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Flashcards in Somesthesis Deck (77)
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1
Q

Light touch

A

Detected by cutaneous extero-receptors that are rapidly adapting (detect transient events)
Transmitted by A-beta fibers

2
Q

Proprioception

A

Perception of body projections and movement (including info from muscles, joint capsules, ligaments, tendons, and vestibular system)
More deeply situated by groups I-a, I-b, and II afferents
Nervous system must compare output to muscle with input from muscle and tendons

3
Q

Gross touch

A

Detected by cutaneous extra-receptors that are rapidly adapting (detect transient events)
Transmitted by A-beta and A-delta fibers

4
Q

Temperature

A

Separate sets of fibers and thermoreceptors that respond to increases and decreases in skin temperature
Slowly adapting neurons
Cold receptors: A-delta and C fibers
Warmth receptors: unmyelinated afferents

5
Q

Fast pain

A

Pain from cutaneous tissues comes from A-delta fibers

6
Q

Muscle afferents

A

info about contractile status

7
Q

Deep receptors

A

Joints and proprioception

8
Q

Cutaneous receptors

A

Subserve tactile sensation

9
Q

SI (primary somatosensory cortex)

A

Complete map of body represented in postcruciate gyrus, projects to primary motor cortex (MI)

10
Q

Oral and facial projections (from VCM)

A

terminate more laterally

11
Q

Trunk and limb projections (from VCL)

A

terminate medially

12
Q

Slow pain

A

Pain from cutaneous tissues comes from C fibers

13
Q

Dentin

A

Radially oriented tubules with odontoblasts protruding in at dento-pulpal interface
Changes in hydrodynamic pressure in tubules cause odontoblast to move -> afferents -> pain
A-delta = sharp localized pain
C = diffuse, poorly localized aching

14
Q

Trigeminal ganglion

A

cell bodies of receptors which innervate facial skin and oral cavity, analogous to dorsal root ganglia; reflects 3 incoming branches (V1, 2, 3)

15
Q

Subnucleus oralis

A

Division of V spinal nucleus
Represents oral cavity (tooth pulp, gingival, palate, buccal mucosa)
Mediates oral cavity reflexes (chewing and defensive)

16
Q

Subnucleus interpolaris

A

Division of V spinal nucleus
Represents head and oral cavity
Mediates tactile facial reflexes

17
Q

Subnucleus caudalis

A

Division of V spinal nucleus
Complete representation of face and oral cavity
Relay of pain and thermal sensation

18
Q

C fibers

A

Lightly myelinated or unmyelinated
Smaller diameter axons, slower conducting
Pain and temperature

19
Q

Spinothalamic tract

A

formed by axons that cross the spinal cord at levels in which their cell bodies are located
Interruption reduces pain and temp sensations contra laterally, targets ventrocaudal thalamus

20
Q

Spinoreticular tract

A

many fibers terminate in medullary reticular formation, some relay in midbrain reticular formation, involved in arousal and motivational-affective reactions to nociceptive stimulation

21
Q

Reticular

A

most primitive motor system

22
Q

Tooth pulp

A

Contains endings of A-delta and C afferents -> pain
A-beta afferents -> non-painful sensations
Directly sensitive to mechanical disturbances

23
Q

Nociceptors

A

pain receptors

24
Q

Gracile fasiculus

A

Receives input from sacral, lumbar, and lower thoracic roots, representing lower trunk and legs

25
Q

Pacinian corpuscle

A

Fast adapting A-beta touch fibers
Laminated with central neurotic, sensitive to minimal skin distortion (gingival)
More sensitive

26
Q

Meissner’s corpuscle

A

Specialized fast adapting receptors
Located within dermal papillae of glabrous skin and supplied by A-beta class fibers
Less sensitive

27
Q

Hair cells

A

A-beta fibers
Quickly adapting
No sustained discharge if hair is bent for more than a few seconds

28
Q

Slowly adapting

A

Discharge for the duration of the stimulus

Maintained events

29
Q

Free nerve endings

A

Nociceptors that detect pain
Subspecialized, myelinated and unmyelinated
A-delta fibers in skin and mucosa

30
Q

Cuneate fasiculus

A

Added lateral and gracile fascicles at ind-thoracic cord level
Transmits input from upper trunk, arms, and neck

31
Q

Dorsal column senses

A

light/fine touch, proprioception of trunk and limbs

32
Q

Internal arcuate fibers

A

Axons from cells in dorsal column nuclei

Cross to other side of brainstem and form medial lemniscus

33
Q

Rapidly adapting

A

Discharges briefly then stops
Potentials at start and end of stimulus
Transient or high frequency events

34
Q

I-a fibers

A

Fast conduction axons involved in muscle stretch, primarily spindle receptors in proprioception

35
Q

A-delta fibers

A

Large diameter, conduct slightly slower than A-beta

Touch, temperature, and pain

36
Q

A-beta fibers

A

Large diameter, more rapidly conducting axons

Supply majority of touch receptors

37
Q

Ventral quadrant senses

A

pain, temperature, crude touch

38
Q

Motor pathways

A

Motor nucleus of V -> motor neurons to muscles of mastication
Trigeminal nerve -> muscles of mastication

39
Q

Somesthesis

A

body sensibility or somatosensory capacities

40
Q

Interoceptors

A

located within the viscera and respond to changes in internal environment

41
Q

Merkel cells

A

slowly adapting touch receptors located in hairy skin in face, glabrous skin of hand

