I Can’t Sleep - Homeostasis | Calming Bedtime Reading for Sleep

Episode Date: June 23, 2025

Relax with this calm bedtime reading created to ease insomnia and bring restful sleep. Tonight’s gentle episode explores homeostasis, the vital process that helps living organisms maintain balance and stability in changing environments. You’ll learn how the body regulates temperature, fluids, and energy, along with the science behind this remarkable system, all shared in Benjamin’s steady, peaceful narration. There’s no whispering or hypnosis—just tranquil, fact-filled storytelling to quiet your mind and reduce stress. Press play, breathe deeply, and drift into calm sleep while learning something meaningful. Want More? Request a topic: https://www.icantsleeppodcast.com/request-a-topic Listen ad-free & support the show: https://icantsleep.supportingcast.fm/ Shop sleep-friendly products: https://www.icantsleeppodcast.com/sponsors Join the discussion on Discord: https://discord.gg/myhGhVUhn7 This content is derived from the Wikipedia article on Homeostasis, available under the Creative Commons Attribution-ShareAlike (CC BY-SA) license. Read the full article: Wikipedia - Homeostasis. Learn more about your ad choices. Visit megaphone.fm/adchoices

You're listening to a Glassbox media podcast. What if I told you that most of the modern day self-help advice you've been hearing could actually make you worse? The key to a better life isn't about feel-good gimmicks that sound catchy. The Mentally Stronger Podcast gives you access to a licensed therapist who shares science-backed tools that will actually change your life. Hi, I'm Amy Morin, psychotherapist, mental strength trainer, and international best-selling author. In each episode, we cover research-back strategies, like how to stop relying on willpower and start creating habits for lasting change. And the five mental strength-building exercises you can do from your couch.

I also speak to world-class experts like Dr. Nicole Kane, who shares how to permanently heal anxiety by addressing the root cause. With over 200 episodes in our catalog, this podcast is for you if you're ready to crush self-doubt, conquer challenges, and become stronger than ever with therapist-approved strategies that can change your life. Listen to Mentally Stronger with therapist Amy Morin, wherever you get your podcasts. Welcome to the I Can't Sleep Podcast, where I help you learn a little and sleep a lot. I'm your host, Benjamin Boster, and tonight let's fall asleep learning about homeostasis. In biology, homeostasis,

is the state of steady internal physical and chemical conditions maintained by living systems. This is the condition of optimal functioning for the organism and includes many variables such as body temperature and fluid balance being kept within certain preset limits, homeostatic range. Other variables include the pH of extracellular fluid, the concentrations of sodium, potassium, and calcium ions, as well as the blood sugar level, and these need to be regulated despite changes in the environment, diet, or level of activity.

Each of these variables is controlled by one or more regulators, or homeostatic mechanisms, which together maintain life. Homeostasis is brought about by a natural resistance to change when already in optimal conditions, and equilibrium is maintained by many regulatory mechanisms. It is thought to be the central motivation for all organic action. All homeostatic control mechanisms have a, at least three interdependent components for the variable being regulated, a receptor,

a control center, and an effector. The receptor is the sensing component that monitors and responds to changes in the environment, either external or internal. Receptors include thermoreceptors and mechanoreceptors. Control centers include the respiratory center and the renin angiotensin system. An effector is the target actadon to bring about the change back to the normal state. At the cellular level,

effectors include nuclear receptors that bring about changes in gene expression through upregulation or downreferral. regulation and act in negative feedback mechanisms. An example of this is in the control of bile acids in the liver. Some centers, such as the renal angiotensin system, control more than one variable. When the receptor senses a stimulus, it reacts by sending action potentials to a control center. The control center sets the maintenance,

range, the acceptable upper and lower limits for the particular variable, such as temperature. The control center responds to the signal by determining an appropriate response and sending signals to an effector, which can be one or more muscles, an organ or a gland. When the signal is received and acted on, negative feedback, is provided to the receptor that stops the need for further signaling. The cannabinoid receptor type 1, located at the presynaptic neuron, is a receptor that can stop stressful neurotransmitter release to the post-synaptic neuron. It is activated by endocanabinoids such as anandamide and arachidanolamide and two arachid

ragged and oil esanolamide via a retrograde signaling process in which these compounds are synthesized by and released from post-synaptic neurons and travel back to the pre-synaptic terminal to bind the CB1 receptor for modulation of neurotransmitter release to obtain homeostasis. The polyunsaturated fatty acids are lipid derivatives of omega-3 or of omega-6. They are synthesized from membrane phospholipids and used as precursors for endocanabinoids to mediate significant effects in the fine-tuning adjustment of body homeostasis. The word homeostasis uses combining forms of homeo and stasis, neo-latin from Greek, homoias, similar, and stasis,

yielding the idea of staying the same. The concept of the regulation of the internal environment was described by French physiologist Claude Bernard in 1849. and the word homeostasis was coined by Walter Bradford Cannon in 1926. In 1932, Joseph Barcroft, a British physiologist, was the first to say that higher brain function required the most stable internal environment. Thus, to Barcroft, homeostasis was not only organized by the brain, homeostasis served the brain.

