CARDIOVASCULAR AND RESPIRATORY SYSTEMS.
BLOOD PRESSURE PROBLEMS.
Baro reflex 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 hence
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 specialised 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 an 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 brain stem, in response to increased
Baroreceptor impulses the NTS activates the parasympathetic system the PSNS and inhibits the sympathetic system the
SNS has the PSNS and SNS have opposing effects on blood pressure's PSNS activation and SNS inhibition work together
in the same direction to maximise 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 decrease heart rate stroke volume and at the same time causes Vasco dilation 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 intention, 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. Baroreceptor reflexes are a short-term
response to sudden changes of blood pressure resulting from everyday activities and emotional states if hypertension or
hypotension persists for an extended period of time the Baroreceptors will reset to the new normal levels. In hypertensive
patients for example Baro reflex mechanism is adjusted to a higher normal pressure and therefore maintains hypertension
rather than suppresses it.
POSTURAL ORTHOSTATIC TACHYCARDIA SYNDROME.
It is a syndrome of symptoms predominantly caused by an exaggerated heart rate increase in response to standing POTS is
a frequent problem with a prevalence of about one in 500, it typically presents in late adolescence or early adulthood and
there is an observed female turn male ratio of at least four to one.
The clinical features of POTS can be divided into those related to the cardiovascular response and those whose
relationship is less direct to the cardiovascular symptoms are universal among patients and can include light headedness,
palpitations, exercise intolerance and in a minority of patient’s syncope
Non cardiovascular symptoms are not present in all patients but when they are they can include fatigue, anxiety, tremor,
headache, mental clouding often referred to patients as a brain fog and a variety of GI symptoms such as nausea and
bloating, it is common for the onset of symptoms to be described as following a viral infection, pregnancy, surgery, or
intense psychological stress.
Whether this represents a true association or as a form of recall bias is unknown, complicated by the relatively long
duration of time that usually passes between symptom onset and diagnosis being made.
BLOOD PRESSURE PROBLEMS.
Baro reflex 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 hence
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 specialised 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 an 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 brain stem, in response to increased
Baroreceptor impulses the NTS activates the parasympathetic system the PSNS and inhibits the sympathetic system the
SNS has the PSNS and SNS have opposing effects on blood pressure's PSNS activation and SNS inhibition work together
in the same direction to maximise 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 decrease heart rate stroke volume and at the same time causes Vasco dilation 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 intention, 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. Baroreceptor reflexes are a short-term
response to sudden changes of blood pressure resulting from everyday activities and emotional states if hypertension or
hypotension persists for an extended period of time the Baroreceptors will reset to the new normal levels. In hypertensive
patients for example Baro reflex mechanism is adjusted to a higher normal pressure and therefore maintains hypertension
rather than suppresses it.
POSTURAL ORTHOSTATIC TACHYCARDIA SYNDROME.
It is a syndrome of symptoms predominantly caused by an exaggerated heart rate increase in response to standing POTS is
a frequent problem with a prevalence of about one in 500, it typically presents in late adolescence or early adulthood and
there is an observed female turn male ratio of at least four to one.
The clinical features of POTS can be divided into those related to the cardiovascular response and those whose
relationship is less direct to the cardiovascular symptoms are universal among patients and can include light headedness,
palpitations, exercise intolerance and in a minority of patient’s syncope
Non cardiovascular symptoms are not present in all patients but when they are they can include fatigue, anxiety, tremor,
headache, mental clouding often referred to patients as a brain fog and a variety of GI symptoms such as nausea and
bloating, it is common for the onset of symptoms to be described as following a viral infection, pregnancy, surgery, or
intense psychological stress.
Whether this represents a true association or as a form of recall bias is unknown, complicated by the relatively long
duration of time that usually passes between symptom onset and diagnosis being made.
