1. Lundy-Ekman Chapters 14, 15 and 16
Brainstem
Lundy-Ekman
Chapters 14, 15 and 16

2. Components of the Brainstem
Midbrain
Pons
Medulla
Rostrally – diencephalon
Caudally – spinal cord
Page 358 A and B (good pictures)

3. Midbrain structures Dorsal surface Ventral surface Tectum
Superior colliculus
Inferior colliculus
Ventral surface
Cerebral peduncles
Interpeduncular fossa

4. Pontine Stuctures Cerebellar peduncles Superior cerebellar peduncle
Middle cerebellar peduncle
Inferior cerebellar peduncle

5. Medullary structures
Pyramids
Pyramidal decussation

6. Segments of the brainstem
Basilar region
Tegmentum
Tectum
Basilar : anterior
Tegmentum : posterior
Tectum: only in midbrain, roof over cerebral aqueduct

7. Basilar region Predominantly motor structures Descending tracts
Motor nuclei: pons, substantia nigra
Pontocerebellar axons

8. Tegmentum Cranial nerve nuclei Reticular formation
Ascending sensory tracts and sensory nuclei
Medial longitudinal fasciculus – fiber tract that coordinates head and eye movements

9. Tectum Superior and inferior colliculi Pretectal area
Reflexive control of eye movements
Movements of head

10. Caudal Medulla

11. Pyramids
Medial lemniscus
Dorsal column nuclei and tracts
Spinal trigeminal nucleus and tract
Inferior olivary nucleus

12. Rostral Medulla

13. Note the cerebellar peduncles

14. Pons

15. Corticobulbar, corticopontine, and corticospinal tracts Pontine nuclei
Pontocerebellar tract
Cerebral cortetx  corticopontine tract  pontine nuclei  pontocerebellar tract  cerebellum
Brachium pontis – Middle cerebellar peduncle

16. Midbrain Cerebral peduncles (crus cerebri) Red nucleus
Cortico- bulbar, spinal and pontine tracts
Red nucleus
Substancia nigra
Medial lemniscus and spinothalamic tracts
Periaqueductal gray
Oculomotor nucleus
Tectum

19. Parkinson’s Disease

20. Sensory and Motor Organization of the Brainstem
Development lectures
Brainstem – page 358
Motor medial (GSE)
Sensory lateral (SSA and GSA)
Visceral (in between)
Visceral motor medial
Visceral sensory lateral

21. Overview of Cranial Nerves
Arise from the brain
Innervate the head and neck
12 pairs of cranial nerves

22. Location of Cranial Nerves
Page 358
Cerebrum – I
Diencephalon – II
Midbrain – III, IV
Pons – V
Pontomedullary border – VI, VII, VIII
Medulla – IX, X, XI, XII

23. Functions of Cranial Nerves
Same overall functions as spinal nerves, though a cranial nerve may not have all categories of functions
Motor
Sensory
Autonomic
Some cranial nerves have special functions
Smell
Vision
Taste
Vestibular

24. Three main functions
Motor innervation to muscles of face, eyes, tongue, jaw and two neck muscles.
Somatosensory information from skin and muscles of face and TMJ, and special sensory information (olfactory, visual, auditory, vestibular, taste, and visceral sensations)
Parasympathetic regulation of heart rate, blood pressure, digestion, breathing, and some eye muscles.

25. Lesions of Cranial Nerves
Damage to cranial nerve in periphery (trauma, inflammation)
Ipsilateral deficits
Damage to cranial nerve nuclei in CNS (stroke)
Usually ipsilateral deficits
Can help localize lesion in the brain
Damage to upper motor neurons that control cranial nerves (stroke)
Usually do not see significant weakness due to bilateral innervation of CN nuclei. (One significant exception)

26. Consciousness Awareness of self and surroundings
Regulate alertness, sleep and attention

27. Brain components Reticular formation
Ascending reticular activating system (ARAS)
Project to cerebral parts of consciousness systems (basal forebrain, thalamus, cerebral cortex)
Basal forebrain – in telencephalon
All regions must be intact for consciousness

28. Basal forebrain Projects to widespread areas of cortex
May contribute to:
Modulation of level of awareness
Sleep/wake cycle
Neurotransmitter
Damaged in Alzheimer’s disease
Neurotransmitter: ACh

29. Consciousness Pathways
RF neurons receive sensory info
Multisynaptic transmission through RF
Rostral RF (rostral pons and midbrain) project to intralaminar nuclei of thalamus
Intralaminar nucleus to widespread regions of cerebral cortex
Also direct pathways from RF to cerebral cortex
Raphe – to cortex
Locus ceruleus – to cortex and hypothalamus

30. Disorders of Consciousness
To have a loss of consciousness
Brainstem RF
ARAS
Cerebrum
Hypothalamic/Thalamic activating systems
Function of entire cerebral cortex

31. States of altered consciousness
Coma
Stupor
Sleep
Coma – loss of consciousness, unarousable, not reversible by strong stimuli
Stupor – only arousable by strong stimuli
Sleep – temporary, physiological loss of consciousness – arousable by environmental stimuli

32. Locked-in state
Not loss of consciousness – may appear to have impaired consciousness
Practically complete loss of voluntary motor function
Injury usually in ventral pons
Loss of corticospinal, most corticobulbar
Usually some sparing of eye movements
Open eyes
Some vertical movement of eyes