Homeostasis is an almost exclusively biological term, referring to the concepts described by Bernard and Canon, concerning the consistency of the internal environment in which the cells of the body live and survive. The term cybernetics is applied to technological control systems, such as thermostats, which function as hemostatic mechanisms, but are often defined much more broadly than the biological term of homeostasis. The metabolic processes of all organisms can only take place in very specific physical and chemical environments. The conditions vary with each

organism, and also with whether the chemical processes take place inside the cell or in the interstitial fluid bathing the cells, the best known homeostatic mechanisms in humans and other mammals are regulators they keep the composition of the extracellular fluid or the internal environment, constant, especially with regard to the temperature, pH, osmality, and the concentrations of sodium, potassium, glucose, carbon dioxide, and oxygen. However, a great many other homeostatic mechanisms, encompassing many aspects of human physiology, control other entities in the body, where the levels of variables are higher or lower than those needed, they are often prefixed with hyper and hypo respectively,

such as hypersermia and hypothermia, or hypertension and hypotension. If an entity is homeostatically controlled, it does not imply that its value is necessarily absolutely steady in health. Core body temperature is, for instance, regulated by a homeostatic mechanism with temperature sensors in, amongst others, the hypothalamus of the brain. However, the said point of the regulator is regularly reset. For instance, core body temperature in humans varies during the course of the day, i.e. has a circadian rhythm, with the lowest temperatures occurring at night and the highest in the afternoons.

Other normal temperature variations include those related to the menstrual cycle. The temperature regulator's set point is reset during infections to produce a fever. Organisms are capable of adjusting somewhat to varied conditions. such as temperature changes or oxygen levels at altitude by a process of acclimatization. Homeostasis does not govern every activity in the body. For instance, the signal be it via neurons and hormones, from the sensor to the effector is of necessity, highly variable in order to convey information about the direction and the direction and and magnitude of the error detected by the sensor.

Similarly, the effector's response needs to be highly adjustable to reverse the error. In fact, it should be very nearly in proportion, but in the opposite direction to the error that is threatening the internal environment. For instance, arterial blood pressure mammals is homeostatically controlled and measured by stretch receptors in the walls of the aortic arch and carotid sinuses at the beginnings of the internal carotid arteries. The sensors send messages via sensory nerves to the medulla oblongata of the brain, indicating whether the blood pressure has fallen or risen, and by how much. The medulla oblongata then distributes messages along motor or efferent nerves belonging to the autonomic nervous system

to a wide variety of effector organs, whose activity is consequently changed to reverse the error in the blood pressure. One of the effector organs is the heart, whose rate is stimulated to rise tachycardia when the arterial blood pressure falls, or to slow down bradicardia, when the pressure rises above the set point. Thus, the heart rate, for which there is no sensor in the body, is not homeostatically controlled, but is one of the effector responses to errors in arterial blood pressure. Another Another example is the rate of sweating. This is one of the effectors in the homeostatic control of body temperature, and therefore highly variable in rough proportion to the heat load that threatens to destabilize the body's

core temperature, for which there is a sensor in the hypothalamus of the brain. Mammals regulate their core temperature using input from thermoreau. receptors in the hypothalamus, brain, spinal cord, internal organs, and great veins. Apart from the internal regulation of temperature, a process called allostasis can come into play that adjusts behavior to adapt to the challenge of very hot or cold extremes and to other challenges. These adjustments may include seeking shade and reducing activity, seeking warmer conditions, and increasing activity or huddling. Behavioral Cermal Regulation takes precedence over physiological thermoregulation, since necessary changes can be affected more quickly,

and physiological thermoregulation is limited in its capacity to respond to extreme temperatures. When the core temperature falls, the blood supply to the skin is reduced by intense vasic restriction. The blood flow to the limbs, which have a large surface area, is similarly reduced and returned to the trunk via the deep veins which lie alongside the arteries. forming Venné commandantus. This acts as a counter-occurrent exchange system that short-circuits the warmth from the arterial blood directly into the venous blood,

