Sphingolipids and the CNS Sphingolipids encompass a complex range of membrane lipids in which a fatty acid is linked to a long sphingosine carbon backbone, primarily C18-sphinganine (18:0) and C18-sphingosine (C18:1) in mammals. Figure 1 shows a schematic representation of the sphingolipid metabolic pathway. Ceramide is central in sphingolipid metabolism and is produced by de novo and recycling pathways.37 In de novo synthesis, serine and palmitoyl-CoA are substrates of serine palmitoyl-transferase (SPT), the rate limiting enzyme that generates ketosphinganine (bottom). Ketosphinganine is reduced to form sphinganine, which is then N-acylated with fatty acids of different chain lengths by ceramide synthases (CerS), producing dihydroceramides.
In a night sleep there can be as many as 20 to 30mins per hour of involuntary breathing pauses. This kind of pauses are often accompanied by the sound of snoring, but this does not necessarily mean that everyone who snores has sleep apnea. People with this disorder usually end up sleeping during the daytime and have excessive fatigue. This is mainly because
Narcolepsy is a sleep disorder where the brain is unable to control sleep- wake cycles causing drowsiness. Narcolepsy is divided into two types; with cataplexy (type 1) and without cataplexy (type 2). In order to be diagnosed with narcolepsy, one must experience periods of an overwhelming need to sleep and sporadic napping daily for 3 months. For type 1 narcolepsy, they must experience cataplexy, sudden loss of voluntary muscle tone triggered by strong emotion. The person should also have a sleep latency of less than or equal to 8 minutes.
When the person does not get sleep, it is considered as total sleep deprivation, this is usually seen when a person experiences a situation such as studying all night. The other type of sleep deprivation is partial sleep deprivation where it is more likely due to sleep disorder, medical conditions, medications, work, or lifestyle. Therefore, partial sleep deprivation is most likely to be more evident among the medical practitioners. (Weinger & Ancoli-Israel, 2002). Sleep deprivation can have a huge impact on various cognitive abilities, from executive functions to simple alertness.
According to Emily Richmond from The Atlantic, adolescents’ circadian rhythms, also known as the “internal clocks” works differently than other age groups. The circadian rhythm controls a human’s responses to stimuli and regulates sleeping patterns. She asserts that it is hard for adolescent to fall asleep earlier in the evening than other age groups (Richmond). According to the Sleep Center of the University of California Los Angeles, most teens in general do not get enough (CDC). Teens are at their important stage of growth and development, therefore they require more sleep than adults.
Throughout the urea cycle, the amino acid, arginine, is changes into ornithine- this is another amino acid when hydrated, that is when water was added. During this reaction, urea is the product formed (Nelson and Cox 2008). Figure 1 shows the urea cycle, occurs specifically in the mitochondria and cytosol in the liver. (Nelson and M.Cox 2008). Urea is made in the liver by means of enzymes in the urea cycle.
Metabolism is also regulated by hydrophobic hormones which enter their target cells and are able to interact with intracellular receptor molecules. The movement of substrates into the cells compartments is also controlled by the energy charge. The charge depends on the amounts of ATP, ADP and AMP which are all relatively regulated.
It involves initial activation of the carboxylic acid moiety with ATP, generating an acyl adenylate and pyrophosphate. Bound acyl adenylate reacts with coenzyme A (CoASH) to yield a high energy xenobiotic-CoA thioester intermediate that will link the activated acyl group to the amino group of the acceptor amino acid with regeneration of CoASH.101 Glutathione conjugation involves conjugation of the tripeptide glutathione with a xenobiotic that is enzymatically catalyzed by glutathione transferases. The detoxification pathway of xenobiotics via glutathione is discussed in
Formal polysomnography (PSG) is the standard measurement for assessing sleep. The size of the PSG machine, the number of electrodes, wires and sensors that are needed in addition to the need for a PSG technician to interpret the results, makes formal PSG impractical for critical care. Due to the challenges of measuring sleep in the ICU it is not routinely done. Since sleep is rarely measured in the ICU, it is difficult to determine the effect of sleep deprivation and disruption on delirium. The relative influence of environment, illness and interventions on sleep in critically ill patients is essentially unknown (Friese, 2008) (Drouot et al., 2008).
Light hurts his eyes, and sleep seems to help at times. The patient is not getting enough sleep at night and he is having trouble going to sleep. He describes the pain as pulsating pain in the temporal region. There is no identified trigger. • Identify any relevant secondary diagnoses (differential diagnoses are eliminated in part two).
Next, GRB2 binds to the phosphotyrosine residues of the activated receptor. Then GRB2 binds to the guanine exchange factor SOS. When the GRB2-SOS complex docks to phosphorylated EGFR, SOS becomes activated. Activated SOS then promotes the removal of GDP from a member of the RAS. RAS can then bind GTP and become active.
The α2- globulin, Angiotensinogen is secreted from the liver. Renin in turn hydrolyzes the plasma globulin present in Angiotensinogen which acts as a precursor protein to form the precursor hormone Angiotensin I. Angiotensin I in its inactive state is converted to Angiotensin II which is active, this is done by angiotensin converting enzyme (ACE) secreted from the lungs (Ghany, 2011).. ACE also cleaves bradykinin to inactivate it producing fragments of the inflammatory mediator. Angiotensin II is present as an octapeptide acts as a vasoconstrictor hormone that results in the increase of blood pressure, renal perfusion and filtration rate by the glomerulus. Angiotensin II acts as a mediator for the Renin-Angiotensin-Aldosterone system, it does this by activating Angiotensin type 1 (AT1) receptor and Angiotensin type 2 (AT2) receptor.
These compounds target muscarinic acetylcholine receptors to produce their response, which will be made into a concentration/effect curve. Muscarinic acetylcholine receptors The muscarinic acetylcholine receptor (MAR) is a G protein– coupled receptor whose activation leads to opening of K+channels and subsequent hyperpolarization of the plasma membrane2. The binding of acetylcholine leads to the activation of a G protein, which binds to and releases ion channels. These ion channels can allow a varity of ions to move in or out of the cell, including K+, Na+ and Ca2+. There are five different types of MAR, M1-M5.
Each pause in breathing, called an apnea, can last for several seconds to several minutes, and may occur at least 5 times in an hour. There are two types of sleep apnea, obstructive sleep apnea and central sleep apnea. Obstructive sleep apnea is more common of the two forms of apnea, and it is caused by a blockage of the airway, usually when the soft tissue in the back of the throat collapses during sleep. Sleep apnea has substantial impact on general health. Not only does the poor and fragmented sleep caused by obstructive sleep apnea result in daytime sleepiness and consequent increased risk of motor vehicle and occupational accidents, but neurocognitive function, mood, and quality of life can be impaired as well.
Delta waves are a cycle of electroencephalographic (a test that detects electrical activity in your brain) activity has a frequency of under four hertz. Stage 3 typically only takes up 4% to 6% of sleep time, but is thought of as the most important stage. Stage 4 is very similar to stage 3 and even sometimes the two stages are combined because of their extreme similarity. It is the deepest part of sleep and is the point where night terrors or sleepwalking may occur. It takes up about 12% to 15% of total sleep time.