The Human Operating Manual

Anatomy & Physiology

Anatomy & Physiology

Biohacker handbook

Structure and Functions of the Digestive System

The most important parts of the digestive tract in terms of functions are the esophagus, stomach and duodenum in the upper gastrointestinal tract and the jejunum, ileum, colon, and rectum in the lower gastrointestinal tract. The digestive system also includes the salivary glands, pancreas, liver, spleen, and gallbladder. The main function of the digestive system is to break down food and absorb nutrients from the small intestine into the circulatory system. Digestion can be broken down into mechanical digestion and chemical digestion. We often forget that eating slowly and chewing your food creates a greater sense of fullness and increase the nutrients better.


The capacity of an empty adult stomach is approximately 75ml. It can take in roughly a liter of food. The stomach secretes gastric juices which contain hormones and enzymes, hydrochloric acid (HCl) to break down food, and intrinsic factor for the absorption of B12. The acidity of the gastric juice usually destroys harmful micro-organisms but some people have a deficiency in the production of HCl, due to stress, poor diet, or harmful chemicals. Hypochlorhydria contributes to nutritional deficiencies, osteoporosis, infections, and stomach cancer. Acid blockers may cause anemia, B12 deficiency, and overgrowth of stomach and intestinal bacteria.


  • Gastrin: Promotes the formation of hydrochloric acid and increases gastric movement
  • Histamine: Contributes to the regulation of stomach acidity through H2 receptors
  • Cholecystokinin: Curbs the emptying of the stomach
  • Somatostatin: Inhibits the secretion of gastrin, secretin, and histamine in the stomach -> slows down digestion
  • Gastric inhibitory peptide (GIP): Inhibits the secretion of HCl and reduces gastric movement
  • Enteroglucagon: Inhibits the secretion of HCl and reduces gastric movement
  • Leptin: Regulates appetite
  • Ghrelin: Stimulates appetite and promotes the emptying of the stomach

Enzymes/other compounds:

  • Pepsin: Breaks down proteins into peptides
  • Lipase: Breaks down fats into fatty acids
  • Intrinsic factor (IF): Binds to B12 and promotes its absorption in the small intestine
  • Mucin: Mucous matter that protects the stomach lining from damage
  • Gastric lipase: Breaks down fat into fatty acids

Small Intestine (SI)

Roughly 7m in length and contains the duodenum, jejunum, and ileum. It continues to break down food and is assisted by bile (formed in the liver but secreted through the gallbladder) as well as pancreatic juice, which contains plenty of digestive enzymes.

The SI breaks down macronutrients. Proteins are broken down into peptides and amino acids. Fats into fatty acids and glycerol. Carbohydrates into monosaccharides (e.g. glucose) and starch into oligosaccharides. Once broken down, they are absorbed through the intestinal wall.


  • Cholecystokinin: Stimulates gallbladder contractions and intestinal movements. Stimulates the secretion of insulin, glucagon, and pancreatic polypeptides
  • Secretin: Stimulates pancreatic bicarbonate, enzymes, and insulin. Curbs the movements of the stomach and SI. Inhibits the secretion of gastrin
  • Vasoactive intestinal peptide (VIP): Relaxes the smooth muscles of the intestine, and promotes the secretion of water and electrolytes in the pancreas and SI. Releases other hormones from the pancreas, intestine, and hypothalamus
  • Enteroglucagon: Inhibits the secretion of insulin
  • Glucagon-like peptide-1: Promotes the secretion of insulin


  • Amylase: Breaks down carbohydrates into shorter chains of saccharides or sugars
  • Lactase: Breaks down lactose into glucose and galactose (not present in 75% of world population)
  • Maltase: Breaks down maltose into glucose
  • Sucrase: Sucrose into fructose and glucose
  • Glucoamylase: Breaks down glucose polymers (e.g. starch) into glucose
  • Trypsin: Proteins into amino acids
  • Chymotrypsin: Proteins into amino acids
  • Aminopeptidase and dipeptidase: Polypeptides and dipeptides into peptides and amino acids
  • Lipase (several types): Triglycerides into fatty acids and glycerol
  • Phospholipase: Phospholipids into fatty acids and other fat soluble substances


1.5m long and consists of the cecum, ascending colon, transverse colon, descending colon, and sigmoid colon. Maintenance of bacterial strain in the intestine as well as the absorption of water and the remaining nutrients. K vitamins, thiamine (B1), and riboflavin (B2). The bacterial strain feeds on the fiber mass in the feces and produces fatty acids which are used as a source of energy. They also help to remove waste products and toxins.

The appendix produces hormones that regulate eating (peptides). It also acts as a storage space for beneficial bacteria, and may offer protection from some infections.

