Physiology

Question 1

Nervous control of resp. Including Hering-Breuer relfex

Answer 1

Resp. Centres in hind brain; pons & m.oblongata

Baroreceptors in bronchioles send signals via vagus nerve to resp. Centres
Recognition of degree of lung inflation
Promotes expiration
Prevents inspiration & over-inflation

Question 2

RR regulation

Answer 2

Controlled by central chemoreceptors in m.oblongata - monitor blood ph
Decreased ph due to increased co2
resp. Acidosis
Stimulates resp. Centres to increase RR to remove co2

Question 3

Blood o2 regulation

Answer 3

Peripheral chemoreceptors in walls of aorta & carotid
Respond to variations in o2 tension
Signals sent to resp. Centres to stimulate/depress RR

Question 4

Effect if GA on CNS resp. Centres

Answer 4

Depress function
Less sensitive to physiological changes
Risk of hypoventilation & hypotension
May lead to:
Hypoxia
Cell death
Cardiac arrest

Question 5

What does the CVS regulate

Answer 5

Cardiac output
BP
SVR

Question 6

Define cardiac output

Answer 6

Volume of blood ejected by heart per min.

Dependent on HR & stroke volume

Question 7

Define strike volume

Answer 7

Volume of blood ejected per beat

Question 8

What is HR controlled by

Answer 8

Autonomic NS

In response to epinephrine

Question 9

What is BP influenced by

Answer 9

Cardiac output

SVR

Question 10

How is BP regulated

Answer 10

Feedback from baroreceptors in arterial walls, esp. carotid
Elevated BP causes wall distension stimulating baroreceptors to signal m.oblongata
Sympathetic NS dampened; parasymp. NS stimulated -
Reduced HR & contraction force
Medullary vasomotor centres also suppressed -
Vasodilation in capillary beds
Reduced SVR
BP decreases

Question 11

Define SVR

Answer 11

Resistance to blood flow through vessels
Increases as vessels constrict
Controlled by network of pre-capillary sphincters

Question 12

Relaxation/constriction of pre-capillary sphincters dependant on

Answer 12

Local metabolic factors:
If local req. high, o2 decrease & co2 accumulates
Causes relaxation of sphincters
Tonic vasoconstrictor nerve discharged by symp. NS constricts sphincters
Hormones & drugs -
Epinephrine; sedatives & anaesthetics

Question 13

Effect of GA on vasomotor centre function

Answer 13

Decreased

Reduced SVR & BP

Question 14

Cause of hypotension

Answer 14

Reduced cardiac output or stroke volume

Question 15

Define o2 flux

Answer 15

Volume of o2 reaching peripheral tissues per min.

Lowered by decreased cardiac output & blood o2

Question 16

Effect of anaesthesia on liver

Answer 16

Affects reciprocal mechanisms in hepatic artery & portal vein (hepatic blood supply)
May reduce cardiac output resulting in reduced hepatic blood flow

Question 17

Effect of anaesthesia on kidneys

Answer 17

Kidneys req. 20% of cardiac output to maintain GFR

GA May lead to reduced renal blood flow due to reduced cardiac output & BP