Regulation of systemic circulation

Decrease of tone of precapillary sphincters Influences of metabolic products on the diameter of vessels Increase of Н + ions, pyroveniger and lactic acids, decrease of pO 2 and increase of pCO 2 in tissues Dilatation of arterioles Increase of blood flow in organs

Basal tone of vessels Smooth muscles of vessels wall don’t relax whole. It all time has some tension – muscular tone. Tonic condition is connect with changes of electrical characteristic and some contraction of muscles. Tone of smooth muscles support by two mechanisms: myogenic and neuro-humoral. Miogenic regulation play the main role in the support of vessel tone. When absent all nervous and humoral influences, present vessel tone or basal tone. In the base of basal tone is possibility of some smooth cells to the spontaneously activity and spread of excitation from cell to cell; it provide rhythmical changing of tone. It present in arterioles, precapillares sphincters. Influences, which decrease level of membrane potential, increase frequency of spontaneously impulses and amplitude of contraction of smooth muscles. Hyper polarization of membrane leads to disappeared of spontaneously excitability and muscles contraction.

Role of mechano- and chemoreceptor in regulation of the vessels tone From mechanoreceptors of aorta arc sensory information transmit by left depressor (aortic) nerve, brunch of n.vagus to the medulla oblongata. Excitation from mechanoreceptors of carotid sinus zone lead by Sino carotid nerve (brunch of glossopharingeal nerve) to the medulla oblongata.

Characteristic of afferent link Sensory innervations of heart and vessels is present by nerve ending. Receptors divided by it function on mechanoreceptors, which are reacted on the changing of arterial pressure and chemo receptors, which are reacted on the changing of chemical composition of blood. Irritation for mechanoreceptors is the speed and level of tissues stretching by increase or pulse wave of blood pressure. Angioreceptors are present at all vessel system and have the whole receptor field, it maximal presents at the main reflector zones: aortic, sino-carotid, in the vessels of pulmonary cycle of the blood circulation. At the answer on the each systolic increase of arterial pressure, mechanoreceptors of that zones generate impulses, which disappeared in the diastolic decrease of pressure. Minimal threshold of excitation of mechanoreceptors is 40 mm Hg, maximal is 200 mm Hg. Increase of pressure higher than that level don’t lead to addition increase of impulsation.

Central mechanisms, which regulate connection between level of cardiac output and tone of vessels, working by help of complex of nervous structures, which named vasomotor center. Structures of vasomotor center are present in spinal cord, medulla oblongata, hypothalamus, cortex of big hemisperes. Spinal level of regulation is in the lateral root of thoracic and lumbar segments and consist of nervous cells, axons of which produce the vasculoconstrictors fibers. That neurons support their level of excitation by help of impulses from higher structures of nervous system. Central part in regulation of vascular tone

Vasomotor center of medulla oblongata is the main center of regulation of blood flow. It located on the bottom of 4 ventricle, in it upper part. Vasomotor center divided on pressor and depressor zones. Pressor zone support increase of arterial pressure. It connect with the increase of tone of resistive vessels. Also increase frequency and strength of heart contraction and as result minute volume of blood flow. Regulatory influences of neurons of pressor zone act by help of increase of tone of sympathetic nervous system on heart and vessels. Depressor zone support decrease of arterial pressure, heart work. It is the place of changes the impulses, which are coming from mechanoreceptors of reflector zones and cause central inhibition of tonic impulses of vasoconstrictors. Parallel the information from that zone by help of parasympathetic nerves go to heart. As result, decrease work and stroke volume of blood. Also, depressor zone act reflector inhibition of pressor zone.

Role of brain cortex and hypothalamus in regulation of blood flow Centers of hypothalamus give the descendent influences on the vasomotor center of medulla oblongata. In hypothalamus present depressor and pressor zones. That is why hypothalamic level give the same double reaction as bulbar center. Posterolateral part of hypothalamus cause excitation of vasomotor center. Anterior part of hypothalamus can cause mild inhibition of one. Some zones of cortex also give the descendent influences on the vasomotor center of medulla oblongata. Motor cortex excites vasomotor center. Anterior temporal lobe, orbital areas of frontal cortex, cingulated gyrus, amygdale, septum and hippocampus can also control vasomotor center. That influences form as a result of compare the information, which enter in higher part of nervous system from different receptor zones. It support realization of cardio-vascular component of emotions, reaction of behavior.

Nervous efferent link of regulation of vascular tone Neural mechanism of efferent regulation of blood flow act by - Preganglionic sympathetic neurons, body of which present in the anterior root of thoracic and lumbar part of spinal cord and postganglionic neurons, which are present in para- and prevertebral sympathetic ganglion. - Preganglionic parasympathetic neurons of nucleus of n. vagus, nucleus of pelvic nerve, which present in sacral part of spinal cord, and their postganglionic neurons. - For hole visceral organs is efferent neurons of metasympathetic nervous system, which are present in the intamural ganglion of their wall. All neurons is the end way from efferent and central influences, which throught the adrenergic, cholinergic and other mechanism of regulation act on heart and vessels.

