Midterm

• Afferent refers to something coming into the CNS
• Efferent refers to something outgoing from the CNS
• The autonomic nervous system is also known as visceral motor system
• The ANS is responsible for maintaining physiologic homeostasis
• The ANS is controlled by the visceral motor nuclei in hypothalamus
• A preganglionic neuron is a small myelinated nerve fiber belonging to the ANS with a cell body in CNS.
• The ANS is a two neuron circuit
• A postganglionic neuron is a nonmyelinated nerve fiber belonging to the ANS with a cell body in PNS ganglion
• The two divisions of the ANS are:

  1. Parasympathetic
  2. sympathetic
• The sympathetic postganglionic neurons are located in:

  1. sympathetic trunk ganglia
  2. prevertebral ganglia
  3. adrenal medulla
• The parasympathetic postganglion neurons are localized in small clusters embedded in the target effector
• Adrenergic refers to action mediated by norepinephrine (noradrenaline)
• Cholinergic refers to action mediated by acetylcholine
• The three classes of transmitter in the ANS:

  1. Adrenergic
  2. Cholinergic
  3. Neuropeptidergic
• The two types of receptors in the ANS are:

  1. Adrenergic
  2. Cholinergic
• In the sympathetic pathway:

  acetylcholine --> norepinephrin
• In the parasympthetic pathway:

  acetylecholine --> acetylecholine
• The location of the CNS visceral motor neurons in the sympathetic ANS is the lateral gray horns of spinal segments T1-L2
• The location of the CNS visceral motor neurons in the parasympathetic ANS is the brain stem and spinal segments S2-S4
• Cranial Nerve I: Olfactory Nerve

  • Role: Olfactory transduction
  • Key brain structure: olfactory bulb --> olfactory tract
  • Structures served: roof of nasal cavity
  • Classification: sensory
• Cranial Nerve II: Optic Nerve

  • Role: visual transduction
  • Key brain structure: optic tract --> optic chiasm
  • Structures served: retina
  • Classification: sensory
• Cranial Nerve III: Occulomotor

  • Role: eye movement
  • Key nuclei: midbrain-pontine junction
  • Structures served: eye muscles
  • Classification: motor
• Cranial Nerve IV: Trochlear

  • Role: eye movement
  • Key nuclei: midbrain
  • Structures served: eye muscles
  • Classification: motor
• Cranial Nerve V: Trigeminal

  • Role: sensation of touch, pain, temperature in face and mastication
  • Key nuclei: pons
  • Structures served: facial somatosensory receptors and muscles of mastication
  • Classification: sensory & motor
• Cranial Nerve VI: Abducens

  • Role: eye movement
  • Key nuclei: Pontomedullary Junction
  • Structures served: eye muscles
  • Classification: motor
• Cranial Nerve VI: Facial Nerve

  • Role: Facial expression, lacrimation, taste
  • Key nuclei: Pontomedullary Junction
  • Structures served: Taste receptors & facial muscles
  • Classification: sensory & motor
• Cranial Nerve VIII: Vestibulocochlear

  • Role: auditory transduction
  • Key nuclei: Pontomedullary junction
  • Structures served: Vestibular nerve & cochlear nerve
  • Classification: sensory
• Cranial Nerve IX: Glossopharyngeal

  • Role: Taste, facial movement, gag reflex
  • Key nuclei: medulla
  • Structures served: posterior tongue, muscles of third pharyngeal arch
  • Classification: sensory & motor
• Cranial Nerve X: Vagus

  • Role: parasympathetic nervous system
  • Key nuclei: medulla posterior to olive
  • Structures served: multiple organs
  • Classification: sensory & motor
• Cranial Nerve XI: Spinal Accessory

  • Role: Neck and shoulder movement
  • Key nuclei: medulla posterior to olive
  • Structures served: larynx, muscles of neck and shoulders
  • Classification: motor
• Cranial Nerve XII: Hypoglossal

  • Role: Tongue Movement
  • Key nuclei: medulla anterior to olive
  • Structures served: tongue muscles
  • Classification: motor
• The twelve cranial nerves are:

  1. Olfactory nerve
  2. Optic nerve
  3. Occulomotor
  4. Trochlear
  5. Trigeminal
  6. Abducens
  7. Facial Nerve
  8. Vestibulocochlear
  9. Glossopharyngeal
  10. Vagus
  11. Spinal accessory
  12. Hypoglossal
• Three cerebellar peduncles:

  1. superior cerebellar peduncle
  2. middle cerebellar peduncle
  3. inferior cerebellar peduncle
• Superior cerebellar peduncle is from the cerebellum to rest of brain
• Middle cerebellar peduncle is from the cortex to the spine
• Inferior cerebellar peduncle is spinal input to cerebellum
• Three major brainstem structures:

  1. Midbrain
  2. Pons
  3. Medulla Oblongata
• Four key midbrain structures:

  1. Cerebral peduncle
  2. Superior Colliculi
  3. Inferior Colliculi
  4. Aqueduct
• Cerebral peduncle is a white matter bundle that carries motor information between the cerebrum and pons/spinal cord
• Inferior colliculi is responsible for quick auditory response