The Western diet consists of large amounts of processed foods that promote inflammation in the gut, which leads to irritable bowel disorders (IBD), such as ulcerative colitis and Crohn’s disease. Genetically predisposed individuals seem to suffer due to changes in the bacterial strain of the intestine and disturbances in the immune response. These diseases are also linked to leaky gut syndrome. A diet that removes antinutrients and reduces inflammation is usually beneficial for the recovery of IBDs.


Connected to the small intestine and the gallbladder. The endocrine part with islets (2% of the pancreas) secretes hormones like insulin and glucagon, while the exocrine part boosts the digestive process.


  • Glucagon (from alpha cells): Raises the concentration of glucose in the blood by converting glycogen stored in the liver and muscles
  • Insulin (beta cells): Lowers the concentration of glucose in the blood by promoting its absorption into muscles and adipose tissue. Other metabolic effects like blood sugar regulation
  • Somatostatin (delta cells): Inhibits the secretion of insulin and glucagon. Inhibits the secretion of digestive enzymes
  • Pancreatic polypeptide (gamma cells): Regulates the secretion functions of the pancreas (endocrine and exocrine). Increased secretion after eating-> reduced appetite, less food eaten


  • Trypsinogen: Is converted into trypsin by enteropeptidase in the SI.
  • Chymotrypsinogen: Converted into chymotrypsin by enteropeptidase in the SI.
  • Carboxypeptidase: Cleaves the amino acids at the ends of proteins.
  • Pancreatic lipase: Breaks down triglycerides into fatty acids and glycerol.
  • Phospholipase: Breaks down phospholipids into fatty acids and other fat-soluble substances.
  • Pancreatic amylase: Breaks down starch and glycogen into glucose.
  • Nucleases: Breaks down nucleic acids (DNA and RNA).
  • Elastase (several): Breaks down elastin and a few other proteins into amino acids.


During diabetes, macrophages can release inflammatory cytokines into otherwise healthy cells, causing nearby cells to become insulin resistant. Excess blood sugar causes damage to the entire vasculature, increasing heart disease and stroke risk. High blood sugar also causes nerve damage by damaging capillaries (peripheral artery disease). Diabetes can also damage your kidneys, affecting filtration, resulting in kidney disease. Not to mention the massive increased risk of Alzheimer’s with diabetes. Macrophages can also trigger inflammation in adipose tissue.

Moderate muscle strength has been shown to lower the risk of diabetes by 32% compared to those with low muscle strength. No major change with greater muscle.

Glucosamine inhibits glycolysis, resulting in the body requiring energy from fat stores instead of glucose. It has also been shown to mimic calorie restriction and extend life-span.


It has a double blood supply via the portal vein and the hepatic arteries. Also contains the bile duct system which collects bile produced by the liver.

Carbohydrate metabolism:

  • Produces glucose from amino acids, lactic acid, and glycerol
  • Breaks down glycogen into glucose
  • Forms glycogen from glucose
  • Fat metabolism:
    • Oxidizes fatty acids into energy
    • Produces large amounts of cholesterol, phospholipids, and lipoproteins (LDL, HDL, VLDL)

Heart Function

Blood flows into the atria, atrioventricular valves remain closed until the ventricles relax and expand. As the pressure difference evens out, blood flows into the ventricles (diastole phase). During the systolic phase, the atrioventricular valves close due to pressure caused by the blood, the ventricle pressure increases, the ventricles contract, the semilunar valves open, and blood enters the aorta (left side) or pulmonary artery (right side).

The electrical functioning of the pace-making cells (sinus node initiates contraction, atrioventricular node, internodal pathways, and His bundle and Purkinje fibers) is governed by their sodium, potassium, and calcium ion channels. Calcium has a particularly crucial role in the contraction of the cardiac muscle. The contraction involves three electrical phases: prepotential (before contraction), depolarization (during), and repolarization (relaxation).

Heart rate is regulated by the ANS as well as signals relayed by hormones. PNS slows (sent by the brainstem via the vagus nerve) and SNS speeds it up via nerve fibers. Neurotransmitters (adrenaline and noradrenaline) secreted by the adrenal gland medulla as a reaction to stress boost the activation of the SNS, increasing the heart rate. Relaxation activates the PNS nerve impulses and the heart rate slows down due to acetylcholine.

Heart rate can be regulated through breathing: inhaling momentarily increases the heart rate whilst exhalation reduces it. Heart rate variability (HRV).

Heart rate and blood pressure are also regulated by the baroflex. Blood pressure in the upper torso and head increase while lying down, causing a signal to be sent to the brain via baroreceptors in the neck and aortic arch. The vasomotor center in the medulla oblongata sends a signal to the heart, reducing heart rate and cardiac contractive force.