42
Q

Dorsal column pathway (forelimb and cranial trunk)

A

DRGC -> cuneate fasiculus -> synapse in cuneate fasiculus -> cross as internal arcuate fibers -> medial lemniscus -> VCL -> internal capsule -> somatosensory cortex

43
Q

Face somesthetic pathway (light touch)

A

Trigeminal ganglion cells -> trigeminal nerve -> prinicpal/chief sensory nucleus -> joins medial lemniscus -> VCM -> somatosensory cortex

44
Q

Face somesthetic pathway (proprioception from muscles of mastication)

A

Mesencephalic nucleus -> spinal tract of V -> trigeminal nerve -> muscles of mastication
Mesencephalic nucleus cells have peripheral processes in muscle proprioceptors, cell bodies in mesencephalon, and central processes terminating in motor nucleus of V

45
Q

Face somesthetic pathway (crude touch, pain, temp)

A

Trigeminal ganglion cells -> spinal trigeminal tract -> spinal trigeminal nucleus then:

a. crossed spinothalamic tract -> VCM -> internal capsule -> somatosensory cortex
b. crossed spinoreticulothalamic tract -> reticular formation, IL, hypothalamus -> IL to internal capsule -> widespread cortical areas
c. some cross and join medial lemniscus -> VCM -> somatosensory cortex

46
Q

Dorsal column pathway (hindlimb and caudal trunk)

A

DRGC -> gracile fasiculus -> synapse in gracile nucleus -> cross as internal arcuate fibers -> medial lemniscus -> VCL -> internal capsule -> somatosensory cortex

47
Q

Ventral quadrant pathways

A

DRGC -> dorsal horn cells -> crossed spinothalamic tract -> VCL -> internal capsule -> somatosensory cortex
DRGC -> dorsal horn cells -> crossed spinoreticulthalamic tract -> reticular formation, IL, hypothalamus -> IL to internal capsule -> widespread cortical areas

48
Q

What tracts compose the dorsal columns?

A

gracile fasciculus and cuneate fasciculus

49
Q

Which tract serves the upper limbs?

A

cuneate fasciculus

50
Q

Which tract serves the lower limbs?

A

gracile fasciculus

51
Q

Where do the fibers which form the dorsal column tracts have their cell bodies? Do they arise/project ipsi or contra?

A

Soma are in the dorsal root and fibers arise ipsi.

No synapse in the dorsal horn

52
Q

Are the dorsal column tracts arise with large or small fiber input?

A

large

53
Q

What modalities are carried in the dorsal columns?

A

muscle, joint, hair, and touch receptors

54
Q

Where do dorsal column tracts terminate?

A

cuneate and gracile nuclei (respectively)

55
Q

Where does the medial lemniscus originate? Do these fibers arise on the ipsi or contra side?

A

Axons from the dorsal column nuclei (gracile/cuneate) cross (contra) and form the medial lemniscus

56
Q

What modalities are carried by the medial lemniscus?

A
Direction of movement across skin
Differentiation of tactile sensation
Posture/dexterity of extremities
Skin localization
Shapes and textures
Foot adapting m. 
Joint, hair, touch receptors
57
Q

What body regions are represented in the medial lemniscus?

A

entire body

58
Q

Where does the medial lemniscus terminate?

A

VCL thalamic nucleus

59
Q

Tracts composing the ventral ascending pathways?

A

Spinothalamic and spinoreticular tracts (ST, SR)

60
Q

Do these tracts carry modalities around with large or small peripheral afferent input?

A

small

61
Q

What modalities do the ventral tracts carry?

A

pain, temperature and touch (PTT)

62
Q

Where do the fibers that comprise the tracts have their cell bodies?

A

Spinal dorsal horn

63
Q

Do these cells ascend ipsi or contra?

A

bilateral

64
Q

Where do the SR tacts fibers terminate?

A

medullary reticular formation, IL complex, hypothalamus

65
Q

Where do the ST tract fibers terminate?

A

VC thalamus and IL

66
Q

How are the SR and ST tracts similar/different?

A

Modality: PTT (same)
Origin: spinal dorsal horn (same)
Course: SR- bi, ST- contra
Terminate: SR- IL, ST- VCL

67
Q

Sensory modalities of the trigeminal nerve? Where are the cell bodies?

A

Face: PTT, cell bodies are in the trigeminal ganglion

68
Q

What is the spinal tract of V?

A

the central process of the trigeminal ganglion which disperses input to all levels of the trigeminal complex

69
Q

Where are the cells of origin of the ST of V?

A

trigeminal ganglion

70
Q

Where does the ST of V terminate?

A

sensory nucleus and spinal nucleus of V

71
Q

Which trigeminal nucleus is a/w transmittance of light touch?

A

chief sensory nucleus of V

72
Q

How is proprioception transmitted to the cerebral cortex?

A

mesencephalic nucleus of V

73
Q

Pain to the cerebral cortex?

A

subnucleus caudalis of spinal nucleus V

74
Q

The primary cortex is in the:

A

posterior postcruciate gyrus

75
Q

the foot is:

A

more medial compared to the face (on the gyrus)

76
Q

difference in projection pattern: VCL/VCM/IL

A

VCL: specific
VCM: specific
IL: diffuse

77
Q

What is the IL nucleus? What does it receive and where does it project?

A

IL nucleus: intralaminar nucleus of the thalamus
Receive: SR and ST tracts
Projects diffusely to cortex and other brain regions