Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Neuroscience > Lecture 20 > Flashcards

Lecture 20 Flashcards

1
Q

What are the two major input components of the somatic sensory system?

A 
Mechanical stimuli (light touch, vibration, pressure and cutaneous tension)
Painful stimuli and temperature
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does input and interpretation of the two major components enable us to do?

A

Identify the shape and textures of objects
Monitor the internal and external forces acting on the body
Detect potentially harmful circumstances
Have a sense of ourselves within our environment and so plan our actions accordingly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where are hair follicles located?

A

Widespread in epithelia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the modality of hair follicles?

A

Varied according to type

- Both rapid and slowly adapting subtypes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where are Meissner’s corpuscles (Tactile) located?

A

Dermal papillae of skin, especially palms, eyelids, lips and tongue etc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the modality of Meissner’s corpuscles?

A

Light touch, texture (movement)

  • Sensitive to 30-50 Hz
  • Rapidly adapting
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where are Pacinian corpuscles (Lamellated) located?

A

Dermis, joint capsules, viscera

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the modality of Pacinian corpuscles?

A

Deep pressure, stretch, tickle, vibration

  • Sensitive to 250-350 Hz
  • Rapidly adapting
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where are Ruffini corpuscles located?

A

Dermis, subcutaneous tissue, joint capsules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the modality of Ruffini corpuscles?

A

Heavy touch, pressure, skin stretch, joint movements (kind of proprioceptor…?
- slowly adapting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Where are Merkel (or Tactile) Discs located?

A

Superficial skin (epidermis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the modality of Merkel discs?

A

Light touch, texture, edges, shapes

- slowly adapting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are examples of encapsulated nerve endings?

A

Pacinian corpuscles, Ruffini Corpuscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are examples of unencapsulated nerve endings?

A

Merkel discs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Where are free nerve endings located?

A

Widespread in epithelia and connective tissues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are modalities for free nerve endings?

A

Pain, heat , cold

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the difference between cellular receptors and the molecular receptors?

A

Cellular receptor is “device” made of cells that detects changes in the body or the environment
Molecular receptor is a molecule, usually located on the surface of a cell with a transmembrane linkage to the cytoplasm, that detects changes in the molecular environment (e.g. growth factors, hormones etc)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the different classes of mechanoreceptor response?

A 
Rapidly adapting  (phasic receptors)
 - Give information about changes in the stimulus
Slowly adapting (tonic receptors)
 - Continue to respond as long as stimulus is present (gives information about persistence of stimulus)
19
Q

How are primary afferent axons classified?

A

According to conduction velocity which broadly reflects diameter (faster = larger diameter)

20
Q

What is the difference between the labeling of axons coming from the skin and from the muscles?

A

Skin: Letters (A,B,C; A = largest/fastest, C = slowest/smallest)
Muscles: Roman numerals (I, II, III and IV; largest to smallest)

21
Q

Are pain fibers fast?

A

No

22
Q

How is the sensory information is organized?

A

Into layers in the spinal cord dorsal horn

  • The cell bodies of sensory neurons are grouped in the DRG and their projections are organized to different layers of the dorsal horn:
  • e.g. information from different classes of hair follicle is represented in different layers
  • Applies to different sensory modalities e.g. pain vs touch
  • Sensory information remains spatially organized as it is carried into the brain by different pathways…
23
Q

What are the two somatosensory projection pathways?

A

1, The medial lemniscal tracts

  • carry mechanoreceptive and proprioceptive signals to the thalamus
    2. The Spinothalamic tract
  • carries pain and temperature signals to the thalamus
24
Q

What are the three neurons which reach higher centers?

A
  1. First-order neurons
    - detect the stimulus and treatment to spinal cord
  2. Second-order neurons
    - relay the signal to the thalamus, the “gateway” to the cortex
  3. Third-order neurons
    - carry the signal from the thalamus to the cortex
    (second order neurons cross the midline: commisural)
25
Q

How are the axons of the medial lemniscal pathway organized?

A

Topographically

  • First-order axons from the upper body follow the lateral pathway and synapse on second-order neurons in the cuneate nucleus
  • First-order axons from the lower body (below vertebra T6) follow the more medial pathway and synapse on neurons in the gracile nucleus
  • Together these are known as the dorsal column nuclei
26
Q

After the second order axons cross the midline in the medial lemniscal pathway, where do they ascend?

A

Medial lemniscus
- then topology is reversed, relative to the midline, so that lower body axons are more lateral on reaching the thalamus

27
Q

Where do third-order axons synapse?

A

Lower body axons synapse on more medial cortical neurons

28
Q

What does the topographic projection imply?

A

Map of the body in the cortex

  • This indicates that the map is very fine, not simply lower vs upper body
  • This reflects the fact that each DPG innervates a specific domain of the body called a dermatome
29
Q

What does each sensory ganglion innervate?

A

Specific region of skin called a dermatome

30
Q

Why do dermatomes arise?

A

Because the dermis of each region is derived from a specific embryonic structure called the somite

31
Q

What are somites?

A

Iterated stuctures that give rise to the underlying musculature and skeleton

32
Q

In the embryo, what is each sensory ganglion (DRG) associated with?

A

A specific somite and subseqquently innervates the tissues arising from that somite

33
Q

What is notable about the somatosensory homunculus?

A

Representations not proportional

- number of different receptors (more specifically axons) in each different regions on the body

34
Q

What are receptive fields?

A

Each sensory neurons has a receptive field
The size of the receptive field for any particular neurons will vary depending on where it is in the body
The size of a receptive field can be measured by assessing the ability to discriminate two sharp points set apart at different distances

35
Q

When does two point discrimination occur?

A

If the subject feels two pin points then the distance between the points is larger than the receptive field

36
Q

Where receptive fields are large, discrimination is…?

A

Low (legs and arms)

37
Q

Where receptive fields are small, discrimination is…?

A

High (fingers)

38
Q

More cortex is dedicated to areas where receptive fields are …?

A

small

39
Q

Why is the amount of derived information is also higher?

A

The number of receptors (nerve endings) may be similar, the number of endings from different neurons per unit area is higher

40
Q

The number of sensory neurons innervating a particular area is related to…

A

the behavioral significance of that area

41
Q

Cortical representation is determined by behavioral significance. This implies…

A

While the representation of the hand is large in human cortex, in rodents it is the fields corresponding to whiskers that dominate

42
Q

How is sensory modality also represented in the cortex?

A

While the somatotopic map is preserved in the coronal plane throughout the postcentral gyrus, different sensory modalities are localized along the sagittal axis

  • 3b: texture and shape discrimination
  • 2: finger coordination, shape and size discrimination
  • 3a: proprioception sensory input from muscles etc. - sense of body position
43
Q

What is cortical map plasticity?

A

Amount of cortex dedicated to specific area between species

e. g. monkeys
- digits were removed; other parts of the body take over the are
e. g. Taxi drivers
- area of cortex dedicated to mapping of streets are increased

Neuroscience (28 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions