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Case 20: Neuroanatomy (Sleep) - Coggle Diagram
Case 20: Neuroanatomy (Sleep)
Methods of Studying Sleep
List the Methods of Studying Sleep
Methods of Studying Sleep include:
Polysomnographic Recording
Deep Brain Electrodes
Actigraphy
Polysomnographic Recordings include:
Electroencephalography (EEG)
EEG measures thee activity of the brain
Electromyography (EMG)
EMG measures neck muscle activity
Electro-Oculography (EOG)
EOG measures the eye movement and activity
Electrocardiography
EKG) measures the activity of the heart muscle
Scientific Definition of Wake and Sleep
Outline the Scientific Definition of Wake and Sleep
Wake refers to a period of low magnitude, high frequency EEG activity and increased muscle tone
Sleep in humans is decided in NREM (Non-Rapid Eye Movement) Sleep and REM (Rapid Eye Movement) Sleep
NREM Sleep refers to a period of high magnitude, low frequency EEG activity and reduced muscle tone
NREM Sleep is also known as deep sleep
REM Sleep refers to a period of low magnitude, high frequency EEG activity with muscle atonia and rapid eye movement
Explain why the Humans have more NREM Sleep Stages compared to Rats
Human Cerebral Cortex is thicker than that of Rats
Therefore, the Humans Have 4 Stages of NREM Sleep
Describe the features of the EEG Profile in Humans
NREM Sleep in Humans has Four Stages
Stage 1 is similar to Wakefulness but it has an increased amplitude
Stage 2/3 have Sleep Spindle and K-Complex
Sleep Spindle and K-Complex precedes Deep Sleep aka NREM Stage 4
REM Sleep has similar waves in frequency and amplitude to Wakefulness
Electrographic Signs of Wake
Outline the Electrographic Signs of Wake
Electrographic Signs of Wake are divided into:
Gamma and Beta Rhythms
Alpha Rhythms
Theta Rhythms
Gamma Rhythms of 15-120 Hz and Beta Rhythms of 15-30 Hz are associated with Features of Quiet Wake
Alpha Rhythms of 8-14 Hz play a role in internally directed thought processes
Alpha Rhythms of 8-12 Hz occur when the Brainstem and the Thalamus (Thalamocortical) are communicating with the Cortex
Thalamocortical control and Brainstem control
Theta Rhythms of 4-8 Hz are associated with attention/memory in Humans and REM in all Mammals
Theta Rhythms are thought to be under Brainstem control
Brain Reticular and Basal Forebrain Activating Systems
Bremer made at a transection at the mid-collicular level resulting in cats sleeping for extended periods
Moruzzi and Magoun caused an electrical stimulation of the Midbrain at the Reticular Formation this resulted in cats remaining awake for extended periods of time
This highlighted the Brainstem Reticular and Basal Forebrain Activating System
Ascending Reticular Activating System (ARAS)
Dorsal ARAS
Ventral ARAS
Ascending Reticular Activating System (ARAS)
Outline the Ascending Reticular Activating System
Ascending Reticular Activating System (ARAS) involves the communication between the Reticular Formation and the Forebrain (Cerebral Cortex) in order to promote wakefulness
Reticular Formation extended across the Brainstem (From the Midbrain to the Pons to the Medulla Oblongata)
Reticular formation is a collection of nuclei
It communicates with very specific different types of nuclei in the brainstem and Midbrain
Reticular Formation and the nuclei communicate with the Cerebral Cortex via different regions of the Diencephalon
Dorsal ARAS
Ventral ARAS
Dorsal Ascending Reticular Activating System (ARAS)
In the Dorsal ARAS, the Reticular Formation and the Brainstem Nuclei communicate with the Thalamus
Thalamus then communicates with the Cerebral Cortex to promote Wakefulness
Ventral Ascending Reticular Activating System (ARAS)
In the Ventral ARAS, Reticular Formation and the Brainstem Nuclei communicate with the Nuclei of the Hypothalamus
Lateral Hypothalamic Nuclei (LH)
Tubero-Mammillary Nucleus (TMN)
Tubero-Mammillary Nucleus (TMN) is crucial for maintaining wakefulness
Hypothalamic Nuclei communicate the information of maintaining wakefulness with the Basal Forebrain
Basal Forebrain contains Basal Nuclei such as the Corpus Striatum, Substantia Nigra and Subthalamus
Basal Forebrain then communicates with the Cerebral Cortex to promote wakefulness
Neurotransmitter System Promoting Wakefulness
List the Neurotransmitters and Neuro-Modulator which promote Wakefulness
Acetylcholine
Serotonin
Norepinephrine
Orexin (Hypocretin)
Histamine
Dopamine
Glutamate
Electrographic Signs of NREM (Non-Rapid Eye Movement) Sleep