Muscle contractions also increase the heart rate. Proprioceptors are sensory receptors in the muscles, joint capsules, and tendons that assess the nature of movement. Increased activity increases heart rate and circulation via vasomotor connection.

Factors that increase heart rate and cardiac contractility:

  • Nerves that increase heart rate: Noradrenaline released by cells
  • Baroreceptors: Lower activity->lower blood pressure
  • Proprioceptors: Increased activity during exercise
  • Chemoreceptors: Decreased blood oxygen levels, increased level of hydrogen ions, CO2, and lactic acid in the blood
  • Limbic system: Preparing for exercise, strong emotional reactions
  • Thyroid hormones: Increased production of hormones T3 and T4
  • Calcium: Increased Ca2+ level
  • Potassium: Decreased K+ level
  • Sodium: Decreased Na+ level
  • Body temperature: Increased body temperature
  • Nicotine, caffeine, stimulants: Increased heart rate

Factors that decrease heart rate and contractility:

  • Nerves that decrease heart rate (vagus nerve): Acetylcholine released by cells
  • Baroreceptors: Increased activity-> higher blood pressure
  • Proprioceptors: Decreased activity after exercise
  • Chemoreceptors: Increased blood oxygen level and decreased level of hydrogen ions, CO2, and lactic acid in blood
  • Limbic system: Relaxation
  • Thyroid hormones: Decreased production of hormones T3 and T4
  • Calcium: Decreased Ca2+ level
  • Potassium: Increased K+ level
  • Sodium: Na+ level
  • Body temperature: Decreased body temperature
  • Theanine, taurine, relaxants: Decreased heart rate

Factors affecting cardiac output:

Heart rate (HR): autonomic innervation, hormones, fitness levels, age

Stroke volume (SV): Heart size, fitness levels, gender, contractility, duration of contraction, preload (EDV), afterload (resistance). SV = EDV – ESV

Cardiac Output (CO) = HR x SV

Heart Disease

When the endothelial lining of the arteries is damaged, fats can cross into the arterial wall and form plaques. Inflammatory cytokines are then released to attract WBCs. When the plaques rupture, they can cause clots. The fat molecules that cause plaque apparently come from bad gut bacteria rather than the diet (what do the bad gut bacteria eat though?). Suggesting a diet high in resistant starches may allow good bacteria to produce short-chain, anti-inflammatory fatty acids. Could be caused by toxic mold exposure (causing postural orthostatic tachycardia syndrome). Inflammation can also disrupt the communication between the nervous system and the endocrine system, leading to fatigue and blood pressure instability, and ADHD and Asperger’s symptoms.

Heart disease is rooted in SNS overload, mineral deficiencies, and an unwillingness to treat the vessels in your body more like the roots and vessels in a plant:

  1. Autonomic nervous system imbalance: HRV testing suggests that many patients who have had a myocardial infarction (MI) have reduced PNS activity in the days, weeks, and months leading up to it. Most MIs result from a combination of chronically low PNS activity and a temporary stressful event like a hard workout. A consequence of chronic stress, diabetes, hypertension, smoking, and a lack of physical activity.
  2. The problem isn’t coronary arteries: The heart can do its own bypass in the case of a chronic disruption of blood flow through one of 3 major coronary arteries. It is only in the case of chronic diseases like diabetes that MIs occur. Get an adequate intake of good, clean water and a high intake of a full spectrum of minerals (calcium, phosphorus, zinc, magnesium, potassium, and trace minerals).
  3. Metabolic acidosis: The production and buildup of lactic acid in heart tissue. When the heart finds itself in a stressful situation and its mitochondrial can’t produce enough energy, it undergoes a glycolytic shift and begins to ferment sugar for fuel. Lactic acid accumulates in the surrounding tissues and eventually leads to angina or chest pain. The lactic acid leads to a lower pH in the heart, which prevents calcium from entering myocardial and inhibits the contraction of heart fiber muscles. Eventually cell death occurs in the surrounding tissue, and this is called a MI.

Dr. Cowan: Strophanthus improves the PNS function and cardiac microcirculation and converts lactic acid into pyruvate, the heart’s preferred fuel.

Takotsubo Cardiomyopathy (broken heart syndrome): more likely to die of a heart attack caused by chronic anxiety or a poor relationship than of heart attack caused by squatting, deadlifting, or running a marathon. A sudden or temporary weakening of the heart muscle, often triggered by emotional stress. Lethal ventricular arrhythmias, ventricular rupture, and heart failure.

Eliminate chronic stress, keep yourself well hydrated, consume adequate minerals, ensure your heart is not constantly burning glucose as fuel, and fix any weak or broken relationships in your life.

