Introduction to physiology

Physiology is the study of the function of living
organisms & their parts.
-In human physiology, we are concerned with characteristics of the human body that allow us to sense our environment, to move about , to think & communicate , to reproduce & to perform all of the functions that enable us to survive & thrive as living beings .
-The very broad subject of human physiology
includes the functions of molecules & sub cellular components of the human body ; functions of organs such as heart ; organ systems such as the cardiovascular system ; as well as the interaction & communication between the various organ system .

-Homeostasis:-

-Is the maintenance of a stable internal environment.
-So , homeostasis means simply the maintenance of constant conditions in the internal environment of the body.
-Essentially , all organs & tissues of the body perform functions that help to maintain these stable conditions.
-The body can be divided into several major functional system , each of which performs a particular task in maintaining homeostasis as follows:-
-The cardiovascular system transports fluid & solutes , including nutrients & waste products through all parts of the body.
-It keeps the fluids of the internal environment continually mixed by pumping blood through the vascular system .
-As the blood passes through the capillaries , a large portion of its fluid diffuses back & forth into the interstitial fluid that lies between the cells , allowing continuous exchange of substances between the cells & interstitial fluid & between the interstitial fluid & the blood .
-The respiratory system provides oxygen for the body & removes carbon dioxide .
-The gastrointestinal system digest food & absorbs different nutrients , including carbohydrates , fatty acids , & amino acids into the extracellular fluid .
-The kidneys regulate the extracellular fluid composition by controlling excretion of salts , water , & waste products of the chemical reactions of the cells. By controlling body fluid volumes & composition , kidneys also regulate blood volume & blood plasma .
-The nervous system directs the activity of the muscular system , thereby providing locomotion . It also controls the function of many internal organs through the autonomic nervous system , & it allows us to sense our external & internal environments & to be intelligent beings so that we can attain the most advantageous conditions for survival.
-The endocrine glands secrete hormones that control many of the metabolic functions of the cells , such as growth , rate of metabolism & special activities associated with reproduction .
-The musculoskeletal system consists of skeletal muscle , bones , tendons , joints , cartilage & ligaments . This system provides protection of internal organs as well as support & movement of the body.
-The integumentary system , composed mainly of skin , provides protection against injury & defense foreign invaders as well as dehydration of underlying tissue . In addition , the skin acts as an important means of maintaining a constant temperature in the body .
-The immune system also acts as one of the body’s chief defense mechanism , providing protection against foreign invaders , such as bacteria & viruses , that the body is exposed to daily .
-The reproductive system provides for formation of new beings like ourselves ; even this can be considered a homeostatic function for it generates new bodies in which trillion of additional cells can exist in a well regulated internal environment .