Introduction to Physiology COMPLETED

Question 1

Define the internal environment and name the fluids which are part of it

Answer 1

Cells need a carefully regulated fluid filled environment to function. The internal environment must remain stable despite changes in the external environment.

Extracellular fluid (ECF)
1. Interstitial fluid
2. Blood plasma

Intracellular fluid (IF)

Question 2

Draw and label or describe a box diagram of the body showing its subdivision into extracellular fluid (ECF), plasma, interstitial fluid (IF), and intracellular fluid (ICF).
Include what they are separated by?

Answer 2

ECF include mainly: (Blood plasma and interstitial fluid (surrounds cells)) and transcellular fluid. ECF is outside of cell.
ICF is separate from the above and is inside the cell.

Separating body fluid:
1. Between blood plasma and interstitial fluid are capillary endothelium.
2. Between Interstitial fluid and Intracellular fluid is cell plasma membrane.

Question 3

Describe the relative osmolality’s of intracellular fluid (ICF) and extracellular fluid (ECF).

Answer 3

Definition of osmolality:
Total concentration of all particles that are free in a solution measured in (mOsm = milliosmoles per kg of water

Extracellular fluid:
Found outside of cells and is a combination of blood plasma and interstitial fluid. ions include Na+ and Cl- (highest ion levels) Cl-, Ca2+(lowest) and K+(a lot lower in ECF than ICF).

Intracellular fluid:
Found inside of cells, that have lower concentration of ions which include Na+, Cl- and Ca2+ but a high K+ ion level compared to ECF.

Question 4

Describe the relative distribution of the following ions between the intracellular fluid (ICF) and extracellular fluid (ECF): Na+, K+, Cl-, and Ca2+

Answer 4

Sodium (Na+):
ECF - High
ICF - Low due to the action of the action potential, which actively transports sodium out of the cell and potassium into the cell.

                   Potassium (K+): ECF - Low due to action potential ICF - High

                    Chlorine (Cl-): ECF - High ICF - Low can still move in/out to maintain electrochemical balance.

                   Calcium (Ca2+): ECF - Higher than ICF due to neuromuscular signalling. ICF - Low Maintained and regulated at this level because it is stored in organelles.

Question 5

Diagram and describe the phospholipid structure of a cell membrane.

Answer 5

Phospholipid bilayers are amphipathic.

Hydrophobic tail - Non-polar, poor interaction with water molecules.

Hydrophilic head: Polar, interacts with water molecules

Question 6

Define homeostasis and give examples of the vital parameters that it regulates

Answer 6

The relatively constant steady state of our internal environment is achieved by homeostasis.

Examples include: temperature, fluid balance and blood pressure.

Question 7

Diagram or describe the basic components of a homeostatic negative feedback loop

Answer 7

1. Stimulus - any change, that disrupts the normal/steady state. Specialised sensory receptors detect this change.
2. Receptors - sense vital input.
3. Control centre - compares input against a set point.
4. Output signal - signal from control centre to effector.
5. Effector - enables a change to return vital input.