Circulation and Microcirculation

Systemic circulation involves the function of the left hand side of the heart and its circulation. The left ventricle pumps oxygen-rich blood into the aorta and into the body. The spent blood returns to the right atrium via the superior and inferior vena cava. Pulmonary circulation involves the function of the right hand side of the heart and its circulation. The right ventricle pumps spent blood, rich in CO2, to the lungs where is it oxygenated. From the lungs, the blood travels to the left atrium via the pulmonary vein.

Microcirculation refers to circulation within arterioles, capillaries, and venules at a tissue level. Delivery of O2, removal of CO2, and a regulator of blood flow and pressure. Microcirculation has an important role in the inflammatory response. Inflammation triggers an activation response in many circulatory cells (such as white blood cells and platelets), cells lining blood vessels (endothelial cells and blood flow regulating pericytes), and cells surrounding blood vessels (mast cells and phagocytic cells or macrophages). This is why inflammation often causes heat and swelling.

The flow volume of the microcirculation stays consistent, regardless of pressure changes, due to arteriole wall muscles contracting and relaxing according to various stimuli. Many different mechanisms assist microcirculation, like metabolic, electrical, neural, and mechanical (muscle-based) regulation.

Smoking, alcohol consumption, poor diet, stress, sleep deprivation, air pollution, environmental pollution, and ack of exercise will prematurely degrade the efficiency and control of microcirculation.

Capillary walls allow biochemical exchange but proteins can’t pass through. This is why molecules attached to carrier proteins (such as hormones) are not effective at the tissue level.

Three metabolic mechanisms are currently known:

  • Diffusion causes oxygen, glucose, amino acids, etc. to flow from capillaries into interstitial fluid. Metabolic waste flows from interstitial fluid back into capillaries.
  • In bulk flow, the exchange occurs via small fat molecules. The flow of substances from the capillaries into the interstitial fluid is called filtration. Conversely, reabsorption refers to the flow of substances from the IF to circulation.
  • In transcytosis, large molecules such as proteins, hormones, and immunoglobulins move into the IF with the help of vesicles via endothelial cells of the capillaries. The transfer occurs through exocytosis: the fluid sac surrounding the protein merges with the cell membrane, moving the protein into the IF.

The lymphatic system consists of a comprehensive network of lymphatic vessels, lymph nodes, and other lymphoid tissues, the spleen and the thymus. Lymph fluid play a role in fluid balance regulation, immune system function, and carrying fatty acids. Lymphatic circulation returns the fluid absorbed from the microcirculation back into circulation. It also carries fat from the intestine into circulation. Lymph is pumped via voluntary muscles, respiratory muscles, and smooth wall muscles of the lymphatic vessels rather than a heart-like pump.

Lymph consistency resembles blood plasma and contains lymphocytes and small amounts of other WBCs. Lymph also contains metabolic waste, cellular waste, bacteria, and proteins.

Lymphocytes are produced in bone marrow and matured in the thymus (T cells) or the marrow (B cells). Mature lymphocytes move into the spleen, lymph nodes and other lymphoid tissues such as tonsils and adenoids, lymphoid tissue of the intestine, and the walls of respiratory and urinary tracts.

Respiratory System and Respiratory Capacity

Breathing, voice production, regulation of acid-base balance, and the removal of waste products.

Physiology of the respiratory system:

  • Nasal cavity: Cilia, nasal hair, and mucus purify inhaled air. Humidfying, heating or cooling air
  • Oral cavity: Passing air into the trachea
  • Pharynx: Fighting impurities. Contains a great deal of lymphatic tissue (tongue, adenoids, and tonsils)
  • Epiglottis: Preventing food from entering the trachea
  • Larynx: Connecting the pharynx and trachea, participating in voice production
  • Trachea: Feeding air into the brochi, mucus secretion
  • Lungs: The right lung has three lobes, the left has two. Gas exchange takes place in the alveoli
  • Bronchi: Feeding air into the alveoli
  • Alveoli: Gas exchange through diffusion (O2 into the body, CO2 out)
  • Pleural cavity: Protecting the lungs, reducing friction caused by breathing. Pleural cavity normally has negative pressure which holds the lungs close to the thracic wall
  • Diaphragm: Expanding the thoracic cavity, enabling airflow into the lungs. On inhalation, the contraction of the diaphragm expands the thoracic cavity and by extension the lungs

Respiration is regulated by the medulla oblongata. Influenced by CO2, O2, and H+ in the blood (humoral regulation). Corresponding nervous regulatory mechanisms include the mechanical movements of the chest, stimuli form the air entering the lungs, signals sent by proprioceptors, and changes in body temperature. Pain also has a significant effect on respiration.