returning into the trunk, causing minimal heat loss from the extremities in cold weather. The subcutaneous limb veins are tightly constricted, not only reducing heat loss from this source, but also forcing the venous blood into the countercurrent system in the depths of the limbs. The metabolic rate is increased, initially by non-shivering thermogenesis, followed by shivering thermogenesis if the earlier reactions are insufficient to correct the hypothermia. When core temperature rises are detected by thermoreceptors,

the sweat glands in the skin are stimulated via colonergic sympathetic nerves to secrete sweat onto the skin, which, when it evaporates, cools the skin and the blood flowing through it. Panting is an alternative effector in many vertebrates, which cools the body also by the body, also by the evaporation of water, but this time from the mucus membranes of the throat mouth.

Blood sugar levels are regulated within fairly narrow limits. In mammals, the primary sensors for this are the beta cells of the pancreatic islets. The beta cells respond to a rise in the blood sugar level by secreting insulin into the blood and simultaneously inhibiting their neighboring alpha cells from secreting glucagon into the blood. This combination, high blood insulin levels, and low glucagon levels,

act on effector tissues, the chief of which is the liver, fat cells, and muscle cells. The liver is inhibited from producing glucose, taking it up instead and converting it to glycogen and triglycerides. The glycogen is stored in the liver, but the triglycerides are secreted into the blood as very low-density ipoprotein, VLDL particles, which are taken up by adipose tissue,

there to be stored as fats. The fat cells take up glucose through special glucose transporters, Glute 4, whose numbers in the cell wall are increased as a direct effect of insulin acting on the cells. The glucose that enters the fat cells in this manner is converted into triglycerides via the same metabolic pathways as are used by the liver, and then stored in those fat cells together was the VLDL-derived triglycerides that were made in the liver. Muscle cells also take up glucose up through insulin-sensitive glute4 glucose channels and convert it into muscle glycogen.

A fallen blood glucose causes insulin secretion to be stopped and glucagon to be secreted from the alpha cells into the blood. This inhibits the uptake of glucose from the blood by the liver, fat cells, and muscles. Instead, the liver is strongly stimulated to manufacture glucose from glycogen through glycogenalysis and from non-carbohydrate sources, such as lactate and deanimated amino acids, using a process known as gluconeogenesis. The glucose thus produced is discharged into the blood, correcting the detected error, hypoglycemia.

The glycogen stored in muscles remains in the muscles and is only broken down during exercise, to glucose 6-phosphate and thence to pyruvate to be fed into the citric acid cycle or turned into lactate. It is only the lactate and the waste products of the citric acid cycle that are returned to the blood. The liver can take up only the lactate, and by the process of energy-consuming gluconeogenesis,

converted back to glucose. Iron homeostasis is a crucial physiological problem, process that regulates iron levels in the body, ensuring that this essential nutrient is available for vital functions while preventing potential toxicity from excess iron. The primary site for iron absorption is the duodenum, where dietary iron exists in two forms. Heem iron sourced from animal products and non-heem iron found in plant foods. Heem iron is more efficiently absorbed than non-heem iron, which requires factors like vitamin C for optimal uptake.

Once absorbed, iron enters a bloodstream bound to transfarin, a transport protein that delivers it to various tissues and organs. Cells uptake iron through transfarin receptors, making it available for critical processes, such as oxygen transport and DNA synthesis. Excess iron is stored in the liver, spleen, and bone marrow, as ferretin and hemocidarin. The regulation of iron levels is primarily controlled

by the hormone hepcidin, produced by the liver, which adjusts intestinal absorption, and the release of stored iron based on the body's needs. Disruptions in iron homostasis can lead to conditions such as iron deficiency anemia or iron overload disorders like hemochromatosis, highlighting the importance of maintaining the delicate balance of this vital nutrient for overall health. Copper is absorbed, transported, distributed, stored, and excreted in the body according to complex homeostatic processes, which ensure a constant and sufficient supply of the micronutrient, while simultaneously avoiding excess levels. If an insufficient amount of copper is ingested for a short period of time,

copper stores in the liver will be depleted. Should this depletion continue, a copper health deficiency condition may develop. If too much copper is ingested, an excess condition can result. Both of these conditions, deficiency, and excess can lead to tissue injury and disease. However, due to homeostatic regulation, the human body is capable of balancing a wide range of copper intakes for the needs of healthy individuals. Many aspects of copper homeostasis are known at the molecular level. Copper's essentiality is due to its ability to act as an electron donor or acceptor as its oxidation state fluxes between CU1 plus cupris and CU2 plus cupric.

