Blood Circulation System and It Regulation. Blood Circulation in Facial Region

5/20/2018 Blood Circulation System and It Regulation. Blood Circulation in Facial Region

1/23

Theme

Blood circulation system and its

regulation.

Blood circulation in facial region


2/23

Electrophysiological properties

of the contractive myocardium

The main electrophysiological properties of thecontractive myocardium are automaticity,contractility, conductability and excitability.

Automaticity is property to contract replying toelectrical impulses, originated in pacemaker cellsof the conduction system of the heart.

Contractility is property to contract replying to

irritation.Conductibility is property to spread electricalimpulses through the conduction system andcontractive myocardium.

Excitability is property to reply the irritation.


3/23

Automaticity of the heartStructure of conduction system. Action potentials that originate in thesinoatrial node (SA-node) spread to adjacent myocardial cells of the

right and left atria through the gap junction between these cells.

Since the myocardium of the atria is separated from the myocardium of

ventricles by the fibroses skeleton of the heart, the impulse cannot be

conducted directly from the atria to the ventricles. Besides that atriahave to contract before ventricles to guarantee pumping of blood.

Once the impulses spreads through the atria, it passes to the atrio-

ventricular node (AV-node), which is located on the inferior portion of

the internal septum. From here, the impulse continues through the

atrio-ventricular bundle, or bundle of His, beginning at the top of theinterventricular septum. The atrio-ventricular bundle divides into right

and left bundle branches, which are continues with Purkinje fibers

within the ventricular walls.


4/23

Function of pacemaker centers.

Some other regions of the heart, including the areaaround SA-node and the atrio-ventricular bundlecan potentially produce pacemaker potentials. Therate of spontaneous depolarization of these cellshowever is slower, than that of SA-node.

A pacemaker other than SA-node is called asectopic pacemaker or ectopic focus.

In a normal heart, however, only one regiondemonstrates spontaneous electrical activity andby this means functions as a pacemaker - SA-node.


5/23

As it determined SA-node produce 60-90 impulsesper minute, AV-node - 40-50, bundle of His - 20-30 and Purkinje fibers 10-20 impulses per minute.

The potential pacemaker cells are stimulated byaction potential from SA-node before they canstimulate themselves through their own pacemaker

potentials. If action potentials from the SA-node

are prevented from reaching these areas (throughblockade of conduction), they will generatepacemaker potentials at their own rate and save assites for the origin of action as pacemakers.


6/23

Cardiac cycle

Period fro end of one heart contraction to end of next, is called cardiaccycle. There are two phases systole, when heart contracts and diastole,when heart dilates. Diastole can be divided into:

- Period of isometric relaxation, during which ventricles begin to relax

and pulmonary valves close;- Period of rapid filling of ventricles, when AV valves open;

- Atria systole, when atria contract and pump 20-30 % blood intoventricles.

Systole is composed by:

- Period of isometric contraction, when ventricles begin to contract andAV valves are closed;

- Period of ejection: during rapid ejection 70 % empting occur and inslow ejection last 30 % empting occur;

- Protodiastole.


7/23

Physiological analysis of cardiac

output

Stroke work output is the amount of blood that leftventricle pump to aorta during each cardiac cycle.Volume of blood on each ventricle at end of

diastole is called end-diastolic volume andmeasures 120-140 ml. Volume of blood in theeach ventricle at end of systole is called endsystolic volume and measures 50-60 ml.

Blood volume, which heart pumps per minutecalled as minute blood volume. It may becalculated by multiply stroke volume to rate ofheartbeat and normally equal to 4-6,5 l/min. In

physical exercises it rises to 10 l/min and more.


8/23

Heart sounds

Movement of heart structures in heart contraction produces

heart sounds. First heart sound occurs at beginning of

systole, mainly due to closure of AV valves. Second heart

sound occurs at the end of systole, mainly due to closure of

semi lunar valves. Third heart sound occurs at beginning ofmiddle third diastole is produced by oscillation of blood

back and forth between walls of ventricles initiated by

inrushing blood from atria. Fourth heart sound occurs

when atria contracts. First and second heart sounds canhead by ear. Abnormal heart sounds are known as heart

murmurs. Functional murmurs appear because of

insufficient function of heart valves.


9/23

Effects of catecholamynes are transmitted

by alfa- and beta-adrenoreceptors

Adrenalin and noradrenalin stimulate heat activityand cause positive regulatory effects:

- Positive inotropic effect - increasing strength of

heart contractions;- Positive chrono-tropic effect - increasingheartbeat rate;

- Positive dromo-tropic effect - increasing heart

conductibility;- Positive bathmo-tropic effect - increasingexcitability of heart muscle.

Nor-epinephrine increases permeability of cardiac

fiber membrane to Na+and Ca2+.


10/23

Effects of acetylcholin

Effects of acetylcholin leads to increase of K+permeability through cell membrane in conductivesystem, which leads to hyper-polarisation and

cause such effects to the heart activity:- Negative inotropic effect - decreasing strength ofheart contractions;

- Negative chrono-tropic effect - decreasing

heartbeat rate;-Negative dromo-tropic effect - decreasing heartconductibility;

- Negative bathmo-tropic effect - decreasing

excitability of heart muscle.


11/23

Effects of ions

-Ca2+ causes spastic contraction of heart.

Decreasing Ca2+causes cardiac flaccidity.

Excessive concentration of K+

causes decreasingheart rate. Impulse' transmission through AV

bundle is blocked. If K+ level was previously

decreased, increasing Concentration of K+capable

normalize cardiac rhythm. Na+ competes Ca2+ incontractile process. So increasing Na+may depress

cardiac contraction.


