Cerebral Vasculature and the Notion of Autoregulation Flashcards
What are circumventricular organs?
What are their functions?
- Midlines structures around the third and fourth ventricles that are in contact with blood and cerebrospinal fluid.
- They facilitate communication between the CNS and peripheral blood.
List 7 circumventricular organs.
1 - Pineal gland.
2 - Median eminence.
3 - Subfornical organ.
4 - Subcommissural organ.
5 - OVLT.
6 - Area prostema.
7 - Posterior pituitary.
Which cells line the vasculature of the brain?
Astrocytes.
List the components of the neurovascular unit.
1 - Endothelial cells.
2 - Tight junctions (forming the blood-brain barrier).
3 - Basal lamina covered with pericytes.
4 - Smooth muscle.
5 - Neural cells.
What is the rate of production of cerebrospinal fluid?
0.35 ml/min.
Describe the composition and pH of CSF.
- Na+ = 148 mM.
- K+ = 3mM.
- Cl- = 120-130 mM.
- Glucose = 50-75 mM.
- Protein = 15-45 mM.
- pH = 7.3 mM.
What are arachnoid granulations?
Projections of the arachnoid membrane into the dural sinuses that allow cerebrospinal fluid to pass from the subarachnoid space into the venous system.
What is the range of blood flow to the brain?
750-900 ml per minute.
What is the resting oxygen consumption of the brain?
50ml per minute.
Why does moderate stimulation of the sympathetic nervous system only cause little change in cerebral blood flow?
Because the autoregulatory mechanisms of the cerebral vasculature override the effects of sympathetic stimulation.
How are space-occupying lesions of the brain compensated for in order to maintain intracranial pressure?
What is this known as?
- Venous volume and cerebrospinal fluid volume decrease to accommodate for the volume of the mass.
- Arterial volume and neural tissue remain unchanged.
- This is known as the Monro-Kellie hypothesis.
Define stroke.
Ischaemic damage to the brain caused by an occlusion of blood supply.
Which artery is most commonly occluded in strokes?
The middle cerebral artery.
