Homeostasis

Question 1

What is meant by homeostasis?

Answer 1

Maintenance of a constant internal environment, with all processes working optimally.

Question 2

Describe the process of negative feedback.

Answer 2

• Magnitude of change of variable is monitored by a receptor
• Info fed back to integrating system
• Compared to reference level
• Difference between actual level and reference level generates a signal
• Signal fed back to effector mechanism
• Brings about response to restore variable to reference level

Question 3

What is the difference between negative and positive feedback?

Answer 3

In negative feedback, a deviation from a reference range brings about a response to return the variable to the reference range.
In a feedforward mechanism, a deviation of a variable from a reference range generates a response which leads to a further deviation from that reference range.

Question 4

What is the difference between negative feedback mechanisms and feed-forward mechanisms?

Answer 4

Negative feedback mechanisms can only produce a response to correct deviation from a certain range after this deviation has occurred.
Feed-forward mechanisms can PREDICT deviation from the reference range and bring about a response to correct if BEFORE it has actually happened.

Question 5

What proportion of total body water is Extracellular fluid?

Answer 5

1/3

Question 6

What proportion of total body water is Intercellular fluid?

Answer 6

2/3

Question 7

What two compartments of body fluid make up the extracellular fluid of the body?

Answer 7

Plasma and interstitial fluid

Question 8

Why are females considered ‘less wet’?

Answer 8

They have a higher proportion of fat: muscle tissue. Fat tissue has a lower water content than muscle.

Question 9

What is the main difference in constituents of the blood plasma and interstitial fluid?

Answer 9

Presence of plasma proteins in blood plasma and their absence in ISF.

Question 10

How is the volume of distribution calculated?

Answer 10

Substance injected that will stay in only one body part

Vol= (mass injected- mass removed)/ conc.

Question 11

What three body fluid compartments can be measured directly?

Answer 11

Plasma
ECF
Total Body Water

Question 12

How is the volume of plasma in the body measured?

Answer 12

Using dyes or radioactive labels attached to plasma proteins

Question 13

How is the volume of ECF in the body measured?

Answer 13

Using radioactive ions, insulin or sucrose

Question 14

How is the volume of Total Body Water measured?

Answer 14

Using a loading dose of radioactive water (D20)

Question 15

How is the volume of ISF in the body calculated?

Answer 15

ISF= ECF - PV

Question 16

How is the volume of ICF in the body measured?

Answer 16

ICF= TBW- ECF

Question 17

By what mechanism are most physiological responses triggered?

Answer 17

Negative feedback

Question 18

What is the average volume of water found in the body? i.e. Average TBW volume

Answer 18

42L

Question 19

What Is the average ECF found in the body?

Answer 19

14L

Question 20

What Is the average ICF found in the body?

Answer 20

28L