L1- Homeostasis Flashcards
what does homeo mean
sameness
what does stasis mean
standing still
definition of hoemostasis
the process by which cells, tissues and organisms maintains its parameters within a normal range of values
what needs to be kept constant (8)
- oxygen
- carbon dioxide
- salts
- nutrients
- pH
- electrolytes
- temp
- volume and pressure
what maintain homeostasis
feedback loops
negative feedback loops
stops when effector ceases
examples of negative feedback loop
temperature control and glucose control
when you are hot
1) vasodilation
2) sweating
3) pilorection
4) stretching out
vasodilation
arterioles dilate so more blood enters skin capillaries and heat is lost
sweating
sudorific glands secrete sweat which removes heat when water changes state
pilorelaxation
hair lies flat
when you are cold
1) vasoconstriction
2) shivering
3) pilorection
4) curling up
shivering increase body temp
rapid contraction and relaxing of skeletal muscles produces heat via respiration
negative feedback loop of blood glucose control
- Eats meal and blood sugar goes up
- Pancreas produces insulin which acts on the liver and muscle cells to increase uptake of sugar from blood
- Glucose stored as glycogen or used by body (e.g. muscle cells)
- Blood sugar lowered
give three examples of a positive feedback loop
- coagulation
- sepsis
- birth process- Ferguson relex
Ferguson reflex
baby head pressing on cervix causes it to stretch, Cervix nerves feedback got the pituitary which releases oxytocin.
Oxytocin causes the cervix to contract which stretches it even more etc
in simple positive feedback loops occur when
output enhances or exaggerates original stimulus- stops when the initiator ceases
Core body temperature
36.5- 37.5 degrees celsius
core temperature..
fluctuates throughout the day and shows circadian rhythm
where should core temp be measured from
head and neck
where is body temp controlled
the hypothalamus
hypothermia temp
35
symptoms of mild hypothermia
- shivering
- fatigue
- slurred speech
- confusion
- forgetfulness
- muscle stiffness
fever
37.5 - 40 degrees
fever symptoms
place sweaty skin, cramps in stomach arms and legs
heat stroke
40 to 46
heat stroke symptoms
flushed dry skin, hot to touch, bounding pulse
heat exhaustion
46+
heat exhaustion symptoims
unconsciousness/ fitting/seizures, confused, headache, dizzy, uncomfortable
severe hypothermia
26-32 degrees
severe hypothermia symptoms
shivering stops, muscle are right, very slow weak pulse
- serve reduction in response level
no vital signs
below 28
with body temp remember
NOT DEAD UNTIL WARM AND DEAD
Warm patient up before declaring death
normal pH
7.35 to 7.45- very narrow range which is safe
organs responsible for acid use balance
- lungs- respiratory
- kidneys- metabolic
alkalosis
above 7.45
acidosis
below 7.35
death below
7 and above 7.8
gastric acid pH can damage
oesophagus- causing oesophagitis
if stomach loses mucus
acid can cause ulcers and perforation
limit of tissue survival in terms of pH
6.8 to 7.7
name some buffering systems of ICF
- phosphate buffer system
- protein buffer systems (haemoglobin buffer system and amino acid buffers)
what use haemoglobin buffer system
RBC
buffer systems of ECF
carbonic acid0bicarbonate buffer system
sodium phosphate buffering system used to
regulate intracellular pH
carbonic acid
bicarbonate important in blood- uses RBC as an intermediary
antacids and give an example
used to neutralise acids by virtue of their alkalinity and its insolubility
e.g. aluminium hydroxide
how are pH and blood gases classified
using arterial blood gas test
too much water is
toxic
- metabolic failure
how much water do we need everyday
2.5 litres
in men how much of body weight is made up of water
60% and in elderly
in women how much of body weight is made up of water
5–55% (more fat)
how much of water is held extraceulllarly
1/3
how much water is held intracellularly
2/3
interstitial fluid volume
80% of ECF volume
plasma volume
20% of EC volume
worked out body fluid question
- Intracellular Fluid Volume is 2/3 of total body water = 2/3 x 42L = 28 Litres
- Extracellular Fluid Volume is 1/3 of total body water = 1/3 x 42L = 14 Litres
- Interstitial Fluid Volume is 80% of ECF volume = (80/100%) x 14L = 11.2 Litres
- Plasma volume is 20% of ECF volume = (20/100%) x 14L = 2.8 Litres
- But, in practice numbers are rounded up and down, so:
- ICF volume = 11 litres and plasma = 3 litres
who have the highest percentage of total body water
infants
the higher the percentage body fat
the lower percentage total body water
three classes of tonicity
isotonic
hypertonic
hypotonic
isotonic
concentration of solutes int he cell is the same as outside
hypertonic
concentration of solutes int he cell is higher than outside the cell
hypotonic
the concentration of solutes int he celll is lower than outside the cell
tonicity is maintained by
plasma proteins such as Albumun
osmolality
uses tonicity to stop too much water leaving the blood (using albumin)
tonicity and osmalility work
in the opposite way to hydrostatic pressure
if too much water
cell will swell
- enzymes stop working
- cell will lyse
patients need what sort of IV drips
isotonic solution
what concentration of saline is giving
0.9% NaCl
definition of tonicity
The relative [solutes] dissolved in solution which determine the direction and extent of diffusion
how is tonicity different to osmotic pressure
Unlike osmotic pressure, tonicity is influenced by solutes that cannot cross the membrane
solutes able to cross the membrane
do not affect tonicity because they will always equilibrate with equal concentrations on both sides of the membrane without net movement
what happens when their isn’t enough water?
- coagulation problems
- cells initially absorb water from interstitial places
- then from each other
- then tissues die
- increases osmolality
- -> ADH increases
- -> stopping urine production- tissue dies
as organs die of dehydration water is absorbed from the
brain, liver kidney and finally the heart
osmolality is not dependent on
temperature and pressure
osmolarity is
dependent on temp and pressure
where is osmotic pressure taken from
plasma and urine
oedema
fluid retention in interstitial tissue
peripheral oedema results in
swollen annkles
oedema caused by
- presence of plasma proteins in the interstitial space
- lymphatics blocked or damage
e.g. in heart failure and kidney failure
when does oedema occur
when hydrostatic pressure is higher than osmotic pressure
