Processes Modulating The Propensity To Stay Awake Or Fall Asleep
Most behaviors, such as foraging, courting and predator defense, are incompatible with sleep, and animals need to carefully coordinate the timing of sleep and wakefulness to maximize their survival. The probability of an individual entering a particular sleep/wake state depends on multiple factors, including previous sleep history, circadian time, environmental cues, and internal needs . Here, we will focus on homeostatic, circadian, and motivational processes modulating sleep/wake states. A better understanding of these circuits will not only reveal how brain states are regulated, but also how the brain balances conflicting needs. It is important to note that there are additional factors that can modulate sleep/wake behaviors, such as breathing and immune state , yet they are beyond the scope of this review.
Stage 5 Sleep Of The Sleep Cycle
Stage 5 of the sleep cycle, or REM sleep, is the stage of sleep associated with dreaming. It is very different physiologically from the other stages of sleep. The EEG resembles wake time. However, the skeletal muscles are atonic, or without movement. The breathing is more erratic and irregular. The heart rate often increases. It is theorized that muscle atonia evolved in order to protect the individual from injury during sleep.
Vmp Cell Deficiency Increases Wakefulness In Mice
VMP GABAergic neurons exhibited higher c-Fos expression during night. A, Example of double-labeled cells for c-Fos and mCherry counterstained with DAPI in VGAT-CreM4/VMP mice. Scale bar, 10 m. B, Line drawings showing typical distribution of c-Fos/mCherry double-labeled cells . C, Wakefulness during 3 h before killing the mice. D, Percentage of double-positive neurons for c-Fos and mCherry among mCherry-positive neurons in the VMP. **p< 0.01 compared with light period. Data are presented as the mean ± SEM . RN, Red nucleus SN, substantia nigra IP, interpeduncular nucleus.
Recommended Reading: Which Of The Following Is Absent During Rem Sleep
Importance Of Body Homeostasis
We understand body homeostasis as the existing tendency in the body to actively and constantly seek a state of balance, in such a way that the cells of our body can survive by maintaining a stable internal composition.
Maintaining this balance is essential, since the activation or maintenance of different bodily processes requires energy, which in turn requires elements to be used as fuel. Not having them will cause a series of tissue damage that can lead to death.
The same happens if we are not able to activate or stop some of the aforementioned bodily processes, necessary for our survival.
It is important to bear in mind that homeostasis acts based on the existence of changes that can occur both within the body and come from the outside, also using mechanisms of action that link both environments .
In this sense, it must be taken into account that living beings can withstand certain levels of variation and imbalance and that the mechanisms that allow homeostasis can be damaged or altered throughout the life cycle, being important to take this into account in order to introduce factors external factors that correct possible deficits.
Another body mechanism that is continuously regulated is the internal body temperature. The correct functioning of our tissues and organs can be affected by excessive cold or heat, to the point of being able to lead us to death from hypothermia or hyperthermia.
Circadian Regulation Of Sleep
Sleep disorders are complex phenomena. A detailed correlation of sleep-wake regulation and clinical states is beyond the scope of this chapter, but a few examples can help to bridge the basic science concepts to everyday clinical scenarios. Since the first description of the hypocretin/orexin system 20 years ago, a body of literature investigating the physiologic and pathophysiology role of this system, as well as the potential for drug development, has emerged. Disruption of this system has been linked to pathological sleep-wake states such as insomnia and narcolepsy. A role for the hypocretin/orexin system in other sleep disorders and in sleepiness associated with other neurological disorders has also deserved some investigation. Recent results indicate that subjects with head trauma or encephalitis may have moderately but significantly decreased hypocretin levels. A few selected subjects with Guillain-Barré syndrome, Parkinsons disease , multiple system atrophy, and other neurodegenerative disorders have also been found to have shallow hypocretin levels. Importantly, central actions of orexin regulate motivated behaviors, stress response, and energy/glucose metabolism by coordinating regions of the central autonomic network and the endocrine system, these multiple actions of orexin being critical to maintaining life.
