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systolic pressure

why does the systolic pressure not increase by alot after exercise
Reply 1
Because when you exercise your heart doesn’t beat with more force, it beats more frequently which is what people mean when they say your heart works faster during exercise.
Reply 2
Original post by HT_3105
Because when you exercise your heart doesn’t beat with more force, it beats more frequently which is what people mean when they say your heart works faster during exercise.

thank you
Original post by Jasminea937
why does the systolic pressure not increase by alot after exercise

Hi just thought I should clarify this.

The answer above is not quite correct - both the heart rate and the force of contraction increase during exercise [positive chronotropic and inotropic effects, respectively [both mediated by the action of adrenaline and noradrenaline on the heart]]; the systolic blood pressure does not rise substantially cos these catecholamines also lead to peripheral vasodilatation [mainly of muscle arteries] so that the peripheral resistance is reduced.

[B.p. is a function of cardiac output and peripheral resistance]

M [specialist biology tutor]
Reply 4
Original post by macpatgh-Sheldon
Hi just thought I should clarify this.

The answer above is not quite correct - both the heart rate and the force of contraction increase during exercise [positive chronotropic and inotropic effects, respectively [both mediated by the action of adrenaline and noradrenaline on the heart]]; the systolic blood pressure does not rise substantially cos these catecholamines also lead to peripheral vasodilatation [mainly of muscle arteries] so that the peripheral resistance is reduced.

[B.p. is a function of cardiac output and peripheral resistance]

M [specialist biology tutor]

This is simply wrong, catecholamines cause peripheral vasoconstriction.
Original post by boatmoad
This is simply wrong, catecholamines cause peripheral vasoconstriction.

Hi there young man - this question and its possible answers are NOT "simply wrong" BUT RATHER "highly complex and confusing" - let me try to explain as empirically as I can:-

Yes you are right that catecholamines can cause vasoconstriction by stimulating alpha-1 adrenoceptors, but there are several other factors that interplay to result in variable effects on b.p.

e.g.
Firstly, adrenaline has both alpha and beta adrenergic effects, so that yes it can cause vasoconstriction via the alpha-1 effect, but the alpha-2 effect [on presynaptic receptors] tends to block the release of NA hence dampening the vasoconstrictive effect. Secondly, one of the [diverse] actions of adrenaline on beta-2 receptors is to cause vasodilatation of muscular arterioles [medium-sized arteries], which adds to the vasodilatory effect of the action of adrenaline on alpha-2 receptors, so the situation is highly complex NOT "simple" at all!

In conclusion, what will happen to b.p. during exercise will depend on various factors, far beyond what you need to know at A level - if you are studying at degree level, particularly in medicine or pharmacology, then try to grasp the above; if at school/college, I would stick to the basics in my previous post in order to avoid confusion to OP and others, which I tried to keep simple for OP, who I assume is doing A level biology.

If at medical school or PG level, it might also help to know that neurotransmitters are not pure agonists or antagonists - there is a continuum [kinda spectrum] between agonist activity and antagonistic activity, so that an agonist will have some blocking activity and vice versa, hence the corollary that some beta-adrenoceptor antagonists have a noticeable ISA [Intrinsic Sympathomimetic Activity] e.g. pindolol, so will cause less bradycardia and a weaker negative inotropic effect than other beta-blockers without significant ISA.

If you need more detail, you know where to find me.
M
(edited 2 months ago)
Reply 6
Original post by macpatgh-Sheldon
Hi there young man - this question and its possible answers are NOT "simply wrong" BUT RATHER "highly complex and confusing" - let me try to explain as empirically as I can:-

Yes you are right that catecholamines can cause vasoconstriction by stimulating alpha-1 adrenoceptors, but there are several other factors that interplay to result in variable effects on b.p.

e.g.
Firstly, adrenaline has both alpha and beta adrenergic effects, so that yes it can cause vasoconstriction via the alpha-1 effect, but the alpha-2 effect [on presynaptic receptors] tends to block the release of NA hence dampening the vasoconstrictive effect. Secondly, one of the [diverse] actions of adrenaline on beta-2 receptors is to cause vasodilatation of muscular arterioles [medium-sized arteries], which adds to the vasodilatory effect of the action of adrenaline on alpha-2 receptors, so the situation is highly complex NOT "simple" at all!

In conclusion, what will happen to b.p. during exercise will depend on various factors, far beyond what you need to know at A level - if you are studying at degree level, particularly in medicine or pharmacology, then try to grasp the above; if at school/college, I would stick to the basics in my previous post in order to avoid confusion to OP and others, which I tried to keep simple for OP, who I assume is doing A level biology.

If at medical school or PG level, it might also help to know that neurotransmitters are not pure agonists or antagonists - there is a continuum [kinda spectrum] between agonist activity and antagonistic activity, so that an agonist will have some blocking activity and vice versa, hence the corollary that some beta-adrenoceptor antagonists have a noticeable ISA [Intrinsic Sympathomimetic Activity] e.g. pindolol, so will cause less bradycardia and a weaker negative inotropic effect than other beta-blockers without significant ISA.

If you need more detail, you know where to find me.
M

Good answer.

The effect of catecholamines depends on which adrenoreceptor it binds to. If it binds to alpha-1 receptors (e.g. in the gut, skin) it will cause vasoconstriction, however, if it binds to beta-2 receptors (e.g. skeletal muscle) it will cause vasodilation. This helps redistribute blood from the gut to muscles during exercise.
Original post by Jpw1097
Good answer.

The effect of catecholamines depends on which adrenoreceptor it binds to. If it binds to alpha-1 receptors (e.g. in the gut, skin) it will cause vasoconstriction, however, if it binds to beta-2 receptors (e.g. skeletal muscle) it will cause vasodilation. This helps redistribute blood from the gut to muscles during exercise.

@Jpw1097 Thank you for this valuable input. BTW time flies: are you an SHO now? What specialty if I may ask? Hearty congrats!
Reply 8
Original post by macpatgh-Sheldon
@Jpw1097 Thank you for this valuable input. BTW time flies: are you an SHO now? What specialty if I may ask? Hearty congrats!

Thanks very much. I am an SHO indeed. Currently working in O&G.

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