Exam 2 (Pt. 9)

Question 1

Free-Running Rhythms of Three Animals of Different Species - Onset/Offset

Answer 1

The time of activity onset (and offset) occurred earlier (A, B) or later (C) each day. Thus each individual had a free-running period either shorter (A, B) or longer (C) than 24.0 hours.

Question 2

The Circadian System Model

Answer 2

Question 4

Suprachiasmatic Nucleus (SNC) & Circadian Rhythms

Answer 4

Double-plotted drinking record from a squirrel monkey before (A) and after (B, C) receiving a histologically verified total SCN lesion. The approximately 25-h drinking rhythm prelesion (A) persisted with a reduced amplitude for over 90 days postlesion (B) before finally decaying into arrhythmia (C).

Question 5

Projections of the SCN/Subparaventricular Zone Complex and Their Likely Functions

Answer 5

Question 6

Continuum of States of Arousal

Answer 6

Question 8

Suprachiasmatic Nucleus (SNC) & Circadian Rhythms - Relationship

Answer 8

Suprachiasmatic Nucleus (SCN) ablation results in loss of circadian rhythms.

Question 10

The Arousal Continuum from Highest to Lowest Levels

Answer 10

Question 11

Electrophysiological Correlates of Waking and Sleep Stages - Vertex Spike

Answer 11

Characteristic EEG patterns seen during different stages of sleep in humans are shown here. The sharp wave called a vertex spike appears during stage 1 sleep. Brief periods of sleep spindles are characteristic of stage 2 sleep

Question 12

Electrophysiological Correlates of Waking and Sleep Stages - Deeper Sleep

Answer 12

Deeper stages of slow-wave sleep show progressively more large, slow delta waves.

Question 13

Electrophysiological Correlates of Waking and Sleep Stages - Similarity

Answer 13

Note the similarity of activity during waking, stage 1 sleep, and rapid eye movement (REM) sleep.

Question 14

Properties of Slow-Wave and REM Sleep

Answer 14

Question 15

Sleep Stages & Sleep Architecture

Answer 15

Note the progressive lengthening of REM episodes (blue) and the loss of stages 3 and 4 sleep as the night goes on.

Question 16

Evidence for Bremer’s 1937 Passive Sensory Theory of Sleep - Procedure

Answer 16

Transecting the neuraxis at the level between the superior and inferior colliculi removed much of the ascending sensory input to the forebrain.

Question 17

Evidence for Bremer’s 1937 Passive Sensory Theory of Sleep - Conclusion

Answer 17

This produced a cat that appeared to be sleeping; hence, Bremer concluded that depriving the rostral brain produced sleep.

Question 18

Evidence for Moruzzi and Magoun’s Active Reticular Activating-System Theory of Sleep - Procedure

Answer 18

In the late 1940’s Moruzzi and Magoun made small lesions in the core of the brain stem so that most of the classic ascending sensory pathways were left intact.

Question 19

Evidence for Moruzzi and Magoun’s Active Reticular Activating-System Theory of Sleep - Conclusion

Answer 19

Nevertheless, these animals displayed a sleep-like EEG pattern. Hence they concluded that the reticular formation produced sleep through an active process.

Question 20

The Nature & Extent of the Reticular Formation - Diagram

Answer 20

MBRF=midbrain reticular formation; MRF=medullary reticular formation; PRF=pontine reticular formation; TRF=thalamic reticular formation; HYP=hypothalamus.

Question 22

Brain Stem Reticular Formation

Answer 22

The reticular formation is thought to activate the rest of the brain.

Question 23

Ascending Arousal Systems - Projections

Answer 23

The ascending arousal system sends projections from the brainstem and posterior hypothalamus throughout the forebrain.

Question 24

Ascending Arousal Systems - Cholinergic Fibers

Answer 24

Neurons of the laterodorsal tegmental nuclei and pedunculopontine tegmental nuclei (LDT and PPT) (blue circles) send cholinergic fibers (ACh) to many forebrain targets, including the thalamus, which then regulate cortical activity.

Question 25

Ascending Arousal Systems - Aminergic Nuclei

Answer 25

Aminergic nuclei (green circles) diffusely project throughout much of the forebrain, regulating the activity of cortical and hypothalamic targets directly.

Question 26

Ascending Arousal Systems - Neurotransmitter

Answer 26

Neurons of the tuberomammillary nucleus (TMN) contain histamine (HIST), neurons of the raphé nuclei contain 5-HT and neurons of the locus coeruleus (LC) contain noradrenaline (NA).

Question 27

Ascending Arousal Systems - Sleep-Promoting

Answer 27

Sleep-promoting neurons of the ventrolateral preoptic nucleus (VLPO, red circle) contain GABA and galanin (Gal).

Question 28

Descending Projections from the Ventrolateral Preoptic Area (VLPO) that Terminate on Major Brain Stem “Arousal Nuclei” - VLPO Axon

Answer 28

Axons from the VLPO directly innervate the cell bodies and proximal dendrites of neurons in the major monoamine arousal groups.

Question 29

Descending Projections from the Ventrolateral Preoptic Area (VLPO) that Terminate on Major Brain Stem "Arousal Nuclei" - Interneuron

Answer 29

Within the major cholinergic groups, axons from the VLPO mainly innervate interneurons, rather than the principal cholinergic cells.

Question 30

Hypocretin/Orexin Arousal Mechanisms - Effects On

Answer 30

Question 31

Hypocretin/Orexin Arousal Mechanisms - Orexin-Stimulating

Answer 31

Question 32

Hypocretin/Orexin Arousal Mechanisms - Hypocretin Arousal Pathway

Answer 32

Question 33

The Neural Substrates for the Interaction of Circadian Rhythm Control and Arousal/Sleep Mechanisms

Answer 33

Question 34

A Model of Sleep Employing the Concept of an Interaction Between a Circadian Rhythmic Process and a Sleep-Wake Process - Main Idea

Answer 34

Sleep is assumed to result from the action of process C and process S.

Question 35

A Model of Sleep Employing the Concept of an Interaction Between a Circadian Rhythmic Process and a Sleep-Wake Process - Rhythmicity

Answer 35

Process C follows a circadian rhythm and is independent of sleeping and waking. Rhythmicity Process S, on the other hand, depends on sleep-wake behavior; S declines during sleep and rises continuously during sleep deprivation.

Question 37

Variation in States of Arousal - Variation

Answer 37

Over the course of time, physiological, behavioral and cognitive functions vary in level of arousal/intensity.

Question 38

Variation in States of Arousal - Reason

Answer 38

The fluctuations depend upon changes in neural activity at both the systems and cellular levels.

Question 39

Variation in States of Arousal - Level

Answer 39

At a system level, there are neural substrates that control rhythmic changes in level of arousal. At a cellular level, neurotransmitters and drugs affecting these neurotransmitters act to change levels of activity and arousal.

Question 51

The Nature & Extent of the Reticular Formation - Conclusion

Answer 51

The concept of a reticular activating system has changed dramatically from the time of Moruzzi and Magoun’s experiments. Specific cell groups containing NE, ACh and 5HT have been implicated in projections to the thalamus and cortex and as being important in the control of arousal.