Baroreceptor Reflex cont.

Question 1

what would the effectors be in this reflex?

Answer 1

the heart (ie varying heart rate and stroke volume)
 and blood vessels (ie varying systemic vascular resistance)

Question 2

what is MAP equal to?

Answer 2

MAP = stroke volume x heart rate x systemic vascular resistance

Question 3

what is autorhythmicity

Answer 3

the heart muscles can still contract even in the absence of external stimuli

Question 4

how can stroke volume be modified?

Answer 4

> it can increase if the contractile strength of the heart is increased
sympathetic nerves innervate the ventricular myocardium and stimulation increases the force of contraction

Question 5

how is the intrinsic control of stroke volume regulated?

Answer 5

via the Frank-Starling Mechanism (Starling’s Law of the Heart)

Question 6

what type of vasculature has the most resistance?

Answer 6

arterioles

Question 7

what causes vasoconstriction and what is the effect on SVR and MAP?

Answer 7

• contraction of vascular smooth muscles
• and it increases SVR and MAP

*and oppositely vasodilation is causes by relaxation of vascular smooth muscle and decreases SVR and MAP

Question 8

what is the neurotransmitter for sympathetic nerve fibres?

Answer 8

noradrenaline

acting on alpha receptors

Question 9

what is the vasomotor tone?

Answer 9

the fact that vascular smooth muscle is partially constricted at rest

**is caused by a tonic discharge of sympathetic nerves resulting in a continuous release of noradrenaline

Question 10

what is significant about baroreceptors only responding to acute changes in ABP

Answer 10

> the firing rate of baroreceptors decreases if high ABP is sustained
they will reset, and so will only fire if there is an acute change above the ‘new level’