Chapters 32 33 Tripple

Reticular Formation „ „

From medulla to midbrain 4 nuclear groups … Median „

raphe

Serotonin

… Paramedian … Medial … Lateral

Raphe Nuclei „

Magnus, obscurus, pallidus … Medulla … Input

from spinal cord, trigeminal nuclei, periaqueductal gray matter … Output to cerebellum, dorsal horn of spinal cord, trigeminal nuclei … Pain mechanisms

Raphe Nuclei „

Pontis, dorsal raphe, superior central … Pons

& midbrain from PFC, limbic system, hypothalamus … Output to forebrain, cerebellum, brainstem … Wakefulnesss, alertness, sleep … Inputs

1

Medial Group „

„

Input from spinal cord, collaterals from spinothalamic tract & trigeminal/auditory nuclei, SC, cerebellum, hypothalamus, cerebral cortex Output to …

spinal cord

…

intralaminar nuclei of the thalamus (centromedian & parafascicular), basal cholinergic nuclei

„

„

Motor control

Alertness, consciousness

Paramedian Group Input from spinal cord, cerebral cortex, vestibular nuclei „ Output to cerebellum „ AKA precerebellar nuclei „

Lateral Group „

Parvocellularis & lateralis … Sensory

input from contralateral red nucleus, spinal cord, trigeminal/auditory/vestibular sensory systems. … Output to both cerebellar hemispheres, medial group (reticular formation) … Parvocellularis … Inputs

„

Expiratory center

2

Lateral Group „

Pedunculopontine … … …

„

Parabrachial nucleus … … … …

„

Input from cerebral cortex, globus pallidus, substantia nigra (SNPr) Output to thalamus, SNPc Locomotion Input from amygdala, nucleus solitarius Output to hypothalamus, preoptic area, amygdala, intralaminar thalamic nuclei Autonomic regulation Involved in Parkinson’s, hence autonomic disturbances

Cuneiform & subcuneiform …

Similar connections/functionality as medial group

Reticular nucleus of the thalamus R.F. continues into the thalamus „ Inputs from cerebral cortex, other thalamic nuclei „ Output to thalamic nuclei „ Inhibitory „ Gates activities of other thalamic nuclei „

Summary Table

3

NT Systems „

Cholinergic

„

Monoaminergic

… ACh

… Dopamine … Noradernergic … Adrenergic … Serotonin

Cholinergic System „

Rostral pons-caudal midbrain … Pedunculopontine „

…

Progressive supranuclear palsy

… Basal „

(lateral)

Arousal and movement

forebrain

Nucleus basalis of Meynert … …

Output to cerebral cortex Degenerates in Alzheimer’s ƒ Memory deficits

Monoaminergic System „

Dopamine …

Mesostriatal „ „

…

Mesolimbic „

…

SN to striatum Damaged in Parkinson’s Overactivity -> schizophrenic hallucinations

Mesocortical „

Cognitive deficits in Parkinson’s

„

Noradrenergic … … …

Locus ceruleus Lateral tegmental NE system Ascending fibers „

…

Attention, sleep-wake, mood

Descending fibers „

Autonomic functions …

E.g. blood pressure

4

Monoaminergic System „

Serotonin … Rostral

raphe serotonergic „

Depression, OCD, aggression, anxiety

… Sleep „

Loss = insomnia

Functions „ „

Arousal and Alertness Somatic motor

„

… Cortical

-> alpha & gamma motor neurons

„

Somatic sensory … Cortical

-> sensory nuclei in brainstem (cranial nerve), spinal cord

Visceral motor … Medial „ „ „

… Lateral „ „ „

group

Inspiratory response Decrease heart rate Lower blood pressure

group

Expiratory Increase heart rate Increase blood pressure

Ascending Reticular Activating System „ „ „

From R.F. to intralaminar nuclei of thalamus to cortex Arousal & attention Associated with EEG pattern … Desynchronization „

Low voltage, high frequency

„

Stimulation

„

Destruction

… Enhances

learning

… coma

5

Sleep „

What is it good for? … Rest/regeneration … Memory?

„

What happens when we don’t sleep? … Emotionally

disturbed

… Psychotic

Phases of Sleep „

Slow wave … … … … …

„ „ „

I – drowsiness, 1-7 min II – light sleep III – moderately deep sleep …

„

Slow waves start appearing in EEG

IV – deep sleep … …

…

„

75% of sleep period Reduced muscle tone Drop in HR, BP, resp. Synchronized slow EEG 4 stages

50% of EEG is slow waves BP, HR, resp. & oxygen consumption are low

90-100 mins

REM (paradoxical)

…

25% of sleep period Hypotonia, esp. neck muscles Increase in BP, HR Irregular & rapid resp Erection Teeth grinding Dreaming REMs (50-60/min) PGOs (pons, LGN, Occipital cortex) spikes Rapid, low voltage irregular EEG (desynchronization) Deep sleep

…

10-30 mins

… … … … … … … … … …

„

But easier to wake up than deep sleep of Stage IV

Drug Effects on Sleep „

Barbituates/Alcohol … Suppress … Don’t

„

REM sleep dream

Benzodiazepines … E.g.

valium Stage IV … Feel less rested … Suppress

6

Sleep and Arousal Mechanisms „

Cholinergic … Awake … REM

„

sleep

Aminergic … Awake

only

Initiated by ventrolateral preoptic nucleus (hypothalamus)

Aminergic System Promotes Wakefulness Excite cortex „ Inhibit sleep promotion „

7

REM vs non-REM sleep

Orexins NTs involved in sleep „ Increase activity of aminergic neurons „

… Increase

„

wakefulness

Destruction … Narcolepsy

Parasomnias „ „

Slow-wave/non-REM sleep Somnambulism … … …

„

Night Terror … … … …

„

Stage III-IV Agitation, fear, screaming, autonomic (fight/flight) Lasts 2-10 mins, then return to deep sleep, with no memory of it More common in children

Catathrenia … … …

„

Sleep-walking More common in children No memory

Nocturnal groaning On expiration during slow wave & REM sleep No memory

REM intrusion …

Enact dream, dangerous

8

Narcolepsy Recurrent, brief attacks of irresistible daytime sleep „ Often associated with cataplexy „

… Sudden

loss of muscle tone

„

Triggered by emotions

„

Decrease in orexin

… Laughter,

surprise, fright, excitement, rage

9