Humoral and intra cardiac mechanisms of heart ‘ regulation.

HumoralHumoral and intra cardiac and intra cardiac mechanisms of heart ‘ mechanisms of heart ‘

regulation.regulation.

Humoral regulation of heartHumoral regulation of heart Effects of thyroid hormonesEffects of thyroid hormones Thyroid hormones increase transmission process Thyroid hormones increase transmission process

in ribosome and nucleus of cells. Intracellular in ribosome and nucleus of cells. Intracellular enzymes are stimulated due to increasing protein enzymes are stimulated due to increasing protein synthesis. Also increases glucose absorption and synthesis. Also increases glucose absorption and uptake of glucose by cells, increases glycolisis uptake of glucose by cells, increases glycolisis and gluconeogenesis. In blood plasma increases and gluconeogenesis. In blood plasma increases contents of free fatty acids. contents of free fatty acids.

All these effects of thyroid hormones lead to All these effects of thyroid hormones lead to increase activity of mitochondria in heart cells increase activity of mitochondria in heart cells and ATP formation in it. So, both activity of heart and ATP formation in it. So, both activity of heart muscle and conduction of impulses are muscle and conduction of impulses are stimulated.stimulated.

Effects of adrenocortical Effects of adrenocortical hormoneshormones

Aldosterone causes increasing Na+ and Cl- Aldosterone causes increasing Na+ and Cl- in blood and decreases K+. This is actually in blood and decreases K+. This is actually for producing action potential in the heart. for producing action potential in the heart. Cortisol stimulates gluconeogenesis and Cortisol stimulates gluconeogenesis and increase blood glucose level. increase blood glucose level.

Amino acids blood level and free fatty acids Amino acids blood level and free fatty acids concentration in blood increases also. concentration in blood increases also. Utilization of free fatty acids for energy Utilization of free fatty acids for energy increases. These mechanisms actual in increases. These mechanisms actual in stress reaction. So heart activity is stress reaction. So heart activity is stimulated.stimulated.

Hormones of Langerhans’ islets Hormones of Langerhans’ islets effectseffects

Insulin promotes facilitated diffusion of glucose into Insulin promotes facilitated diffusion of glucose into cells by activation glucokinase that phosphorilates cells by activation glucokinase that phosphorilates glucose and traps it in the cell, promotes glucose glucose and traps it in the cell, promotes glucose utilization, causes active transport of amino acids utilization, causes active transport of amino acids into cells, promote translation of mRNA in ribosome into cells, promote translation of mRNA in ribosome to form new proteins. Also insulin promotes glucose to form new proteins. Also insulin promotes glucose utilization in cardiac muscle, because of utilization utilization in cardiac muscle, because of utilization fatty acids for energy. fatty acids for energy.

Clucagone stimulate gluconeogenesis, mobilizes Clucagone stimulate gluconeogenesis, mobilizes fatty acids from adipose tissue, promotes utilization fatty acids from adipose tissue, promotes utilization free fatty acids foe energy and promotes free fatty acids foe energy and promotes gluconeogenesis from glycerol. So both hormones gluconeogenesis from glycerol. So both hormones can increase strength of heartbeat.can increase strength of heartbeat.

Endocrine function of heartEndocrine function of heart

Myocardium, especially in heart Myocardium, especially in heart auricles capable to secretion of auricles capable to secretion of regulatory substances as atria Na-regulatory substances as atria Na-ureic peptide, which increases loss of ureic peptide, which increases loss of Na+ in increase of systemic Na+ in increase of systemic pressure, or digitalis-like substances, pressure, or digitalis-like substances, which can stimulate heart activity.which can stimulate heart activity.

Intrinsic regulationIntrinsic regulation Intrinsic regulation is performed in Intrinsic regulation is performed in

response changes of blood volume, response changes of blood volume, flowing into the heart. It is known as Frank flowing into the heart. It is known as Frank Starling low. Within physiological limits Starling low. Within physiological limits heart pumps all blood that comes to it heart pumps all blood that comes to it without allowing excessive damming of without allowing excessive damming of blood in veins. blood in veins.

Cardiac contraction is directly proportional Cardiac contraction is directly proportional to initial length of its fibers. In end-to initial length of its fibers. In end-diastolic volume over 180 ml excessive diastolic volume over 180 ml excessive stretching heart fibers occurs and strength stretching heart fibers occurs and strength of next cardiac contraction decreases.of next cardiac contraction decreases.

Anrep's effectAnrep's effect

Increase of blood flow in aorta and so Increase of blood flow in aorta and so coronary arteries leads to excessive coronary arteries leads to excessive stretching surrounding myocardial stretching surrounding myocardial cells. cells.

