Week 13 : Homeostasis


  • The process by which the body achieves this environment.
  • Homeostatic mechanism regulates internal conditions that change due to external environmental conditions.
  • Homeostasis depends on negative feedback. The body has the control system that detects change and directs responses.
  • Homeostasis is a steady internal state, keeps conditions in the body constant.
  • The brain and the adrenal system (hormones) do most of the regulating.


  • The part of the body that helps maintain homeostasis.
  • Part of the brain that regulates the body’s blood pressure, hunger, temperature, thirst, and other key functions.

Blood Sugar Levels

  • Insulin is a hormone that regulates blood glucose levels. Insulin binds to receptors on liver cells as stored molecules, glycogen.
  • As the glucose level decreases, the pancreas allows the alpha cells to release the hormone glucagon. The glucagon binds to the receptors on the liver cells break down glycogen to glucose.


  • The process of maintaining an internal temperature within the range is called thermoregulation. Thermoregulation balances heat gain and loss through adaptation.
  • Common categories in adaptation that help animals to thermoregulate:
    • Increasing metabolic heat production
    • Insulation
    • Circulatory adaptation
    • Evaporative cooling
    • Behavioural response
  • Heat is gained or lost in four ways.
    • Conduction is the transfer of heat by direct contact.
    • The transfer of heat by movement of air or liquid past a surface is called convection.
    • Radiation, on the other hand, is the emission of electromagnetic waves.
    • Evaporation is the loss of heat from the surface of liquid in the formation of water vapour (gas).
  • Ectothermic Animals (Cold-blooded)
    • Like lizards, fishes, most amphibians, and invertebrates maintain their internal temperature by gaining heat from external sources.
  • Endothermic Animals (Warm-blooded)
    • Mammals, birds, most insects and a few reptiles, obtain heat from their metabolism.

Salt and Water Balance

  • Osmoregulators adapt their body in regulating salt concentrations or in maintaining the optimum salt concentrations inside their body.
  • Moreover, aquatic invertebrates are known as osmoconformers because they vary their body fluid according to the changes that happen in seawater.
  • Among the specialized structures in invertebrates for osmoregulation and excretion are protonephridia and metanephridia which are considered as nephridial organs.


The Human Excretory System

  • Filtration, Reabsorption, Secretion, and Excretion are the key processes of the urinary system.
  • Filtration is a process wherein blood pressure forces water and small molecules through a capillary wall into the kidney tubule. Filtration membrane permits fluid and solutes including glucose, amino acids, sodium, potassium, chloride, bicarbonate, salts, and urea to pass and become part of the filtrate.
  • Reabsorption prevents the danger posed during filtration and refines the filtrate. This process reclaims about 90% of valuable solutes such as glucose, salt, and amino acids from the filtrate.
  • Substances in the blood are transported into filtrate by the process of secretion.
  • Urine, which is the final product, is excreted via the ureters, urinary bladder, and urethra in a process called excretion.



The Immune System

  • Immunity is the ability of the body to resist and fight infection. Three defences protect the body from infections:
  • Complement Immunity – a set of proteins that circulate in inactive form of blood.
  • Innate Immunity – is a series of defences that it is the same whether or not the pathogens have been encountered before. It acts right away upon infection.
  • Adaptive immunity tailors to specific pathogens encountered by an organisms during its lifetime.
  • Inflammatory Reaction attracts phagocytic white blood cells to the bacterial invasion site undergoing the following changes to be expected; redness, pain, swelling , and heat.
  • Never ever add warm compress in areas exhibiting those kinds of symptoms, this will lead increase swelling and pain.
    • Macrophage – communicate / kill enemies / cause inflammation / activate other cells.
    • Neurophil – activate other cells / kill enemies
    • Natural Killer Cell – communicate / kill enemies
    • Complement – mark / disable enemies 1
    • Mast Cell – communicate / fight worms / cause inflammation / activate other cells
    • Monocyte – standby mode / kill enemies / strategic decisions
    • Follicular Dendritic Cell – activate other cells
    • Dendritic Cell – activate other cells / strategic decisions
    • Memory Helpter T Cell – communicate / remember enemies / activate other cells
    • Basophil – activate other cells / cause inflammation / fight worms
    • Eosinophil – cause inflammation / fight worms / activate other cells
    • Virgin helper T cell – standby mode / activate other cells
    • Helper T Cell – communicate / kill activate other cells.
    • Memory Helper T Stem Cell – communicate / remember enemies
    • Virgin Killer T Cell – standby mode / kill infected cells
    • Antibodies – mark / disable enemies II
    • Killer T Cell – kill infected cell
    • Memory Killer T Cell – kill infected cells / remember enemies
    • Virgin B Cell – produce antibodies / standby mode
    • B Cell – produce antibodies / activate other cells.
    • Memory B Cell – remember enemies / produce antibodies
    • Memory B Stem Cell – remember enemies / produce antibodies
    • Memory Killer T Stem Cell – remember enemies / kill infected cells



