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Flashcards in Somatosensory System Deck (45)
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1

Neostriatum

Largest part of basal ganglia
= caudate nucleus + n. accumbens + putamen

2

Amygdala connections

Hippocampal formation, dorsomedial thalamus, medial prefrontal cortex
input: nociceptive pathways

3

Axial section through the internal capsule is

a very important site of strokes

4

How are sensory axons in peripheral nerves classified?

according to their diameter and conduction speed

5

Characteristics of sensory axons in skin

Aβ-15μm, 70m/sec
• Aδ-3μm, 20m/sec
• C-unmyelinated

6

Characteristics of sensory axons in muscle + tendon

I- up to 20μm,100m/sec
• II- < 10μm, 50 m/sec
• IV- unmyelinated, 1μm, 1m/sec

7

c-fibres

Nociceptive unmyelinated primary afferents

8

Sensory receptors are classified as

Rapidly Adapting or Slowly Adapting. RA receptors signal
stimulus changes; SA receptors signal prolonged stimulus contact.

9

Name 4 cutaneous receptors

1. Meissner’s corpuscles (RA) important for two point
discrimination- concentrated in skin of fingers and around
mouth etc.
2. Merkel’s discs (SA) also important for discriminative touch
3. Ruffini endings (SA) Skin stretch
4. Pacinian corpuscles (RA)- vibration

10

Cutaneous receptors are all innervated by

Aβ fibres

11

Muscle stretch is detected by

Muscle spindles - Ia afferents -> also receive type II (Ab afferents)

12

Tension is detected by

Golgi tendon organs 1b afferents

13

Pain and temperature is detected by

c fibres plus A gamma

14

The central axons of primary afferents _____ on entering the cord and innervate several ______

bifurcate, segments

15

C-fibres run up and down...

Lissauer’s tract

16

myelinated afferents run up and down in the _______

Dorsal columns

17

DRG contains

cell bodies of sensory neurones

18

C-fibres end in _____..
A Delta fibres end in _____
Ia afferents end in_______
Aβ afferents end in….

laminae II, laminae I and V, laminae IX

19

Clarke’s column

thoracic nucleus

20

C-fibres mainly end in _____ but _____ is mainly populated
by interneurons- ______ neurons are not found in
_____

lamina II, spinothalamic tract, lamina II

21

Major nociceptive pathway in experimental animals

the spino-parabrachial pathway

22

Chronic pain is ______- not physiological. It involves changes in the _______ and
_______ (as well as the neurons) of the spinal cord

pathological, microglia, astrocytes

23

The modality of the stimulus is denoted by

the axons that are activated

24

altered-allodynia occurs when

mechanoceptive fibres activate
nociceptive pathways in the spinal cord

25

Periaqueductal grey function

Sends axons to the nucleus raphe magnus in the medulla and the locus ceruleus.

26

Stimulation of PAG

extremely powerful analgesic effect throughout
the body

27

Raphe nuclei function

These send serotonergic (5HT) fibres all over the CNS. Receives input from PAG and modulates nociceptive transmission in dorsal horn of spinal cord

28

Nucleus raphe Magnus

Raphe-spinal axons project down to superficial dorsal horn of spinal cord - they can turn the gain on the nociceptive pathways up or down

29

Locus ceruleus

Largest noradrenergic nucleus -> descending noradrenergic fibres -> analgesic effect

30

Syringomyelia

Destruction of crossing fibres leads to loss of pain and temperature over affected segments, which are usually cervical. Sensation from below the lesion is unaffected