According to Frank Starling low According to Frank Starling low cardiac contraction is directly cardiac contraction is directly proportional to initial length of its proportional to initial length of its fibers. So increase of coronary blood fibers. So increase of coronary blood flow leads to stimulation heartbeat.flow leads to stimulation heartbeat.

Boudichi phenomenonBoudichi phenomenon

In evaluation heart beat rate In evaluation heart beat rate increase of every next heart increase of every next heart contraction is observed. contraction is observed.

It caused by rising of Ca2+ influx into It caused by rising of Ca2+ influx into myocardial cells without perfect myocardial cells without perfect outflow, because of shortening of outflow, because of shortening of cardio cycle duration. cardio cycle duration.

Effects of nn. vagiEffects of nn. vagi

Effects of nn. vagus on Effects of nn. vagus on the heart activity. the heart activity. Parasympathetic Parasympathetic stimulation causes stimulation causes decrease in heart rate decrease in heart rate and contractility, and contractility, causing blood flow to causing blood flow to decrease. decrease.

It is known as negative It is known as negative inotropic, dromotropic, inotropic, dromotropic, bathmotropic and bathmotropic and chronotropic effect. chronotropic effect.

Effects of acetylcholinEffects of acetylcholin Effects of acetylcholin leads to increase of K+ Effects of acetylcholin leads to increase of K+

permeability through cell membrane in permeability through cell membrane in conductive system, which leads to hyper-conductive system, which leads to hyper-polarisation and cause such effects to the heart polarisation and cause such effects to the heart activity:activity:

- Negative inotropic effect - decreasing strength - Negative inotropic effect - decreasing strength of heart contractions;of heart contractions;

- Negative chrono-tropic effect - decreasing - Negative chrono-tropic effect - decreasing heartbeat rate;heartbeat rate;

-Negative dromo-tropic effect - decreasing heart -Negative dromo-tropic effect - decreasing heart conductibility;conductibility;

- Negative bathmo-tropic effect - decreasing - Negative bathmo-tropic effect - decreasing excitability of heart muscle.excitability of heart muscle.

Location of receptors in the Location of receptors in the heartheart

Heart muscle contains, both Heart muscle contains, both chemical and stretch receptors chemical and stretch receptors in coronary vessels, all heart in coronary vessels, all heart cameras and pericardium. cameras and pericardium. Stretch receptors are irritated by Stretch receptors are irritated by changing blood pressure in heart changing blood pressure in heart cameras and vessels. cameras and vessels.

Chemo sensitive cells, which are Chemo sensitive cells, which are stimulated by decrease O2, stimulated by decrease O2, increase of CO2, H+ and increase of CO2, H+ and biological active substances biological active substances also, are called as also, are called as chemoreceptors. chemoreceptors.

Reflexes from atriaReflexes from atria When atria pressure increase due to increasing blood When atria pressure increase due to increasing blood

volume, atria stretched. Signals pass to afferent volume, atria stretched. Signals pass to afferent arterioles in kidneys to cause vasodilatation and arterioles in kidneys to cause vasodilatation and glomerullar capillary pressure, thereby increasing glomerullar capillary pressure, thereby increasing glomerullar filtration. Signals also pass to hypothalamus glomerullar filtration. Signals also pass to hypothalamus to decrease antidiuretic hormone secretion and so fluid to decrease antidiuretic hormone secretion and so fluid reabsorbtion. It causes decreasing both blood volume reabsorbtion. It causes decreasing both blood volume and arterial pressure to normal.and arterial pressure to normal.

Other reflex reaction is known as atria and pulmonary Other reflex reaction is known as atria and pulmonary artery reflex. When atria pressure increase due to artery reflex. When atria pressure increase due to increasing blood volume, atria stretched. Low-pressure increasing blood volume, atria stretched. Low-pressure receptors, similar to baroreceptors, in atria and receptors, similar to baroreceptors, in atria and pulmonary arteries stretched and stimulated. Signals pulmonary arteries stretched and stimulated. Signals pass to vasomotor center and inhibit vasculomotor pass to vasomotor center and inhibit vasculomotor area. Arterial pressure decreases to normal.area. Arterial pressure decreases to normal.

Reflex reactions from Reflex reactions from receptors of pericardium, receptors of pericardium,

endocardium and coronary endocardium and coronary vesselsvessels

Reflex reactions from receptors of Reflex reactions from receptors of pericardium, endocardium and coronary pericardium, endocardium and coronary vessels lead to stimulation n. vagus. It vessels lead to stimulation n. vagus. It leads to parasympathetic stimulation of leads to parasympathetic stimulation of the heart.the heart.

