L1- Homeostasis, body fluids, pH and temp

Question 1

Define homeostasis

Answer 1

Homeo= sameness 
stasis= standing still

Question 2

What needs to be maintained constant in the internal envrionment?

Answer 2

• Conc of o2, co2, salt and electrolytes
• conc of nutrients, waste products
• pH
• temp
• volume and pressure

Question 3

Difference between a) negative and b) positive feedback loops?

Answer 3

a) mechanism that reverses a change bringing the system back to optimum
b) the mechanism that increases a change taking the system further from optimum

Question 4

a) Thermoregulation is an example of what?

b) Outline responses the body makes when temp is too i) hot ii) too cold

Answer 4

a) Negative feedback
b)
i)
- Vasodilation: arterioles dilate so more blood enters skin capillaries and heat is lost
- Sweating: glands secrete sweat which removes heat when water changes state
- pilorelaxation: hairs flatten
- stretching out: sa increases

ii)
- vasoconstriction: arterioles get smaller to reduce blood goign to skin
- shivering; rapid contraction and relaxation of skeletal msucles, heat produced by respiration
- piloerection: hairs stand up
- curling up: smaller SA

Question 5

Outline the negative feedback response after someone has just eaten

Answer 5

1. Stimulus: BGL rising
2. Beta cells of pancreas detect high bGL
3. Pancreas secretes insulin causing liver to take up glucose and store it as glycogen
4. more body cells also take up more glucose
5. BGL decline back to normal and insulin release stops

Question 6

Outline the positive feedback response involved in blood clotting (after a cut for example)

Answer 6

1. break or tear in blood vessel wall
2. Clotting occurs as platelets adhere to site and release chemicals
3. Released chemicals attract more platelets (positive feedback)
4. Clotting proceeds, newly formed clot grows
5. feedback cycle ends after clot seals break

Question 7

When does a) positive and b) negative feedback stop?

Answer 7

a) when the initiator ceases

b) when the effector ceases

Question 8

What is the normal range for core body temperature?

Answer 8

37 degrees, plus of minus 0.5 degrees

Question 9

Which part of the body controls the thermostat?

Answer 9

Hypothalamus

Question 10

a) What is it called and b) what happens when core body temperature is outside the normal range, i.e. in the following:
i) 37.5-40
ii) 40-46
iii) 46+
iv) 32-36.5
v) 28-32
vi) 28 and below

Answer 10

i) a) Fever and b) Pale sweaty skin, cramps in stomach, arms and legs
ii) a) Heat stroke and b) Flushed dry skin, hot to touch, strong bounding pulse
iii) a) Heat exhaustion and b) Unconsciousness/fitting/seizures, confused/restless, headace, dizzy, uncomfortable
iv) a) Mild hypothermia b) Shivering, fatigure, slurred speech, confusiom, forgetfulness, muscle stiffness
v) a) Severe hypothermia b) Shivering stops, rigid muscles, very slow weak pulse, noticeable drowsiness, severe reduction in response
vi) a) No vital signs b) unconsciosuness, dilated pupils. pulse un detectable, appearance of death

Question 11

If someone appears dead and their body temp is below 28 degrees but feel cold, when are they actually dead?

Answer 11

Warm and dead

Question 12

Normal range for ph in tissues (including blood) ?

Answer 12

7.35-7.45

Question 13

What are the 2 main organs that are responsible for maintaining acid balance?

Answer 13

• Lungs- respiratory balance

- kidneys-metabolic balance

Question 14

Blood pH levels terms:

a) pH 6-7
b) pH 7-7.35
c) pH 7.35-7.45
d) pH 7.45-7.8
e) pH 7.8-9

Answer 14

a) Death
b) Acidosis
c) Normal pH
d) alkalosis
e) Death

Question 15

How much fluid (approx) a day is needed to maintain a healthy adult?

Answer 15

2.5 L of fluid

Question 16

What are the body fluid compartments and how much fluid is in each?

