Brainstem Modulation

Question 1

what is the reticular activating system (RAS)

Answer 1

reticular formation and other brainstem regions involved in mediating the the shift from sleep to waking

Question 2

what does a transection of only ascending sensory pathways in the RAS do

Answer 2

no effect on sleep-wake states

Question 3

what happens when the brainstem is transected at the spino-medullary junction

Answer 3

no effect on sleep-wake states

Question 4

what happens when the mid brain is transected between the the inferior and superior colliculi

Answer 4

results in a perpetual sleep like state

Question 5

what results from stimulation of the reticular formation in the midbrain

Answer 5

wakes sleeping animals

Question 6

what is synchronized activity

Answer 6

• occurs when many neurons fire simultaneously, then simultaneously stop firing
• large voltage deflection in the EEG
• associated with non-waking states

Question 7

what is desynchronized activity

Answer 7

• occurs when neurons in a given region do not fire in synchrony with many other neurons
• EEG trace looks largely flat
• Occurs during alert wakefulness

Question 8

how are sleep states differentiated

Answer 8

• Certain rhythmic patterns in the EEG
• Presence or absence of eye movements
• degree of muscle tone

Question 9

what is EEG

Answer 9

electroencephalography (EEG); extracranial recordings of neuronal activity

Question 10

what is EOG

Answer 10

electrooculography (EOG); recordings of electrical signals from extraocular muscles of the eyes

Question 11

what is EMG

Answer 11

electromyography (EMG); recordings of electrical signals from muscles

Question 12

what are sleep wake states controlled by

Answer 12

• midbrain reticular formation, thalamus, and cerebral cortex
• neuromodulary centers

Question 13

what are the anatomical substrates of the awake state

Answer 13

1. MRF excites thalamic cells
2. thalamic cells depolarize enough to fire in an ongoing way
3. Ongoing thalamic input excites cortex, causing desynchronized EEG

Question 14

what are the anatomical substrates of the onset of sleep state

Answer 14

1. MRF firing slows
2. thalamic cells fire in bursts that alternate with firing in the neocortex
3. Slower frequency with deeper stages of sleep; in stage 4 sleep: 3-4 Hz, delta waves

Question 15

what is the location of the reticular formation

Answer 15

runs longitudinally within the brainstem from the medulla to the upper midbrain

Question 16

describe the reticular formation

Answer 16

• RF neurons span large territories within the brainstem
• Long dendrites run perpendicular to the neuroaxis
• Axons branch extensively along the neuroaxis
• Integrate input from and send output to many regions of the nervous system

Question 17

what are the afferents of the RF

Answer 17

• spinoreticular tracts: visceral and somatic sensory input (ascending)
• motor signals from the cortex, superior colliculus, and the cerebellum (descending)

Question 18

what are the efferents of the RF

Answer 18

• reticulospinal tracts: posture, visceral motor (descending)
• cerebellum, thalamus, intralaminar nuclei of the thalamus (ascending)

Question 19

what are the cholinergic nuclei

Answer 19

• pedunulopontine tegmental nuclei (PPT)
• laterodorsal tegmental nuclei (LDT)

Question 20

what is the function of the cholinergic nuclei

Answer 20

regulate sleep-wake states and attention

Question 21

what are the dopaminergic nuclei

Answer 21

• substantia nigra pars compacta (SNc)
• Ventral tegmental area (VTA)

Question 22

what is the nigrostriatal pathaway

Answer 22

SNc –> striatum

Question 23

what is the mesolimbic pathway

Answer 23

VTA –> limbic structures

Question 24

what is the mesocortical pathway

Answer 24

VTA –> prefrontal cortex

Question 25

what are the noradrenergic nuclei and its function

Answer 25

locus coerulus
regulates sleep-wake states, attention, mood

Question 26

what are the serotonergic nuclei and their functions

Answer 26

raphe nuclei
regulates sleep-wake states, mood, and pain