Homeostasis

Question 1

What is the general equation of life?

Answer 1

Nutrients + O2 = Waste (CO2) + Energy

Question 2

What works together to support the equation of life?

Answer 2

Co-operating body systems.

Question 3

What gives rise to homeostasis?

Answer 3

The threat of disruption to the balance of the equation of life.

Question 4

What does homeostasis mean?

Answer 4

Home = similar/ Stasis = state

Similar condition

Question 5

What is homeostasis?

Answer 5

Homeostasis is the regulation of an internal steady environment in the body in response to disruption.

Question 6

What does a failure to maintain a constant internal balance cause?

Answer 6

Pathology.

Question 7

What are common disruptions to the internal state?

Answer 7

Temperature
Diet
Exercise

Question 8

What is the difference between external and internal variables in homeostasis?

Answer 8

External- activity (e.g. eating doughnut)

Internal- temp/pH, conc etc.

Question 9

When is homeostasis less effective?

Answer 9

Extreme conditions.

Question 10

What mechanisms are used to maintain homeostasis?

Answer 10

Negative feedback
Feed-forward control
Positive feedback

Question 11

What is the most important mechanism of homeostatic control?

Answer 11

Negative feedback.

Question 12

How does negative feedback work?

Answer 12

When a condition that is homeostatically regulated is sensed to have shifted from the normal range, a signal is generated that produces a response which corrects the original disturbance and brings the condition back to normal.

Question 13

What is the homeostatic response proportional to?

Answer 13

The disturbance to condition caused.

Question 14

What are the characteristics of negative feedback?

Answer 14

Oscillation around a set point

Restores the internal condition AFTER disturbance

Question 15

What is feed-forward control?

Answer 15

Sophisticated form of negative-feedback control in which additional receptors recognise changes in the environment PRIOR to them causing a disruption and allow a response to be activated earlier. (E.g. going back for a coat in the cold after sensing temp).

Question 16

What is positive feedback control?

Answer 16

Opposite of NFC. Whilst this tries to restore less disruption, positive feedback control triggers further disruption to the system.

Question 17

Where is positive feedback control usually seen?

Answer 17

Pathology- although seen in some physiological processes such as nerve transmission.

Question 18

How is the integration of distal body systems achieved in homeostasis?

Answer 18

Endocrine / nervous system.

Question 19

What homeostatic mechanisms of the endocrine/nervous system are active?

Answer 19

Neural/endocrine reflexes.

Question 20

Why is homeostatic maintenance of water important?

Answer 20

Water controls everything else in the body.

Question 21

What is water input regulated by?

Answer 21

Thirst mechanism.

Question 22

What is water output regulated by?

Answer 22

Excretion / urinary tract mechanism (kidney function).

Question 23

What is prioritised above water regulation?

Answer 23

Body temperature

Question 24

What 3 compartments is water split between?

Answer 24

• Intracellular fluid

Extracellular fluid

• Interstitial fluid
• Plasma

Question 25

What is intracellular fluid?

Answer 25

Fluid within the cells.

Question 26

What does the extracellular fluid consist of?

Answer 26

Interstitial fluid | Plasma

Question 27

What is the interstitial fluid?

Answer 27

Fluid in-between cells.

Question 28

What is plasma?

Answer 28

Fluid component of blood.

Question 29

What are the barriers that must be crossed between compartments?

Answer 29

Plasma > Interstitial fluid (Plasma membrane- plasma proteins filtered out) Intersistial fluid > Intracellular fluid (Cell membrane)

Question 30

How is water distributed across the fluid compartments?

Answer 30

1/3 extracellular, 2/3 intracellular.

Question 31

Why does H20 distribution vary with gender?

Answer 31

Females have more fat- fat is 10% water whereas water is 70% water.

Question 32

Why does H20 distribution vary with age?

Answer 32

Elderly have lower water concentration- again due to fat and muscle distribution.

Question 33

What does plasma do?

Answer 33

Freely exchanges nutrients with the ISF- they are homogeneous with the exception of plasma proteins being unable to cross the capillary wall.

Question 34

What is the dilution principle?

Answer 34

M=CV

Question 35

What must be sampled in the dilution principle?

Answer 35

Plasma- least barrier reduction; only compartments of which plasma is a component can be measured directly.

Question 36

What compartments can be measured using the Dilution Principle?

Answer 36

Plasma proteins- since these cannot cross the plasma membrane, dyes or radioactive tags are used. Extracellular volume- freely crosses capillary walls but cannot cross cell membrane due to size. Total body water- no barriers to water in the body.