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ANAT 321 - circuitry of the human brain > intro / sensory systems (I) > Flashcards

intro / sensory systems (I) Flashcards

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1
Q

Our mind is a pattern of _____ running on a special kind of machine: our brain

A

information processing

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2
Q

Central nervous system (CNS) components

A
  1. Brain
  2. Spinal cord
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3
Q

Peripheral nervous system (PNS) components

A

Everything else that connects to the CNS…

  1. Afferent fibers (sensory neurons)
  2. Efferent fibers (motor neurons)
  3. Autonomic fibers
  4. Enteric nervous system
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4
Q

What is the ultimate purpose of the nervous system?

A

The nervous system uses sensory data and stored knowledge of the structure of the world to produce motor responses that yield the highest possible inclusive fitness for the organism.

→there is a continuous flow of sensory information that allows us to complete various actions (continuous interaction)

chart slide 7

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5
Q

Main functions of sensory information

A
  1. Perception
  2. Control of movement
  3. Regulation of the function of internal organs
  4. Maintenance of arousal
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6
Q

Advantages of sensory perception

A
  1. Enables extraction of information about the world to then use it to guide behaviour
  2. Gives us conscious sensations
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7
Q

Somatic sensory system

A

The somatic sensory system encodes sensory information about the skin surface (e.g. touch, vibration, temperature, pain) and sensory information from inside the body (e.g. visceral pain).

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8
Q

Common properties of sensations

A
  1. Modality
  2. Intensity
  3. Duration
  4. Location
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9
Q

Modality

A

Quality of the sensation

→i.e. somatic sensation (vision, hearing,…)

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10
Q

Submodality

A

A subcategory within the larger modality as a result of underlying neurological explanations

→i.e. warmth, fine touch, heat

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11
Q

How is somatic sensory information conveyed to the brain from the body?

A

Through two parallel pathways,

  1. Dorsal column-medial lemniscal pathway
  2. Anterolateral pathway
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12
Q

Dorsal column-medial lemniscal pathway

A
  • fine touch & proprioception
  • Aa & Ab fibers

→The name dorsal-column medial lemniscus comes from the two structures that carry the sensory information: the dorsal columns of the spinal cord, and the medial lemniscus in the brainstem.

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13
Q

Anterolateral pathway

A
  • pain & temperature
  • Ad & C fibers

→The pathway crosses over at the level of the spinal cord, rather than in the brainstem

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14
Q

Proprioception

A

The body’s ability to sense movement, action, and location.

→sensory information coming from muscles and joints (feedback from limbs), which enables you to have good control over your limbs since you are aware of where they are in space

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15
Q

Primary somatic sensory afferents

A

Detect stimuli on the skin surface and convey somatic sensory information to the CNS.

→first in the sensory pathway
→different fibers have different physiological/anatomical/ morphological properties
→different endings transduce different sensations

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16
Q

Primary somatic sensory afferent types

A
  1. Aa
  2. Ab
  3. Ad
  4. C
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17
Q

Draw the dorsal column-medial lemniscal pathway

A

☆slide 18☆

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18
Q

Draw the anterolateral pathway

A

☆slide 18☆

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19
Q

T or F: Primary somatic sensory afferents have the same morphology as other neurons.

A

False.

They have an unusual morphology.

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20
Q

Draw + explain the morphology of a typical neuron

A
  • dendrites, cell body, axon, presynaptic terminal
  • dendrites are where the synapses are, where the neuron receives input from other neurons
  • based on that input from all the synapses,
    a decision to fire an AP is made
  • the AP will propagate down the axon and to the presynaptic terminal
  • the AP is then a message that will be sent to other parts of the nervous system
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21
Q

Draw + explain the morphology of a primary somatic sensory afferent

A
  • no dendrites
  • consist of one long axon (one end in the skin, the other going up to the CNS)
  • cell body lies outside of the spinal cord
  • presynaptic terminal in the CNS
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22
Q

Sensory transduction

A

The first step in sensory processing which transforms sensory information from the external (or internal) environment into the opening/closing of ion channels in receptor cells.

→essentially, transforming input into electrical signal

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23
Q

Sensory transduction example: Stretch-activated ion channels

A

Indentation of the skin causes opening of ion channels in low-threshold stretch-activated mechanoreceptors.

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24
Q

Sensory transduction example: Primary sensory fiber

A

Pressure on the skin surface is encoded as action
potentials in primary sensory fiber.

→more stretching, higher frequency, ending more depolarized
→less stretching, lower frequency, weaker receptor potential

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25
Q

How can neurons alter the way they convey information?

A

By changing (1) the pattern & (2) frequency of APs.

NOT by changing the size & duration of APs

26
Q

Sensory receptors

A

Sensory receptors (e.g. the endings of primary somatic sensory fibers) act as filters, extracting specific forms of sensory information
and ignoring others.

27
Q

T or F: All fibers have the same sensory receptors.

A

False!

Different fibers tend to have specialized endings, which allows them to extract different kinds of somatic sensory information.

