The Fundamental Concepts Of Mammalian Life PDF

The Fundamental Concepts Of Mammalian Life Peter Lechner, M.D., Prof  The 6 Characteristics of Life Metabolism Reproduction & Excitability Fertility Communication Differentiation Growth  Metabolism – what for? M. consi...

The Fundamental Concepts Of Mammalian Life Peter Lechner, M.D., Prof  The 6 Characteristics of Life Metabolism Reproduction & Excitability Fertility Communication Differentiation Growth  Metabolism – what for? M. consists of many chemical processes during which substances ( mostly molecules ) are either formed ( anabolic) or degradated ( catabolic ). Catabolism: Uses substances ( nutrients and oxygen ) to produce energy ( ATP ). Anabolism: Uses energy ( ATP ) to create substances.  Metabolism – simplified model Glucose + Oxygen >>>>> ATP + Water + Carbondioxide C6H12O6 + O2 >>>> ATP + H2O + CO2 vs. Amino-acids + ATP >>>> Proteins ATP = Adenosin Tri Phospate, biologically storable form of energy  Metabolism - Nutrients Macro-nutrients Carbohydrates – Saccharides ( glucose ecc., starch ) Proteins ( essential and non-essential amino-acids) Fat ( saturated and unsaturated fatty acids, cholesterol ) Micro-nutrients Vitamins ( water soluble or fat soluble ) Trace elements ( metals like zinc, copper, iron) Minerals ( sodium, potassium, magnesium )  Metabolism – Energy supply Proteins: 1g equ. 4.2 kcal. Fat: 1g equ. 9.2 kcal Carbohydrates: 1g equ. 4.1 kcal ( alcohol: 1g equ. approx. 7.0 kcal) Remeber: 1 kcal = 4.19 kJ ( kilo Joule )  Metabolism – Energy demand Basic energy demand : 1.500 kcal ( 6.3 MJ/day) – 1.700 kcal ( 7.1 MJ/day) (while at rest in the morning at normal temperature) Energy demand at work: white-collar ( brain-) workers: 8.4 – 9.6 MJ/day blue-collar ( physical) workers: 15 – 20 MJ/day Energy demand in sports: up to 4.3 MJ per hour  Excitability - Definition E. is every living being´s ability to REACT TO CHANGES in it´s environment. „Triggers“ are: light, sound, heat/cold, motion ecc. Sensory organs ( receptors ) receive INFORMATION that is processed by the brain.  Excitability - Information To be available, every information must be „coded“ in a defined sytem. For example: numbers and letters represent information. Bits and bytes also represent information. The „biological information code“ is an electric voltage ( potential ) at every cell´s membrane.  Excitability- electrophysiologal „basics“ Cell „at rest“: Stable relation between (more) potassium in the cell and ( less) potassium outside the cell >>> -70 to -100 mV. Stimulated cell: Potassium outfl ux and simultaneous sodium infl ux >>> -5 – 0 mV The changes in membrane-voltage ( de-polarization and subsequent re-polarization) lead to an ELECTRIC CURRENT.  Communication -systems Nerves & transmitter substances Hormones Messenger –substances of the immune system ( i.e interleukins, interferones, ecc.).  Communication – the nervous system When a nerve´s end ( receptor ) is stimulated, an electric current occurs that is conducted along the nerval fibre to a SYNAPSIS ( junction between two nerve cells or between nerve and muscle cell, ecc.). Here the information ( „electricity“) is transformed into a chemical reaction: Transmitters are released that bind to receptors in the post-synaptic cell. This reaction again creates electric energy, and so on……. ELECTRO-CHEMICAL COUPLING.  Communication –the hormone system I Hormones are synthesized in ENDOCRINE GLANDS ( thyroid, pancreas, ovaries, testicles ecc.) and released into the blood stream. Via the blood they reach their target organs/ cells, where they bind to receptors on the cell membrane or inside the cell. The chemical reaction between the hormone and ist receptor ( both molecules!) has a specific effect:  Communication –the hormone system II Examples for hormone effects: Insulin ( pancreas ): decrease in blood glucose Glucagon ( pancreas): rise of blood glucose Thyroxin ( thyroid): activated metabolism, rise of body temperature, accelerated heart beat rate. Estrogen/gestagen ( ovaries): fertility, reproduction. Androgenic hormones: ( testicles): fertility, sexual activity, muscle growth. Somatotropin ( pituary gland ) : growth……..  