Baroreflex Regulation of Blood Pressure, Animation.

Baroreflex Regulation of Blood Pressure, Animation.


Baroreflex, or baroreceptor reflex, is one
of the mechanisms the body uses to maintain stable blood pressure levels or homeostasis. Baroreflex is a rapid negative feedback loop
in which an elevated blood pressure causes heart rate and blood pressure to decrease. Reversely, a decrease in blood pressure leads
to an increased heart rate, returning blood pressure to normal levels. The reflex starts with specialized neurons
called baroreceptors. These are stretch receptors located in the
wall of the aortic arch and carotid sinus. Increased blood pressure stretches the wall
of the aorta and carotid arteries causing baroreceptors to fire action potentials at
a higher than normal rate. These increased activities are sent via the
vagus and glossopharyngeal nerves to the nucleus of the tractus solitarius – the NTS – in
the brainstem. In response to increased baroreceptor impulses,
the NTS activates the parasympathetic system – the PSNS – and inhibits the sympathetic
system – the SNS. As the PSNS and SNS have opposing effects
on blood pressures, PSNS activation and SNS inhibition work together in the same direction
to maximize blood pressure reduction. Parasympathetic stimulation decreases heart
rate by releasing acetylcholine which acts on the pacemaker cells of the SA node. Inhibition of the sympathetic division decreases
heart rate, stroke volume and at the same time causes vasodilation of blood vessels. Together, these events rapidly bring DOWN
blood pressure levels back to normal. When a person has a sudden drop in blood pressure,
for example when standing up, the decreased blood pressure is sensed by baroreceptors
as a decrease in tension. Baroreceptors fire at a lower than normal
rate and the information is again transmitted to the NTS. The NTS reacts by inhibiting parasympathetic
and activating sympathetic activities. The sympathetic system releases norepinephrine
which acts on the SA node to increase heart rate; on cardiac myocytes to increase stroke
volume and on smooth muscle cells of blood vessels to cause vasoconstriction. Together, these events rapidly bring UP blood
pressure levels back to normal. Baroreflex is a short-term response to sudden
changes of blood pressure resulted from everyday activities and emotional states. If hypertension or hypotension persists for
a long period of time, the baroreceptors will reset to the “new normal” levels. In hypertensive patients for example, baroreflex
mechanism is adjusted to a higher “normal” pressure and therefore MAINTAINS hypertension
rather than suppresses it.

44 thoughts on “Baroreflex Regulation of Blood Pressure, Animation.”

  1. What effects are observed when the body is inverted such as during certain yoga and gymnastic exercises?
    Heard that the baroreflex mediated by the carotid sinuses gets 'stimulated' by inversion and thereby produces a reduction of BP; this effect is said to become sustained with repetition of the exercises.

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  3. This is out of the scope of the video, but is there a way to reverse the new hypertensive normal after chronic hypertension?

  4. lam not understanding when the body using the baroreflexe ?? during response any effect ??? please anyone answer

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