The contraction and dilation of bronchi is regulated by the ANS. The SNS has a bronchodilatory effect (adrenaline and noradrenaline) by way of beta receptors. The corresponding bronchoconstrictory effect (acetylcholine) of the PNS occurs by way of muscarinic receptors.

Respiration can be broken down into clavicular breathing, costal breathing, diaphragmatic breathing, and deep breathing.

Respiratory gas exchange takes place in the alveoli where oxygen binds with the hemoglobin of the RBC. The oxygen saturation of hemoglobin is dependent on the partial pressure of oxygen and carbon dioxide in the tissue, temperature, blood pH, and carbon monoxide. One hemoglobin molecule can bind four oxygen molecules. Low hemoglobin leads to anemia, which may cause fatigue, vertigo, and breathlessness. May be caused by lack of iron, vitamin B12 or folate, bone marrow disorders, bleeding or increased hemolysis of RBC.

Skeletal Muscles and Motor Control

Muscle fibers consist of myosin and actin filaments (myofibril). During a muscle contraction they slide over each other. The contraction is triggered by an action potential transmitted by an alpha motor neuron. The action potential spreads into the muscle fiber via T-tubules. From here, the signal spreads to the terminal cisternae of the sarcoplasmic reticulum, releasing calcium and eliciting the muscle contraction.

Three main types of skeletal muscle cells: slow contracting but high endurance type I cells and fast contracting type IIA and IIX cells. Type I cells are active in aerobic conditions. Type IIA cells utilize both aerobic and anaerobic energy. Type IIX cells create a strong contraction but become fatigued quickly. Latest studies have also specified other muscle cell types based on their properties: IC, IIC, IIAX, IIXA.

Genetics and training have an effect on muscle type ratio and are determined by a muscle biopsy. Also varies on the muscle area. Quadriceps contain 50-70% fast muscle cells whereas the soleus contains 90% slow muscle cells. Individuals with the R allele of the ACTN3 gene usually do well in sports requiring strength and speed. Champion sprinters have shown a 71% fast cell ratio (average being the opposite).

Motor units can be divided into groups based on contractility and endurance of the muscle cells. Either slow-twitch (S) or fast-twitch (F) units. Fast units are further divided into fatigue resistant (FR), fatigue-intermittent (Fint), and fatigable (FF). The fastest motor units are activated in maximal movements such as changes of direction and jumps.

Metabolism – The Cornerstone of Energetic Life

The continuous process of breaking down organic matter and forming new substances within the tissue of the body. It is regulated by hormones, various growth factors, vitamins, minerals, and the ANS.

Long-term imbalance of metabolic pathways may lead to various metabolic disorders. Genetic hereditary enzyme dysfunctions may also cause innate metabolic disorders (mutation of the MTHFR gene may cause an increased level of homocysteine and increased cerebrovascular disorders).

Examples of metabolism include the breakdown of carbohydrates, proteins, and fats into energy (the citric acid cycle), the removal of superfluous ammonia through urine (urea cycle), and the breakdown and transfer of various chemicals. The first pathway discovered was glycolysis, where glucose is broken down into pyruvate supplying ATP and NADH to cells.

Aerobic Energy System

Cellular respiration. The processes involved are glycolysis, pyruvate oxidation, the citric acid cycle, and the electron transport chain. Using glucose and oxygen to create ATP as an energy source in a mitochondria. Byproducts are CO2 and water.

  • Aerobic glycolysis is the first phase, which occurs under aerobic conditions. A glucose molecule is broken down into pyruvate, simultaneously producing 2 ATP molecules and 2 NADH molecules. Glycolysis also takes place under anaerobic conditions, but the end result is lactate or lactic acid.
  • Citric acid cycle, or Krebs cycle takes place in the mitochondria. The primary metabolic compound of the citric acid cycle is acetic acid (acetyl coenzyme A) produced from fatty acids, carbohydrates and proteins. Hydrogen ions and electrons are transferred to the inner mitochondrial membrane for oxidative phosphorylation (binding energy to ATP molecules through oxidation) and the electron transport chain. The reaction releases NADH and small amounts of ATP and CO2. The citric acid cycle involves 10 steps, each affected by B vitamins and certain minerals such as magnesium, iron, and the liver’s main antioxidant glutathione. The reactions are inhibited by heavy metals such as mercury, arsenic, and aluminum.
  • Most of the energy captured is by NADH molecules. For each acetyl coenzyme A molecule, 2 NADH molecules are generated and then used for energy in the reaction that follows (oxidative phosphorylation). The regulation of the citric acid cycle is determined by the availability of various amino acids as well as feedback inhibition (if too much NADH is produced, several enzymes of the citric acid cycle are inhibited, slowing down reactions).
  • Oxaloacetate acts as a compound used to fulfill a sudden need to produce energy (e.g. in the brain or muscles). Taking an oxaloacetate supplement may help to boost regeneration of mitochondria in the brain, reduce silent inflammation in the body, and increase nerve cell numbers.
  • Oxidative phosphorylation consists of two parts: the electron transport chain and ATP synthase. Oxidative phosphorylation produces the most energy generated in aerobic conditions (ATP). It is a continuation of the citric acid cycle. In the electron transport chain, H+ ions are released into the mitochondrial intermembrane space. Through ATP synthase, the H+ released from the intermembrane space move back into the mitochondrion. Using energy in the process, ATP synthase converts the ADP used for energy into ATP again. Ubiquinone (COQ10) acts as a contributor to the electron transport chain. Statins have been found to be a contributing factor to COQ10 deficiency.
  • Fatty acids broken down in the digestive system are used for energy in the mitochondria. During beta-oxidation, the fatty acids are activated by being bound to coenzyme A. The result is acetyl coenzyme A, which is used for energy production in the citric acid cycle. The oxidation of long-chain fatty acids requires carnitine acyl transferases in which the fatty acids are transported from the cytoplasm into the mitochondrion. Such transfer of short and medium-chain fatty acids isn’t necessary as they move there by diffusion.

