Session 5: Control of the internal environment

Question 1

Distinguish the difference between normal value and normal range.

Answer 1

Normal value: the ave. value of a group of healthy individuals
Normal range: the different values of a normal individual

Question 2

How do the concepts normal range, non-lethal limits, and lethal limits differ w/ regards to homeostasis/

Answer 2

Normal range: variations that appear in a healthy individual
Non-lethal limits: homeostasis is disrupted but won’t lead to death
Lethal limits: homeostasis is disrupted and leads to death

Question 3

What are the 3 levels at which control systems of homeostasis apply their influence?

Answer 3

1. Cellular level - genetic control system operate in all cells to help control intra- and extracellular functions
2. Organ level - controls functions of individual parts of organs
3. Entire body - controls interrelation between organs

Question 4

Briefly explain the regulation of O2 [ ] in the ECF.

Answer 4

• control mechanism depends on heamoglobin
• present in all RBC
• haemoglobin combines w/ O2 as blood passes
  through the lungs
• does not release O2 if too much is already in tissue
  fluid
• if O2 is too little, sufficient O2 is released to re-
  establish adequate O2 [ ]
• called the Oxygen-buffering function of haemoglobin.

Question 5

Briefly explain the regulation of CO2 in the ECF.

Answer 5

• If CO2 continuously accumulated in the cells, all
  energy-giving reactions would be ceased.
• Higher than normal CO2 [ ] excites the respiratory
  centre
• This leads to rapid breathing, thus higher expiration
  of CO2
• excess CO2 is removed from blood and TF and
  returns to normal

Question 6

What is the formula for ABP(arterial blood pressure)?

Answer 6

ABP= cardiac output x total peripheral resistance

• CO= SV X HR
• stroke volume x heart rate

Question 7

What is the importance of Na+/K- pumps in creating electrical potentials in the CM?

Answer 7

• Maintains cell volume

- Enables nerve cells to generate action potentials

Question 8

Note the 3 levels at which homeostasis applies their influence.

Answer 8

1. Cellular level- genetic control systems operate in all
   cells to help control intra- and extracellular functions
2. Organ level- within organs: control functions of different parts of the organs
3. Entire body- controls interrelations between organs,
   e. g hunger

Question 9

Briefly explain the regulation of O2 as a homeostatic control.

Answer 9

• Depends on hemoglobin
• Present in all RBC
• Hemoglobin combines w/ O2 as blood passes
  through the lungs
  -