Chapter 9 - Somatic Sensory System: Touch and Proprioception Flashcards Preview

PSY2013 - Biologisk Psykologi II (2017) > Chapter 9 - Somatic Sensory System: Touch and Proprioception > Flashcards

Flashcards in Chapter 9 - Somatic Sensory System: Touch and Proprioception Deck (27)
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1
Q

What is the cause of the variable performance on two-point discrimination tasks observed when testing different regions of the body?

A

Regional differences in receptive field size and innervation density are the major factors that limit the spatial accuracy with which tactile stimuli can be sensed.

2
Q

On the —–, stimuli are perceived as distinct if they are separated by roughly 2mm, but the same stimuli applied to the —- are not perceived as distinct until they are at least 40 mm apart!

A

Fingertips, forearm.

3
Q

Sensory afferents are differentiated by the temporal dynamics of their response. What are the two different groups, and what is the primary difference between them?

A
  1. Rapidly adapting afferents
  2. Slowly adapting afferents
    They are different in how fast they adapt to stimulation. Rapidly adapting afferents are thought to be particularly effective in conveying information about changes in ongoing stimulation such as those produced by stimulus movement. Slowly adapting afferents are better suited to provide information about the spation attributes of the stimulus, such as size and shape.
4
Q

Which cutaneous sensory afferents are most closely studied?

A

Those that are found in the glabrous (hairless) portions of the hand.

5
Q

Name four different classses of mechanoreceptive afferents that innervate the glabrous skin of the hand.

A
  1. Merkel cell afferents
  2. Meissner afferents
  3. Pacinian afferents
  4. Ruffini afferents
6
Q

Rapidly adapting or slowly adapting?

  1. Merkel cell afferents
  2. Meissner afferents
  3. Pacinian afferents
  4. Ruffini afferents
A
  1. Merkel cell afferents - SLOW
  2. Meissner afferents - RAPID
  3. Pacinian afferents - RAPID
  4. Ruffini afferents - SLOW
7
Q

What is the role of proprioceptors?

A

The role of proprioceptors is primarily to give detailed and continuous information about the poisition of the limbs and other body parts in space.

8
Q

How do proprioceptors in muscle spindles work?

A

Sensory afferents are coiled around the central part of the intrafusal spindle and, when the muscle is stretched, the tension on the intrafusal fibers activates mechanically gated ion channels in the nerve endings, triggering action potentials.

9
Q

Mention three different classes of proprioceptors found in muscles and tendons.

A
  1. Muscle spindles.
  2. Goldi tendon organs
  3. Joint receptors
10
Q

What are Golgi tendon organs?

A

Goldi tendon organs are encapsulated afferent nerve endings located at the end of a muscle and a tendon.

11
Q

What is a tendon?

A

A tendon (or sinew) is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. (NO: sene)

12
Q

What is the name of the central pathway that conveys tactile information from the body?

A

The doral column-medial lemniscal system

13
Q

What is the name of the central pathway that conveys tactile information from the face?

A

The trigeminothalamic system.

14
Q

The axons of the cutaneous mechanosensory afferents enter the …

A

The axons of the cutaneous mechanosensory afferents enter the spinal cord through the dorsal roots.

15
Q

The axons of the cutaneous mechanosensory afferents enter the spinal cord through the dorsal roots; the majority ascend (contra/ipsilaterally) through …

A

The axons of the cutaneous mechanosensory afferents enter the spinal cord through the dorsal roots; the majority ascend ipsilaterally through the dorsal columns.

16
Q

The axons of the cutaneous mechanosensory afferents enter the spinal cord through the dorsal roots; the majority ascend ipsilaterally through the dorsal columns to a nuclei in …

A

The axons of the cutaneous mechanosensory afferents enter the spinal cord through the dorsal roots; the majority ascend ipsilaterally through the dorsal columns to the lower medulla, where they synapse on neurons in the dorsal column nuclei.

17
Q

The dorsal columns of the spinal cord. That’s columns, plural. How many are there, and why?

A

The dorsal columns on the spinal cord are topographically organized such that the fibers conveying information from loewr limbs lie most medial and travel in a circumscribed bundle known as fasciculus gracilis, while those that convey information from the upper limbs, trunk, and neck lie in a more lateral bundle known as the fasciculus cuneatus.

18
Q

The dorsal columns on the spinal cord are topographically organized such that the fibers conveying information from loewr limbs lie most medial and travel in a circumscribed bundle known as fasciculus gracilis, while those that convey information from the upper limbs, trunk, and neck lie in a more lateral bundle known as the fasciculus cuneatus. Where do these axons first synapse?

A

In the lower medulla, in two different nuclei - depending on the column (gracilis or cuneatus).

19
Q

The dorsal columns carrying information from mechanosensory afferents synapse in the gracile and cuneate nucleus in the lower medulla. Where do the second-order neurons synapse?

A

They synapse contralaterally in the ventral posterior lateral nucleus (VPL) in the thalamus.

20
Q

As the second-order neurons, carrying mechanosensory information from the body, leave the gracile and cuneate nuclei and cross the midline they form a tract known as the medial lemniscus. Give some funfacts about that name.

A

Lemniscus means “ribbon”, because the crossing looks like the crossing of two ribbons. In anatomy this crossing is called a decussation, from the Roman numeral X, or decem (10).

21
Q

Third-order neurons, carrying mechanosensory information from the body leave the ventral posterior lateral nucleus (VPL) of the thalamus and synapse on …

A

Third-order neurons, carrying mechanosensory information from the body leave the ventral posterior lateral nucleus (VPL) of the thalamus and synapse on the primary and secondary somatosensory cortex.

22
Q

The cutaneous mechanoreceptor information from the face is conveyed centrally along which nerve?

A

The trigeminal ganglion (cranial nerve V).

23
Q

The cutaneous mechanoreceptor information from the face is conveyed centrally along the trigeminal ganglion and terminate in …

A

the pons.

24
Q

The cutaneous mechanoreceptor information from the face is conveyed centrally along the trigeminal ganglion and terminate in the pons. Second-order neurons carrying this information ascend and terminate in …

A

the ventral posterior medial (VPM) nucleus of the thalamus.

25
Q

Third-order neurons, carrying mechanosensory information from the face leave the ventral posterior medial (VPM) nucleus of the thalamus and synapse on … …

A

neurons in the primary and secondary somatosensory cortices.

26
Q

What is the gyrus and lobe of the primary somatosensory cortex?

A

The primary somatosensory cortex in humans (also called SI) is located in the postcentral gyrus of the parietal lobe.

27
Q

The thalamus is not just a relay, and the somatosensory cortices are not just sensory processing. What is often forgotten about the cortex?

A

The descending neurons from the cortex to the thalamus, vastly outnumbers the ascending neurons to the cortex.