Communication –the immune system The immune system has the ability to differentiate between „own“ and „foreign“. It MUST tolerate every chemical substance and structure that is part of the organism, and it must identify, attack and eliminate every foreign substance or structure ( virusses, bacteria, transplants, organic implants ecc.) This requires a constant FLOW OF INFORMATION between all components of the immune system ( i.e. white blood cells, leucocytes) Messenger substances ( immuno-mediators) are INTERLEUKINS/ INTERFERONS  Reproduction & Fertility Reproduction is a cell´s ability two divide into two daughter cells. Ist the basic precondition for regeneration and tissue repair. MITOTIC REPRODUCTION: Like the „mother cell“, every ( identical) „daughter cell“ contains 23 pairs ( 46) chromosomes. MEIOTIC REPRODUCTION: the „mother cell“ with its 46 chromosomes is divided into two ( different) daughter cells with 23 chromosomes each ( germ cells only! ).  Differentiation Omni-potency: In the single-cell-organism, ONE cell expresses all 6 characteristics of life. Differentiation: A specialized cell is „reduced“ to one special function –and looses some of the other ones.  Growth The 3 mechanisms of growth Increase in NUMBER of cells Increase in SIZE of cells Increasing extra-cellular VOLUME  Regulation and Adaptation - Definitions Regulation: Maintenance of the INTERNAL ENVIRONMENT while the external environment is subject to CHANGES. Adaptation: Adjustment of SUPPLY to DEMAND.  Principle of HOMEOSTASIS Vital parameters like blood-pressure, core-temperature, ph-value, blood- glucose-level, ecc. are constantly surveyed by „sensors“ and automatically held constant.  The regulatory circuit 1 Vital parameters have to be maintained within physiological limits all the time. They are constantly surveyed/ measured by sensors/ receptors and AUTOMATICALLY corrected when necessary.  The regulatory circuit 2 A SENSOR constantly MEASURES the ACTUAL VALUE. A REGULATOR permanently COMPARES the NOMINAL VALUE ( upper and lower physiological limit, i.e. physiological range ) to the ACTUAL VALUE and induces ADJUSTING ACTION the result of which is again observed by the sensor and reported to the regulator. = NEGATIVE FEED-BACK CIRCLE  Examples: The body´s core temperature is approx. 37.5 o C. The temperature-regulation centre in the brain permanently measures the blood temperature and induces reactions to changes: Increased temp.: sweat, dilatation of skin´s blood vessels ….. Reduced temp.: activation of metabolism, constriction of skin´s vessels, „shivering with cold“ (i.e. enhanced muscle activity).  Examples The body´s physiological ph-value is 7.36 – 7.42 *) ( ph = -log[ H +], > 7.42 alkalosis, < 7.36 acidosis). Buffer systems : Blood proteins ( albumin) and their binding capacities. Kidney: Elimination of alkali/ acids Lung: Expiration of carbon dioxide. (H2 O + CO2 = H2CO 3). *) receptors in virtually every cell, predominantly in lung and kidneys The Negative Feedback Cycle  TRF ( thyreotropic hypothalamic area (brain) releasing factor) releases s stimulates u p pituary gland p Regulation of releases r thyroid function e thyreotropic s hormone (TSH) s stimulates e s releases THYROID Thyroid hormones T3, T4 nutrit. supply IODINE  Pituary gland s releases u p „Anti-Baby LH/ FSH Pill“ p r stimulates e s releases s Ovaries/follicles Estrogen/ e progesteron s mature egg PREGNANCY  Adaptation to ( physical ) work Forced respiration ( increased O2-uptake) Accelerated glykolysis ( muscle-/ liver glycogen). Dilatation of muscle vessels ( rising blood supply) Accelerated heart beat rate ( rising blood supply!!!) „ work“ means increased energy demand in muscles  Adaptation to ( phsical ) work 2 Oxygen is required for AEROBIC glycolysis. Glucose is required to be „burned“/ metabolized. Its „biological storage form“ is glycogen ( in liver and muscles). Increased perfusion is required for the transport of glucose and oxygen into the working muscle. Accelerated heart beat increases blood-volume per time, i.e. muscle perfusion.  Inspiratory vs. expiratory air/ physical composition Nitrogen 79 p.c. Nitrogen 79 p.c. Oxygen 20 p.c. Oxygen 16 p.c. CO2 0.03 p.c. CO2 4 p.c others 1 p.c. others 1 p.c.  Oxygen pressure and air pressure - a „basic“ calculation: The percentage of oxygen in inspiratory air is 20 p.c. The share that oxygen has in the air pressure ( 760mm Hg) is therefore also 20 p.c., i.e. 152 mm Hg. pO2 = 152 mm Hg at Zero-altitude ( sea level )  Adaptation to altitude 1 Air pressure decreases with altitude and is approx. 380 mm Hg at 5.500m. Oxygen pressure decreases to the same extent and is therefore approx. 75 mm Hg at 5.500 m. At high altitudes an OXYGEN DEFICIENCY occurs.  Adaptation to altitude 2 Accelerated breathing Accelerated heart freqency Accelerated production of red blood cells ( long-time adaptation). What happens BEYOND THE LIMITS? Increase of pressure in the“ fl uid compartment“ of lungs in comparison to the „gas compartment“ >>>> effusion of Cerebral edema ( due to capillary toxicity of hypoxia) >>> coma >>>> death.