Somatosensory System

Question 1

Neostriatum

Answer 1

Largest part of basal ganglia

= caudate nucleus + n. accumbens + putamen

Question 2

Amygdala connections

Answer 2

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

Question 3

Axial section through the internal capsule is

Answer 3

a very important site of strokes

Question 4

How are sensory axons in peripheral nerves classified?

Answer 4

according to their diameter and conduction speed

Question 5

Characteristics of sensory axons in skin

Answer 5

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

Question 6

Characteristics of sensory axons in muscle + tendon

Answer 6

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

Question 7

c-fibres

Answer 7

Nociceptive unmyelinated primary afferents

Question 8

Sensory receptors are classified as

Answer 8

Rapidly Adapting or Slowly Adapting. RA receptors signal

stimulus changes; SA receptors signal prolonged stimulus contact.

Question 9

Name 4 cutaneous receptors

Answer 9

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

Question 10

Cutaneous receptors are all innervated by

Answer 10

Aβ fibres

Question 11

Muscle stretch is detected by

Answer 11

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

Question 12

Tension is detected by

Answer 12

Golgi tendon organs 1b afferents

Question 13

Pain and temperature is detected by

Answer 13

c fibres plus A gamma

Question 14

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

Answer 14

bifurcate, segments

Question 15

C-fibres run up and down…

Answer 15

Lissauer’s tract

Question 16

myelinated afferents run up and down in the _______

Answer 16

Dorsal columns

Question 17

DRG contains

Answer 17

cell bodies of sensory neurones

Question 18

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

Answer 18

laminae II, laminae I and V, laminae IX

Question 19

Clarke’s column

Answer 19

thoracic nucleus

Question 20

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

Answer 20

lamina II, spinothalamic tract, lamina II

Question 21

Major nociceptive pathway in experimental animals

Answer 21

the spino-parabrachial pathway

Question 22

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

Answer 22

pathological, microglia, astrocytes

Question 23

The modality of the stimulus is denoted by

Answer 23

the axons that are activated

Question 24

altered-allodynia occurs when

Answer 24

mechanoceptive fibres activate

nociceptive pathways in the spinal cord

Question 25

Periaqueductal grey function

Answer 25

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

Question 26

Stimulation of PAG

Answer 26

extremely powerful analgesic effect throughout

the body

Question 27

Raphe nuclei function

Answer 27

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

Question 28

Nucleus raphe Magnus

Answer 28

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

Question 29

Locus ceruleus

Answer 29

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

Question 30

Syringomyelia

Answer 30

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

Question 31

A syrinx

Answer 31

fluid-filled cavity

Question 32

Ventrolateral cordotomy

Answer 32

Performed to relieve pain in right leg -> disrupts left spinothalamic tract

Question 33

Which cranial nerves are different?

Answer 33

1. II -> optic nerve = cns tissue

2. I -> olfactory have cell bodies in mucus membrane and different glial cells

Question 34

Cranial nerves containing somatosensory fibres

Answer 34

1. V - Trigeminal -> face, cornea, nasal cavity, mouth
2. IX - Glossopharyngeal -> back of tongue
3. X - Vagus -> somatic afferents to ear, larynx

Question 35

The main somatosensory cranial nerve is ______. It has 3 branches:

Answer 35

V trigeminal

1. Opthalmic
2. Maxillary
3. Mandibular

Question 36

Trigeminal neuralgia

Answer 36

a neuropathic pain that feels as if it is coming from part of the territory supplied by the trigeminal nerve

Question 37

Which relationship can give rise to trigeminal neuralgia?

Answer 37

Superior cerebellar artery near trigeminal roots

Question 38

Post herpetic neuralgia follows

Answer 38

Shingles

Question 39

The large primary afferent in the _____ ___ has function of _____ with cell body in _____ _____

Answer 39

Upper pons, discriminative touch, trigeminal ganglion

Question 40

Trigeminal nuclei extend through …..

Answer 40

most of the brainstem

Question 41

Trigeminal sensory nuclei extends from x to y

Answer 41

X - midbrain

Y- spinal cord

Question 42

Effects of a Posterior Inferior Cerebellar

Artery (PICA) lesion

Answer 42

PICA supplies dorsolateral medulla

so…

Question 43

Visceral afferent fibres carry

Answer 43

taste or other information from the viscera including the carotid sinus and body. They all end in the nucleus of the solitary tract

Question 44

Vestibular and cochlear fibres end in X and Y

Answer 44

end in the vestibular and cochlear nuclei

Question 45

Nucleus of the solitary tract receive _____. It’s important for ____

Answer 45

visceral afferent (taste and general visceral afferent) information. It is an important centre for autonomic control and parts of it form the dorsal inspiratory
respiratory centre.