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Module: BIOM – 1010

Lecturer: Dr Bonab

Date: 14/10/16

Homeostasis: Acid-Base Balance
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Homeostasis is the condition of equilibrium in the body’s internal environment
 This is done through the constant interactions between the body’s regulatory systems
 In response to a changing condition, the body can shift along points in a narrow range that is
compatible with maintaining life
 Glucose in the blood, for example, must be kept between 70 and 100mg per 100ml of blood

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Water is a very important component when maintaining homeostasis
 It can stabilise your body temperature
 Water can absorb large amounts of heat and remain at a stable temperature
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 Fluid within a cell is termed intracellular fluid (40% of body weight / 25L)
 Fluid outside is termed extracellular fluid (20% of body weight / 12L)
 The fluid that fills the gaps between cells is known as interstitial fluid
 The ECF within blood vessels is termed plasma
 The ECF within lymphatic vessels is called lymph
 The ECF in and around the brain and spinal cord is cerebrospinal fluid
 The ECF is joints is synovial fluid
 The ECF in the eyes is called aqueous humour and vitreous body

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Homeostasis in the body is continually being disturbed from the external and internal environments
 External examples include intense heat or a lack of oxygen
 Internal examples include a fall in glucose level etc
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Oxytocin then stimulates
milk ejection

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A solutions acidity or alkalinity is expressed on the pH scale from 1-14
 A pH of 7 means there is one ten-millionth of a mole of hydrogen ions per litre
 This is the midpoint where the concentration of H+ and OH- are the same
 Even though strong acids and bases are continuously being taken into and formed by the body, the
pH of fluids inside and outside stay relatively constant
 H+ ions make a solution acidic
 OH- ions make it basic
 The pH remains constant due to the presence of buffer systems which convert strong acids and
bases into weak ones
 A buffer is a chemical that resists change to pH
 One important buffer system in the body is the carbonic acid-bicarbonate buffer system
 Carbonic acid (H2CO3) can act as a weak acid whereas a bicarbonate ion (HCO3-) can
act as a weak base

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