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Bio question

How does LVH affect the parasympathetic or sympathetic
Hi,
If left ventricular hypertrophy has penetrated the A level syllabus, then I need to check the specs again!!

Basically, the muscle mass of the LV enlarges and this can be diagnosed quite easily on a chest radiograph and ECG; more advanced/invasive investigations do not add much value.

If the LV is beating harder [because of increased muscle tissue [myocardium], then cardiac output is likely to rise, and probably blood pressure, too:-

B.p. = CO * peripheral resistance

This increase ion bp will stimulate the baroreceptors in the carotid sinus, so that higher frequency of signals will be sent to the hypothalamus, in turn increasing parasympathetic outflow and reducing sympathetic outflow in a bid to reduce blood pressure towards normal. These changes will tend to have negative inotropic and negative chronotropic effects on the heart.

If you find this beyond your depth, do ask and I shall try to simplify [u might prefer to use google].

Be safe!
M.
Reply 2
Original post by macpatgh-Sheldon
Hi,
If left ventricular hypertrophy has penetrated the A level syllabus, then I need to check the specs again!!

Basically, the muscle mass of the LV enlarges and this can be diagnosed quite easily on a chest radiograph and ECG; more advanced/invasive investigations do not add much value.

If the LV is beating harder [because of increased muscle tissue [myocardium], then cardiac output is likely to rise, and probably blood pressure, too:-

B.p. = CO * peripheral resistance

This increase ion bp will stimulate the baroreceptors in the carotid sinus, so that higher frequency of signals will be sent to the hypothalamus, in turn increasing parasympathetic outflow and reducing sympathetic outflow in a bid to reduce blood pressure towards normal. These changes will tend to have negative inotropic and negative chronotropic effects on the heart.

If you find this beyond your depth, do ask and I shall try to simplify [u might prefer to use google].

Be safe!
M.


hey, im doing btec l3 science and i havent been teached about para and sympa outflow lol, can u make it simpler please
thanks but i do know about carotid sinus bit lol
Sure!

If bp rises due to one or more of several reasons [e.g. vasoconstriction [narrowing of the medium-sized arterioles will raise peripheral resistance:- think about this analogy: if you are pumping water into a hose from a fixed tap, the pressure generated will be greater if the hose is narrow, yeah? Similarly narrow arterioles will result in higher bp.].

The carotid sinus [which you have heard of you say] has receptors that can detect pressure [called baroreceptors - you might know that a barometer measures atmospheric pressure]. As these baroreceptors are on the inside of the sinus, they can detect the pressure of the blood passing them [in simple terms]. So if the bp is high [as is likely with LVH] the carotid sinus will send more impulses to the brain, which will react by reducing nerve impulses sent to heart via the sympathetic system and increase the impulses via the parasympathetic system [the latter in the vagus nerve i.e. the 10th cranial nerve].

The action of the parasympathetic system as regards the heart is to slow it down and reduce force of contraction [negative chronotropic and inotropic effects, respectively [you might have heard of a chronometer i.e. v accurate watch - chrono is to do with time]]. The sympathetic system does the opposite so you can work out its effects on the heart, yeah?

Good luck!
M.
Reply 4
Original post by macpatgh-Sheldon
Sure!

If bp rises due to one or more of several reasons [e.g. vasoconstriction [narrowing of the medium-sized arterioles will raise peripheral resistance:- think about this analogy: if you are pumping water into a hose from a fixed tap, the pressure generated will be greater if the hose is narrow, yeah? Similarly narrow arterioles will result in higher bp.].

The carotid sinus [which you have heard of you say] has receptors that can detect pressure [called baroreceptors - you might know that a barometer measures atmospheric pressure]. As these baroreceptors are on the inside of the sinus, they can detect the pressure of the blood passing them [in simple terms]. So if the bp is high [as is likely with LVH] the carotid sinus will send more impulses to the brain, which will react by reducing nerve impulses sent to heart via the sympathetic system and increase the impulses via the parasympathetic system [the latter in the vagus nerve i.e. the 10th cranial nerve].

The action of the parasympathetic system as regards the heart is to slow it down and reduce force of contraction [negative chronotropic and inotropic effects, respectively [you might have heard of a chronometer i.e. v accurate watch - chrono is to do with time]]. The sympathetic system does the opposite so you can work out its effects on the heart, yeah?

Good luck!
M.

Thank you! this really helped a lot and appreicate you taking your time to reply :smile:
Reply 5
Original post by macpatgh-Sheldon
Hi,
If left ventricular hypertrophy has penetrated the A level syllabus, then I need to check the specs again!!

Basically, the muscle mass of the LV enlarges and this can be diagnosed quite easily on a chest radiograph and ECG; more advanced/invasive investigations do not add much value.

If the LV is beating harder [because of increased muscle tissue [myocardium], then cardiac output is likely to rise, and probably blood pressure, too:-

B.p. = CO * peripheral resistance

This increase ion bp will stimulate the baroreceptors in the carotid sinus, so that higher frequency of signals will be sent to the hypothalamus, in turn increasing parasympathetic outflow and reducing sympathetic outflow in a bid to reduce blood pressure towards normal. These changes will tend to have negative inotropic and negative chronotropic effects on the heart.

If you find this beyond your depth, do ask and I shall try to simplify [u might prefer to use google].

Be safe!
M.

I actually think this is quite a difficult question the answer. The effect on the autonomic nervous system depends on the cause of the LVH. The most common causes of LVH are secondary to increased afterload, such as hypertension, aortic stenosis, rather than diseases of the heart muscle itself, such as hypertrophic cardiomyopathy.

In the case of increased afterload, there is reduced cardiac output, and so the baroreflex increases sympathetic outflow increasing heart rate and contractility, and also promotes LVH.

If the LVH is caused by something like hypertrophic cardiomyopathy, then as you have said, this may in theory increase parasympathetic outflow if the LVH increases cardiac output. However, the LVH and remodelling is pathological, and the LVH reduces the size of the LV chamber, which impairs filling, ultimately reducing stroke volume and cardiac output, which increases sympathetic outflow.
(edited 2 years ago)

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