Homeostasis Flashcards
What is homeostasis? (with latin meaning)
Latin means similar condition (not identical/STATIC) the body operates within normal ranges/parameter. to stay In a normal state. The body maintains in these similar but not identical ranges.
What does homeostasis require the integration of?
Integration of organ systems:
Nervous, endocrine, musculoskeletal to seek supply and access nutrients.
respiratory for o2,
alimentary to break down food etc,
cardio to transport 02 and nutrients + transport waste
respiratory + alimentary + renal to dispose of waste.
What systems coordinate and control other systems for homeostasis
Nervous and endocrine
Why do these systems (Nervous and endocrine ) need to integrate effectively for homeostasis
in order to maintain an optimum internal environment and ultimately produce energy = homeostasis
What level of regulation is needed for homeostasis?
Cellular level, tissue level and system level.
What is pathology (Latin meaning)
Pathology [latin pathos means suffering]:
body not tolerant of substantial changes in the internal environment (ph, fluid, temperature, hormone concentration). Failure to adequately correct imbalances results in illness and disease or pathology.
Define the study of physiology
how all different systems in the body: Respiratory, Cardiovascular, GI system, work together to maintain a constant internal environment which all processes work optimally
Explain Negative feedback (key mechanism and most common way homeostasis maintained.)
when condition homeostatically disturbed. e.g. temperature disturbed = shiver/sweating. negative feedback = condition that triggered the response is removed or switched off by the homeostatic response. the response is proportional to the disturbance.
Example of negatvie feedback
Negative feedback: hot and working outside –> loses body water by evapouration –> body fluid more concentrated–> internal receptor sense change in internal concentration–> thirst pathway stimulated –> person seeks and drinks water –> water added to body fluid decrease concentration
Characteristics of Negative feedback system
- oscillation around the set point
- restored regulated condition AFTER its initial disturbance, but CANNOT PREVENT it happening. promote response to correct
explain feed-forward (more sophisticated)
can predict change. additional receptors permit system to anticipate change and therefore activate a response earlier
Example of feed-forward system
Kidneys detect body fluid concentration and PRE-EMPTS a state of dehydration. Responds by producing smaller volumes of urine. Kidney reabsorbs more water, higher concentration urine.
Explain Positive feedback mechanisms
Opposite to negative feedback:
(aims to restore disturbance to optimum)
sets off a chain of events leading to greater disturbance.
leads to instability often - common in pathophysiology, rare in normal physiology
Example of positive feedback normal physiology
for normal nerve function ovulation sexual behaviour
In action potential - initial trigger positive Na in nerve-cell take charge with. inside cell positive = depolarisation. makes the membrane more permeable to na+ to take in more positive (cycle builds more reaction) until trigger an action potential.
Example positive feedback in pathophysiology
Blood glucose in diabetes. mean ingested - increased blood glucose –> pancreas doesn’t respond. –> cell doesn’t break down glucose. -> body triggers starvation –> liver produces glucose –> increase blood glucose further.. cycle increase blood glucose.
why is Water balance critical for life?
water balance
the process that is homeostatically controlled.
makes up 60% body weight
maintenance critical as affects the concentration of everything else in the body -
everything in the body is dissolved in an aqueous solution.
average daily waterbalance in adult male in thermoneutral environment (neurtal temperature)
GAIN Drinking 1,200 ml Eating 1000 Metabolic 250 Total = 2550ml LOSS Insensible - 900ml (from skin and lungs) Sweat 50 - (up to 3l hr) Faeces - 100 Urine 1500 (o.5L –> 20L/day) Total ml 24 hour = 2550ml
Which processes are regulated in order to maintain water?
Input - regulated thirst mechanism Output - regulated by kidney function (urinary loss)
What other processes alter water balance but control is not aimed at maintaining water balance?
other processes e.g. sweat temperature regulation, the conflict between water and temp regulation. (kidney problems)
Where is water contained in our body?
