Introduction to Human Physiology PDF

**Summary** 1. 2. 3. 4. Introduction ================================== ##### Physiology - studies the **physical and chemical mechanisms** that are responsible for the origin, - describes the "vital" functions of living organisms and their organs, tissues...

**Summary** 1. 2. 3. 4. Introduction ================================== ##### Physiology - studies the **physical and chemical mechanisms** that are responsible for the origin, - describes the "vital" functions of living organisms and their organs, tissues, cells, and molecules. - each type of life - own functional characteristics (plant → the simplest virus→ the Introduction ============ ##### Physiology - Vast field of physiology can be divided into: - cellular physiology, - plant physiology, - viral physiology, - bacterial physiology, - invertebrate physiology, - vertebrate physiology, - mammalian physiology, - human physiology, - and many more subdivisions. Introduction ============ ##### General physiology - - functional -- **physiology** - - - - - - -  Introduction ============ ##### Human Physiology ###### Properties of human body: - organized into complex structures based on organic molecules - - - - Introduction ================================== ##### Human Physiology - **responds to stimuli** from the environment - - - adaptation under widely varying conditions is the basis of survival, otherwise would make life impossible. - hunger makes us seek food, - fear makes us seek refuge - **growth and development** - **reproduction** Introduction ============ ##### Human Physiology - **Integrates multiple functions** of the cells, tissues, and organs into the complex functions of the living human being. - This integration requires **communication and coordination** by a vast array of control systems that operate at every level: - the genes that program synthesis of molecules - to the complex nervous and hormonal systems that coordinate functions of cells, tissues  Introduction ================================== ##### 2.Cells - the Living Units of the Body ###### Each type of cell - **need a constant environment** for proper functioning - is specially adapted to **perform one or a few particular functions** - Introduction ============ ##### Cells - the Living Units of the Body - **Common characteristic** of all living human cells: - **oxygen needs -** O2 reacts with carbohydrate, fat, and protein to release the **energy** - the general chemical mechanisms for changing **nutrients** into energy are basically the same in all cells, - all cells **deliver products** of their chemical reactions into the surrounding fluids, - when cells of a particular type are destroyed, the remaining cells of this type usually Introduction ============ ##### Cells - the Living Units of the Body - **Particular characteristics** -- the specific function - each type of cell is specially adapted to perform one or a few particular functions:  3.Homeostasis ============= ##### Internal environment - normal function of individual organ/system - interconnection of organ systems work "hand in hand" with each other. - The cells within an organ or a tissue often share information, - The individual cells must act in concert to perform the proper function of the organ or tissue Homeostasis ================================= ##### Internal environment - the "milieu extérieur" that physically surrounds the whole organism; - the "milieu intérieur" internal environment - "the organic liquid that circulates and bathes all the anatomic elements of the tissues, the lymph or the plasma." - isolates the organs and tissues of the body from the vagaries of the physical conditions of the - "fixité du milieu intérieur" (the constancy of the extracellular fluid) is the condition of "free, independent life."- in certain conditions each organ contributes to "compensate and equilibrate" against changes in the external environment. Homeostasis =========== ##### Internal environment ###### Concept of Steady-State Balance - - The amounts added to or lost from the body can vary widely, depending on the environment, access to food and water, disease processes, and even cultural norms. - Homeostasis ================================= ##### Internal environment ###### Concept of Steady-State Balance - - - - 4.The sensitivity of the system (i.e., how much of a deviation from the set point is tolerated) depends on several factors: the nature of the sensor, the time necessary for generation of the effector signals, and how rapidly the effector organs respond to the effector signals. Homeostasis =========== ##### Steady-State Balance Homeostasis ================================= ##### Steady-State Balance Deviations - Water balance determines the osmolality of the body fluids. Cells within the hypothalamus of the brain monitor body fluid osmolality for deviations from the set point (normal range: 280- 295 mOsm/kg H~2~O). - - - - With appropriate responses to these two signals, water input, water output, or both are adjusted to maintain balance and thereby keep body fluid osmolality at the set point. Homeostasis =========== ##### Steady-State Balance Deviations - - #### Volume and Composition of Body Fluids ##### Internal environment - Water constitutes a high proportion of body weight. - The total amount of fluid (a water solution of ions and other substances ) or water is called - In general, total body water correlates inversely with body fat. - Total body water is a higher percentage of body weight when body fat is low / a lower percentage when body fat is high. - Females have a higher percentage of adipose tissue than males → tend to have less #### Volume and Composition of Body Fluids ##### Internal environment - Total body water - two major body fluid compartments: - **intracellular fluid (ICF)** - within the cells and is 2/3 of total body water; - **extracellular fluid (ECF)** - outside the cells and is 1/3 of total body water. - ICF and ECF are separated by the cell membranes. #### Volume and Composition of Body Fluids #### Composition of Body Fluid Compartments ##### Internal environment - The composition of the body fluids is not uniform. - **ICF and ECF** have vastly **different concentrations** of various **solutes.