The endocrine system is one of the body’s main systems for communicating, controlling and coordinating the body’s work. It works with the nervous system, reproductive system, kidneys, gut, liver, pancreas and fat to help maintain and control the following:

  • body energy levels
  • reproduction
  • growth and development
  • internal balance of body systems, called homeostasis
  • responses to surroundings, stress and injury

The endocrine system accomplishes these tasks via a network of glands and organs that produce, store, and secrete certain types of hormones. Hormones are special chemicals that move into body fluid after they are made by one cell or a group of cells. Different types of hormones cause different effects on other cells or tissues of the body.

Glands are small but powerful organs that are located throughout the body. They control very important body functions by releasing hormones.

The following lists of glands make up the endocrine system.

  • Pituitary Gland – The pituitary gland is sometimes called the “master gland” because of its great influence on the other body organs. Its function is complex and important for overall well-being.
  • Thymus – a gland needed early in life for normal immune function.
  • Pineal Gland – Melatonin may stop the action of (inhibit) the hormones that produce gonadotropin, which causes the ovaries and testes to develop and function. It may also help to control sleep patterns.
  • Testes – Males have twin reproductive glands, called testes, that produce the hormone testosterone. Testosterone helps a boy develop and then maintain his sexual traits. Testosterone is a steroid and has been administered to athletes in order to improve performance.
  • Ovaries – The two most important hormones of a woman’s twin reproductive glands, the ovaries, are estrogen and progesterone. These hormones are responsible for developing and maintaining female sexual traits, as well as maintaining a pregnancy. Progesterone controls menstruation in women and plays a role in pregnancy.  Estrogen stimulates development of female sexual characteristics. Estrogen levels may be related somehow to migraine headaches in women.
  • Thyroid – The thyroid is a small gland inside the neck, located in front of your breathing airway (trachea) and below your Adam’s apple. The thyroid hormones control your metabolism, which is the body’s ability to break down food and store it as energy and the ability to break down food into waste products with a release of energy in the process. Thyroxine controls the rate of metabolic processes (how energy is used) in the body and influences physical development.
  • Adrenal Glands – The adrenal cortex produces glucocorticoids (such as cortisol) that help the body control blood sugar, increase the burning of protein and fat, and respond to stressors like fever, major illness, and injury. Adrenaline is released in high stress conditions or in excitement or fear. Adrenaline stimulates heart rate, increases blood pressure, dilates pupils. Cortisol controls mental stimulations, breaks fat and protein to glucose, anti-inflammation. It is usually referred to as the stress hormone as it is involved in response to stress and anxiety.
  • Parathyroid – The parathyroid glands are necessary for proper bone development.
  • Pancreas – The pancreas is a large gland behind your stomach that helps the body to maintain healthy blood sugar (glucose) levels. The pancreas secretes insulin, a hormone that helps glucose move from the blood into the cells where it is used for energy.

Disorders of the Endocrine System:

  • Diabetes Mellitus – a group of metabolic diseases in which a person has high blood sugar, either because the pancreas does not produce enough insulin or because cells do not respond to the insulin that is produced.
  • Osteoporosis – a disease of bones that leads to an increased risk of fracture.
  • Rickets – a softening of bones in children due to deficiency or impaired metabolism of vitamin D, phosphorus or calcium.
  • Cushing’s disease – increased secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary.



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