Cerebral blood flow Karius T#2 Flashcards
What forms the circle of willis
2 ICA’s and basilar artery join
What is the benefit to the circle of willis if blood flow is disrupted?
There is only localized ischemia because other branches can get blood out
What are the sympathetic NT and receptors in the cerebrum, and what are their effects?
NE and NPY, their receptors are alpha adrenergics specifically alpha-1 which results in vasoconstricion when the cardiac output/BP increases
What are the cerebral parasympathetic NT?
Ach, VIP, PHM-27.
They cause vasodilation, but their physiologic relevance is unknown
What NT stimulate nocioceptors on the distal blood vessels in the cerebrum?
Substance P
Neurokinin A
CGRP
All cause dilation
Why does reduced CSF cause headaches? How does activation of the afferents impact the brain in this situation?
The brain is heavier with less CSF so it is putting “torsion” on the blood vessels which are receptive to pain. Activation of Afferents will cause vasodilation and increase the blood flow which is acting to return intracranial volume closer to normal
What dictates where blood in the brain will go, what kind of control is this?
Oxygen consumption dictates where blood will flow, this is called local control
What is the significance of autoregulation of cerebral blood flow?
With high BP, sympathetics will vasoconstrict increasing systemic vascular resistance, but protect the capillaries in the brain and the BBB from damage.
How is cerebral blood flow influenced by intracranial pressures?
As ICP goes up venous outflow will be reduced leading to reduced arterial flow
If the ICP is high and leads to reduced arterial flow in the brain, what will be the systemic effect?
Decrease in brain perfusion activates cardiovascular control centers in medulla to increase BP. The systemic BP will increase drastically, sometimes the systolic BP can be greater than 200 mmHg which will increase pressure causing veins to open in the brain restoring flow
What factors can increase intracranial pressure?
Hydrocephaly
Cerebral edema
Intracranial bleeding
Why is so much (550mL) of CSF made each day?
It is not re circulated
What connects lateral ventricles to the third?
Intraventricular foramen
What connects 3rd to 4th ventricle?
Cerebral aquaeduct
What does the median aperature connect?
4th ventricle to the cisterna magna
