L1- Homeostasis Flashcards by Saskia Chapman

what does homeo mean

sameness

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what does stasis mean

standing still

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definition of hoemostasis

the process by which cells, tissues and organisms maintains its parameters within a normal range of values

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what needs to be kept constant (8)

oxygen
carbon dioxide
salts
nutrients
pH
electrolytes
temp
volume and pressure

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what maintain homeostasis

feedback loops

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negative feedback loops

stops when effector ceases

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examples of negative feedback loop

temperature control and glucose control

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when you are hot

1) vasodilation
2) sweating
3) pilorection
4) stretching out

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vasodilation

arterioles dilate so more blood enters skin capillaries and heat is lost

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sweating

sudorific glands secrete sweat which removes heat when water changes state

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pilorelaxation

hair lies flat

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when you are cold

1) vasoconstriction
2) shivering
3) pilorection
4) curling up

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shivering increase body temp

rapid contraction and relaxing of skeletal muscles produces heat via respiration

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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

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give three examples of a positive feedback loop

coagulation
sepsis
birth process- Ferguson relex

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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

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in simple positive feedback loops occur when

output enhances or exaggerates original stimulus- stops when the initiator ceases

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Core body temperature

36.5- 37.5 degrees celsius

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core temperature..

fluctuates throughout the day and shows circadian rhythm

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where should core temp be measured from

head and neck

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where is body temp controlled

the hypothalamus

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hypothermia temp

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symptoms of mild hypothermia

shivering
fatigue
slurred speech
confusion
forgetfulness
muscle stiffness

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fever

37.5 - 40 degrees

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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