Lec 1 Homeostasis Flashcards
Define Homeostasis
the maintenance of a constant internal environment, using a dynamic equilibrium. the system uses feedback loops - positive and mainly negative
The system is same standing
give examples of what we must maintain?
PH, Temprature, Ion levels, nutrients, amnio acids
what is the temperature scale for humans, giving the normal range?
give some symtoms
normal range is 36.5 - 37.5
below 35 degrees Celsius, humans undergo hypothermia - shivering, weak pulse, rigid muscles, finally unconsciousness
above 37.5 degrees, it is hyperthermia, such as a fever
above 40 is hyperpyrexia
too hot - sweaty, cramping, hot to touch, strong pulse, headache, fits
what are good ways to measure human temperature?
ear
mouth
axillary (armpit)
rectal
explain the negative feedback loops involved in temperature homeostasis
thermoreceptors in our skin (external temp) and hypothalamus and thorax (core temp) detect our temperature. They relay this to the hypothalamus, which has a set point of 37.
unless raised by pyrogens casued by immune cells or bacteria in a fever, that leads to feeling cold and shivers, while being burning hot.
if we are too hot then our response is to sweat, pilorelaxation, increase SA by spreading out and vasodilation. this lowers our temp, which is detected by receptors, relayed ton hypothalamus and we stop these actions.
if we are too cold then we start
piloerection, white fat metablolism, reduce SA, vasoconstriction of capilleries, shivering in adults, and brown fat metabolism in infants. our temp rises, this is detected and actions cease.
what is the Blood Ph range in humans?
what is the ph equation why does it matter?
normal range is 7.34-7.45 the limits for survival are 6.8 - 7.8 below 7.35 we undergo acidiosis above 7.45 we undergo alkalosis the regulation of Ph involves co2 and Hco3- levels
Ph = -log10(H+)
the fact that it is logarithmic means that small changes isn the H+ conc can cause large changes in the ph
how do we measure blood Ph?
using arterial blood gas analysis
what ways can we manage acidosis?
using the lungs, respiratory response
too much H+ in body, we can remove H+ by blowing off co2, so carbonic anhydrase will convert more h2co3 into co2 and h20, thus pushing the equlibrim towars that from h+ and hco3-, reducing total H+ and hence acid levels.
conversly in alkylosis if we reduce breathing rate then blood co2 goes up and hence acidity rises.
the far more effective way is the metabolic response through the kidneys, it is far slower though.
the kidneys will excrete H+ or HCO3- depending on the need to maintain equilibrium
give knowledge on osmolarity and osmolaltiy
they are measures of the concentration of osmotically active solutes in a solution
measures in mOsm/kg and mOsm/L
when measuring Na and K we multiply by 2 as we account for cl- counterpart
which is used clinically and why?
osmolality - because it is a function of mass now, and is independent of temperature and pressure
define isotonic
same osmolarity - equal amounts of H20 on both sides of cell membrane
a balanced equlibruim
what are the affects of osomlality on fluid balance?
it can be isotonic and have no net movement of H2O
if it is hypotonic - lower osmolarity and water moves into the cell, causing cell lysis
if its is hypertonic - higher osmolarity and water exits the cell. cell withers
how is does our body divide our fluids?
we are 40% soild 60% fluid 2/3 of fluid is intracellular 1/3 is extracellular of exracellular - 80% is intersitial fluid 20% is plasma the volume of blood for a standard male is 5 litres
What is an odema ?
fluid retention that can lead to swelling of the limbs
what are the causes of odema?
diagram is helpful so draw if you can.
raised hydro static pressure in capillary
-caused by vasodilation in inflammation
-or congestion (heart failure)
Decreased oncotic pressure in capillary
-liver disease - low albumin
increased oncotic pressure in interstium
-increased vascular permeability in inflammation
impaired lymphatic drainage
how does blood move within a capillary ?
there is hydro static pressure
this is higher at the arterial end than the venous end
it will cause blood to be forced out into interstitial space, it is greater than the oncotic pressure ( force of blood into capillary)
in the middle there is no net movement
at the venous end oncotic/blood osmotic pressure is greater so blood net moves into the capillary
what is a problem with acid in body ?
osepagitis and stricture
gastric acid in the oesophagus, causes it to inflame and close.
why does the body need buffer systems, give examples
to maintain correct pH levels, allowing us to resist changes in pH
amino acids, heamgoblin in the cell
phospate buffer system in the cell
carbonic acid bicarbonate buffer system outside the cell
how does total body water vary
it is different based on gender, and age, and obesity
the older we get the less body water we have
males have more tbw than females
more fat = less % of TBW
give 2 exapmles of feedback loops in the human body
insulin - negative - blood glucose rises - detected in pancreas - insulin released to store glucose as glycogen (reverse is glucagon) - return to normal
clotting of blood - positive - vessel breaks - platelets clot - release chemicals to attract more platelets - clot forms
positive feedback stops when initiator ceases
negative feedback stops when effector ceases
