Cardiovascular autonomic reflexes

The following are eponymous cardiovascular reflexes EXCEPT which one?

a) Anrep effect: acute increase in afterload causes reduction in stroke volume then

reflex restitution

b) Cushing’s reflex: raised intracranial pressure causes hypertension and reflex

bradycardia

c) Bainbridge reflex: an increase in venous pressure causes tachycardia

d) Bowman effect: as heart rate increases, contractility increases

e) Bezold–Jarish reflex: seen in myocardial ischaemia – stimulation of ventricular

receptors cause bradycardia and hypotension

Answer: d

Explanation

The Bowditch effect is the increase in contractility associated with an acute increase in

heart rate, provided the tachycardia is not excessive (thus inducing ischaemia).

The Bowman principle is from pharmacology and regards non-depolarising

muscle relaxants. Less potent non-depolarising muscle relaxants must be given in

larger doses in order to achieve the same maximal effect where sufficient acetylcholine

receptors are occupied to prevent post-synaptic activation by endogenous acetylcholine.

As larger doses are required, the peak plasma concentration and thus gradient

to promote occupation of receptors is greater with these less potent relaxants. In

summary, the onset time is shorter with less potent relaxants. Clinically this is

exploited with rocuronium at high dose (0.9mg/kg) producing flaccid paralysis in

less than 60 seconds thus making it suitable for ‘modified rapid sequence induction’.

The other options are all genuine eponymous cardiovascular reflexes andmay arise in

SBAs or indeed vivas.