Diffusion

Question 1

What are the functions of the CVS?

Answer 1

• nutrients into body (from intestine to liver)
• Fuel to cells (glucose from liver to brain)
• O2 to cells from lungs
• Removal of waste products like CO2, ammonia
• Circulation of hormones
• circulation of immune cells from antibodies
• regulation of pH
• H2O balance (exercise, dehydration, overhydration)
• thermoregulation (exercise, hyperthermia, hypothermia) since about 85% of energy produced just ends up becoming heat while only 15% actually contributes to work (force x distance)
• TRANSPORTTTTTT

Question 2

Who doesn’t need a CVS?

Answer 2

Miss amoeba because only few 100 microns, can make pseudopodia to to uptake food (ex: bacteria) through vacuoles, no need for GI tract nor heart, also lives in water so O2 available there and concentration gradient present so can easily uptake through diffusion

Question 3

What is diffusion?

Answer 3

Spontaneous movement of particles caused by a random thermal motion

Question 4

Distribution of cardiomyocytes and capillaries?

Answer 4

• about 100 microns in length this is a working heart cell or a contractile heart cell, 99.9% of heart cells are contractile, the rest will generate action potentials, on average one capillary per cardiac myocyte bcs O2 consumption of heart is highest of all organs since always functioning DUH you wanna survive
• distance small, amount of fluid by diffusion increases

Question 5

What is flow?

Answer 5

“stuff” that moves across a membrane per unit of time
Flow = D where D is diffusion coefficient (or constant) X concentration gradient (how a quantity changes with distance) X A (cross section area)
Flow is proportional to area

Question 6

What is flux?

Answer 6

Flux = flow/area = D X ((Cout - Cin)/d)

Question 7

What is Fick’s law?

Answer 7

Flow = D X ((Cout - Cin)/d) X A
Both flow and flux heavily depend on the substance diffusing and the substance across which it is diffusing, so D changes basically
concentration gradient (how quickly concentration changes, over distance d Cout falls to Cin, really a spatial rate of change of the gradient of the concentration of O2) is not the same as concentration difference

Question 8

How do O2 and CO2 move in the body?

Answer 8

• Thanks to diffusion like because of different concentration gradients across multiple barriers (ex: from alveola across alveola membrane into interstitial space, across capillary wall into plasma across RBC membrane
• Also convective or bulk flow when pressure allows movmenet of fluid (ex: heartbeat and when O2 enters lungs due to negative pressure from muscles that sucks in air

Question 9

The CVS in sum?

Answer 9

• Kardia => heart
• vas => vessel
• the pump is the heart, the pipes are the vessels and the fluid is the blood
• AKA circulatory system makes sense since fluid moves from one place to another and then comes back full circle hahahahhahah AKA circulation