** - There are also certain differences between **plasma and interstitial fluid** that occur as a result of the exclusion of **protein** from interstitial fluid. #### Volume and Composition of Body Fluids - **Plasma** is the fluid circulating in the blood vessels; is smaller of the two ECF - **Interstitial fluid** is the fluid that actually bathes the cells - an **ultrafiltrate** of plasma, formed by filtration processes across the capillary wall, containing **little, if any, protein** ( the capillary wall is virtually impermeable to large molecules such as plasma proteins). - Plasma and interstitial fluid are separated by the capillary wall. #### Differences in Extracellular and Intracellular Fluids - ECF is in **constant motion** throughout the body - is transported rapidly in the circulating blood and then mixed between the blood and tissue fluids by diffusion through the capillary walls. - The **ECF** contains ions and nutrients needed by the cells to maintain life : - - the **Ca ^2+^** concentration in ECF is higher by approximately four orders of magnitude than in ICF - plus nutrients for the cells, such as **oxygen, glucose, fatty acids, and amino acids** - **carbon dioxide** that is being transported from the cells to the lungs to be excreted - **cellular waste** products that are being transported to the kidneys for excretion. #### Differences in Extracellular and Intracellular Fluids - The **ICF** contains: - **high** potassium **(K ^+^** ) and magnesium (**Mg ^2+^** ), and the balancing anions are **proteins** and - a very **low** concentration of ionized **Ca ^2+^** - is more acidic (has a **lower pH**) - Special **mechanisms for transporting ions** through the cell membranes maintain the ion concentration differences between the extracellular and intracellular fluids. #### Differences in Extracellular and Intracellular Fluids #### Electroneutrality of Body Fluid Compartments - Each body fluid compartment is governed by the **principle of macroscopic electroneutrality -** each compartment must have the same concentration, in mEq/L, of positive charges **(cations)** as of negative charges **(anions).** - Even when there is a potential difference across the cell membrane, charge balance still is maintained in the bulk (macroscopic) solutions. Homeostasis =========== ###### Maintenance of a Nearly Constant Internal Environment - - the lungs - oxygen to the ECF , - the kidneys - constant ion concentrations, - the gastrointestinal system - nutrients. Homeostasis ================================= ##### Extracellular Fluid Transport - Blood Circulatory System - Extracellular fluid is transported through the body in two stages. - - Homeostasis -Blood Circulatory System ===================================== - ##### Extracellular Fluid Transport - once each minute when the body is at rest - as many as six times each minute when a person is extremely active. Homeostasis- Blood Circulatory System ===================================== - ###### Extracellular Fluid Transport - As blood passes through the blood capillaries, continuous exchange of extracellular fluid occurs between the plasma in the blood and the interstitial fluid that fills the intercellular spaces. - The walls of the capillaries are permeable to most molecules in the plasma of the blood (exception of plasma proteins - too large). - Large amounts of fluid and its dissolved constituents *diffuse* back and forth between the blood and the tissue spaces. Homeostasis -Blood Circulatory System ===================================== - ###### Extracellular Fluid Transport - This process of **diffusion** is caused by kinetic motion of the molecules. - The fluid and dissolved molecules are continually moving and bouncing in all directions within the plasma and the fluid in the intercellular spaces, as well as through the capillary pores. - Thus, the extracellular fluid everywhere in the body is continually being mixed -- **ECF homogeneity** throughout the body. Homeostasis - Origin of Nutrients ================================= ###### Extracellular Fluid Transport -Respiratory System - - The membrane between the alveoli and the pulmonary capillaries, the *alveolar membrane,* is only 0.4 to 2.0 micrometers thick, and oxygen rapidly diffuses by molecular motion through this membrane into the blood. Homeostasis - Origin of Nutrients ================================= ##### Extracellular Fluid Transport - - A large portion of the blood pumped by the heart also passes through the walls of the gastrointestinal tract. Homeostasis - Origin of Nutrients ================================= ##### Extracellular Fluid Transport - - Here different dissolved nutrients, including *carbohydrates, fatty acids,* and *amino acids,* are absorbed from the ingested food into the extracellular fluid of the blood. #### Homeostasis -- Metabolism and removal of end products ##### Extracellular Fluid Transport -- Liver -- - Some of the absorbed substances from the from the gastrointestinal tract can't be used in their primary form by the cells. - The liver changes their chemical compositions to more usable forms. - - The liver also eliminates certain waste products produced in the body and toxic substances that are ingested. Homeostasis - Removal of Metabolic End Products =============================================== ##### Extracellular Fluid Transport - Carbon Dioxide - Carbon dioxide is the most abundant of all the - Is released from the blood into the lung alveoli; the respiratory movement of air into and out of the lungs carries the carbon dioxide to the atmosphere. Homeostasis - Removal of Metabolic End Products ====================================================================== - - then **reabsorbing** into the blood the substances needed by the body (as glucose, amino acids, water, and many of the ions) - ###### secretion - **excretion** - especially metabolic waste products such as *urea*, drugs, toxins , pass through the renal tubules into the urine. Homeostasis - Removal of Metabolic End Products ====================================================================== Homeostasis - Removal of Metabolic End Products =============================================== ###### Tegumentary System - The skin and its various appendages (including the hair, nails, glands, and other structures) are important for: - - - mechanical and thermal isolation (cover, cushion, and protect the deeper tissues and organs). Homeostasis - Removal of Metabolic End Products =============================================== ###### Gastrointestinal Tract. - Undigested material that enters the gastrointestinal tract and some waste products of metabolism are eliminated in the feces. ###### Liver. - Among the functions of the liver is the detoxification or removal of many drugs and - The liver secretes many of these wastes into the bile to be eventually eliminated in the feces. Homeostasis -Control Systems of the Body ============================================================== - The human body has thousands of control systems. - Some of the most intricate of these systems **are the genetic control systems** - operate in all cells to help control intracellular and extracellular functions. - The other **two major systems** evolved to communicate and coordinate body functions: - 1\. The **nervous system** integrates tissue functions by a network of cells and cell processes. - 2\. The **endocrine system** integrates organ function via chemicals that are secreted from endocrine tissues or "glands" into the extracellular fluid - hormones. Homeostasis - Regulation of Body Functions ------------------------------------------ - the *sensory **input portion** -* detect the state of the body or the state of the surroundings (receptors -- eye, ear, skin...) - the *central nervous system* (or ***integrative portion*** ) - the brain and spinal cord. The brain can store information, generate thoughts, create ambition, and determine reactions that the body performs in response to the sensations. - Homeostasis - Regulation of Body Functions ------------------------------------------ ###### The nervous system - An important segment of the nervous system is called the *autonomic system.* - It operates at a **subconscious level** and controls many functions of the internal organs: - the level of pumping activity by the heart, - movements of the gastrointestinal tract, - secretion by many of the body\'s glands. ##### The autonomous nervous system - the sympathetic nervous system (SNS) - the parasympathetic nervous system Homeostasis - Regulation of Body Functions ------------------------------------------ ###### Hormone Systems - - - - - - - Homeostasis - Regulation of Body Functions ================================================================ ##### Hormone Systems - ***Endocrine hormones*** are released by glands or specialized cells into the circulating blood and influence the function of target cells (recognized by specific high-affinity receptors) at another location in the body. - ***Neuroendocrine hormones*** are secreted by neurons into the circulating blood and influence the function of target cells at another location in the body. - ***Paracrines*** are secreted by cells into the extracellular fluid and affect neighboring target cells - ***Autocrines*** are secreted by cells into the extracellular fluid and affect the function of the Homeostasis - Regulation of Body Functions ========================================== - pituitary gland , - thyroid gland , - parathyroid glands , - adrenal glands, - pancreas, - ovary, - testis. Homeostasis - Regulation of Body Functions ================================================================  Homeostasis - Regulation of Body Functions ========================================== - ###### Hormone and Nervous Systems - The **nervous system** regulates many **muscular and secretory activities** of the body, - The **hormonal** system regulates many **metabolic functions**. - The nervous and hormonal systems normally work together in a coordinated manner to control essentially all of the organ systems of the body. Homeostasis - Control Mechanism ----------------------------------------------------- - Examples of tightly controlled parameters that affect nearly the whole body are arterial pressure and blood volume. - At the level of the milieu intérieur, tightly regulated parameters include: - body core temperature - plasma levels of oxygen, - plasma glucose, - potassium (K ^+^ ), sodium (Na ^+^), calcium (Ca ^2+^ ) and hydrogen ions (H ^+^ ). Homeostasis =========== ##### Constants - - normal range (**reference range**) -- the interval between which \~95% of values of a reference population fall into -- mean ± 2 SD - 5% of the "normal" population have test results outside the reference range - some parameters vary between a very narrow range (e. g. pH, Na concentration), others a larger range (e. g. blood glucose level) Homeostasis ================================= ##### Constants Homeostasis -Control Mechanism ---------------------------------------------------- Homeostasis -Control Mechanism ------------------------------ ###### The negative-feedback mechanism is: - one of the most common themes in physiology - responsible for homeostasis (prevents large deviations from the normal value) - a process in which the end results will inhibit the initial action from continuing to occur. Homeostasis -Control Mechanism ---------------------------------------------------- - the system must be able **to sense** the vital parameter (e.g., glucose level) or something related to it. - - - the output signal must be able to activate **an effector mechanism** (e.g., glucose uptake and metabolism) that opposes the input signal and thereby brings the vital parameter closer to the set-point (e.g., decrease of blood glucose levels back to normal). Homeostasis -Control Mechanism ==============================  Homeostasis -Control Systems ============================ ###### Positive feedback - is a process in which the end products of an action cause more of that action to occur in a - it amplifies the original action. - leads to instability rather than stability and, in some cases, can cause death. - it is contrasted with negative **feedback**. - Blood clotting - Childbirth - Ovulation Homeostasis -Control Systems ============================ ###### Positive feedback   Homeostasis -Control Mechanism Example ====================================== ###### Regulation of Oxygen Concentrations in the Extracellular Fluid - Because **oxygen** is one of the major substances required for chemical reactions in the cells - This mechanism depends essentially on the chemical characteristics of *hemoglobin,* which is present in all red blood cells. Homeostasis -Control Mechanism Example ============================================================ ###### Regulation of Oxygen Concentrations in the Extracellular Fluid - Hemoglobin combines with oxygen as the blood passes through the lungs. - In the the tissue capillaries, hemoglobin, - does not release oxygen into the tissue fluid if too much oxygen is already there. - - This regulation is called the ***oxygen-buffering function of hemoglobin.*** Homeostasis -Control Mechanism Example ====================================== ###### Regulation of Carbon Dioxide Concentrations in - Carbon dioxide is a major end product of the oxidative reactions in cells. - A higher than normal carbon dioxide concentration in the blood *excites the respiratory center,* causing a person to breathe rapidly and deeply. - This deep, rapid breathing removes excess carbon dioxide from the blood and tissue fluids. Homeostasis -Control Systems ---------------------------- ###### Regulation of Arterial Blood Pressure. - Several systems contribute to the regulation of arterial blood pressure. - The *baroreceptor system -* a **rapidly acting** control mechanism. - Nerve receptors called *baroreceptors* (stimulated by stretch of the arterial wall) -- arch of the aorta and bifurcation of the carotid arteries. ### Homeostasis -Control Systems - ###### Regulation of Arterial Blood Pressure. ### Homeostasis -Control Systems ###### Regulation of Arterial Blood Pressure. - High BP - the baroreceptors send barrages of nerve impulses to the medulla of the brain→ inhibit the *vasomotor center* → decreases the number of impulses transmitted from the vasomotor center through the sympathetic nervous system to the heart and blood vessels → diminished pumping activity by the heart and also dilation of the peripheral blood vessels → decrease the arterial pressure, moving it back toward normal. - Low BP - relaxes the stretch receptors, allowing the vasomotor center to become more Homeostasis ================================= ##### Disturbed homeostasis - in the presence of disease, homeostatic mechanisms continue to operate and maintain vital functions through multiple compensations. - In many cases, these compensations mechanism return the body functions to normal: - In other cases, these compensations may themselves lead to major deviations of the body\'s functions from the normal range, making it difficult to distinguish the primary cause of the disease from the compensatory responses. ##### Disturbed homeostasis - Thus, homeostatic compensations that ensue after injury, disease, or major environmental challenges to the body may represent a "trade-off" that - is necessary to maintain vital body functions - but, in the long term, may contribute to additional abnormalities of body function. - The discipline of ***pathophysiology*** -- mechanisms that alter the various physiological