3 compartments 1. intracellular fluid - water inside cells 2. interstitial fluid - between cells 3. plasma - fluid component of blood *Fluid not water now as other nutrients are mixed in the water.
What compartment(s) make up extracellular fluid?
Interstitial fluid (ISF)
plasma
Can water move freely between 3 compartments? ISF, ICF, P
YES
through osmosis
The body can survive only as long as the composition of ____ is maintained in a state compatible with the survival of ______ (homeostasis)
The body can survive only as long as the composition of Extracellular fluid (interstitial fluid + Plasma) is maintained in a state compatible with the survival of its individual cells. e.g. liver functions ions on either side of the membrane. depends on water availability.
Explain the 3 compartments and what differs in composition.
plasma contains blood vessels
interstitial fluid found OUTSIDE blood vessels and BETWEEN cells
intracellular fluid - inside cells
composition plasma and interstitial are ALMOST identical - only thing NOT found in the interstitial fluid that IS found in plasma is a PROTEIN and BLOOD CELLS
Composition difference between Intracellular (ICF) and extracellular (ECF) (plasma and interstitial)
Composition difference between interstitial and plasma fluid.
The Intracellular fluid differs from extracellular - cell membrane has a VERY selective membrane to allow what is to cross.
blood vessel wall less fussy (ONLY plasma proteins and blood cells)
Extracellular - plasma and interstitial fluid can move freely between the two but plasma has protein NOT interstitial fluid capillary (blood vessel wall) not permeable to plasma protein but other solutes.
Volume in compartments ICF ISF and P
average 70kg 21 yo man
what ratio of these 3 has body water?
Plasma - 3L
Interstitial Fluid (ISF) 11L
(cell membrane selective permeability)
Intracellular fluid (ICF) 28L
= 42L TOTAL
2/3 Intracellular fluid (ICF)
1/3 extracellular fluid (ECF)
(permeable to all but plasma protein and blood cell)
How much total body water?
42L
Common Medical Terminology when homeostasis has failed -
What is greater than normal?
Hyper
hypertonic
hyperosmotic
Common Medical Terminology when homeostasis has failed -
What is less than normal
Hypo
hypotonic
hypoosmotic
Common Medical Terminology when homeostasis has failed -
What is referred to as “in the blood”
Aemia/emia
anaemia, hyperemia, hypercalcAEMIA
Common Medical Terminology when homeostasis has failed -
What is referred to as in the urine?
Uria
proteinuria - protein in urine
ketonuria - ketone in urine
haematuria - blood in urine
Common Medical Terminology when homeostasis has failed -
What is related to glucose
Glyc
Glycosuria - glucose in the urine
hypoglycemia - low blood glucose levels
LEARNING OUTCOME
Define dilution principle
describe the use of the dilution principle in the measurement of body fluid compartments
Why is the plasma compartment so important?
plasma compartment - only compartment we have access to. Not interstitial or intracelular
access through being put substance in or take blood.
What is Plasma?
The fluid component of blood.
continuously moves through blood vessels
where is plasma located?
In the blood vessels
Does plasma move? If so, explain.
Plasma continuously moves by pumping action of heart
The DYNAMIC (changing) component of the extracellular fluid.
What is the dynamic component of the extra cellular fluid (ECF)
Plasma
Does the interstitial fluid move around the body? if yes, how?
No - that isn’t moving around the body the same, just floats around cells. Relatively static.
Can Plasma exchange nutrients with the Interstitial fluid?
Yes! Plasma freely exchanges nutrients (O2, glucose, ions) and waste (CO2 and urea) with the Interstitial Fluid ISF.
because the blood vessel wall is freely permeable to everything apart from plasma protein and blood cells (too large)
When does the exchange of nutrients occur between the plasma and interstitial fluid?
Exchange occurs when blood passes through the capillaries of the body
- Large vessels like arteries have walls too thick for exchange to take place.
Why does nutrient exchange only really occur between the interstitial fluid and plasma when/where it does?