Answer 16

• TOTAL BODY WATER (TBW): 60% of body weight
• TBW made up of:
  a) Intracellular fluid (ICF): 2/3 of TBW
  b) Extracellular fluid (ECF) 1/3 of TBW
• ECF is made up of:
  a) Interstitial fluid: 80% of ECF
  b) Plasma volume: 20% of ECF

Question 17

a) What is the weight of a standard male?

b) What is the volume of blood for the standard male?

Answer 17

a) 70kg

b) 5 Litres

Question 18

Using the standard male, calculate how much fluid (in Litres) in each fluid compartment.

Answer 18

• TBW: 70 x0.6 = 42 Litres
• ICF: 2/3 x 42L= 28 L
• ECF: 1/3 X 42 = 14 L
• Interstitial: 0.8 x 14= 11.2 –> 11 L
• Plasma: 0.2 x 14= 2.8 –> 3 L

Question 19

Compare and contrast the water balance found in:

a) males
b) females
c) early life
d) Older populations

Explain why

Answer 19

Water balance in different populations:

• Fat tissue is least hydrated, skeletal muscle is most hydrated
• higher fat percentage= lower TBW and higher muscle = higher TBW this means:

a) Males have more TBW than females
b) Females have more body fat and less skeletal muscle mass and hence have less TBW
c) Infants have the highest percentage of TBW (least fat)
d) Elderly people have less muscle and less fat

Question 20

What is:

a) Isotonic solution
b) Hypertonic solution
c) Hypotonic solution

Answer 20

a) Same concentration and same amount of water inside and outside the cell
b) Solution is more concentrated than the inside of the cell
c) Solution is less concentrated than inside the cell

Question 21

What happens to a cell when it is placed in a:

a) Hypertonic solution
b) Hypotonic solution

Answer 21

a) The solution is more concentrated, there would be a net movement of water outside of the cell and so the cell would shrink
b) The solution is less concentrated, there would be a net movement of water inside the cell and so the cell would burst and lysis

Question 22

What happens if:

a) Not enough water (dehydration)
b) Too much water (water toxicity)

Answer 22

a) - cells and tissues absorb water from interstitial space then from each other, then tissues die and water absorbed from organs, organs die and then water absorbed from brain liver and kidney and heart
b) - osmotic pressure high, cells absorb water and swell, protein and enzyme stop working, cell burst

Question 23

What is a saline concentration

Answer 23

0.9% NaCl

Question 24

a) What is osmolality?
b) Units
c) How do you calculate?

Answer 24

a) function of the concentration of particles in solution
b) milliOsmoles per kg –> mOsm/kg
c)
- For glucose or urea, osmotic pressure is number of millimoles present
- For a solute that ionises, such as NaCl, would provide 2mOsmoles

Question 25

Calculate the osmolality for a patient with the following plasma concentrations:

a) Sodium is 140 mmoL/L
b) Potassium is 5 mmoL/L
c) Urea is 5 mmoL/L
d) Glucose is 5mmol/L

Answer 25

300 mOsm/kg

Question 26

What is the normal range of osmolality?

Answer 26

280-300 mOsm/kg

Question 27

What is:

a) Hydrostatic pressure
b) Oncotic/osmotic pressure

Answer 27

a) regulated by the action of the heart, tends to force water outwards from capillary into interstitial space
b) Oncotic pressure/ colloidal osmotic: pressure that tends to force water into the capillary from the interstitial space by osmosis due to the presence of plasma proteins

Question 28

What is oedema and outline the process

Answer 28

Oedema: excessive accumulation of fluid in the interstitial space leading to tissue swelling.

Process of Oedema:

• When the capillary hydrostatic pressure is higher than the colloidal osmotic pressure it causes more water to be driven into the interstitial spaces.
• Presence of plasma proteins in the interstitial space
• Lymphatic vessels can be blocked: leads to decreased drainage of interstitial fluids