOs?

A

Group 1b axons (large, myelinated)

51
Q

What are GTOs composed of?

A

A weave of collagen fibers (from tendon) and unmyelinated nerve branchesm within the GTO

52
Q

What happens in a GTO when tension on a tendon is increased?

A

Intertwined fibers are compressed, resulting in increased number of APs to the CNS

53
Q

Spindles sense changes in the ___ of the muscle. GTOs sense changes in ___ of the muscle.

A

Length; tension

54
Q

What are the primary differences between dynamic and static muscle spindle fibers?

A

Dynamic: length is actively changing; sensitive to velocity; rapidly adapting

Static: steady-state phase; slowly adapting

55
Q

How do spindles reset their sensitivity?

A

Gamma motor neurons

56
Q

Activation of static gamma motor neurons reflects information about the ___ of the muscle. What fibers does it reset?

A

Actual length; static bag and nuclear chain fibers

57
Q

Activation of dynamic gamma motor neurons reflects information about the ___ of the muscle. What fibers does it reset?

A

Phasic fluctuations in length; dynamic bag fibers only

58
Q

What is intrafusal creep?

A

Dynamic bag fibers respond to stretch with a viscous resistance; static fibers react uniformly to stretch (no creep). Central regions of the dynamic fibers respond to stretch like a spring. Polar regions react more like a shock absorber.

59
Q

When stretch is slow, the entire spindle act like a ___. When stretch is fast, what happens?

A

Spring (polar region keeps pace)

When stretch is fast, the central region acts like a spring but the polar region lags, resulting in a slight recoil to the stretch - this is intrafusal creep

60
Q

Intrafusal creep allows dynamic fibers to code for ___.

A

Velocity

61
Q

Contraction of the polar regions of the intrafusal fibers allows for restting of the spindles during tension, primarily via ___.

A

Alpha-gamma coactivation

62
Q

What is fusimotor set?

A

The setting of motor system gain before and during motor activation in order to fine tune the motor system to various types of activity.

63
Q

How is muscle tone regulated?

A

Through a negative feedback system

64
Q

What are the two crucial components of a negative feedback system?

A
  1. Gain of the system

2. Loop delay

65
Q

What is the gain of a system?

A

Strength and effectiveness; the larger the gain, the greater the muscle force to a given stimulus

66
Q

What are the three ways in which the CNS can modify gain?

A
  1. Adjusting the level of fusimotor activity
  2. Presynaptic modulation of the inputs to the alpha-motor neurons
  3. Direct input to the alpha-motor neurons by the CNS
67
Q

What is loop delay?

A

Inherent delays built into the motor system which can affect the time it takes to produce or adjust a motor response

68
Q

What are the 5 submodalities of taste?

A

Sweet, salty, sour, bitter, umami

69
Q

Most foods have a distinctive ___ as a result of the interaction of taste and smell occurring simultaneously.

A

Flavor

70
Q

Scattered about the surface of the tongue are small projections called ___. They have three shapes - what are they?

A

Papillae

  1. Ridges (foliate)
  2. Pimples (valate or circumvallate)
  3. Mushrooms (fungiform)
71
Q

Each papilla has from one to several hundred ___. Each of these has 50-150 ___.

A

Taste buds; receptor cells

72
Q

Where on the tongue are the 4 primary taste submodalities distributed?

A

Sweet - anterior
Salty and sour - lateral
Bitter - posterior

73
Q

Taste cells are not true neurons - what are they?

A

Specialized epithelial cells with the morphological characteristics of chemical synapses

74
Q

When a taste cell is activated by an appropriate ___, the membrane depolarizes, resulting in a receptor potential and possibly an AP. Depolarization results in the opening of ___ and release of ___ (specifically). These depolarize the sensory axons and produce AP.

A

Chemical; voltage-gated Ca2+ channels; NT (ATP)

75
Q

How do salt-sensitive taste cells respond to changes in salt concentration?

A

A specialized Na+ channel is open all the time; increases in salt increase the gradient, resulting in a depolarization of the taste cell. This activates the voltage-gated Na+ and Ca2+ channels, triggering release of NT (ATP)

76
Q

The larger the anion in a salt molecule, the more it ___ depolarization.

A

Inhibits

77
Q

The higher the ___, the more sour a food tastes.

A

Acidity

78
Q

How is sourness perceived?

A

Acids dissolve and generate protons. These do two things:

  1. Diffuse through non-gated Na+ channels, resulting in depolarziation
  2. Blocking K+ channels, resulting in depolarization
79
Q

How is bitterness perceived?

A

Stimulus: quinine
Receptors: T2R (poison detectors)
Second messenger system (IP3/DAG)

80
Q

How is sweetness perceived?

A

Stimulus: various
Receptors: T1R2 and T1R3 (both components must be present to activate the receptor)
Second messenger system

81
Q

How is umami perceived?

A

Stimulus: amino acids, especially glutamate
Receptors: T1R1 and T1R3 (both must be present)
Second messenger system

82
Q

What is the primary gustatory cortex (area ___)?

A

Area 43 (in the ventral parietal lobe)

83
Q

Where are the olfactory receptors?

A

Within the nasal cavity (confined to a specialized patch of epithelium)

84
Q

What are olfactory receptor cells?

A

Bipolar neurons with short peripheral processes and long central processes

85
Q

What are olfactory knobs?

A

Projection of short arm of olfactory process

86
Q

What are olfactory cilia?

A

Project from olfactory knob, forming a dense mat

87
Q

What is the central process?

A

Unmyelinated axon, forms bundle with 10-100 other axons, surrounded by Schwann cells and projecting to olfactory bulb

88
Q

What are basal cells?

A

Precursors to new olfactory receptors

89
Q

What happens when an odorant binds to a specific recognition site?

A

G-protein mediated activation of AC -> cAMP -> interacts DIRECTLY with cation channels conducting Na/Ca, resulting in depolarization. Ca also opens Cl channels, which results in further depolarization

90
Q

Olfactory receptors synapse onto second-order neurons in the ___.

A

Glomerulus

91
Q

Within the glomerulus are either tufted or mitral second order neurons. Where do these project?

A

Mitral - all higher levels of olfactory perception

Tufted - only to the anterior olfactory nucleus and the olfactory tubercle

MHD2 (34 decks)

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