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Body Logistics > L1) Homeostasis, pH, core body temperature any body fluids ✔ > Flashcards

L1) Homeostasis, pH, core body temperature any body fluids ✔ Flashcards

1
Q

what is homeostasis?

A

homeo = sameness
stasis = standing still

phsiological process of maintaining the internal environment of the body in a state of dynamic equilibrium

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2
Q

what needs to be maintained constant in the internal environment?

A

temperature
pH
water

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3
Q

what technique does the body use to maintain homeostasis?

A

feedback loops
negative and positive

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4
Q

what does a feedback loop consist of?

A

stimulus
sensor
control centre
effector

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5
Q

what is a negative feedback?

A

when the effector ceases

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6
Q

what is a positive feedback?

A

when the stimulus ceases

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7
Q

what is an example of negative feedback?

A

regulation of blood glucose

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8
Q

what is an example of a positive feedback?

A

regulation of blood clotting
birth

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9
Q

what is the core body temperature?

A

37 ± 0.5 degrees celsius
but this fluctuates throughout day = circadian rhythm

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10
Q

how do we measure temperature?

A

infra-red skin thermometer
tympanic thermometer
temporal film
oral/rectal/axillary thermometer
traditional (mercury)

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11
Q

what is the body response to being too hot?

A

vasodilation
sweating
pilorelaxation
stretching out (large SA)

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12
Q

how does vasodilation help heat loss?

A

arterioles dilate
allows more blood to enter the skin capillaries
heat is lost

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13
Q

how does sweating help heat loss?

A

sudorific glands secrete sweat
removes heat
when water changes state

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14
Q

what is the body response to being too cold?

A

vasoconstriction
shivering
piloerection
curling up (small SA)

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15
Q

how does vasoconstriction help maintain heat?

A

arterioles get smaller
reduce blood going to skin
keeps core temp warm

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16
Q

how does shivering help maintain heat?

A

rapid contraction & relaxation of the skeletal muscles
heat produced by respiration

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17
Q

Briefly describe an overview of temperature control in the body

A

stimulus: low/high temperature
sensor: skin, hypothalamus
control centre: hypothalamus
effector: muscles, blood vessels, hairs on the skin, fat, sweat glands

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18
Q

what is the normal plasma pH?

A

7.35-7.45

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19
Q

what are the two major organs responsible for maintaining acid base balance?

A

lungs - respiratory balance
kidneys - metabolic balance

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20
Q

what is the gastric pH?

A

1.5-3.5

21
Q

what are the limits of human tissue survival?

A

6.8-7.8

22
Q

how do we measure for plasma pH?

A

Arteriole blood gases

23
Q

what are the two extremes of pH trouble?

A

acidosis (pH<7.35)
alkalosis (pH>7.45

24
Q

what are the body’s buffering systems?

A

for blood pH: bicarbonate buffering system
for intracellular pH: sodium phosphate buffering system
additional : calcium (alkali)
all systems also regulate water levels in cells due to presence of ions

25
Q

briefly describe the blood pH buffering system

A

uses erythrocyte as an intermediate
carbonic anhydrase in RBC converts the CO2 into carbonic acid (H2O + CO2 ⇆ H2CO3)
this carbonic acid travels to the lungs where it dissociates into CO2 + H2O)

26
Q

How do antacids work?

A

weak basic alkali salts
neutralise the acidic pH by binding to free H+ ions
and cannot dissociate back into acid (passed through the rectum)

27
Q

what is a clinically relevant antacid?

A

aluminium hydroxide
preferred as insoluble
hence it is milder, long acting and fewer side effects

28
Q

why do we need fluid balance?

A

not enough - dehydration and cell, tissue and organism death
too much - toxicity, metabolic failure and cell tissue, organism death

29
Q

how much fluid is needed each day to maintain a healthy adult?

A

2.5L

30
Q

briefly describe the distribution of water in the body of a 70kg man

A

of total body mass: 60% is fluids
of fluids: 2/3 is Intracellular & 1/3 is Extracellular
of extracellular: 3/4 is Interstitial & 1/4 is plasma

31
Q

How does total body water (TBW) differentiate between different patient groups?

A

the higher the percentage of body fat, the lower the percentage of TBW
hence, different ECF, ICF, plasma and blood volumes

32
Q

what is the order of TBW (most to least)?

A

Infants, Males, Females

33
Q

what are the three different types of tonicity?

A

isotonic
hypotonic
hypertonic

34
Q

what does isotonic mean?

A

same amount of water on both sides of the plasma membrane
solute conc. is same on both sides

35
Q

what does hypotonic mean?

A

more water outside cell
solute conc. higher inside cell
(hypo indicates condition inside cell)

36
Q

what does hypertonic mean?

A

less water outside the cell
solute conc. is lower in cell
(hyper indicates condition inside cell)

37
Q

what is osmosis?

A

movement of water downiest concentration gradient by diffusion

38
Q

what is osmolality?

A

concentration of a solution
the total number of solute particles per kilogram
expressed in milliOsmoles → most/kg

39
Q

How does osmolality differ for solutes that ionise?

A

solutes that ionise can dissociate into independently active solutes (NaCl → Na+ and Cl-)
hence, each milliosmole in solution would provide 2 mOsm

40
Q

what happens if there is not enough water?

A

initially, cells and tissues absorb water from the interstitial space
then from neighbouring cells (cell sacrifice)
then as tissues die, water absorbed from organs
then as organs die, water absorbed from brain, liver, kidney and heart

41
Q

briefly describe bulk water flow

A

presence of aquaporin exist on different sides of cells
different aquaporin isoforms have different affinities for water (slow/fast)
this allows for discrete water flow

42
Q

what is bulk water flow regulated by?

A

amount of glycerol in cell

43
Q

what is oedema?

A

fluid retention
‘dropsy’

44
Q

what causes oedema?

A

hydrostatic pressure > osmotic pressure

45
Q

what is hydrostatic pressure?

A

force exerted by the fluid on the vessel wall

46
Q

what is osmotic pressure?

A

force applied by the solute/colloid to prevent osmotic movement across the membrane
colloid osmotic pressure = oncotic pressure

47
Q

how is the osmotic pressure measured?

A

measured from the number (concentration) of solute molecules present in a solution

48
Q

what is peripheral oedema?

A

retention of fluids in the peripheries - i.e. ankles

49
Q

how does oedema occur?

A

oedema occurs when the lymphatics get blocked or damaged and fluid retains in the interstitial fluid

Body Logistics (15 decks)

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