General Physiology Introduction

• Introductory information about General Physiology, authored by Assist. Prof. M. Özge Atasayan from Biruni University.

Course Learning Objectives

• Define physiology.
• Compare basic medical sciences.
• Identify the levels of organization of human body.
• Describe human body fluid composition.
• Define homeostasis.
• Understand negative and positive feedback mechanisms.

Anatomy and Physiology Defined

• Anatomy describes the structures of the body, what they are made of, where they are located, and their associated structures.
• Physiology studies the functions of anatomical structures, both individual and cooperative.

Human Anatomy Types

• Gross anatomy (macroscopic anatomy) examines large, visible structures.
• Microscopic anatomy examines cells and molecules.
• Cytology is the study of cells.
• Histology is the study of tissues.

Human Physiology Specializations

• Cell physiology focuses on the functions of cells.
• Organ physiology concerns the functions of specific organs.
• Systemic physiology studies the functions of organ systems.

Levels of Organization

• Atoms -> Molecules -> Cells -> Tissues -> Organs -> Organ systems -> Organisms -> Populations of one species -> Ecosystem of different species -> Biosphere
• Physiologists study of how specific organs and systems work and their advantages, using information from other fields.

Detail on Specific Organizational Levels

• Cellular level: Cells are the smallest living units in the body.
• Tissue level: A tissue is a group of cells working together.
• Organ level: Organs are made of two or more tissues working together.
• Organ system level: An organ system is a group of interacting organs.
• Humans have 11 organ systems.
• Organism level: An individual life form is an organism.

The Organ Systems

• Integumentary, Skeletal, Muscular, Nervous, Endocrine, Cardiovascular, Lymphatic, Respiratory, Digestive, Urinary, Male Reproductive, Female Reproductive

Common Features of Human Cells

• Covered by a membrane.
• Produce ATP through oxidation of carbohydrate, protein, and fatty acids.
• Removal of secondary metabolites and wastes.
• Nutrient consumption and energy production mechanisms are similar.
• Nearly all cells have the ability to reproduce additional cells.

Average Adult Male Body Composition

• Water: 60%.
• Minerals: 7%.
• Proteins and related substances: 18%.
• Fat: 15%.

Body Fluid Compartments

• In lean adults, body fluids constitute 50% of female and 60% of male total body mass.
• Body fluid composition of tissue varies by Tissue types, Gender, and Age.
• Tissue types: Lean tissues have higher fluid content than fat tissue.
• Gender: Males have more lean tissue; females have a greater amount of adipose tissue.
• Age: Lean tissue is lost with age; the value of total body water tends to decrease with age.
• Total body water separates into two main compartments by a membrane freely permeable to water
• Intracellular fluid (ICF) inside cells- About 2/3 of body fluid
• Extracellular fluid (ECF) outside cells - About 1/3 of body fluid

Types of Extracellular Fluid (ECF)

• Plasma (IVF): Fluid portion of blood
• 5 liters of total blood volume, with 3.5 liters being plasma
• Interstitial fluid is the major portion of ECF. It has a similar composition to plasma, except for little protein, and consists of Lymph, Transcellular fluid and Mesenchymal tissue fluid
• Transcellular fluid: Secretions of secretory cells and cavities, e.g., saliva, sweat, bile, intraocular fluids, cerebrospinal fluid, gastrointestinal secretions.
• Transcellular fluid includes cerebrospinal fluid (CSF), lymph, synovial fluid, pleural fluid, pericardial fluid, and aqueous humor.
• Mesenchymal tissue fluid: Dense connective tissue, cartilage, and bones contain 6% of body water.

Body Fluid Compositions

• Made up of water and dissolved solutes
• Organic substances include protein, glucose, fatty acids, hormones, and enzymes.
• Inorganic substances include electrolytes like sodium, chloride, potassium, calcium, and bicarbonate.

Components and Properties of Body Fluids

• Electrolytes are salts and minerals that can conduct electrical impulses in the body.
• Electrolytes are charged, existing as Cationic: positively charged (Na, K, Ca) and Anionic: negatively charged (Cl, HCO3, PO4)
• Electrolytes: Control fluid balance, water moves according to osmotic gradients, and have a greater osmotic power than nonelectrolytes.
• Plasma membrane separates ICF and ISF
• Blood vessel wall separates ISF and plasma
• Hydrophobic nature of the the cell membrane prevents free exchange of ions and proteins

Fluid Movement

• Normal distribution of total body water in fluid compartments is kept constant by osmotic and hydrostatic pressure
• Hydrostatic pressure is exerted by a fluid against a capillary wall and pushes the fluid out of the capillary, potentially causing edema
• Osmotic pressure is exerted by the flow of water through a semipermeable membrane
• Too many proteins in plasma cause water to be sucked into blood vessels, pulling fluid back into the capillary.
• An elevation of blood pressure also impacts fluid movement.

Fluid Movement

• Fluid leaves plasma at the arteriolar ends of capillaries due to hydrostatic pressure outwar
• Fluid returns to plasma at the venular ends of the capillaries because of colloid osmotic pressure inward
• Hydrostatic pressure within interstitial spaces forces fluid into lymph capillaries
• Interstitial fluid is in equilibrium with transcellular and intracellular fluids
• Plasma and interstitial fluid: The larger concentration of proteins is a key difference, as the capillary endothelium is freely permeable to water and to small solutes (inorganic icons, glucose, urea) but has limited permeability to larger solutes (proteins, lipids).