Anaerobic Energy System

High-intensity sports activities. ATP is produced by breaking down glucose polymers (glycogen) stored in muscles and the liver by utilizing the free ATP molecules immediately available in the muscle cells.

During anaerobic glycolysis, glucose is broken down into pyruvate which is then converted into lactic acid (lactate) during the lactic acid fermentation process.

  • The creatine phosphate system is one of the main energy systems for the muscles. 95% of the body’s creatine is located in the skeletal muscles. Creatine phosphate (phosphocreatine) is synthesized in the liver from creatine and phosphate from ATP. Red meat is a source of creatine, but it can also be synthesized from amino acids (arginine and glysine). It significantly increases force generation in skeletal muscles. Creatine is formed and recycled in the creatine phosphate shuttle. The shuttle transports high-energy ATP molecule phosphate groups from mitochondria to myofibrils, forming phosphocreatine through creatine kinase. Used for fast muscle contraction. Unused creatine is transported via the same shuttle into mitochondria where it is synthesized into creatine phosphate. Used phosphocreatine forms creatinine which exits the body in urine via the kidneys. The blood creatinine levels are measured to determine the kidney’s filtering capability. The higher the muscle mass, the higher the volume of creatinine secreted.

The body’s main energy storage systems

Glycogen is a large sized molecule formed of several glucose molecules. It is stored in the liver (10% of the weight), muscle cells (2%), and, to a lesser extent, RBC. In addition to glucose, glycogen binds triple the amount of water. Because of this, a person’s body weight may fluctuate by several kgs with a 24 hour period. The glycogen in the liver acts as an energy reserve for the entire body’s energy production needs, and those of the CNS in particular. The amount of glycogen present is determined by physical exercise, the basal metabolic rate and eating habits.

Glycogen stores are useful for regulation of blood sugar between meals and during intensive exercise. Glucose may also be used for energy under anaerobic conditions. Conversely, fatty acids are broken down into energy only in aerobic conditions. A metabolically active glycogen breakdown product is glucose 6-phosphate in which the glucose molecule binds with one phosphate group. It may be used for energy in a muscle under either aerobic or anaerobic conditions, utilized via the liver as glucose elsewhere in the body or converted into ribose and NADPH for use in various tissues.

Adipose tissue is the body’s main long-term energy storage system. It consists of connective tissue cells and vascular endothelial cells. Fat cells contain a lipid droplet consisting of triglycerides and glycerol. Adipose tissue is located under the skin, in bone marrow, between muscles, around internal organs (visceral fat) and breast tissue. Adipose tissue is also hormonally active, as it produces leptin, adiponectin, and resistin that regulate the energy metabolism and body weight. In lipolysis, adipose tissue is oxidized by lipase and triglyceride lipase into free fatty acids and glycerol. Fatty acids are used for energy in the muscles, liver, and heart; glycerol is mainly used in the liver.

Insulin inhibits lipolysis. If the body’s stored insulin levels are consistently elevated, the fatty acids circulating in the blood are stored in the adipose tissue. This is called lipogenesis.

The Structure and Functions of the Brain

The corpus callosum white matter may be enhanced through exercise, meditation, neurofeedback, playing musical instruments, or acupuncture.

There are 12 cranial nerves and 31 spinal nerves.

