Introduction to cellular homeostasis Flashcards Preview

BS1060 Physiology, Pharmacology & Neuroscience > Introduction to cellular homeostasis > Flashcards

Flashcards in Introduction to cellular homeostasis Deck (16):
1

Homeostasis

The tendency towards a relatively stable equilibrium between interdependent elements, especially as maintained by physiological processes.

2

Importance of homeostasis

Maintaining a constant internal chemical composition and temperature vs variable external conditions.

3

General homeostatic principle

Variable set point disturbed -> sensor detects disturbance -> effector action counteracts imbalance

4

Biological variables controlled by homeostasis

-Nutrient/water intake
-Waste product excretion
-Body temperature
-Extracellular fluid composition

5

Parameters that need to be kept in narrow range for optimal cell functon

-Water level
-Ion concentrations
-Solute concentrations
-pH

6

Na+ cellular fluid concentrations

Intracellular fluid: 10-15 mmol/L
Extracellular fluid: 135-147 mmol/L

7

K+ cellular fluid concentrations

Intracellular fluid: 120-150 mmol/L
Extracellular fluid: 3.5-5 mmol/L

8

Cl- cellular fluid concentrations

Intracellular fluid: 20-30 mmol/L
Extracellular fluid: 95-105 mmol/L

9

HCO3- cellular fluid concentrations

Intracellular fluid: 12-16 mmol/L
Extracellular fluid: 22-28 mmol/L

10

Ca2+ cellular fluid concentrations

Intracellular fluid: ~10-7 mmol/L
Extracellular fluid: 1.1-1.4 mmol/L

11

Why are Na+ and Cl- so concentrated in extracellular fluid?

High NaCl concentration is the result of evolution from organisms living in salty sea water.

12

Epithelia

Interface between internal environment of body and external space (skin, lungs, intestines).
-> maintains constant composition and volume of ECF
-> provides stable environment for cells

13

How is homeostasis achieved?

Regulation of exchange of molecules/ions between both cytosol and ECF along with cytosol and intracellular compartments.
-> possible due to nature of cell membrane (phospholipid bilayer & membrane proteins)

14

What are phospholipid bilayers permeable to?

-hydrophobic molecules
-gases
-small uncharged molecules

15

Membrane permeability coefficient

J = P x (C1-C2)
J: net rate of solute movement
P: permeability coefficient
C1, C2: concentrations on both sides of membrane

16

Why are cell membranes much more permeable to ions, glucose and other molecules compared to pure lipid bilayers?

They contain specialist transporters.