28
Q

Sensory receptor types

A
  1. Merkel cells (SA1)
  2. Ruffini endings (SA2)
  3. Meissner corpuscle (RA1)
  4. Pacinian corpuscle (RA2)
  5. Free nerve ending
29
Q

What do SA & RA refer to?

A

They refer to the fiber.

→SA = slow-adapting
→RA = rapid-adapting

30
Q

Which sensory receptors are found in the dermis?

A
  1. Meissner corpuscle
  2. Pacinian corpuscle
31
Q

Which sensory receptors are found in the epidermis?

A
  1. Merkel cells
  2. Ruffini endings
  3. Free nerve endings
32
Q

Which sensory receptors allow for the detection of touch?

A
  1. Merkel cells
  2. Ruffini endings
  3. Meissner corpuscle
  4. Pacinian corpuscle
33
Q

Role of Merkel cells & Ruffini endings

A

Good at detecting constant pressure throughout the pulse/stimulus (they will eventually desensitize, but it takes awhile).
→ filters out info about vibration

34
Q

Role of Meissner corpuscle & Pacinian corpuscle

A

Only fire at the beginning of the pressure pulse and the end, good at detecting c changes in pressure on the skin surface (i.e., vibrations).
→ filters out info about constant pressure

35
Q

Role of free nerve endings

A
  • no specialized ending associated with them
  • responsible for detection of temperature and pain
36
Q

Labeled line coding

A
  • each submodality is mediated by a specific receptor/fiber type and a specific labeled line.
  • labeled line coding refers to the fact that the brain perceives information arriving from a specific neuronal tract as the adequate stimulus of the primary afferent sensory receptor, even if a different stimulus activates it.
  • it doesn’t matter how it is activated, but once a labeled line is activated, then you will feel it

☆go read examples on slide 24☆

37
Q

Combinatorial processing

A

Perceived sensations (e.g., wetness, color perception, the smell and taste of food) are typically caused by activation of multiple receptor types and integration of multiple parallel channels by the brain.

→there is no labeled line for wetness, but the sensation can be felt due to the activation of multiple labeled lines and it interprets the relative activation of those different labeled lines
→sensation felt due to the brain’s interpretation based on relative activation of the different receptors

38
Q

Afferent

A

Incoming information.

→EX: primary somatic sensory afferents

39
Q

Efferent

A

Outgoing information.

→EX: efferent motor neurons

40
Q

Ascending

A

Heading up to higher levels of the nervous system.

→from spinal cord to cortex
→EX: ascending sensory afferents

41
Q

Descending

A

Heading down from higher levels of the nervous system

→EX: descending corticospinal projections

42
Q

Ipsilateral

A

On the same side of the body.

43
Q

Contralateral

A

On the opposite side of the body.

44
Q

Which characteristics define sensory fibers?

A
  1. Size of diameter
  2. Myelination of axon
45
Q

Which fibers are the fastest?

A

Those with the largest diameter and most myelination.

→Aa

46
Q

Large diameter & well-myelinated fibers

A
  1. Aa
  2. Ab

→correspond to specialized sensory endings
→responsible for fine touch and proprioception

47
Q

Small diameter, thinly myelinated or unmyelinated fibers

A
  1. Ad
  2. C

→correspond to free nerve endings
→responsible for pain and temperature sensation

48
Q

Aa fiber role

A

Muscle spindles, Golgi tendon organs

49
Q

Ab fiber role

A

Low threshold mechanoreceptors

50
Q

Ad fiber role

A

Free nerve endings

51
Q

C fiber role

A

Free nerve endings

52
Q

Explain what occurs at the level of sensory fibers when you touch something hot.

A

When you touch something hot, the fast pain (jolting) occurs quickly by Ad fibers, but then a slower and throbbing pain occurs, which is caused by C fibers

53
Q

Receptive fields

A

The primary somatic sensory neurons innervate a specific region of the body surface. A stimulus within this receptive field will excite the cell.

→each nerve ending has its own receptive field
→this concept applies to all sensory modalities
→receptive fields are combined together and integrated

54
Q

Size of receptive fields

A
  • High acuity regions → small receptive field
    →more sensory neurons innervating
    →EX: fingertips
  • Low acuity regions → large receptive field
    →less sensory neurons innervating
    →EX: torso
55
Q

Give an example on how precision is not synonymous with acuity.

A

☆read p.29☆
+ review in visual system section :)

56
Q

Medial

A

Towards the middle/center

57
Q

Lateral

A

To the side of, or away from, the middle of the body

58
Q

Dorsal

A

Refers to the back portion of the body

59
Q

Ventral

A

Refers to the front part of the body

60
Q

Rostral/Anterior

A

Refers to a structure found toward the front of the body (situated toward the oral or nasal region)

61
Q

Caudal/Posterior

A

Situated in or directed toward the hind part of the body (i.e. tail)

ANAT 321 - circuitry of the human brain (8 decks)

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