Lecture 2: Principles of Homeostasis

Question 1

What does ECF stand for?

Answer 1

Extracellular Fluid

Question 2

What is the homeostatic benefit of being a multi-cellular organism?

Answer 2

Cells specialise and combine to make tissues and organ systems, allowing for control of a stable internal environment.

Question 3

How much of our body water is contained in ICF?

Answer 3

2/3

Question 4

What does ICF stand for?

Answer 4

Intracellular Fluid

Question 5

How much of our body water is contained in ECF?

Answer 5

1/3

Question 6

How much of the ECF is ISF?

Answer 6

approx. 4/5

Question 7

What does ISF stand for?

Answer 7

Interstitial Fluid

Question 8

How much of the ECF is plasma?

Answer 8

approx. 1/5

Question 9

What is the definition of ‘Homeostasis’?

Answer 9

The maintenance of relatively constant conditions in the internal environment (ECF) in the face of external (or internal) change.

Question 10

What is the K+ concentration in the ECF?

Answer 10

3.5-5mmol/L

Question 11

What is the glucose concentration in the ECF?

Answer 11

Fasting = 3.5-6mmol/L
Non-Fasting = 3.5-8mmol/L

Question 12

What is the Ca++ concentration in the ECF?

Answer 12

2.2-2.6mmol/L

Question 13

What is the Na+ concentration in the ECF?

Answer 13

135-145mmol/L

Question 14

What is the role of Sodium in the ECF?

Answer 14

Action potential generation and ECF volume control, affecting blood pressure (BP).

Question 15

What is the role of Calcium in the ECF?

Answer 15

Structural component of bone and teeth, involved in neurotransmission, muscle contraction, essential for blood clotting, regulates enzyme function.

Question 16

What is the role of glucose in the ECF?

Answer 16

To produce ATP.

Question 17

What are the effects of acidosis?

Answer 17

Decreased neural function, decreased consciousness.

Question 18

What are the effects of alkalosis?

Answer 18

Over-excitable nerves and muscles, leading to ‘pins and needles’, muscle spasms and convulsions.

Question 19

What is the optimal core body temperature?

Answer 19

36-37.5 ° C

Question 20

What happens when the core body temperature is too high?

Answer 20

Proteins denature.

Question 21

What happens when the core body temperature is too low?

Answer 21

Chemical reactions slow down, preventing normal cell function. As nerve cells cease to function properly, the body can no longer thermoregulate, temperatures decrease, and the cycle continues… ☠

Question 22

_________ is the random movement apart of particles, which is rapid over a short distance, for example, between cells and capillaries.

Answer 22

DIFFUSION is the random movement apart of particles, which is rapid over a short distance, for example, between cells and capillaries.

Question 23

Is energy required for simple diffusion? Why?

Answer 23

No. Because it is a passive mode of transport, molecules travel down the concentration gradient with no extra energy required.

Question 24

Can all substances diffuse through the lipid bilayer?

Answer 24

No, only some substances can.

Question 25

What are membrane channels?

Answer 25

They are channels through the cell membrane which allow for the movement of (often specific) molecules through them. They can often open and close.

Question 26

Which type of membrane channel opens/closes spontaneously?

Answer 26

Leak Channels

Question 27

What are ligand gated channels?

Answer 27

Membrane channels which open/close in response to a change.

Question 28

What are voltage gated channels?

Answer 28

Membrane channels which open/close in response to membrane potential.

Question 29

What is another name for Carrier Mediated Passive Transport?

Answer 29

Facilitated Diffusion.

Question 30

How does Carrier Mediated Passive Transport work?

Answer 30

Proteins within the cell membrane bind to molecules outside the cell, change their shape and then release them into the cell.

Question 31

What is it called when energy from ATP hydrolysis is used to move substances against the concentration gradient?

Answer 31

Primary Active Transport

Question 32

The sodium - potassium pump is an example of what type of transport?

Answer 32

Primary Active Transport | 3Na⁺ out, 2K⁺ in

Question 33

Active transport maintains _____ _________.

Answer 33

Active transport maintains IONIC GRADIENTS.

Question 34

What is exocytosis?

Answer 34

A process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.

Question 35

What is endocytosis?

Answer 35

The taking in of matter by a living cell by invagination of its membrane to form a vacuole.

Question 36

What is osmosis?

Answer 36

The net movement of water across a membrane DOWN its own concentration gradient (towards the higher solute concentration).

Question 37

What causes osmotic pressure?

Answer 37

Differences in solute concentration, due to fluid shifts.

Question 38

What is osmolarity?

Answer 38

The total number of solute particles per liter of solution.

Question 39

What is tonicity?

Answer 39

The effect a solution has on a cell. Eg., hypertonic, hypotonic, isotonic.

Question 40

What is the osmolalirity of the ECF and ICF?

Answer 40

275-300mosmol/L

Question 41

What is the pH of the ECF?

Answer 41

7.35-7.45