Homeostasis Body Fluids What is Homeostasis Homeostasis is

Homeostasis & Body Fluids

What is Homeostasis? Homeostasis is the maintenance of a constant environment in the body All living organisms must maintain a stable internal environment in order to function properly

n Body cells work best if they have the correct n Temperature n Water levels n Glucose and electrolyte concentration n Your body has mechanisms to keep the cells in a constant environment.

Factors homeostatically regulated include: Concentration of nutrient molecules n Concentration of water, salt, and other electrolytes n Concentration of waste products n Concentration of O 2 = 100 mm. Hg and CO 2 = 40 mm. Hg n p. H = 7. 35 n Blood volume 4 -6 L and pressure 120/80 n Temperature = 37 o C n

Homeostasis Vs. Illness

Homeostasis

Balancing the Internal and External Environment Cells, the fundamental units of life, exchange nutrients and wastes with their surroundings: The intracellular fluid is “conditioned by”… the interstitial fluid, which is “conditioned by” … the plasma, which is “conditioned by” … the organ systems it passes through. ICF ISF plasma organs internal environment external environment

Homeostatic Control Mechanisms Feedforward - term used for responses made in anticipation of a change n Feedback - refers to responses made after change has been detected n Types of feedback systems n Negative n Positive n

Feedback Mechanisms n Negative feedback n original stimulus reversed n most feedback systems in the body are negative n used for conditions that need frequent adjustment n Positive feedback n original stimulus intensified n seen during normal childbirth

Feedback Mechanisms آﻠﻴﺎﺕ ﺍﻟﺘﻐﺬﻳﺔ ﺍﻟﺮﺟﻌﻴﺔ n Negative feedback ﺍﻟﺘﻐﺬﻳﺔ ﺍﻟﺮﺟﻌﻴﺔ ﺍﻟﺴﺎﻟﺒﺔ n most feedback systems in the body are negative n original stimulus is reversed n used for conditions that need frequent adjustment n n ﺍﻟﺘﻨﻈﻴﻢ ﺍﻟﺮﺟﻌﻲ ﺍﻟﺴﺎﻟﺐ ﻳﺆﺪﻱ ﺇﻟﻰ ﺍﺳﺘﺠﺎﺑﺎﺕ ﺗﺤﺮﻙ ﺍﻟﻤﺘﻐﻴﺮ ﻓﻲ ﺍﺗﺠﺎﻩ ﻣﻀﺎﺩ ﻻﺗﺠﺎﻩ ﺍﻟﺘﻐﻴﺮ ﺍﻟﻤﺒﺪﺋﻲ Positive feedback ﺍﻟﺘﻐﺬﻳﺔ ﺍﻟﺮﺟﻌﻴﺔ ﺍﻟﻤﻮﺟﺒﺔ n original stimulus is intensified n seen during normal childbirth

Negative Feedback Loop

Homeostasis – Negative Feedback n Blood glucose concentrations rise after a sugary meal (the stimulus), the hormone insulin is released and it speeds up the transport of glucose out of the blood and into selected tissues (the response), so blood glucose concentrations decrease (thus decreasing the original stimulus). n Glucose concentration is regulated by 2 main hormones from the pancreas called insulin and glucagon

Glucose homeostasis Insulin Glucagon

Positive Feedback During Childbirth Stretch receptors in walls of uterus send signals to the brain n Brain induces release of hormone (oxytocin) into bloodstream n Uterine smooth muscle contracts more forcefully n More stretch, more hormone, more contraction etc. n Cycle ends with birth of the baby & decrease in stretch n

Maintenance of Homeostasis Nervous system n Controls and coordinates bodily activities that require rapid responses n Detects and initiates reactions to changes in external environment n Endocrine system n Secreting glands of endocrine regulate activities that require duration rather than speed n Controls concentration of nutrients and, by adjusting kidney function, controls internal environment’s volume and electrolyte n

Body Fluids

Body Fluid Compartments n In lean adults, body fluids constitute 55% of female and 60% of male total body mass n Intracellular fluid (ICF) inside cells n About n 2/3 of body fluid Extracellular fluid (ECF) outside cells n Interstitial fluid between cell is of ECF n Plasma in blood is of ECF n Also includes lymph, cerebrospinal fluid, synovial fluid, aqueous humor, pleural, pericardial, and peritoneal fluids

Body Fluid Compartments

One Cell And Its Associated Fluids Copyright 2005 Wadsworth Group, a division of Thomson Learning

Fluid Balance n n n 2 barriers separate ICF, interstitial fluid and plasma n Plasma membrane separates ICF from surrounding interstitial fluid n Blood vessel wall divide interstitial fluid from plasma Body is in fluid balance when required amounts of water and solutes are present and correctly proportioned among compartments An inorganic substance that dissociates into ions in solution is called an electrolyte Water is by far the largest single component of the body making up 45 -75% of total body mass Process of filtration, reabsorption, diffusion, and

Water & Body Fluids n Water Balance -Intake/output = 2. 5 liters/day -Regulated by hypothalamus & kidneys -Carefully controlled by: 1. Intake (liquid, foods, metabolic water) affected by thirst & satiety 2. Output (losses via kidneys, skin, lungs, feces) affected by blood salts, volume & blood pressure

How The Body Regulates Blood Volume

n Sources of Body Water Gain and Loss Fluid balance related to electrolyte balance Kidneys excrete excess water through dilute urine or excess electrolytes through concentrated urine Body can gain water by n Ingestion of liquids and moist foods (2300 m. L/day) n Metabolic synthesis of water during cellular respiration and dehydration synthesis (200 m. L/day) Body loses water through n Kidneys (1500 m. L/day) n Evaporation from skin (600 m. L/day) n Exhalation from lungs (300 m. L/day) n n n

Fluid & Electrolyte Balance Electrolytes – salts that dissolve in water, forming ions n Dissociation of salt in water n Ions n Cations: + charged particles n Anions: - charged particles n Electrolyte solution n Copyright 2005 Wadsworth Group, a division of Thomson Learning

Fluid & Electrolyte Balance n n Electrolytes attract water - affects fluid distribution in the body by osmosis Water follows electrolytes Electrolyte concentration regulated by kidneys Electrolytes & proteins act as buffers to maintain the p. H of body fluids – acid/base balance Copyright 2005 Wadsworth Group, a division of Thomson Learning

Electrolytes in body fluids n Ions form when electrolytes dissolve and dissociate n 4 general functions n Control osmosis of water between body fluid compartments n Help maintain the acid-base balance