Homeostasis

Question 1

What is meant by negative feedback?

Answer 1

Bringing back monitored variables within a set range

Question 2

What is the overall goal of homeostasis?

Answer 2

To allow maintenance of an optimum internal environment

Question 3

What is defined as feed forward systems?

Answer 3

When the body anticipates and responds to changes in the environment before they have an effect.

Question 4

Give two examples of feed forward mechanisms?

Answer 4

Salivating before eatingSkin activates response to temperature before internal body temperature change arises

Question 5

What is positive feedback?

Answer 5

An initial disturbance sets off a train of events that leads to an even greater disturbance.eg - action potential

Question 6

How does daily input and output of water compare on a daily basis?

Answer 6

It is the same

Question 7

What fraction of body water is ICF?

Answer 7

Two thirds

Question 8

How much of ECF is plasma?

body compartments

Answer 8

20%

Water can move freely between these compartments, although movement is subject to forces such as osmosis.

Question 9

Importance of the nature the of barriers which seperate the body compartments

Answer 9

the composition of interstitial fluid and plasma is almost identical as water & other components can move freely between the two bc the blood vessel capillary is very permeable. The only difference is that potein is found in plasma but not in interstitial fluid. (protein can’t cross because it’s too big)

However the composition of the intracellular fluid is very different to the composition of the external fluid because the cell membrane that surrounds the cell is very selective in what it allows to cross between the intersititial fluid and the intracellular fluid.

Average 70Kg, 21yo man water is distributed thus:

Question 10

Important facts :

Answer 10

Question 11

Plasma Compartment

Answer 11

Question 12

Extracellular Fluid

Answer 12

Question 13

Why do women and old people have lower water content?

Answer 13

Women have a higher proportion of body fat

Old people have less muscle

Question 14

What is the only difference in composition between ISF and plasma?

Answer 14

Plasma contains plasma proteins

Question 15

Concentration =

Answer 15

Mass/volume

Question 16

What is the only region who’s water content can be directly measured?

Answer 16

Plasma

Question 17

Give examples of substances that can be used to measure the ECF?

Answer 17

Sucrose

Na+Cl-

(Substances that can not pass over the plasma membrane)

Question 18

What is used to measure the water content of the plasma?

Answer 18

Radioactively labelled or dyed proteins

Question 19

Dilution principle

Answer 19

Question 20

Compartments that can be measured directly using the Dilution Principle :

Answer 20

Question 21

Method of practise of dilution principle

Answer 21

Question 22

How do you measure total body water?

Answer 22

Using a radioactive water (deuterium oxide)

Question 23

EXTRA FACTS

Answer 23