Introduction to physiology & control system of the body Dr. Aiad Siam Al-Azhar University 1st year

Definition Greek word Physis = nature, Logos = word Is the study of the mechanical, physical & biochemical functions of living organisms

The goal of physiology To explain the physical & chemical factors that are responsible for the origin, development and progression of life

Fields of Physiology Traditionally: 1- plant physiology 2- animal physiology Include: viral, bacterial, cellular, human

Human physiology Explain the specific characteristics & mechanisms of the human body that make it a living being

Cells as the living units of the body The basic living unit of the body is the cell Each organ is an aggregate of many different cells held together Each type of cells is specially adapted to perform one or few particular function Although the cells of the body often differ markedly from one another, all of them have certain basic characteristics

Subdivisions of Human Physiology Myophysiology Respiratory physiology Cardiovascular physiology Renal physiology Reproductive physiology Neurophysiology Endocrinology Neuroendocrinology Cell physiology Comparative physiology Exercise physiology

The internal environment 60% of the body weight is water 60% Intracellular, 40% extra-cellular ECF has ions & nutrients needed by the cells to maintain cell life, thus, all cells live in essentially the same environment (ECF) So, ECF is called Internal Environment

Homeostasis Maintenance of nearly constant conditions in the internal environment All organs & tissues of the body perform functions to maintain these constant condition Eg: lung, kidney, GIT

Systems contributed in ECF transport Cardiovascular system: ECF transported through the body in 2stages: 1- movement of blood through the body in the blood vessels 2- movement of fluid between the blood capillaries & IC spaces between the tissue cells

Cardiovascular system

Systems contributed in nutrients of ECF 1- Respiratory system: Supply O2 to cells, which picked up by blood in the alveoli 2- GIT : Supply carbohydrate, aminoacids, fatty acids, which is absorbed by GIT then picked up by blood 3- liver & other organs: - Not all absorbed substances can be used in their absorbed form by the cells - Liver changes the chemical compositions of many substances to be usable 4- Musculoskeletal system: Move the body to obtain food

Systems contributed in removal of metabolic product 1- Respiratory system: - CO2 released from blood into alveoli - CO2 is the most abundant of all the end products of metabolism 2- Kidneys: Remove other waste products when the blood pass through the kidney

Systems contributed in regulation of body functions I 1- Nervous system: composed of 3 major portions: a- sensory input: - Detect the state of the body or the surroundings - Eg: skin, ear, eye b- CNS: brain + spinal cord Store information, generate thought, determine rxns that the body performs in response to the sensations c- Motor output: Carry out ones desires Autonomic NS: - Operate at a subconscious level & controls many functions of the internal organs - Egs: heart rate, GIT movement, glands secretion

Systems contributed in regulation of body functions II 2- Hormonal system: Endocrine glands secrete chemical substances called hormones Regulate cellular function egs: insulin, thyroid, PTH NS mainly regulates muscular & secretory activities of the body, Hormonal system regulate many metabolic functions

Control systems of the body The most important control system is genetic control system 2 types of control systems: 1- within organs: control functions of individual parts of the organs 2- through out the entire body: control the interrelation between organs Egs: a- respiratory system + NS regulate [Co2] b- liver & pancreas regulate [glucose]

Egs of control mechanisms Regulation of [O2] & [Co2] in ECF: Regulation of arterial BP (baroreceptor system)

Characteristics of control systems Feed-back mechanism 1- negative feedback 2- positive feedback Feed-forward mechanism

Negative feedback Most control systems have such a characteristics Def: serious of changes that return the factor toward a certain mean value, to maintain homeostasis. If some factors become excessive or deficient Egs: 1- ↑ or ↓ Co2 expiration according to Co2 level in ECF 2- BP regulation

Gain of the negative feed back Def: the degree of effectiveness with which a control system maintains constant conditions Gain= Correction/ error

Positive feed back A cycle which initiate the stimulus again causes more of the same effect Egs: bleeding→ heart weakness Positive feed back can be overcome by the negative feed back Useful positive feedback: 1- blood clotting 2- child birth 3- action potential In each useful positive feed back, it is a part of an overall negative feed back Eg: positive feed back clotting process is a negative feed back process for maintenance of normal blood volume

Feed-forward mechanism More complex type of control systems Eg: for rapid movements, there is no time for nerve signals to travel from the peripheral parts to the brain and vice versa Brain use a principle called feed-forward control where nerve signals from moving parts appraise the brain whether the movement is performed correctly If further correction is needed, this is done again which is called Adaptive control (delayed negative feedback)