Outline the Electrographic Signs of NREM Sleep
Electrographic Signs of NREM Sleep include:
Thalamocortical Spindles (Sleep Spindles)
Thalamocortical Spindle in Stage 2 of NREM Sleep
Hippocampal Sharp Wave and High Frequency ripples (K-Complex)
Hippocampal Sharp Wave and high frequency ripples occurs in Stage 2 of NREM Sleep
Delta Rhythms of 1-4 Hz and Slow Oscillations of less than 1 Hz
Generation and Maintenance of NREM Sleep
List the areas of the Brain which generate and maintain NREM Sleep
Ventrolateral Pre-Optic Nucleus (VLPO)
Median Pre-Optic Area (MnPO)
Outline the features of the Ventrolateral Pre-Optic Nucleus(VLPO)
Ventrolateral pre-Optic Nucleus is located within the Hypothalamus
Ventrolateral Pre-Optic Nucleus it contains GABA and Galanin:
GABA is an Inhibitory neurotransmitter
Galanin is an Inhibitory neurotransmitter
VLPO projects to different nuclei in the Ascending Reticular Activating System
By doing that the VLPO is able to carry out its Function to:
Consolidate sleep
Generate and Maintain sleep
Regulate the depth of sleep
Median Pre-Optic Area (MnPO)
Outline the features of the Median Pre-Optic Area (MnPO)
Median Pre-Optic Area is also located in the Hypothalamus
MnPO Area contains GABAergic sleep active neurons
This means that the Neurons in the MnPO Area secrete the GABA neurotransmitter
GABA is an inhibitory neurotransmitter
GABA inhibits the activity of other neurons
MnPO Area has increased activity in response to increased homeostatic sleep pressure
BOTH the VLPO and MnPO Area project on the ARAS and inhibit the ARAS thus promoting sleep
Wake-NREM Transitions and Flip-Flop Model
Describe the mechanism of the Wake-NREM Sleep Transitions and Flip-Flop Model
During Wakefulness:
Lateral Hypothalamic Nucleus secretes Orexin to the Tuber-Mammillary Nuclei, and the Brainstem Nuclei (Dorsal Raphe and Locus Coeruleus)
Orexin is an Excitatory Neuro-Modulator
Orexin stimulates the Tuber-Mammillary Nuclei to secrete GABA/Histamine
GABA/Histamine inhibits the activity of the Ventrolateral Pre-Optic Nuclei (VLPO)
This results in the promotion of Wakefulness
GABA/Histamine is an Inhibitory Neurotransmitter
Orexin stimulate Dorsal Raphe (DR) to secrete Serotonin
Serotonin inhibits the activity of the Ventrolateral Pre-Optic Nuclei (VLPO)
This results in the promotion of Wakefulness
Orexin stimulates the Locus Coeruleus (LC) to secrete Norepinephrine (noradrenalin)
Noradrenalin inhibits the activity of the Ventrolateral Pre-Optic Nuclei (VLPO)
This results in the promotion of Wakefulness
During the promotion of Sleep:
Ventrolateral Pre-Optic Nuclei secretes GABA/Galanin
GABA and Galanin are inhibitory neurotransmitters
GABA/Galanin inhibit the activity of the Lateral Hypothalamic Nucleus
GABA/Galanin inhibits the activity of the Tuber-Mammillary Nucleus
GABA/Galanin inhibits the activity of the Brainstem Nuclei known as DR and LC
This results in the inhibition of the ARAS and the promotion of Sleep
NREM Sleep Homeostasis
Describe the Criteria that Nuclei Must Fulfill in order to Induce NREM Sleep
Sleep Factors
Criteria that Nuclei must fulfill in order to induce NREM Sleep is as follows:
Induce Sleep Behaviour
Increase their activity with increasing Sleep Propensity or an Increase in Sleep Pressure
Act on Neurons involved in sleep-wake/generate wakefulness
For Example:
Adenosine
NO
Prostaglandin D
Cytokines
Electrographic signs of REM Sleep
Outline the Electrographic Signs of REM Sleep
Theta Activity
Theta Activity occurs in REM Sleep
Type 1 Theta Activity of 4-7 Hz is seen in behavioural immobility
Type 2 Theta Activity of 7-12 Hz is seen in waking associated with movement
PGO Waves
PGO Waves are synchronised activity in the Pons, Lateral Geniculate Nucleus (LGO) and Occipital Cortex
PGO Waves occur prior to REM Sleep and during REM Sleep
Muscle twitches and Atonia
Muscle Twitches and Atonia are a cardinal feature of REM Sleep
NOTE: REM Sleep requires many different criteria for it to occur
NOTE: Lateral Geniculate Nucleus is located in the Thalamus and it is responsible for processing Vision
Muscle Atonia and Twitches
Outline the different states of Wake-Sleep seen in the Graphs
When an individual is WAKE and EATING:
EMG has high amplitude
EEG has a low amplitude and high frequency activity
EOG has a small increase in amplitude
LGN indicates some activity
When an individual enters NREM:
EMG will have a decreased amplitude
Muscle will become more atonic
