L1 Water Balance and Homeostasis PDF

M D Hello Everyone Hope You Are Having A Wonderful Physiological Day ☺☺☺ ARE YOU READY ? LET'S GET STARTED! Homeostasis and Water Balance Sem 1 Mahmoud El Tohamy M.D, Ph.D. Lecturer of Medical Physiology Faculty of Medicine, MNU Dr.m.eltohamy@...

M D Hello Everyone Hope You Are Having A Wonderful Physiological Day ☺☺☺ ARE YOU READY ? LET'S GET STARTED! Homeostasis and Water Balance Sem 1 Mahmoud El Tohamy M.D, Ph.D. Lecturer of Medical Physiology Faculty of Medicine, MNU [email protected] The human body consists of trillions of cells all working together for the maintenance of the entire organism. While cells may perform very different functions, all the cells are quite similar in their metabolic requirements. Maintaining a constant internal environment with all that the cells need to survive (oxygen, glucose, Extracellular fluid mineral ions, waste removal, (ECF) and so forth) is necessary for the well-being of individual cells and the well-being of the entire body. 5 The concept of homeostasis was first articulated by the French scientist Claude Bernard (1813-1878) in his studies of the maintenance of stability in the "milieu interior“. The term itself was coined by American physiologist Walter Cannon, author of The Wisdom of the Body (1932). The word comes from the Greek homoios (same, like, resembling) and stasis (to stand, posture)  Homeostasis Def Are the mechanisms that keep the internal environment ??? Constant. Significance: This is very important as the cells lie in the internal environment →keeps normal functions of cells as: 1. Body water 2. Body temperature 3. Arterial blood Pressure 4. Composition of ECF as regard, Ions, pH and glucose 7  Homeostasis Range: There is a narrow range of change in homeostasis; more than this range the cell function is greatly affected Body systems: All body systems performs their functions to maintain homeostasis Body functions regulated by; A) Nervous mechanism by nervous system (rapid) B) Endocrine system: by hormones (slow) 8  Feedback Mechanisms Def Feedback mechanisms are the mechanisms that keep the system constant Types They are 2 types : A) Negative feedback: the response inhibits the stimulus. B) Positive feedback: the response increases the stimulus. 9  1. Negative Feedback These mechanisms keep the system constant, and the response inhibits the stimulus. a) ↑ CO2 → hyperventilation → washout of excess CO2 → ↓ CO2 to normal. b) ↑ blood glucose→↑ insulin secretion → ↑ glucose utilization → ↓ glucose level to normal. c)↑ arterial blood pressure (ABP) → reflex vasodilatation and ↓ heart rate → ↓ arterial blood pressure back to normal. 10 11 12  2. Positive Feedback These mechanisms disturb the system and the response increases the stimulus Examples a) Death cycles→ fatal cycles leads to death 13  2. Positive Feedback These mechanisms disturb the system and the response increases the stimulus Examples a) Death cycles→ fatal cycles leads to death 14  2. Positive Feedback b) Some positive feedback cycles are useful e.g., during labor: Cervical dilatation→↑ es the uterine contractions→ descent of baby → more cervical dilatation → more uterine contractions → more descent of baby, till complete labor. 15  Body water Total body water constitutes: In adult male ➔ 60% of the total body weight. In adult female ➔ 50% because their bodies contain much fat ➔ decreases the percentage of water.  Body water Total body water constitutes: Children ➔ contain more water (70%) than adults, so water loss ➔ rapid dehydration. In old age ➔ the water content is decreased.  Functions of body water 1-It is required for all chemical reactions inside the body. 2-It acts as powerful solvent that dissolve various substances. 3-It is important in regulation of body temperature through sweating. 4-It moistens tissues such as mouth, eyes and nose.  Functions of body water 5-Helps digestion. 6-Helps absorption. 7-Filteration at the level of the capillaries. 8-Excretion in gastrointestinal tract (GIT) and kidney. 9-Refractive medium in the eye.  Water Balance Def Body water is kept constant by adjusting water input and water output Insensible water loss (about 700ml) Sweating (100 ml) Endogenous water 200 ml/day Feces (about 100ml) Exogenous water Urine (about 1500 2200 ml/day ml) Water Input Water output 2400 ml/day 2400 ml/day 20  Control of Water Input ↓ blood volume (Hypovolaemia) Thirst Center Angiotensin II Thirst sensation ↑ plasma osmolarity (Hypertonicity) Increased water intake ↓ plasma osmolarity ↑ blood volume 21  Control of Water Output ↓ blood volume (Hypovolaemia) Posterior pituitary ADH secretion Angiotensin II ↑ plasma osmolarity (Hypertonicity) ↓ plasma osmolarity ↑ blood volume ↓ Urine volume 22 Any Questions ?? Thank You