Lecture 1- Homeostasis Flashcards
Define homeostasis
- homeo = sameness , stasis = standing still
What is an example of negative feedback loop?
- blood glucose concentration - for example insulin secreting cells detect high blood glucose conc
What is an example of a positive feedback loop?
Blood clotting :
1) tear in a blood vessel which activates platelets at the site of the wound which release chemicals.
2) these chemicals attract more platelets at the site of the wound.
3) clotting occurs - after clot seals the break positive feedback ends
What is our core body temp?
37+-0.5
At what temperature would someone would have a fever?
38 degrees.
What are the symptoms of a fever ?
- pale , sweaty, cramps in limbs and stomach
What temperature would someone be considered to have heat stroke ?
40 degrees +
What are the symptoms of a heat stroke ?
- hot to touch of the skin
- bounding pulse
What temperature would someone be considered to have heat exhaustion?
46 degrees
What are symptoms of heat exhaustion?
- confusion , seizures , unconsciousness
At what degrees Would someone be considered mild hypothermic ?
Below 36.5 degrees
What are the symptoms for mild hypothermia ?
- shivering
Confusion
Slurred speech
What degrees is someone considered severely hypothermic ?
32 degrees and be,ow
What are the symptoms of someone severely hypothermic ?
- shivering stops , muscle become rigid , weak pulse
What is the normal blood Ph ?
7.35-7.45
Blood in the …. is more alkali..
Arteries (7.45)
What helps to regulate blood Ph ?
- kidney metabolic balance and lungs respiratory balance.
What happens when someone has a blood Ph in a range of 7-7.35?
Acidosis - which is characterised by headaches , coma , tremors
What could possibly be the cause of acidosis ?
- hyperventilating which increases co2 concentration.
And build up of lactic acid or poor excretion by the kidneys
What is alkalosis ?
- when blood ph range is between 7.45-7.8
What are two ways to try and treat acidosis ?
1) mechanical ventilation
2) bicarbonate solution infusion
What is an explanation of heart burns ?
Vomiting - which causes gastric juice which is acidic from the stomach to reach the pharynx/ oesophagus.
- pharynx/ oseophagus does not have goblet cells so acid reflux damages epithelium which causes the heart burn.
How to treat heart burns a?
- antacids
- aluminium hydroxide is the best one to use as it has fewer side effects as it is insoluble.
t what ph can human tissue survive at ?
6.8-7.8
What is % of a 70kg man is water?
60%
What proportion of fluids makes up the ICF and ECF?
ICF - 2/3
ECF : 1/3
What is the promotion of fluid that makes up IF and plasma from ECF?
1/4 plasma
IF : 3/4
What are the differences between dehydration and water toxicity?
Water toxicity is when you drink too much water. This can lead to hyponatraemia where the Serum Na+ is below/equal to 135 mol/L.
This is where water from outside cells enters cells causing them to swell and burst.
In the brain this could lead to brain oedema which causes seizures , brain damage , coma and even death.
Dehydration
- tissue and cells become dehydrated where the cells give up their water to the intertestial fluid where the cells shrink.
- this can cause thirsty ness , dry mouth , low urine output volume.
This can lead to dizziness , confusion , weight loss.
As a result of dehydration , what happens when there is a reduction in blood plasma volume ?
- this could lead to an increased haematocrit , which in turns increases blood viscosity where as a result increases workload of the heart because of the increased viscosity which again may even cause blood clots because the blood is stickier.
what is the main cause of oedema ?
- when water is consumed too quickly or there is a blockage in urine production , body fluids become too diluted and there is a reduction in sodium concentration in the ECF which causes a shift in osmotic pressure.
Define Pyrexia
Raised body temperature
Is pyrexiananprotective or destructive instinct?
Protective? When there is an infection chemicals called pyrogens are released into the bloodstream - even by pathogens sometimes. The pyrogens bind to receptors in the hypothalamus which causes an increase in temperature.
What is and aNd what causes a rigor?
- this occurs at a very high fever where an infection is detected.
- often characterised by exaggerated shivering.
What is
A febrile seizure?
- occurs in a child.
- child loses consciousness and both their arms and legs shake uncontrollably.
- happens at fevers above 38 degrees.
Define isotonic
Equal concentrations of solutes inside and outside the cell.
Define hypotonic
Lower water potential inside the cell than outside the cell so water enters a cell from surrounding solution causing lysis of a cell.
Definehypertonic solution
Water potential inside cell is greater than outside cell so water moves out of the cell causing cell to become flaccid
What is another cause of oedema in relation to hydrostatic pressure ?
- raised hydrostatic pressure in the capillary which causes more fluid to enter the intertestial fluid. This can result from congestion eg heart failure. Or vasodilation during inflammation.
What is another cause of oedema in relation go oncotic pressure ?
- decreases omcotic pressure in the capillary which could be due to liver disease as less albumin is produced.
