Homeostasis Sleep Facts

Maintaining internal stability in the face of life’s relentless chaos, homeostasis is your body’s way of keeping things boring—which, fortunately, is perfect for sleep. From blood sugar to body temp, it’s all about not rocking the boat. Ideal for bedtime stories, relaxation, and insomnia relief.

Transcript

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 pre-set 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 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 acted on 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 downregulation 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 renin-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 postsynaptic neuron. It is activated by endocannabinoids such as anandamide, N-arachidinoylethanolamide, And 2-arachidinoylesanolamide via a retrograde signaling process in which these compounds are synthesized by and released from postsynaptic neurons and travel back to the presynaptic 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 endocannabinoids to mediate significant effects in the fine-tuning adjustment of body homeostasis. The word homeostasis uses combining forms of homeo and stasis, Neolatin from Greek homoios, Similar, And stasis, Standing still, Yielding the idea of staying the same. The concept of the regulation of the internal environment was described by French physicist 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 Cannon 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 hemiostatic 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 that keep the composition of the extracellular fluid, Or the internal environment, Constant, Especially with regard to the temperature, PH, Osmolality, 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 hyposermia, 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 set 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 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 in 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, Bradycardia, 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 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 thermoreceptors 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 thermoregulation takes precedence over physiological thermoregulation, Since necessary changes can be effected 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 vasoconstriction. 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 venae comedontis. This acts as a countercurrent 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 cholinergic 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 evaporation of water, But this time from the mucous membranes of the throat and 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, GLUT4, 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 with the VLDL-derived triglycerides that were made in the liver. Muscle cells also take up glucose up through insulin-sensitive GLUT4 glucose channels and convert it into muscle glycogen. A fall in 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 glycogenolysis and from non-carbohydrate sources such as lactate and de-animated 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, Convert it back to glucose. Iron homeostasis is a crucial physiological 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, Heme iron sourced from animal products and non-heme iron found in plant foods. Heme iron is more efficiently absorbed than non-heme iron, Which requires factors like vitamin C for optimal uptake. Once absorbed, Iron enters a bloodstream bound to transferrin, A transport protein that delivers it to various tissues and organs. Cells uptake iron through transferrin 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 ferritin and hemiocitrin. 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 homeostasis can lead to conditions such as iron deficiency anemia or iron overload disorders like hemochromatosis, Highlighting the importance of maintaining the 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+, Cuprous, And Cu2+, Cupric. As a component of about a dozen cuproenzymes, 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 CuO2 dismutase and has a role in iron homeostasis as a cofactor of ceruloplasmin. Changes in the levels of oxygen, Carbon dioxide, And plasma pH are sent to the respiratory center and the brainstem 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 organs, The diagram, And other muscles of respiration. An increased level of carbon dioxide in the blood or decreased level of oxygen will result in a deeper breathing pattern and 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 under water. The partial pressure of carbon dioxide is more of a deciding factor in the monitoring of pH. However, At high altitude, Above 2500 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 erythropoietin, 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 hematocrit 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 hematocrits 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 hematocrits. 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 values by vasoconstriction and vasodilation of the arteries. High pressure receptors called baroreceptors 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, ANP, Into the blood. This acts on the kidneys to inhibit the secretion of renin and aldosterone, Causing the release of sodium and accompanying water into the urine, Thereby reducing the blood volume. This information is then conveyed via afferent nerve fibers 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 arterioles. The arterioles 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 arterioles 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 cholinergic 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 arterioles 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 preganglionic sympathetic nerves to secrete epinephrine adrenaline into the blood. This hormone enhances the tachycardia and causes severe vasoconstriction of the arterioles to all but the essential organs in the body, Especially the heart, Lungs and brain. These reactions usually correct the low arterial blood pressure hypotension very effectively.

Reviews

Thanks Benjamin, bored me right to sleep. I think it even knocked the kitty out! 😁😻