Homeostasis Flashcards
What is the meaning of Homeostasis ?
Homeo = sameness and stasis = standing still
What needs to be maintained constantly in an internal environment?
Concentration of oxygen, carbon dioxide, salt and other electrolytes
• Concentration of nutrients, waste products
• pH
• Temperature
• Volume and pressure
What are the example of negative feed and back and positive feedback ? (Explain)
Negative feedback
- temperature
- blood glucose
Positive feedback loops
- regulation of clotting (platelets and chemokines)
- labour (oxytocin , hypothalamus, pituitary gland)
What happens when you go above normal for body temp range ?
Fever (above 37.5) - stomach, leg and arm cramps and pale sweaty skin Heat stroke (40) - flushed dry skin, strong bounding pulse, hot to touch Heat exhaustion (46) - seizures, unconscious, restless and dizzy
What happens if core body temperature range ?
Mild hypothermia (below 36.5) shivering, fatigue, confusion and muscle stiffness
Severe hypothermia (32)- very slow and weak pulse(find hard to pump blood around) , severe reduction is response, stop shivering, rigid muscles
No vital signs (below 27/28) - unconscious, dilated pupil, pulse undetectable
Appears dead
Not dead until warm and dead so warm up then check pulse
Normal pH in blood and plasma ?
7.35-7.45
What are the 2 major organs responsible for maintaining acid base balance ?
The lungs-respiratory balance
The kidneys-metabolic balance
What is the normal gastric pH and how is the stomach protected ?
1.5-3.5
Stomach is protected by a layer of mucous, if you lose the protective mucous layer this can lead to gastric ulceration and perforation.
How is carbon dioxide circulated around the body?
Co2 binds to haemoglobin of RBC
Co2 converted to bicarbonate by carbonic anhydrase in the RBC
Bicarbonate can leave RBC and travel in blood
Another carbonic anhydrase can convert bicarbonate back to Co2, the partial pressure of CO2 is low and can diffuse across the membrane and out into the external space
What buffering system do other cells use and how does it work
Other cells use a sodium phosphate buffering system to regulate intracellular pH and transport systems.
Protons can move other molecules backwards and forwards across the cell membrane
Sodium and phosphate as ion can regulate and the amount of water inside and outside the cell.
Clinical relevance of buffering systems?
Antacids antacids neutralise acids (slightly alkaline e.g. calcium or magnesium, acts to neutralise proton present in gastric juice)
solubility is a factor
Aluminium hydroxide is mildly alkaline, but insoluble so good acid neutraliser.
How can we measure blood pH?
Arterial blood gas, we take this as it has more oxygen, than Co2
It includes information this includes
-pH of blood
-Electrolyte
On the blood gas there should be all the patients details and name and their temp
What happens to cell tissues and organs when there is too much or too little water?
- Not enough – dehydration and cell, tissue, organism death
- Too much – toxicity, metabolic failure and cell, tissue, organism death
Approximately 2.5 litres of fluid
Total body water in male, women and babies and why is it different ?
Normal - M60, F50, I70
Lean- M70,F60,I80
Obese - M50,F42,I60
Age : as we get older, we lay down more fat and we displace some of the water , so the older you are the lower the amount of total body water
Females lay more fat down than men and have less body water
What is Isotonic, Hypotonic and Hypertonic ?
ISO = the same amount of water on both sides of the plasma membrane
HYPO= less water inside - swelling/inflate and burst
HYPER= more water inside - cell shrinks
What happens when not enough water?
Cells and tissues initially absorb water from interstitial space
Then from each other (sacrifice of cells)
Then as tissues die, water absorbed from organs
Then as organs dies, water absorbed from brain, liver and lastly kidney and heart
What causes dehydration/water loss
Hot humid water, excessive sweating , vomiting and Diarrhoea and burns lead to water loss.
Water loss leads to decrease in plasma volume
Water loss leads to increase in osmolality -which is the measure of the concentration of electrolytes and material around cells increases
ADH increases , produces by pituitary gland and acts to switch off kidney
Oliguria - switching off kidneys, olig means less and uria means urea production
What happens if there is too much water?
Osmotic pressure high
Cells absorb water and swell
Enzyme and proteins stop working
Cells keep swelling until they burst
Patients need isotonic IV
What is osmolality ?
Number of solute particles per Kg
What is the measurement of osmotic pressure in tissues
Plasm
Urine