Don’t Miss: Does Fitbit Alta Hr Automatically Track Sleep
Why Does Caffeine Wake You Up
Melatonin is not the only chemical that determines our sleep schedule. Adenosine also plays an important role: it slows down the activity of neurons.It gradually builds up in our bodies when we are awake and makes us feel sleepy by the end of the day. Then, when we sleep, adenosine molecules break down, so the cycle can start all over again. Our neurons, or nerve cells, are embedded with adenosine receptors. When adenosine binds to these receptors, a variety of proteins that inhibit neurons are released. This suppression of nerve cell activity is what causes the feeling of drowsiness.
Caffeine has a chemical structure similar to that of adenosine . Both molecules have a double-ring structure, which allows caffeine to bind to adenosine receptors. Unlike adenosine, however, caffeine does not activate these receptors or suppress neuron activity. By reducing the concentration of available adenosine receptors, caffeine slows the rate of reaction: Less-bound adenosine means we feel less sleepy.
F Other Sleep Muscle Tone
1. REM sleep behavior disorder
REM sleep behavior disorder is a human manifestation of the syndrome originally observed in cats following large lesions of the brain stem reticular formation including sites involved in muscle atonia . Sporadic cases can also be observed in cats and dogs without experimenter-induced lesions . This disorder was first formally described in humans in a landmark study by Schenck, Mahowald and colleagues in 1986 and has a reported prevalence of 0.5% . RBD involves uncontrolled movements and muscular expression of dream sequences leading to sleep fragmentation and injury to patients and their sleeping partners . In the sleep laboratory such activity is correlated with enhanced EMG activity during sleep, whereas other aspects of REM sleep are normal. It is more common in people aged over 50 years old and affects more men than women. Acute RBD can be induced by various medications , whereas the cause of the chronic form is unknown. The acute form of RBD is managed by withdrawal of the offending medication, whereas the chronic form can be well managed symptomatically by clonazepam or melatonin treatment prior to bedtime .
2. Restless legs syndrome
A) Pathogenesis of Rls
B) Treatment and Animal Models of Rls
3. Periodic limb movements
4. Other disorders of motor control during sleep
Inappropriate activation of motor programs during sleep also occurs in bruxism , sleepwalking , nocturnal sleep-related eating disorder , and sexsomnia .
Don’t Miss: Sleep Analysis On Health App
Switching Sleep On And Off
The researchers headed by Prof. Dr. Antoine Adamantidis discovered that a small population of these thalamic neurons have a dual control over sleep and wakefulness, by generating sleep slow waves but also waking up from sleep, depending on their electrical activity. The research group used a technique called optogenetics, with which they used light pulses to precisely control the activity of thalamic neurons of mice. When they activated thalamic neurons with regular long-lasting stimuli the animals woke up, but if they activated them in a slow rhythmical manner, the mice had a deeper, more restful sleep. This is the first time that an area of the brain has been found to have both sleep and wake promoting functions. “Interestingly, we were also able to show that suppression of thalamic neuronal activity impaired the recovery from sleep loss, suggesting that these neurons are essential for a restful sleep after extended period of being awake”, says Dr. Thomas Gent, lead author of the study. This shows that the thalamus is a key player in both sleep and wake. The study has now been published in the journal Nature Neuroscience.
Is A Circadian Rhythm The Same As A Biological Clock
Biological clocks help regulate the timing of bodily processes, including circadian rhythms. A circadian rhythm is an effect of a biological clock, but not all biological clocks are circadian. For instance, plants adjust to changing seasons using a biological clock with timing that is distinct from a 24-hour cycle.
