Classification of cranial nerve nuclei

Question 1

I. Basics
1. Where are motor nuclei located?

Answer 1

They are located medially, sensory nuclei are found laterally

Question 2

II. Motor (efferent) nuclei
1. What are the general characteristics of Motor (efferent) nuclei?

Answer 2

Contain multipolar neurons
-> their axons leaves the brain and terminates on target (muscle, gland)

Question 3

II. Motor (efferent) nuclei
2. What are the 3 types of motor nuclei?

Answer 3

1. Somatomotor nuclei (SM) / general somatic efferent (GSE) (lie close to the midline)
2. General visceromotor nuclei (GVM) (laterally)
3. Branchiomotor nuclei (BM) / special visceromotor (SVM)

Question 4

II. Motor (efferent) nuclei - Somatomotor nuclei (SM) / general somatic efferent (GSE) (lie close to the midline)
3A. What are characteristics of Somatomotor nuclei (SM) / general somatic efferent (GSE) (lie close to the midline)?

Answer 4

• Multipolar neurons send their axons to innervate striated muscles of eye and form the dorsomedial nuclear column:
  1. Oculomotor nucleus (CN III)
  2. Trochlear nucleus (CN IV)
  3. Abducent nucleus (CN VI)
  4. Hypoglossal nucleus (CN XII)

Question 5

II. Motor (efferent) nuclei - Somatomotor nuclei (SM) / general somatic efferent (GSE) (lie close to the midline)
3C. Which nuclei form the dorsomedial nuclear column?

Answer 5

1. Oculomotor nucleus (CN III)
2. Trochlear nucleus (CN IV)
3. Abducent nucleus (CN VI)
4. Hypoglossal nucleus (CN XII)

Question 6

II. Motor (efferent) nuclei - General visceromotor nuclei (GVM) (laterally)
4A. What are the characteristics of General visceromotor nuclei (GVM) (laterally)?

Answer 6

• Parasympathetic innervation, secretomotor (CN III, CN VII, IX, X)
  1. Edinger-Westphal nucleus
  2. Superior salivatory nucleus
  3. Inferior salivatory nucleus
  4. Dorsal vagal nucleus
• Innervate viscera: smooth muscles / glands (e.g., salivary glands, SM of thoracic viscera)

Question 7

II. Motor (efferent) nuclei - General visceromotor nuclei (GVM) (laterally)
4B. How does innervation occur with General visceromotor nuclei (GVM) (laterally)?

Answer 7

1. Cranial nerve nuclei contain the preganglionic parasympathetic neurones. Axons leave the brain and end in autonomic parasympathetic ganglion, synapsing with neuron in the ganglion
2. Axon of the postganglionic neuron reach the target organ. Only exception is the adrenal medulla, which receives the preganglionic fiber directly

Question 8

II. Motor (efferent) nuclei - Branchiomotor nuclei (BM) / special visceromotor
(SVM)
5A. What are the characteristics of Branchiomotor nuclei (BM) / special visceromotor (SVM)

Answer 8

1. Nuclei from the ventrolateral nuclear column (CN V, VII, IX-X-XI)
   - Motor nucleus of trigeminal nerve
   - Motor nucleus of facial nerve
   - Nucleus ambiguous
2. Innervate….
   - striated muscles (developed from branchial arches)
   - Muscles of mastication and facial expression
   - Pharynx and larynx

Question 9

III. Sensory (afferent) nuclei
1. What are the characteristics of sensory nuclei?

Answer 9

• Contain multipolar neuron, but they receive inputs from sensory nerves - these fibers synapse on the neurons

Question 10

III. Sensory (afferent) nuclei
2. What are the 4 types of sensory nuclei?

Answer 10

1. General viscerosensory nuclei (GVS)
2. Special viscerosensory nuclei (SVS)
3. General somatosensory nucleus (GSS)

Question 11

III. Sensory (afferent) nuclei
3. What are the characteristics of General viscerosensory nuclei (GVS)?

Answer 11

• Relay neurons lie lateral to the visceral motor
• Receive afferent fibers from interoceptors, chemoreceptors and baroreceptors
  => Lateral ala cinerea nucleus (part of the solitary nucleus)

Question 12

III. Sensory (afferent) nuclei
4. What are the characteristics of Special viscerosensory nuclei (SVS)

Answer 12

• For taste
• Relay neurons receive afferent inputs from taste fibers coming from the taste buds
  => Solitary nucleus

Question 13

III. Sensory (afferent) nuclei
5. What are the characteristics of General somatosensory nucleus (GSS)?

Answer 13

• Receive afferent fibers from body receptors: mechano-, noci- or thermoreceptors from skin, muscles and joints of the head)
• 3 different sensory subtypes exist: Epicritic, Protopathic, Proprioceptive
  => Chief sensory nucleus of trigeminal nerve
  => Spinal trigeminal nucleus
  => Mesencephalic trigeminal nucleus

Question 14

III. Sensory (afferent) nuclei - General somatosensory nucleus (GSS)
5A. Meaning of Epicritic

Answer 14

fine / discriminative touch and pressure, vibration

Question 15

III. Sensory (afferent) nuclei - General somatosensory nucleus (GSS)
5B. Meaning of Protopathic

Answer 15

important for survival – pain, rough (crude) touch, temperature

Question 16

III. Sensory (afferent) nuclei - General somatosensory nucleus (GSS)
5C. Meaning of Proprioceptive

Answer 16

position of muscles and joints. Afferent inputs from muscle spindles + tendon organs

Question 17

III. Sensory (afferent) nuclei
6. What are the characteristics of Special somatosensory nuclei (most laterally)

Answer 17

• Receive afferent fibers carrying vestibular and auditory signals
• Belong to organs of special senses. (hearing and balance)
  => Vestibular nuclei
  => Cochlear nuclei

Question 18

IV. Extra - Fill in the table

Answer 18