General Concepts of Living Organisms and Homeostasis

General Concepts of Living Organisms and Homeostasis

I. Characteristics of Life

Life is characterized by 3 fundamental features:

• Constant Change:

• It is a continuous metabolic process, including two stages:

• Anabolism: Absorption and transformation of matter into nutrients.

• Catabolism: Decomposition of matter, release of energy, and excretion of metabolic products.

• Responsiveness to Stimuli:

• It is a manifestation of life, a reaction to external agents.

• The stimulus threshold is the minimum intensity to produce a response to each stimulus.

• Reproduction:

• It is the mode of existence of life, ensuring the continuation of the species.

• Reproduction is achieved through the genetic code in DNA, synthesizing multiple functions.

II. Homeostasis

1. Definition:

• Claude Bernard was the first to introduce the concept of homeostasis, the stability of the composition of the internal environment.

• The internal environment accounts for 56% of body weight, including:

• Intracellular fluid: Makes up 2/3 of body fluid, located within cells.

• Contains ions: K+, Mg2+, PO43-.

• Extracellular fluid: Makes up 1/3 of body fluid, located outside of cells.

• Contains nutrients and ions: Na+, Cl-, HCO3-.

2. Mechanisms of Homeostasis Maintenance:

• Homeostasis is maintained by 3 systems:

• Receptor system: Detects changes in the internal environment.

• Transport system: Transports necessary substances and removes waste products.

• Excretory system: Removes waste products from the body.

3. Organ Systems Involved in Maintaining Homeostasis:

• Digestive system: Digests and absorbs nutrients.

• Includes: Mouth, esophagus, stomach, small intestine, large intestine, digestive glands.

• Respiratory system: Gas exchange, supplying oxygen and removing CO2.

• Includes: Nose, trachea, bronchi, alveoli, gas diffusion membrane, lung membrane.

• Liver: Alters the chemical composition of many substances into a form more suitable for cells.

• Stores and decomposes substances.

• Musculoskeletal system: Participates in movement, supports metabolism.

• Skeletal muscle: Movement for searching, processing, and grinding food.

• Smooth muscle: Receives and transports air and nutrients.

• Blood: The most important extracellular fluid, transporting substances throughout the body.

4. Regulation of Function:

• Nervous system: Regulates rapidly and precisely.

• Reflex arc:

• Receptor: Located on skin, mucous membranes, joint surfaces, blood vessel walls, organ surfaces.

• Afferent pathway: Sensory nerves, autonomic nerves.

• Nervous center: Cerebral cortex, subcortical structures, spinal cord.

• Efferent pathway: Motor nerves, autonomic nerves.

• Effector: Muscle or gland.

• Reflex classification:

• Unconditioned reflex: Fixed, instinctive, lifelong, inherited, dependent on the nature of the stimulus and receptor.

• Conditioned reflex: Formed during life, complex reflex arc, individual characteristic, flexible to the environment, center in the cerebral cortex, non-specific conduction pathway, not dependent on the stimulus and receptor.

• Humoral system: Regulates more slowly but with a long-term effect.

• Regulatory factors: Substances dissolved in blood and body fluids, role of gases, ions, hormones.

5. Examples of Homeostasis Regulation:

• O2 regulation: Humoral regulation, dependent on the chemical properties of hemoglobin (Hb).

• CO2 regulation: Nervous regulation, the primary end product of oxidation reactions in cells.

• Ion regulation (K+, Na+, Ca2+, Mg2+):

• Creates membrane potential, action potential, conducts nerve impulses.

• Ca2+ also participates in muscle contraction, blood clotting, and the excitability of nerve fibers.

• Fe2+ regulation: Hemoglobin formation.

• Hormone regulation:

• Thyroid hormones: Increase cellular metabolic activity in the body.

• Insulin from the pancreas: Increases glucose breakdown.

• Parathyroid hormone: Regulates Ca2+ in the blood.

6. Types of Regulatory Mechanisms:

• Negative feedback: More decreases, less increases.

• Positive feedback: More increases, less decreases.

III. Concept of Life

• F. Engels: Defined life as follows: Life is the mode of existence of albuminous bodies, and this mode of existence consists essentially in the constant renewal of the chemical constituents of these bodies.

• Szent Gyergyi: Believes that life is a process of inhibiting an electron, slowing it down.

• Schrödinger: Believes that life is a quantum phenomenon.

IV. Cells

• The cell is the structural and functional unit of all living organisms, including humans, a common characteristic of life.

V. Blood Circulation

• Consists of two phases:

• Phase 1: Nutrients from the blood into the tissues.

• Phase 2: Fluid and nutrients exchange between blood capillaries, interstitial fluid, and cells.

VI. Excretory System

• The final stage in the process of homeostasis creation, eliminating waste products from the body.

VII. Nervous Regulation

• Includes structures:

• Central nervous system: Brain, spinal cord.

• Peripheral nervous system: Motor nerves, sensory nerves.

VIII. Reflexes

• Unconditioned reflexes: Fixed, instinctive, lifelong, inherited, have reflex arcs, species-specific, reflex center located below the nervous system.

• Conditioned reflexes: Formed during life, complex reflex arcs, individual characteristic, flexible to the environment, center in the cerebral cortex, non-specific conduction pathway.

IX. Blood Clotting

• An example of positive feedback regulation, helping the body stop bleeding.

• Harmful effects of positive feedback regulation: Sudden loss of 2 liters of blood.

X. Other Concepts:

• Internal environment: The internal environment of the body.

• Capillary wall: Has small holes so that fluid and most substances can easily diffuse back and forth between capillaries and interstitial fluid.

• Pumping system and blood vessels: Ensures the continuous transport of substances in circulating blood.

Note: This article is a compilation of knowledge from the provided data, may require additional information or correction to be accurate and complete.