week 1

Question 1

what are the two fluid compartments in the body?

Answer 1

extracellular fluid (20% of body weight) consists of plasma (20% of ECF) and Interstitial fluid (80% of ECF)

intracellular fluid (40% of body weight) is fluid inside the cell.

Question 2

define osmosis

Answer 2

osmosis is the movement of water (the solvent) across a semi-permeable barrier to even the concentration of dissolved particles on either side of the membrane.

Question 2

define diffusion

Answer 2

diffusion occurs when a substance in an environment passively spreads through the environment from a region of high concentration down its concentration gradient.

Question 3

what is the difference between concentration, osmolarity and tonicity?

Answer 3

concentration refers to the number of a particular molecule dissolved in a volume of solution. osmolarity describes the total number of dissolved particles in a volume of solution. tonicity is a measure of the osmotic pressure gradient between two solutions and depends on the concentration of only the non-penetrating solutes.

Question 4

what is the structure of a blastocyst?

Answer 4

• outer epithelial layer (trophoblast)
• inner cell mass
• epiblast, embryonic disk and hypoblast forms when inner cell mass splits.

Question 5

how is the notochord, neural plate and neural tube produced?

Answer 5

• cells derived from the primitive node migrate cranially to form the notochord.
• ectodermal cells above the notochord thicken and differentiate, forming the neural plate.
• the neural plate invaginates to form the neural tube.

Question 6

how are the three germ layers produced?

Answer 6

cells of the epiblast migrate medially and into the primitive groove. cells which move into the hypoblast become the embryonic endoderm. cells which move into the space between the epiblast and endoderm become the embryonic mesoderm. cells left in the epiblast become the embryonic ectoderm.

Question 7

what are the three categories of mesoderm and their functions?

Answer 7

1. paraxial mesoderm forms somites, which produce muscle, bone and dermis.
2. intermediate mesoderm which forms the urogenital system (kidneys, gonads, respective duct systems).
3. lateral mesoderm: divided into somatic (parietal) and splanchnic (visceral). forms bones, heart, vasculature, wall of gut, connective tissue.

Question 8

define membrane potential

Answer 8

the membrane potential is measured as the difference in charge across the membrane

Question 9

define resting membrane potential

Answer 9

when the permeability of the cell is due entirely to “leak channels”. resting membrane potential is the charge difference across the membrane when the membrane is at rest.

Question 10

When is an ion at equilibrium potential and how does this relate to the Nernst equation?

Answer 10

there are two sources of potential energy driving the movement of a specific ion across the cellular membrane (chemical concentration gradient and electrical charge gradient). when the two sources of driving force are balanced, the net movement of that ion will be zero and the ion is at equilibrium.

The Nernst Equation predicts the equilibrium potential of any ion.

Question 11

Define Driving Force (DF)

Answer 11

The driving force is the sum of all force on a particlular ion pushing/pulling the movement of an ion.

The further away the Vm is from the Eion, the greater the driving force on that ion.