Homeostasis Flashcards
Define the term homeostasis.
Process describing the maintenance of the internal environment of the body.
Why is it important to maintain an internal environment?
The body needs to be kept at a constant temperature to ensure all chemical reactions can take place without being disrupted.
If the internal environment changed, we would die.
What is the optimum temperature for the body?
37 degrees.
When does diabetes occur?
When the body can no longer maintain it’s optimal blood glucose concentration.
Why does homeostasis require integration of organ systems?
To maintain balance and optimal conditions for cells to function.
How can homeostasis be maintained?
If the input and output are balanced.
Name three everyday challenges to internal environment.
External temperature
Cellular access to nutrients
Exercise
What happens if the body fails to compensate for loss of homeostasis?
Disease/illness/death.
Name the three mechanisms used to maintain homeostasis.
Negative feedback
Positive feedback
Feed-forward
Many diseases are associated w the disfunction/loss of ???
Negative feedback systems.
What does a negative feedback mechanism do?
Triggers a response.
Why is it known as a ‘negative’ feedback mechanism?
The condition that triggers the response has to be removed/ ‘switched off’.
The size of response regarding negative feedback mechanisms is equal to?
The size of disturbance,
While negative feedback restores the regulated condition after initial disturbance, what can’t it do?
Prevent it from happening.
What do feed-forward mechanisms do?
The anticipate change and activate a response earlier to try and reduce any damage.
What do positive feedback mechanisms do?
They set off a chain reaction that often leads to greater disturbance.
Which area are positive feedback mechanisms common in?
Pathology
Give one example of a positive feedback mechanism.
Active potential.
In general, what is the aim of medicine?
To restore homeostasis when disturbed by illness/disease.
How is water balance controlled?
Homeostatically.
What % of your body is made up of water?
Approx 60-70%.
How much water does a human gain in a day? (approx.)
2.5 litres
How do humans lose water?
Sweating, breathing, excretion.
Name a process which maintains to input of water balance.
Thirst mechanisms.
What helps to maintain the output of water.
Regulated by the kidneys.
Why may there be a conflict between maintaining internal water balance and temperature?
Sweating is used to maintain internal body temperature but will impact water balance.
Name the three compartments in which water is a component of.
- Intracellular fluid
- Interstitial fluid (extracellular fluid)
- Plasma (extracellular fluid)
What is meant by the term ‘intracellular fluid’?
Fluid found inside cells.
What is meant by the term ‘interstitial fluid’?
Fluid found between cells.
What is meant by the term ‘plasma’?
The fluid component of blood.
What are the two types of extracellular fluid?
Plasma and Interstitial fluid.
Can water move through these compartments?
Yes- water can move freely through all compartments.
What is the movement of water dependant on?
Osmosis.
Why is the composition of the extracellular fluid important?
The survival of the body is dependant on the composition as it must be compatible with it’s own cells.
Although very similar, how does the composition of the plasma and the interstitial fluid differ?
Plasma contains protein- interstitial does not.
Why is the composition of the intracellular fluid and extracellular fluid different?
The cell membrane that separates the two is very fussy about what can be let through it as it is selectively permeable.
What molecule cannot pass through the cell membrane between the plasma and interstitial fluid and why?
Protein because it is too big.
In the average man (70kg), how much will plasma make up approx?
3l
In the average man (70kg), how much will interstitial fluid make up?
11l
In the average man (70kg), how much does extracellular fluid make up in total?
23l
In the average man (70kg), how much does intracellular fluid make up?
28l
While water can pass through all cell membranes and compartments, what cannot?
Ions
Capillary walls are permeable to everything but…?
Plasma protein and blood cells.
How much water does the average body have?
42l
How much more intracellular fluid do humans have compared to extracellular fluid?
Twice as much ICF.
How much of extracellular fluid is interstitial fluid?
Approx. 80%.
How much of extracellular fluid is plasma?
Approx. 20%.
What does hyper mean?
Greater than normal
What does hypo mean?
Less than normal
What does the suffix emia/aemia mean?
In the blood
What does uria mean?
In the urine.
What does glyc mean?
Related to glucose.
What is the only fluid compartment of blood and how can it be accessed?
Plasma and using a blood sample.
Where does the exchange of the nutrients between the plasma and interstitial fluid take place?
In the capillaries.
/What is the equation for the dilution principle?
v=m/c
What part is crucial when determining the test substance?
The nature of the barriers.
How can plasma be measured directly?
Using dye (e.g. Evan’s blue).
What kind of dye can be used to measure plasma?
Evans blue
How can we measure total body water?
Using a loading dose of heavy water.
How is the volume of interstitial fluid measured indirectly?
ISF=ECF-PV
How can the volume of intracellular fluid be measured indirectly?
IF=TBW-ECF
->tbw=total body water
How do you practice the dilution principle?
Inject a substance that will remain in one compartment (takeaway any lost through excretion etc) and calculate the volume of distribution.
-> amount injected / concentration in fluid sample.
What compartments could you inject a substance into and know it will remain in that one place?
Plasma, ECF, TBW
Why does the composition of ICF different from ECF (especially for ions)?
Because the membrane is selectively permeable.
What are the dominant ions in the ICF?
Potassium ions.
What are the dominant ions in the ECF?
Sodium and chloride ions.
Why is the large concentration gradient between ICF and ECF important?
It is fundamental for nerve and muscle function.
All protein in the extracellular fluid is found where?
In the plasma.
If a healthy woman increased her potassium intake by 8.6 when it was originally 7.2, what would it be after a week?
7.2 as if she is healthy, kidneys should get rid of any excess,
If ECF potassium conc. increased beyond the normal range, what would happen?
Less of a conc. gradient so loss of muscle and nerve function.
If healthy, kidneys should remove excess.
Disease/illness may occur if not sorted.