Parietal Lobe:

  • Primary neurotransmitter: acetylcholine
  • Functions:
    • Compiling the information provided by various senses
    • Compiling the information provided by the field of vision with information regarding the positioning of the eyes, head, and body
    • Connecting intentions and the environment before decision-making

Broca’s area

  • Forming speech
  • Combining words into sentences and assigning meaning to them
  • Recognizing gestures in association with speech

Wernicke’s area

  • Expressing speech and assigning meaning to it
  • Understanding and repeating speech
  • Reading and writing
  • Expressing thoughts

Prefrontal cortex

  • Primary neurotransmitters: dopamine and noradrenaline, glutamate and serotonin
  • Functions:
    • Controlling the limbic system
    • Directing and maintaining focis
    • Assessing and analyzing situations
    • Controlling and assessing activity, learning from previous experience
    • Expressing emotions and empathy
    • Regulating short-term memory

Motor cortex

  • Primary neurotransmitters: acetylcholine and GABA
  • Functions:
    • Controlling body movements
    • Coordinating voluntary movements such as those of the muscles in the body and limbs. Premotor plays a crucial part in performing complex movements
    • Maintaining posture
    • Regulating the internal reflexes of the cortex

Limbic system (fornix, cingulate cortex, corpus callosum, thalamus, hippocampus, amygdala, mammilary body, olfactory bulb, septum)

  • Principal neurotransmitters: noradrenaline, dopamine, serotonin, and glutamate
  • Functions:
    • Regulating emotional life
    • Regulating eating and drinking
    • Fear and “fight or flight” reactions
    • Memory regulation and comparative assessment
    • Storing memories of how easy or difficult learning something was


Microglia release cytokines in response to threat, triggering inflammation. Chronic inflammation can result in neuronal damage.

Ben Greenfield (Boundless)

How We Age

Bones and Skeletal System:

In men, bone density diminishes at age 35. In women, peak bone density is age 30, and postmenopausal women experience an accelerated rate of bone loss. Foot arches become less pronounce, contributing to reduced height. The discs that separate the vertebrae lose fluid, the long bones become brittle due to mineral loss, joints become stiffer and less flexible and can lose some of their fluid, causing cartilage to rub together and wear out. Calcification in and around the joints also occurs. After 30, skeletal muscle mass declines more than 20% in both men and women in the absence of exercise, muscle loading, adequate protein, and heat stress. Strength and flexibility decrease, along with coordination, balance, and height. The CNS has a reduced ability to recruit muscle fibers, posture deteriorates and the risk of breaking bones increases. The gradual breakdown of joints leads to inflammation, joint pain, stiffness, and even physical deformities.

  • Physical activity – particularly stressing the muscle and long bones of the skeletal systems – can help to slow many of these mechanisms down, as can regular sauna exposure, healthy protein intake, and PEMF therapy.

Digestive System:

Digestive activity decreases, leading to constipation, which may be exacerbated by medications like proton pump inhibitors and antibiotics, and by medical conditions, such as diabetes, and IBS. Peristalsis slows down, causing waste to move more slowly through the colon, leading to more water loss, exacerbating constipation further.

Diverticulosis can develop when small pouches in the lining of the colon bulge through weak spots in the intestinal wall. This can lead to gas, bloating, cramps, and even more constipation. If the pouches get inflamed, abdominal pain, cramping, fever, chills, nausea, and vomiting can occur. Cancerous or non-cancerous polyps can also form.

Gastroesophageal reflux disease (GERD) occurs when stomach acid rises into the esophagus, causing heartburn and other symptoms. Natural digestive enzymes decrease with age, leading to a loss of protein absorption, further aggravating sarcopenia. Research has shown that people with chronic diseases or poor energy levels tend to have fewer enzymes in their blood, urine, and tissues.

  • Chewing food more thoroughly, eating adequate fiber and fermented foods, supplementing with digestive enzymes, and consuming amino acids, along with gut health strategies, can all slow the aging of the digestive system and depletion of enzymes.

Respiratory System:

Maximum lung capacity and maximum oxygen utilization (VO2 max) decrease gradually after about age 25, especially if you’re not frequently exercising. You also experience a drop in vital capacity, a weakening of respiratory muscles, and a decline in the effectiveness of lung defense mechanisms, including reduced WBCs on the surface of the lung alveoli.

As the diaphragm and other muscles weaken, you experience a decreased ability to breathe enough air in and out, as well as a decreased ability to keep airways open. Alveoli lose shape and become less functional.

  • Regular cardiovascular exercise and breathwork practices can help to support the aging respiratory system. After all, lung volume is the greatest predictor of health and longevity.

Urinary System:

After age 30-40, 2/3 of us undergo a gradual decline in the rate at which our kidneys filter blood. The kidneys begin to lose tissue, and the number of filtering units known as nephrons decreases. The blood vessels that supply the kidneys can harden, further impairing the kidney’s filtration rate.