Also Check: Garmin Vivoactive 4s Sleep Tracking
A Characteristics Of Sleep
Sleep is defined in the sleep laboratory, in both humans and animals, by recording the electrical field activity of large groups of cortical neurons and muscle cells. Thus scalp electrodes record the electroencephalogram , electrodes placed on or in skeletal muscles record the electromyogram , whereas electrodes placed over or near the muscles responsible for horizontal eye movement record the electro-oculogram . Deep brain electrodes are used to record the activity of individual brain areas or individual neurons. These so-called polysomnographic recordings are used to define the states of wakefulness and sleep as follows : wakefulness is defined by low-voltage fast EEG activity and high muscle tone, NREM sleep is characterized by high-amplitude low-frequency EEG and decreased muscle tone, whereas REM sleep has LVFA coupled with a complete loss of muscle tone and characteristic rapid eye movements which contrast with the slow rolling eye movements observed during NREM. Further characteristics of these three states and the brain circuitry which generates them are discussed in sections IIâIV. A summary of studies involving inactivation of different parts of the brain controlling sleep and wake is provided in . The location of these brain regions is shown in .
Sleep: Theory Function And Physiology
Sleep is an important part of our daily routine. It is estimated that we spend about a third of our time sleeping.
- Quality sleep is just as important for good health as proper nutrition and physical activity.
- Sleep is important to many brain functions, we need sleep to learn effectively and it has been shown that a lack of sleep affects our concentration levels negatively.
- Evidence also shows that sleep affects almost every type of tissue and system in the body and that a chronic lack of sleep can increase the risk for non-communicable diseases such as hypertension, diabetes, cardiovascular disease and obesity.
Sleep is vital to good health!
You May Like: Can Nac Cause Insomnia
How Can I Improve My Sleep
The sleep-wake cycle can be improved through better sleep hygiene. Sleep hygiene is the sum of healthy habits surrounding a regular sleep schedule. Elements of sleep hygiene include:
- Waking up and going to sleep at consistent times
- Exposing yourself to natural light during the daytime
- Eating a healthy diet and exercising regularly
- Avoiding electronics that emit blue light waves before bedtime
- Refraining from caffeine too close to bedtime
- Keeping the bedroom dark, cool, and quiet
Sleep is a critical aspect of overall human health. Making sleep hygiene a priority is a good idea. However, its important to remember that certain sleep and circadian rhythm disorders may not be improved or managed without the help of a doctor.
Factors That Influence These Transitions
People generally require several minutes to calm down and relax enough to fall asleep, and the deepest stages of sleep typically occur 20 or more minutes after sleep onset. However, sleep onset and associated loss of consciousness can occur in an instant. This is particularly obvious in very tired people who can fall asleep at inconvenient and sometimes dangerous times, such as when driving a car. Similarly, waking up from sleep can occur very quickly, for example in response to an alarm clock, although it typically takes people much longer to become fully alert after awakening. There are many internal factors and environmental factors that influence the likelihood of falling asleep or waking up. For example, a powerful sleep drive builds up with prolonged wakefulness and shifts the balance toward sleep. How this occurs is not precisely known, but adenosine is one of the chemicals thought to accumulate during prolonged wakefulness. When it does, it serves to induce sleep by inhibiting wake-promoting neurons. Interestingly, caffeine inhibits the actions of adenosine and therefore helps maintain wakefulness.
The SCN is the bodys master clock.
Don’t Miss: Does The Garmin Vivofit 4 Track Sleep
Sleep Helps Our Brains Consolidate And Preserve Memories
Sleep is critical for memory. The National Sleep Foundation includes aspects of memory as three of the top five things that happen in the brain as we sleep. During sleep, we form new memories, consolidate memories, preserve existing memories, and shed memories deemed unimportant.
Related:How sleep works
Sleep is central to both our short term memory and our long term memory. Without sufficient sleep, our learning potential suffers. As a result, we can experience trouble remembering things like where we put our keys or the name of someone we recently met.
Scientists Identified A Gene Essential For Regulating The Sleep
A single gene can disrupt the sleep-wake cycle.
Our internal biological rhythm, i.e., the internal clock, controls many physiological processes. It works 24/7 and occurs even in the absence of external triggers, such as changes in light or temperature.
The internal clock is located in humans in the hypothalamus. Due to this internal clock, we are most awake from morning until the end of the day.
Like humans, all animals have circadian rhythms. Using Drosophila, the small fly found on ripe fruit, scientists at the University of Geneva studied the mechanisms that regulate these internal clocks. Many genes of Drosophila are conserved between the fly and higher organisms. This makes it possible to extend the scope of discoveries from fruit flies to humans.