Parasympathetic stimulation causes Parasympathetic stimulation causes decrease in heart rate and contractility, decrease in heart rate and contractility, causing blood flow to decrease. It is known causing blood flow to decrease. It is known as negative inotropic, dromotropic, as negative inotropic, dromotropic, bathmotropic and chronotropic effect. bathmotropic and chronotropic effect.

Baroreceptor reflexesBaroreceptor reflexes Increasing arterial pressure stretched and Increasing arterial pressure stretched and

stimulated baroreceptors in carotid sinus and stimulated baroreceptors in carotid sinus and aortic arc. Signals pass through glossopharyngeal aortic arc. Signals pass through glossopharyngeal and vagal nerve to tractus solitarius in medulla. and vagal nerve to tractus solitarius in medulla. Secondary signals from tractus solitarius inhibit Secondary signals from tractus solitarius inhibit vasoconstrictor center and excite vagal center. vasoconstrictor center and excite vagal center.

Peripheral vasodilatation and decrease both heart Peripheral vasodilatation and decrease both heart rate and contractility occur. Arterial pressure rate and contractility occur. Arterial pressure decreases to normal. When arterial pressure decreases to normal. When arterial pressure decreases, whole process occurs, causing decreases, whole process occurs, causing opposite result.opposite result.

Irritation of visceroreceptorsIrritation of visceroreceptors

Irritation of visceroreceptors results in Irritation of visceroreceptors results in stimulation of vagal nuclei, which cause stimulation of vagal nuclei, which cause decreasing blood pressure and heartbeat. decreasing blood pressure and heartbeat. Parasympathetic stimulation causes Parasympathetic stimulation causes decrease in heart rate and contractility, decrease in heart rate and contractility, causing blood flow to decrease. It is known causing blood flow to decrease. It is known as negative inotropic, dromotropic, as negative inotropic, dromotropic, bathmotropic and chronotropic effect. bathmotropic and chronotropic effect.

This mechanism is important for doctor in This mechanism is important for doctor in performing diagnostic procedures, when performing diagnostic procedures, when probes from apparatuses are attached into probes from apparatuses are attached into visceral organs. This may cause excessive visceral organs. This may cause excessive irritation of visceral receptors.irritation of visceral receptors.

Mechanisms of heart auto Mechanisms of heart auto regulationregulation

Greater rate of metabolism or less blood flow Greater rate of metabolism or less blood flow causes decreasing O2 supply and other nutrients. causes decreasing O2 supply and other nutrients. Therefore rate of formation vasodilator substances Therefore rate of formation vasodilator substances (CO2, lactic acid, adenosine, histamine, K+ and H+) (CO2, lactic acid, adenosine, histamine, K+ and H+) rises. When decreasing both blood flow and oxygen rises. When decreasing both blood flow and oxygen supply smooth muscle in precapillary sphincter supply smooth muscle in precapillary sphincter dilate, and blood flow increases. dilate, and blood flow increases.

Moderate increasing temperature increases Moderate increasing temperature increases contractile strength of heart. Prolonged increase of contractile strength of heart. Prolonged increase of temperature exhausts metabolic system of heart temperature exhausts metabolic system of heart and causes cardiac weakness. Anoxia increases and causes cardiac weakness. Anoxia increases heart rate. Moderate increase CO2 stimulates heart heart rate. Moderate increase CO2 stimulates heart rate. Greater increase CO2 decreases heart rate.rate. Greater increase CO2 decreases heart rate.

Atria and pulmonary artery Atria and pulmonary artery reflexreflex

When arterial pressure increases due to When arterial pressure increases due to increasing blood volume, atria stretched. increasing blood volume, atria stretched. Low-pressure receptors, similar to Low-pressure receptors, similar to baroreceptors, in atria and pulmonary baroreceptors, in atria and pulmonary arteries stretched and stimulated. Signals arteries stretched and stimulated. Signals pass to vasomotor center and inhibit pass to vasomotor center and inhibit vasculomotor area. Arterial pressure vasculomotor area. Arterial pressure decreases to normal. decreases to normal.

Excessive stretching of lung tissue causes Excessive stretching of lung tissue causes excitation of n. vagus. It leads to excitation of n. vagus. It leads to parasympathetic stimulation of the heart. parasympathetic stimulation of the heart. Parasympathetic stimulation causes Parasympathetic stimulation causes decrease in heart rate and contractility, decrease in heart rate and contractility, causing blood flow to decrease.causing blood flow to decrease.

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