EEG will have a high amplitude and a low frequency
EOG will have little to no amplitude
LGN will have little to no activity
When an individual is transition from NREM to REM Sleep:
EMG will have no amplitude and infrequent increase in amplitude
This indicates Muscle Atonia and Muscle Twitches
EEG will have a low amplitude with a high frequency
EOG will have a high amplitude indicating rapid eye movement
LGN will have a high amplitude indicating processing of visual information
Brainstem Control of the Muscle Atonia and Muscle Twitches
Describe the Brainstem Control of the Muscle Atonia and Muscle Twitches
Sub-Coeruleus is a nucleus which controls the Muscle Atonia and Muscle Twitches
Sub-Coeruleus Nucleus resides in the Brainstem
Sub-Coeruleus Nucleus communicates with the Ventral Horn of the Spinal Cord via two pathways:
First Pathway
Sub-Coeruleus Nucleus stimulates the Ventral Part of the Gigantic Reticular Nucleus
Gigantic Reticular Nucleus is located in the Brainstem
When stimulated the Gigantic Reticular Nucleus releases GABA or Glycine
GABA and Glycine are Inhibitory Neurotransmitters
GABA or Glycine then project to the Ventral Horn of the Spinal Cord where there Motor Neuron is located
In this way, the GABA and Glycine are able to inhibit the activity of the Motor Neurons
Inhibition of Motor Neurons inhibits Muscle Motor Activity
Second Pathway
Sub-Coeruleus Nucleus communicates directly with the GABAergic Interneuron in the Ventral Horn of the Spinal Cord
Stimulation of the GABAergic Interneuron results in the release of GABA neurotransmitter
GABA then inhibits the Motor Neuron activity which in turn inhibits Motor Muscle Activity
Other REM Phenomena
List the other types of REM Phenomena
Other types of REM Phenomena include:
Increased Heart Rate
Increased Breathing
Altered Body Temperature
REM Sleep Control Mechanisms
List the Types of REM Sleep Control Mechanisms
Location and Neurotransmitter content of REM Sleep
Forebrain Control of the REM Sleep Timing
Outline the Mechanism of Location and Neurotransmitter Content of REM
Location and Neurotransmitter Content of REM involves to REM-on cells and REM-off cells
REM-on Cells
REM-on Cells are brainstem nuclei cells that increase their activity
By increasing their activity the REM-on Cells secrete Acetylcholine
This makes them Cholinergic in nature
By doing this the REM-on cells stimulate other parts and induce REM Sleep
REM-off Cells
REM-off Cells such as the Locus Coeruleus and the Dorsal Raphe increase their activity
By increasing their activity they secretes Neurotransmitters:
LC secretes Norepinephrine
DR secretes Serotonin
The neurotransmitters inhibit the activity of the REM-on Cells and stop REM Sleep
Locus Coeruleus are Dopaminergic and Dorsal Raphe are Serotinogeric
They promote wakefulness
Forebrain Control of REM Sleep Timing
Describe the mechanism of Forebrain Control of Rem Sleep Timing
Lateral Hypothalamic Nucleus in the Hypothalamus is responsible for controlling the REM Sleep Timing
LH Nucleus produces an Excitatory Neuro-Modulator called Orexin (Hypocretin)
Hypocretin Cells have a connection from the Supra-Chiasmatic Nucleus
SCN is involved in Circadian Rhythms
Hypocretin cells also receives information from the Dorsolateral Hypothalamus
Supra-Chiasmatic Nucleus and the Dorsolateral Hypothalamus communicate with the Orexin (Hypocretin) cells to secrete Orexin
Orexin then stimulates the Dorsal Raphe and Locus Coeruleus to suppress REM sleep during Diurnal Active Phase
REVISE LC and DR activity
Sleep Disorders
Outline the features of Insomnia
Insomnia refers to the difficulty in initiating and maintaining sleep
There are Two Types of Insomnia:
Primary Insomnia
Secondary Insomnia
Primary and Secondary Insomnia are graded according to Transient, Acute or Chronic
10-30% of adults have Insomnia
Higher rates of Insomnia in university students compared to the general public
Narcolepsy
Outline the features of Narcolepsy
Narcolepsy refers to a decrease in the number of Orexin Neurons which results in spontaneous REM Sleep
Individuals with Narcolepsy are less able to maintain wakefulness
There are two types of Narcolepsy:
Narcolepsy with Cataplexy
Narcolepsy without Cataplexy
Cataplexy refers to the sudden loss of muscle tone while a person is awake
Sleepwalking (Somnambulism)
Outline the features of Somnambulism
Somnambulism refers to the act of performing both simple and complex tasks while still asleep
REM Behaviour Disorder
