CVR 38 Cor and cerebral circulations

Question 1

What is autoregulation?

Answer 1

Supply and command, adapting to environemnts. Very important concept in physiology allowing us to adapt.

Question 2

How do we control resistance and where is resistance greatest?

Answer 2

SLEEP
SNS - vasoconstrictor
Local mediators - hypoxia, acidemia
Endothelial cell factors - prostoglandin like NO dilater or endothelin
Endocrine ADH - vasopressin, adrenaline RAAS
Paracine histamine - bradykinin serotinin

Arterioles

Question 3

Flow is inverserly proportional to _____

Answer 3

resistance

Question 4

What is reactive hyperaemia?

Answer 4

when flow is restored following temporary cessation. Decrease in R. Bergers test or tourniquette.

Question 5

What is active hyperaemia?

Answer 5

Q increases with metabolism occuring due to arteriole resistance

Question 6

What can affect autoregulation

Answer 6

age, diabetes, vascular disease, drugs

Question 7

What is the circle of willis and what does it allow?

Answer 7

Origin - internal jugular L and R + Vertebral L and R

Distribution - Anterior, Middle, Posterior Cerebral L and R
Anterior and Posterior Communicating
Cerebellar arteries

Redundancy

Question 8

To what does the the CSF freely exchange with?

Answer 8

ISF

Question 9

Energy demands of the brain?

Answer 9

750 cc/min
3.3 ml of 02 per 100 g or 20 % of total body
grey matter needs more
Does not handle hypoxemia well

Question 10

CBP is inversely proportional to ________

Answer 10

resistance

Question 11

Increase in Pac02 means

Answer 11

vasodilation

Question 12

When does loss of conciousness occur

Answer 12

less than 40 mmHg

Question 13

What is the cushing reflex?

Answer 13

increased intracranial pressure (ICP) that results in Cushing’s triad of increased blood pressure, irregular breathing, and bradycardia

Question 14

What happens when the arterial pressure is less than ICP

Answer 14

CNS ischemic response in the medulla. Hypothalamus activates SNS causing vasoconstrictiion increasing ICP

Question 15

Classic signs of riased ICP

Answer 15

papilloedema and medullary compression

Question 16

What is vasovagal syncope

Answer 16

brainstem is activated directlyresulting in enhancement of paraNS and withdrawl of SNS. transient loss of conciousness pallor sweating,

Question 17

When do coronary arteries fill

Answer 17

diastole

Question 18

What determines myocardial oxygen demand?

Answer 18

tension = force per cm length

preload = stretch of ventricular beginning a new systole at end of diastole EDV

afterload = resistance to ventricles during contraction

contractility = work that the heart CAN perform at a given load or availability of intracelluar calcium

Heart rate = total heartbeats in a min

Question 19

Flow relates to ___________________

Answer 19

trans coronary or perfusion pressure