The bladder wall loses elasticity, meaning it cannot hold as much urine, and the muscles controlling the bladder weaken. The urethra can become blocked by an enlarged prostate gland in men or by a prolapsed bladder or vagina in women. Medical conditions, like diabetes, can contribute to incontinence.

  • Deep pelvic core training, adequate hydration and mineral intake, limited consumption of dehydrating foods, such as alcohol and caffeine, and avoidance of excess protein.

Reproductive System:

For women the menstrual cycle stops at around 51 and the ovaries halt production of estrogen and progesterone. The ovaries stop producing eggs, and after menopause, you can no longer become pregnant. Vaginal walls become thinner, drier, less elastic, and possibly irritated. Vaginal yeast infection risk increases, and the external genital tissue and breast tissue thins. The pubic muscle can lose tone, resulting in prolapsed vagina, uterus, or bladder.

Testicular tissue mass decreases and testosterone gradually declines, along with blood flow to the reproductive organs. The volume of fluid remains consistent, with fewer sperm.

  • Maintain regular sexual activity with age.

Endocrine System:

At 30 years old, HGH begins its regression in both men and women and declines at a rate of around 14% per decade. When women transition into menopause, progesterone, testosterone, and estrogen levels begin to fall. At 50, thyroid activity beings to decrease, and hyper or hypothyroidism may occur.

At 50, men may begin to experience andropause. In both men and women, a decline in DHEA can cause increased vulnerability to a variety of cancers.

At 60, as insulin production decreases and insulin cell receptor sensitivity lowers, the ability to metabolize sugar declines, and insulin resistance or diabetes becomes more prevalent.

At 70, hormones that protect against loss of calcium in bones decline, making osteoporosis more prevalent.

  • Organ meat consumption, regular sex, care for the gut, and avoidance of modern plastics and endocrine-disrupting chemicals.

Circulatory System:

At around 40, your heart muscles thicken and blood vessels stiffen, causing the heart to fill more slowly (this can occur earlier if you’re a hard-charging athlete). Increasing blood pressure as the heart works harder, and possibly cardiac arrhythmias. The receptors that monitor blood pressure can also deteriorate, causing dizziness when you stand up from sitting or lying down. Further exacerbated by calcification or excess calcium deposits in the body, manifesting as stiffening of joints, plaque buildup on the teeth, hardening of the arteries, impaired brain function, and general aches and pains.

Many individuals over 60 have enlarged deposits of calcium mineral in their arteries, often cause by a lack of minerals in their diet, dehydration, limescale in tap water, and even synthetic calcium supplements.

Abnormal heart rhythms can develop, leading to arrhythmias like atrial fibrillation. The pacemaker can develop fibrous tissue and fat deposits in some of its pathways and lose some of its cells, resulting in a slower heart rate. The walls of capillaries can thicken, resulting in a slower rate of exchange of nutrients and waste products.

The total water content of blood falls, RBC production falls, and certain WBCs deteriorate. Lymph fluid can stagnate, toxins accumulate, and immune cells are not delivered to the areas of the body where they are most needed. Weakening the immunity and infection fighting ability.

  • Regular cardiovascular exercise, hydration, regular exposure to heat and cold, and the lymph-fluid-circulating strategies.

Nervous System:

Some nerve structure and function is lost. Waste products can collect in brain tissue, causing plaques and tangles. Alzheimer’s and other forms of dementia then increase in risk. Plaques are actually a part of the immune system and release antimicrobial agents to deal with bacteria, viral, or fungal infections in the brain.

By age 40, the lenses in the eyes begin to stiffen, resulting in vision impairment, particularly when focusing on near objects. Hearing loss may develop, which occurs in men sooner than women, and memory tends to worsen.


Stem cell production and availability both decline with age, and a result of this is that the skin’s epidermal cells slow in their reproduction. Melanocytes, which produce pigmentation, decrease in number while the remaining cells increase in size. This can cause thinner, more translucent skin, as well as large pigmented spots. Skin injuries, tearing, and infections become more frequent.

Loss of fat and collagen in the underlying tissues can cause skin to sag and wrinkle, and the connective tissue loses its strength and elasticity. The blood vessels become more fragile, and bruising and bleeding under the skin, cherry angiomas, and other conditions become more frequent.

The skin becomes dry and itchy as the glands that produce oil reduce their production levels. The fat layer beneath the cutaneous layer of skin thins, leading to increased risk of skin injury and a reduced ability to maintain a consistent body temperature. Sweat glands produce less sweat, making it harder to cool off.

  • Stem cell-supporting strategies, along with beauty tactics can help to minimize effects.
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