Physiology 1

Question 1

There are two main fluid compartments (in functional terms)- fluid inside cells, and fluid outside cells. What are the features of each?

Answer 1

Intracellular compartment:

• This refers to the fluid inside the cells
• This is where the largest amount of fluid is
• Blood is a mix of intra (nutrients) and extra (plasma) cellular fluid
• High in K+ ions and proteins, low in Na+ and Cl- ions

Extracellular compartment:

• Consists of interstitial fluid and blood plasma
• Interstitial space- the environment of most cells
• Transcellular- pools of specialised fluids such as aqueous humour (eyes), synovial fluid (in joints), cerebrospinal fluid (spine), and urine in the bladder
• Plasma- the fluid of blood, excluding the contents of blood cell
• Low in K+ ions, high in Na+ and Cl- ions (as we are originally from the ocean!)

Question 2

What are gradients useful for?

Answer 2

1. Storing energy in a readily accessible form
2. An essential part of cellular respiration cycle in mitochondria
3. Drive uptake and excretion of metabolites
4. Fast signalling: action potentials in neurons, preventing multiple sperm fertilisations of a single egg

Question 3

What is a chemical gradient?

Answer 3

A chemical gradient is where there is a concentration between two things, where the higher concentration wants to go to the lower concentration regions

Question 4

What happens when a phospholipid bilayer is shaken?

Answer 4

The bilayer folds over, essentially forming a sphere, such that only the polar heads (which are hydrophilic) are in contact with water, and the non-polar tails are held inside (hydrophobic) away from the water. This is spontaneous through polarity

Question 5

What is a tight junction?

Answer 5

They are almost a ‘fusing together’ of the cells, that allow water to pass into the cell. By regulating the amount of distance between the tight junctions, it decides how easily fluids move in

Question 6

What are gap junctions?

Answer 6

An organised collection of protein channels in cell membranes that allow ions and small molecules to pass between adjacent cells. The protein channels that make up gap junctions consist of two connexions

Question 7

What are the two types of fluid flow around compartments?

Answer 7

1. Bulk flow

2. Diffusion

Question 8

What does bulk refer to?

Answer 8

When all the molecules are moving in the same direction, the best example being in the circulatory system

Question 9

Bulk flow occurs to get fluid to the capillaries, whilst _____ occurs to get it back.

Answer 9

Diffusion

Question 10

Why a molecule not be able to diffuse into a cell?

Answer 10

1. They do not dissolve easily into the membrane (charged ions)
2. Concentration gradient is against them
3. Too big

Question 11

What are the molecular mechanisms used to cope with diffusion issues?

Answer 11

1. Pores and channels to make aqueous diffusion paths for ions (facilitated)
2. Pumps to move molecules against concentration gradient (active)
3. Carries for bigger molecules, and pinocytosis and phagocytosis to ingest REALLY BIG molecules

Question 12

What is osmosis?

Answer 12

The movement of water from a region of high WATER CONCENTRATION to low WATER CONCENTRATION

Question 13

How do water molecules move in and out of cells?

Answer 13

Through aquaporin channels.

Question 14

HP>OP (Arteriole end)- Net filtration?

OP>HP (venule end) - Net reabsorption?

Answer 14

Correct!