Dreier - Spreading Depolarization

Question 1

The Na+ pump consumes how much chemical energy the brain requires?

A. 5%
B. 10%
C. 25%
D. 50%
E. 80%

Answer 1

D. 50%

Question 2

How much of the body’s energy does the brain consume?

Answer 2

20%

Question 3

How much of our daily caloric intake maintains the basal metabolic rate of the Na+ pump?

A. 5%
B. 10%
C. 25%
D. 50%
E. 80%

Answer 3

B. 10%

Question 4

What is the Donnan effect? (and passive Donnan equilibrium?)

Answer 4

• predictable and unequal distribution of permeant charged ions on either side of a semipermeable membrane, in the presence of impermeant charged ions
• at passive Donnan equilibrium - intracellular osmolarity is higher, without active transport, osmosis would cause ceullular swelling

Question 5

What is the Double Donnan steady state?

Answer 5

• only small ions (not proteins) count when calc. osmolarity

- is there a diff in osmolarity bw the 2 sides of the membrane? –> No

Question 6

What happens when neurons go from the ‘double Donnan steady state’ towards a ‘Donnan equilibrium’?

Answer 6

-the neurons swell

Question 7

Which of the following are changes that occur in a neuron when a cytotoxic edema develops?

A. intracellular = -10 mV
B. low external Ca2+ concentration
C. dendritic beading
D. all of the above

Answer 7

D. all of the above

Question 8

What change in MRI is caused by dendritic beading?

Answer 8

• hyperintensity in diffusion weighted images

- hypointensity in maps of the apparent diffusion coefficient

Question 9

What would happen to neurons if the ion concentrations in bulk solutions would change w every AP?

Answer 9

the neurons would swell all the time

Question 10

What are the 3 pathological situations in which neurons suddenly release large amounts of the energy contained in their ion gradients across the membrane?

Answer 10

1. epileptic seizure
2. spreading depolarization
3. death

Question 11

What is spreading depression?

Answer 11

• cells lose their polarity required for typical brain function
• become depolarized
• ‘brain tsunamis’
• collapse of membrane potentials

Question 12

What are the effects of spreading depolarizations?

Answer 12

• cells swell
• dendrites become beaded
• synaptic spines retract
• brain tissues become acidic
• neurovascular coupling is disrupted
• change in blood flow, depletion of energy reserves
• gene expression is changed

Question 13

During spreading depolarization extracellular K+ increases from 3 to 50 mM.

What would ususally be expected when you bathed a cell with an excitable membrane in a solution with K+ at 50 mM?

A. hyperpolarization
B. depolarization

Answer 13

B. depolarization

since the membrane potential is dependent on the K+ equilibrium potential

Question 14

Does a vascular smooth muscle cell dilate or constrict when the cellular membrane depolarizes?

Answer 14

it constricts

since the depolarization opens voltage-gated L-type Ca2+ channels, Ca2+ enters the vascular smooth muscle cell and initiates contraction

Question 15

During spreading depolarization extracellular K+ increases from 3 to 50 mM.

Rise of extracellular K+ to 50 mM depolarizes vascular smooth muscle cells which leads to Ca2+ influx and contraction.

Vascular contraction reduces arteriolar diameters.

Reduction of arteriolar diameters decreases cerebral blood flow.

What is the normal cerebral blood flow response to spreading depolarization?

A. Hyperemia
B. Ischemia

Answer 15

A. Hypermia

-this is not logical