Exchange only occurs as blood passes the capillaries
- Large vessels have too thick walls. Capillaries have very thin walls
thus exchange can freely occur.
Why is it important to know the component difference between interstitial fluid and Plasma?
What is in plasma that isn’t in interstitial fluid?
Plasma has blood cells and Proteins that Interstitial fluid does not:
When we have to measure the components through different compartments of fluid.
We can only measure the plasma component which has the proteins and blood cells that interstitial fluid and intracellular fluid doesn’t
What compartments are effectively homogenous (the same composition) apart from a few components?
The extracellular fluid (ecf) homogenous (apart from plasma protein and blood cells)
ISF devoid of these.
What principle do we remember in measuring body fluid volumes?
What principle?
what 3 things to remember?
The dilution principle.
access plasma only not other ISF ICF
- equation - c = m/v or v=m/c = dilution principle
concentration mass volume
- only plasma can be sampled - only compartment where plasma is a component. (plasma, extra cellular fluid or total body water)
- the NATURE of BARRIERS separating compartments is crucial in determining the test substance.
What is the dilution principle equation?
c=m/v
v=m/c
What areas/compartments can be sampled and calculated in dilution principle?
only plasma can be sampled - only compartment where plasma is a component. (plasma, extra cellular fluid (ECF) or total body water (TBW))
Compartments that can be measured directly using dilution principle?
Explain
- *Plasma volume (PV)** - cannot cross capillary wall use dyes to attach to plasma proteins
- *Extracellular volume ECF** - insulin sucrose (too large to cross cell) - need something to freely cross capillary walls bt not cell membrane.
Total body water TBW - no barrier to water in body, so use loading dose heavy water.
other compartments (where plasma is not) cannot be directly sampled - calculate vol indirectly.
Compartments measured using dilution principle
Equation(s)
ISF = ECF-PV
ICF = TBW - ECF
Method of dilution principle
include equation
- inject substance that will stay in the one compartment only
- calculate the volume distribution
= amount injected (minus any removed by metabolism) divided by concentration in sample fluid
What are the ion differences between intracellular fluid (ICF) and extracellular fluid (ECF)
intracellular fluid have more K+ (potassium), sulphates/phosphates and protein.
extracellular fluid (ECF) has more na+ (sodium) and Cl- bicarbinates HC03-
What ions are important in ECF and ICF
large concentration gradient of Na+ (sodium) Cl- (chloride), K+ (potassium) are fundamental for nerve and muscle function.
Why important to maintain ECF constant
for nerve, muscle function.
what would happen if homeostasis does not operate effectively?
Example - name an disturbance and consequence
K+ (potassium) disrubted.
lose concentration gradient of ECF and if - disrupt muscle and nerve function. Including heart muscle - atrial fibrillation. Can lead to death.
What organ is essential in regulating homeostasis e.g. regulating K+
The kidney plays an essential role in ECF composition. regulate K+ etc.
Why in physiology do they refer to an average healthy 70kg, 21-year-old male.
Proportions of the body usually vary with age and gender, but this is just a standard parameter.
females - less water and more body fat. Men more muscular due to testosterone.
muscle contains 70% water by weight and only 10% water.
the elderly have lower water content as lose muscle mass.
important if treating with lipid or h20 soluble drugs. The proportion of body/water fat will influence the rate at which the drug eliminated in the body.
a healthy 20-year-old female with [k+[ECF of 4.2mmol/l doubles her normal k+ intake. After a week which of these is most likely to be her [K+] plasma?
a) 2.1mmol/l
b) 4.2mmol/l
c) 8.4mmol/l
d) 12.5mmol/l
4.2mmol/l
we are discussing healthy individual the kidney will sort out the excess k+ and excrete excess of urine - thus illustrating its valuable contribution to the homeostasis control of plasma ion concentration.
Areas that can be sampled have plasma
what about other compartments?
What can you do to know the volume of these?
other compartments (where plasma is not) cannot be directly sampled - calculate vol indirectly
