Brainstem

Question 1

What are the components of the brainstem?

Answer 1

1. Midbrain
2. Pons
3. Medulla

Question 2

What is in the dorsal surface of the midbrain?

Answer 2

Tectum

• Superior colliculus – visual map of the world
• Inferior colliculus – auditory map of the world

Question 3

What is in the ventral surface of the midbrain?

Answer 3

1. Cerebral peduncles – contains corticospinals, corticobulbar, corticopontie fibers
2. Interpeduncular fossa – depression between peduncles – CNIII comes out of here

Question 4

What is the anterior segment of the brainstem? middle? posterior?

Answer 4

• Anterior = basilar
• Middle = Tegmentum
• posterior = Tectum (only in midbrain, roof over cerebral aqueduct)

Question 5

What is contained in the basilar region?

Answer 5

1. Descending tracts
2. Motor nuclei: pons, substantia nigra
3. Pontocerebellar axons

Question 6

What is contained in the tegmentum?

Answer 6

1. Cranial nerve nuclei
2. Reticular formation
3. Ascending sensory tracts and sensory nuclei
4. Medial longitudinal fasciculus – fiber tract that coordinates head and eye movements

Question 7

What is contained in the caudal medulla?

Answer 7

1. Pyramids
2. Medial lemniscus
3. Dorsal column nuclei and tracts
4. Spinal trigeminal nucleus and tract
5. Inferior olivary nucleus

Question 8

What is another name for the middle cerebellar peduncle?

Answer 8

Brachium pontis

Question 9

What is contained in the midbrain?

Answer 9

1. Cerebral peduncles (crus cerebri) -Cortico- bulbar, spinal and pontine tracts
2. Red nucleus
3. Substancia nigra
4. Medial lemniscus and spinothalamic tracts
5. Periaqueductal gray
6. Oculomotor nucleus
7. Tectum

Question 10

In the brainstem, where are the motor tracts located? sensory? visceral?

Answer 10

Motor = medial (General Somatic Efferrent; GSE)
Sensory = lateral (S[pecial]SA and GSA)
Visceral = In between, lateral horn (motor medial, sensory lateral)
- General = touch vibration, movement
- special = vision, taste, hearing

Question 11

What are the main functions of cranial nerves that exit the brainstem?

Answer 11

1. Motor innervation to muscles of face, eyes, tongue, jaw and two neck muscles
2. Somatosensory information from skin and muscles of face and TMJ, and special sensory information
3. Parasympathetic regulation of heart rate, blood pressure, digestion, breathing, and some eye muscles

Question 12

What part of the brainstem regulates consciousness? (small damage to this area can produce coal, loss of awareness)

Answer 12

Reticular formation
- small injuries cause problems with consciousness, where as you need significant CC damage to see problems with consciousness

Question 13

Ascending reticular activating system (ARAS); Project to cerebral parts of consciousness systems (basal forebrain, thalamus, cerebral cortex); Basal forebrain – in telencephalon

Answer 13

Reticular formation

Question 14

Projects to widespread areas of cortex; May contribute to: Modulation of level of awareness, Sleep/wake cycle; damaged in Alzheimer’s disease

Answer 14

Basal forebrain

Question 15

What is the neurotransmitter in the basal forebrain?

Answer 15

ACh

Question 16

What damaged areas will result in disorders of consciousness?

Answer 16

1. Brainstem
   - RF
   - Ascending reticular activating system (ARAS) - Project to cerebral parts of consciousness systems (basal forebrain, thalamus, cerebral cortex)
2. Cerebrum
   - Hypothalamic/Thalamic activating systems
   - Function of entire cerebral cortex

Question 17

loss of consciousness, unarousable, not reversible by strong stimuli

Answer 17

Coma

Question 18

only arousable by strong stimuli for short periods of time and not very aware

Answer 18

Stupor

Question 19

temporary, physiological loss of consciousness – arousable by environmental stimuli

Answer 19

Sleep

Question 20

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)

Answer 20

Locked-in state