Question

Adult brain eighs 1.4 kg and density of 1.04 g/cm^3. CSF has a density of 1.007 g/cm^3. a) if experience a collision resulting in your head briefly accelerating at 10g, compare the net force your brain experiences with and without CSF presents. b) CSF normally maintained at 10 mmHg and cerebral capillaries at 25 mmHg. Relationship between CSF volume changes deltaV and pressure is approximately P= (10^deltaV/10 + 9 mmHg), where deltaV is in mL. How much fluid is needed to flow into the CSF to raise pressure to 26 mmHg? c) What happens when the CSF pressure is higher than capillary pressure?

Answer 1

Without CSF the net force experienced by brain = ma = 1.4 x 10g = 1.4 x 10 x 9.81 = 137.34 N

With CSF

Volume of brain = Mass / Density = 1.4 / 1040 =1.346 x 10^-3 m3

Mass of CSF = density of CSF x Volume = 1007 x 1.346 x 10^-3 Kg = 1.35 Kg

So net mass of brain = 1.4 + 1.35 = 2.75 Kg

Force on brain = 2.75 x 10g = 270 N

b) P= (10^deltaV/10 + 9 mmHg)

26 = 10^deltaV/10 + 9

170 = 10^deltaV

Tanking log ₁₀ on both sides

delta V = 2.23 mL amount fluid is needed to flow into the CSF to raise pressure to 26 mmHg

c) When CSF pressure is higher than capillary pressure then the flow is hindered due to formation of fluid shock in the path of flow .