Norepinephrine Epinephrine Action with β-adrenoreceptors of vessel wall Action with β-adrenoreceptors of vessel wall Dilation of vessels Spasm of vessels of skeen, digestive organs, kidney and lungs Peculiarities of influences of catecholamine on the diameter of vessels Adrenal gland medulla Action with α- adrenoreceptors of vessel wall Dilation of vessels of muscles, brain, heart Action with α- adrenoreceptors of vessel wall

Influences of chatecholamines and vasopressin on the vessel tone Influences of chatecholamines from adrenal glands determined by presents of different kinds of adrenoreceptors – α and β. Connection of hormones with α–adrenoreceptors act constriction of vessel wall, with β–adrenoreceptor - relaxation. Adrenalin connect with α– and β–adrenoreceptor, nor epinephrine with α–adrenoreceptor. Adrenalin has strong action on vessels. On artery and arterioles of skin, digestive organs, kidneys and lungs it has constrictive influences; on the vessels of skeletal muscles, brain and heart - dilatatory. On the physical load, emotional load it increase blood flow through skeletal muscles, brain and heart. Vasopressin (antidiuretic hormone) cause spasm of artery and arterioles of organs of abdominal cavity and lungs. But vessels of brain and heart reacted on that hormone by dilatation, which help increase the nutrition of brain and heart.

Rennin–a- a Rennin–angiotensin- aldosteron system Angiotensinogen Cells of liverUxta glomerular cell of kidney Rennin Angiotensin І Angiotensin ІІ Angiotensin converting enzyme Angiotensin ІІІ Adrenal glands Aldosteron Reabsorbtion of water in kidneys Increase of water in body Vascular spasm Increase of arterial pressure

ennin–a-a Role of rennin–angiotensin-aldosteron system in regulation of vessel tone Uxta glomerular cells of kidney produce enzyme rennin as the answer of decrease of kidneys perfusion or increase of influences of sympathetic nervous system. It convert angiotensinogen, which produced in liver, in Angiotensin І. Angiotensin І, by the influences of angiotensin converting enzyme in the vessel of lung, converted in angiotensin II. Angiotensin ІІ has strong vasculoconstrictor influences. It can explain of presents of sensory to angiotensin II receptors in precapillary arterioles. Very big dose of angiotensin II can cause the spasm of vessels of heart and brain. Increase of rennin and angiotensin in blood increase the thirst (need to drink water). Also angiotensin II or angiotensin III, stimulate the production of aldosteron. Aldosteron, which produce in the cortex of adrenal glands, increase reabsorbtion of sodium in kidneys, salivary glands, digestive system, and change the sensation of vessel walls to the influences of epinephrine and norepinephrine. This is the r rr rennin– angiotensin-aldosteron system.

Change the body pose from vertical to horizontal Increase of blood flow to heart Increase the stroke volume Increase of impulsation from mechanoreceptors of aortic arc Activation of depressor part of vasomotor center Inhibition of pressor part of vasomotor center Decrease of frequency and force of heart beat, dilation of vessels Changes of blood flow in the clinostatic pose

Change the body pose from horizontal to vertical Depo of blood in the vein of down part ofbody Decrease of blood flow to heart Decrease of stroke volume Decrease of impulsation from mechanoreceptors of aortic arc Activation of pressor part of vasomotor center Increase of frequency and force of heart beat, vascular spasm Changes of blood flow in the orthostatic pose

Regulation of blood flow in physical exercises In physical exercises impulses from pyramidal neurons of motor zone in cerebral cortex passes both to skeletal muscles and vasomotor center. Than through sympathetic influences heart activity and vasoconstriction are promoted. Adrenal glands also produce adrenalin and release it to the blood flow. Proprioreceptor activation spread impulses through interneurons to sympathetic nerve centers. So, contraction of skeletal muscle during exercise compress blood vessels, translocate blood from peripheral vessels into heart, increase cardiac output and increase arterial pressure.

Bleeding Decrease of filtration in kidneys glomerulus's Decrease of impulsation from mechanoreceptors and increase from chemo receptors of aorta arc and carotid sinus Activation of rennin- angiotensin-aldosteron system Activation of pressor part of vascular- motor centre Increase of influences of sympathetic nervous on heart Increase of heart beat and the strength of heart contraction Spasm of vessels and decrease of capacity of circulatory bed Angiotensin ІІ Increase of Na+ and water reabsorbtion Increase of Volume of Blood Circulation Renew of blood flow in the case of bleeding

Normotonic type of cardio-vascular reaction on the physical load

Interpretation % of increase heart beat - % of increase pulse pressure (increase systolic AP and decrease of diastolic AP) % of increase heart beat - % of increase pulse pressure (increase systolic AP and decrease of diastolic AP) This is rational reaction, because in the case of heart beat increase also increase pulse pressure and stroke volume of blood. This is rational reaction, because in the case of heart beat increase also increase pulse pressure and stroke volume of blood. Increase of systolic pressure is the increase of systole of left ventricle Increase of systolic pressure is the increase of systole of left ventricle Decrease of diastolic pressure is decrease of arteriole tonus, that help of better supply of the blood on periphery Decrease of diastolic pressure is decrease of arteriole tonus, that help of better supply of the blood on periphery

Hypotonic type of cardio-vascular reaction on the physical load Functional insufficiency of heart

Hypertonic type of cardio-vascular reaction on the physical load Functional insufficiency of heart and blood vessels. Predictor of arterial hypertension.

Distonic type of cardio-vascular reaction on the physical load Functional insufficiency of blood vessels. Predictor of autonomic distony.

Step type of cardio-vascular reaction on the physical load Functional insufficiency of regulatory apparatuses of blood flow.

Cardiovascular Adjustments to Exercise

Fetal Circulation No circulation to lungs Foramen ovale Ductus arteriosum Circulation must go to placenta Umbilical aa., vv.

Adult remnants of fetal circulation AdultFetus Fossa ovale Foramen ovale Ligamentum arteriosum Ductus arteriosus Medial umbilical ligaments Umbilical aa.(within fetus) Round ligament (ligamentum teres) of liver Umbilical v.(within fetus) Ligamentum venosum Ductus venosus Medial umbilical ligament Umbilical cord (leaving fetus)

Hepatic Portal System

Thank you!