Homeostasis and body fluids Flashcards
what happens when body gets too little water
dehydration
cell,tissue and organism death
plasmolysis
what happens when the body gets too much water
toxicity
metabolic failure
cell,tissue,organ death
describe the water compartments in the average male (70kg)
- 60% of 70kg is 42L (total body water)
- intracellular fluid is 2/3 of total body water - 2/3 x 42 = 28L
- extracellular fluid is 1/3 of total body water - 1/3 x 42 = 14L
- interstitial fluid volume is 3/4 of extracellular fluid - 3/4 x 14 =10.5L
- plasma volume is 1/4 of extracellular fluid - 1/4 x 14 =3.5L
the volume of blood for a 70Kg male is approx. 5L
examples of positive feedback loops
oxytocin released during childbirth due to the increasing pressure of the head on the cervix.
regulation of blood clotting
what is the difference between a negative feedback loop and a positive feedback loop
negative = the effector causes an effect to reduce the stimulus. stops when the effector ceases
positive = the effector causes an effect that increases the effect of the stimulus. stops when the stimulus ceases.
what is extracellular fluid and what proportion of the body does it make up
water outside cells
1/3 of total body water
what it intracellular fluid and what proportion of the body does it make up
water inside cells
2/3 of the total body water
in elderly people, what percentage of their body is water
50% because they have larger adipose tissue content
what percentage of the body is water in a baby
80%
what percentage of the adult human body is water
60%
one way to treat heartburn or other things caused by acids
over the counter antacids eg. aluminium hydroxide
this neutralises acid
antacids containing aluminium hydroxides are preferred as they are milder, longer lasting, fewer side effects , more soluble, can pass through easily.
describe some acid problems that can occur with gastric juice
it can go into the oesophagus, causing severe issues
the stomach has a protective lining and if it gets damaged or lost then it can lead to gastric ulceration and perforation.
heartburn
what is the ph of gastric juice in the stomach
1-2.5
one way of treating acidosis
infusion of a bicarbonate solution can help increase blood pH
mechanical ventilation can be used for respiratory acidosis to remove the carbon dioxide.
what are the 2 main causes of acidosis
1) metabolic acidosis
- due to increased production of metabolic acids (eg lactic acid)
- inability to excrete acid via kidneys
- controlled by kidneys
2) respiratory acidosis
- caused by excessive build of carbon dioxide due to hyperventilation
what is alkalosis
increase in blood pH above 7.45
what are the symptoms of acidosis
central:
- headache
- sleepiness
- confusion
- loss of consciousness
- coma
respiratory:
- shortness of breath
- coughing
heart:
- increased heart rate
- arrhythmia
gastric:
- nausea
- vomiting
muscular:
- seizures
- weakness
intestinal:
- diarrhoea
what is acidosis
when the blood pH falls below 7.35
what is the normal pH of blood
7.4
what is homeostasis with respect to pH
the regulation of hydrogen ion concentration
acid-base balance
what is a cause of pyrexia
how does that cause pyrexia?
infection
The infection causes the set point in the hypothalamus to increase to a higher temperature. this causes the body to initiate heat generation via shivering and increased metabolic rate to meat the set point which is at a higher temperature.
above 38.5oC = pyrexia (fever)
this increase in temperature is important becomes it is at these temperatures that the immune system works optimally.
what is pyrexia
a fever
temp above 38.5 oC
what is normal body temperature for humans
37oC +/- 0.5oC
what are ways in which the body can cool down
sweating - water evaporates and since water has a high latent heat of vaporisation, the change is state from liquid to gas removes a lot of energy from the body, cooling it down.
vasodilation of arterioles near the skin, increasing blood pressure and increasing heat loss through skin
hairs in skin lay flat and surface of body cools
describes ways in which body temperature can be increased
shivering of skeletal muscles
heat released through metabolic reactions and respiration
vasodilation of the arterioles, decreasing blood flow through them and reducing heat lost through skin
erection of hairs in the skin (piloerection)
what is the function of the hypothalamus
measures the internal body temperature
location of the set point and its control
name the 4 components needed for a homeostatic mechanism to work properly
stimulus/variable
sensor/receptor
a control centre
an effector
what are 3 key factors that need to remain constant in the body?
ph
temperature
water
Define the term homeostasis
physiological process
internal conditions of the body of a living organism, cell or tissue are maintained despite changes in factors both extrinsic and intrinsic.
state of dynamic equilibrium
