Homeostasis Flashcards
Define homeostasis
Process by which cells, tissues and organisms maintain the status quo/ maintain internal conditions despite changes.
What is a negative feedback loop?
Loop where internal conditions are maintain, by returning high or lows levels back to normal.
Give an example of a negative feedback loop?
Maintaining blood glucose levels, maintaining body temperature etc.
What is a positive feedback loop?
Where the original stimulus is exaggerated/ emphasised.
Give an example of a positive feedback loop?
Clotting cascade, Ferguson reflex (baby pushing against cervix)
When does negative feedback loop stop?
When the effector ceases.
When does positive feedback loop stop?
When the initiator/stimulus ends.
What is the normal range of core body temperature?
37 plus/minus 0.5
At what temperature is someone experiencing mild hypothermia?
32.1-35
At what temperature is someone experiencing severe hypothermia?
28-32
At what temperature is someone experiencing a fever?
38-40
At what temperature is someone experiencing a heat stroke/heat exhaustion?
40
What does the body do when you are too hot?
Vasodilation, sweating, pilorelaxation, stretching our
What does the body do when you are too cold?
Vasoconstriction, shivering, piloerection, curling up
What is the normal ph range for the human body?
7.35-7.45
What are the major organs for maintaining acid base balance?
Lungs-respiratory balance and kidneys-metabolic balance
What is the sensor for temperature in the thermoregulatory system?
Nerve cells in the skin and brain
What is the control centre in the thermoregulatory system?
Hypothalamus
Name the buffering systems in the human body?
Carbonic acid, sodium phosphate buffering system.
How much water is in a 70kg man?
70 x 0.6= 42kg
How much water is in females?
50% water in normal females- more fat
How much water is in an infant?
70% - little fat
What is osmolality?
Concentration of a solution expressed as the total number of solute particles per kilogram.
Define isotonic?
Same water potential on both sides of the plasma membrane
Define hypotonic?
Higher water potential outside the cell
Define hypertonic?
Lower water potential outside the cell.
What happens if there is not enough water?
Cells absorb water from interstitial space, then from one another, tissues die, then organs begin to die (end stage organ failure).
What happens if there is too much water?
Osmotic pressure high, cells swell, enzyme and protein stop working and cells swell until they burst.
What is oedema?
Fluid retention, peripheral oedema- swollen ankles
What is hydrostatic pressure?
Force exerted by the fluid on the vessel wall.
What is osmotic pressure?
Force applied by the solute/colloid to prevent osmotic movement across the membrane
What causes oedema?
Hydrostatic pressure is greater than osmotic pressure, lymph blocked or damaged, presence of plasma proteins in interstitial space.
Where do body fluids accumulate?
28kg -intracellular water
14kg -extracellular water (11kg- interstitial water and 3kg plasma)
What is a standard mans circulating blood volume?
3litres plasma + 2litres red blood cells = 5 litres
What is the condition where pH is too low?
Acidosis
What are symptoms of acidosis?
Seizures, headaches, shortness of breath, high HR, vomiting, coma
What is the condition where pH levels are too high?
Alkalosis
What are the two main causes of acidosis?
Metabolic acidosis (increased production of metabolic acids)
Respiratory acidosis (build up of carbon dioxide due to hypo ventilation)