Scientists used infrared sensors to detect the movements of flies movements in tubes to analyze their sleep-wake cycles easily. Over 24 hours, flies sleep for about 10 hours at night, then are active all day, except for a nap of about 4 to 5 hours.
Scientists also observed flies with a deregulated sleep-wake cycle and whose particular area of the brain, called mushroom bodies because of its characteristic shape, is damaged. They analyzed the expression of genes in this area of the brain of healthy Drosophila.
Recommended Reading: Which Of The Following Statements About Sleep Deprivation Is False
What Impacts Circadian Rhythms
Circadian rhythms are impacted by both internal and external factors . Circadian rhythm-related sleep disorders that originate within the body are called intrinsic circadian sleep disorders. Those that originate from outside the body are often referred to as circadian rhythm disorders.
As infants and children age, the sleep-wake schedule shifts, and the needed amount of sleep tapers off. Infants, for example, need between 12 to 16 hours of sleep each day, while school-aged children need nine to 12 hours. Adults should aim to get between seven to nine hours of restful sleep each night.
Many teenagers experience a sleep-phase delay , in which their brain doesnt start producing melatonin until late in the evening. Late nights paired with early school wake-up times can take a significant toll on mental health and make it hard to stay focused.
Blue Light Exposure
Blue light waves are found in fluorescent and LED lights and electronic screens, such as phones, laptops, and television. Exposure to blue light waves at times when the brain should be producing melatonin, which is in the evening for most people, can halt the process and ultimately shift the circadian rhythm. As a result, blue light exposure can make falling asleep more difficult.
Jet Lag and Daylight Saving Time
Crossing two or more time zones can result in jet lag , a sleep-wake disorder that occurs when the body’s internal clock is aligned with the timezone of origin and doesnt match that of the new location.
C Relation Of Rem To Dreams
The lay public is interested in REM sleep largely as a result of its close association with dreaming. Interpretation of dreams is ascribed great significance in many cultures and predates modern science. In western societies, the work of Freud and his counterparts led to a widespread acceptance of dreams as giving important insights into âpsychic disturbance.â However, the findings of modern neuroscience have led to a view of dreaming which asserts that the features of dreams arise from internally generated patterns of brain activation and deactivation during REM sleep, and dream content does not necessarily have any meaning or message for the individual .
A) Activation-Synthesis Hypothesis of Dream Generation
The modern neuroscience view of dreams was laid out by Hobson and McCarley as the activation-synthesis hypothesis . An expanded state-space version of this hypothesis, the AIM model was developed by Hobson to characterize all conscious states . In the activation-synthesis view of dreaming, during the REM state, the brain is activated internally by the activity of the brain stem .
B) Brain Imaging of the Rem/Dreaming State
C) Do Dreams Represent Internal Drives?
Also Check: Can Tramadol Cause Insomnia
Which Part Of The Brain Controls Temperature
The hypothalamus controls temperature. The hypothalamus has a dual system of temperature regulation. Thus, the anterior or rostral portion, composed of parasympathetic centers, is responsible for dissipating heat, while in the posterior portion, with sympathetic centers, it preserves and maintains body temperature.
The perception n of temperature It is relative, since we do not have receptors to perceive the temperature in an absolute way. We are only capable of perceiving sudden changes in temperature for example, when moving our hand from a very cold water pot to a very hot one.
There are two types of receptors, some for cold and others for heat, heterogeneously distributed throughout the skin. Receptors for cold are closer to the epidermis, while receptors for heat are deeper. They are the same receptors they only differ on the level of situation.
The transduction in these receptors is produced by the deformation of the membrane or the cone of the receptor as a result of the dilation or contraction of the skin. This produces the opening of the membrane and the sodium channels.
If the receptors are densely packed together, the sensation of heat will be more intense. The nuclei associated with our having difficulty perceiving cold and heat from the thalamus are intralaminar and to a lesser extent ventricular.