As a component of about a dozen cupro enzymes, copper is involved in key redox, i.e. oxidation reduction reactions, and essential metabolic processes, such as mitochondrial respiration, synthesis of melanin, and cross-linking of collagen. Copper is an integral part of the antioxidant enzyme copper zinc superoxide dismutase, and has a role in iron homeostasis as a co-factor of seruloplasmin. Changes in the levels of oxygen, carbon dioxide, and plasma pH are sent to the respiratory center and the brain stem where they are regulated. The partial pressure of oxygen and carbon dioxide in the arterial blood is monitored by the peripheral chemoreceptors in the carotid artery and aortic arch. A change in the partial pressure of carbon dioxide is detected as altered pH in the cerebrospinal fluid

by central chemoreceptors in the medulla oblongata of the brainstem. Information from these sets of sensors is sent to the respiratory center, which activates the effector organs, the diagram and other muscles of respiration, an increased level of carbon dioxide in the blood, or decrease level of oxygen, or result in a deeper breathing pattern, an increased respiratory rate, to bring the blood gases back to equilibrium.

Too little carbon dioxide, and to a lesser extent, too much oxygen in the blood, can temporarily halt breathing. a condition known as apnea, which free divers use to prolong the time they can stay underwater. The partial pressure of carbon dioxide is more of a deciding factor in the monitoring of pH. However, at high altitude above 2,500 meters, the monitoring of the partial pressure of oxygen takes priority, and hyperventilation keeps the oxygen level constant. With the lower level of carbon dioxide to keep the pH at 7.4,

the kidneys secrete hydrogen ions in the blood and excrete bicarbonate into the urine. This is important in acclimatization to high altitude. The kidneys measure the oxygen content rather than the partial pressure of oxygen in the arterial blood. When the oxygen content of the blood is chronically low, oxygen-sensitive cells secrete eryceropoietin, EPO, into the blood. The effector tissue is the red bone marrow,

which produces red blood cells, RBCs. The increase in RBCs leads to an increased hematric in the blood, and a subsequent increase in hemoglobin that increases the oxygen-carrying capacity. This is the mechanism whereby high-altitude dwellers have higher hematicrites than sea-level residents, and also why persons with pulmonary insufficiency or right-to-left shunts in the heart, through which venous blood bypasses the lungs and goes directly into the systemic circulation, have similarly high hematocrats. Regardless of the partial pressure of oxygen in the blood,

the amount of oxygen that can be carried depends on the hemoglobin content. The partial pressure of oxygen may be sufficient, for example, in anemia. but the hemoglobin content will be insufficient and subsequently as will be the oxygen content. Given enough supply of iron, vitamin B12 and folic acid, EPO can stimulate RBC production, and hemoglobin and oxygen content restored to normal. The brain can regulate blood flow over a range of blood pressure. pressure values, by vasoconstriction and vasodilation of the arteries. High pressure receptors called barrel receptors in the walls of the aortic arch and carotid

sinus at the beginning of the internal carotid artery, monitor the arterial blood pressure. Rising pressure is detected when the walls of the arteries stretch due to an increase in blood volume. This causes heart muscle cells to secrete the hormone atrial natriuretic peptide A&P into the blood. This acts on the kidneys to inhibit the secretion of renal and aldosterone, causing the release of sodium and accompanying water into the urine, thereby reducing the blood volume. This information is then conveyed via aphron nerve-fired. to the solitary nucleus in the medulla oblongata. From here, motor nerves belonging to the autonomic nervous system

are simulated to influence the activity of chiefly the heart and the smallest diameter arteries, called arterials. The arterials are the main resistance vessels in the arterial tree, and small changes in diameter cause large changes in the resistance to flow through them. When the arterial blood pressure rises, the arterials are stimulated to dilate, making it easier for blood to leave the arteries, thus deflating them, and bringing the blood pressure down back to normal. At the same time, the heart is stimulated via colonergic,

parasympathetic nerves to beat more slowly, called bradycardia, ensuring that the inflow of blood into the arteries is reduced, thus adding to the reduction in pressure and correcting the original error. Low pressure in the arteries causes the opposite reflex of constriction of the arterials and a speeding up of the heart rate called tachycardia. If the drop in blood pressure is very rapid or excessive, the medulla oblongata stimulates the adrenal medulla via pre-ganglionic sympathetic nerves to secrete epinephrine adrenaline into the blood. This hormone enhances the tachycardia

and causes severe vasoconstriction of the arterials to all but the essential organs in the body, especially the heart, lungs, and brain. These reactions usually corrects the low arterial blood pressure, hypotension, very effectively.