12/23

Effects of thyroid hormones.

Thyroid hormones increase transmission processin ribosome and nucleus of cells. Intracellularenzymes are stimulated due to increasing protein

synthesis. Also increases glucose absorption anduptake of glucose by cells, increases glycolisis andgluconeogenesis. In blood plasma increasescontents of free fatty acids. All these effects of

thyroid hormones lead to increase activity ofmitochondria in heart cells and ATP formation init. So, both activity of heart muscle andconduction of impulses are stimulated.


13/23

Effects of adrenocortical

hormones.

Aldosterone causes increasing Na+ and Cl- in

blood and decreases K+. This is actually for

producing action potential in the heart. Cortisol

stimulates gluconeogenesis and increase blood

glucose level. Amino acids blood level and free

fatty acids concentration in blood increases also.

Utilization of free fatty acids for energy increases.These mechanisms actual in stress reaction. So

heart activity is stimulated.


14/23

Hormones of islets of Langerhans

Hormones of islets of Langerhans effects. Insulin promotesfacilitated diffusion of glucose into cells by activationglucokinase that phosphorilates glucose and traps it in thecell, promotes glucose utilization, causes active transport ofamino acids into cells, promote translation of mRNA inribosome to form new proteins. Also insulin promotesglucose utilization in cardiac muscle, because of utilizationfatty acids for energy. Clucagone stimulate

gluconeogenesis, mobilizes fatty acids from adipose tissue,promotes utilization free fatty acids foe energy andpromotes gluconeogenesis from glycerol. So both hormonescan increase strength of heartbeat.


15/23

Endocrine function of heart.

Endocrine function of heart. Myocardium,

especially in heart auricles capable to

secretion of regulatory substances as atriaNa-ureic peptide, which increases loss of

Na+ in increase of systemic pressure, or

digitalis-like substances, which canstimulate heart activity.


16/23

Mechanisms of heart auto

regulation

Greater rate of metabolism or less blood flowcauses decreasing O2 supply and other nutrients.Therefore rate of formation vasodilator substances(CO

2

, lactic acid, adenosine, histamine, K+andH+) rises. When decreasing both blood flow andoxygen supply smooth muscle in precapillarysphincter dilate, and blood flow increases.Moderate increasing temperature increases

contractile strength of heart. Prolonged increase oftemperature exhausts metabolic system of heartand causes cardiac weakness. Anoxia increasesheart rate. Moderate increase CO2stimulates heart

rate. Greater increase CO2decreases heart rate.


17/23

Laws of heart

Intrinsic regulation is performed in response

changes of blood volume, flowing into the heart. It

is known as Frank Starling low. Within

physiological limits heart pumps all blood thatcomes to it without allowing excessive damming

of blood in veins. Cardiac contraction is directly

proportional to initial length of its fibers. In end-

diastolic volume over 180 ml excessive stretchingheart fibers occurs and strength of next cardiac

contraction decreases.


18/23

Laws of heart

Anrep's low. Increase of blood flow in aorta andso coronary arteries leads to excessive stretchingsurrounding myocardial cells. According to Frank

Starling low cardiac contraction is directlyproportional to initial length of its fibers. Soincrease of coronary blood flow leads tostimulation heartbeat.

Boudichi phenomenon. In evaluation heart beatrate increase of every next heart contraction isobserved. It caused by rising of Ca2+ influx intomyocardial cells without perfect outflow, because

of shortening of cardio cycle duration.


19/23

General characteristic of central nervous

regulation of heart activity

Central nervous system affects regulation of bloodflow and pumping activity of the heart and

provides very rapid control of arterial pressure.Cerebral cortex control heart activity to correct itdepending on body needs when performing

behavioral reactions. Secondary somatic sensoryzone takes part in analysis of afferent informationfrom the hart. Pre-motor cortex may correct heart

activity by descendant influences throughhypothalamus. Anterior hypothalamus promotes

parasympathetic control of heart activity. Posteriorhypothalamus realizes their effects through

sympathetic nervous system.


20/23

Specialties of vagal innervations

of the heart

Right n. vagus controls mainly right atrium andSA node. Left n. vagus control AV node, His

bundle and all contractile myocardium. So

irritation of right nerve causes bradycardia. Effectsof left nerve lead to decrease of contractility andconductibility.

Effects of nn. vagus on the heart activity.

Parasympathetic stimulation causes decrease inheart rate and contractility, causing blood flow todecrease. It is known as negative inotropic,dromotropic, bathmotropic and chronotropic

effect.


21/23

Sympathetic effects

Sympathetic nerves from Th1-5control activity of the heartand large vessels. First neuron lays in lateral horns of spinalcord. Second neuron locates in sympathetic ganglions.Sympathetic nerve system gives to the heart vasoconstrictor

and vasodilator fibers. Vasoconstrictor impulses aretransmitted through alfa-adrenoreceptors, which are mostspread in major coronary vessels. Transmission impulsesthrough beta-adrenergic receptors lead to dilation of small

coronary vessels. Sympathetic influence produces positiveinotropic, chronotropic, dromotropic, bathmotropic effects,which is increase of strength, rate of heartbeat andstimulating excitability and conductibility also.


22/23

Control of heart activity by

vasomotor center

Lateral portion of vasomotor center transmit

excitatory signals through sympathetic fibers to

heart to increase its rate and contractility. Medial

portion of vasomotor center transmit inhibitory

signals through parasympathetic vagal fibers to

heart to decrease its rate and contractility.

Neurons, which give impulses to the heart, haveconstant level of activity even at rest, which is

characterized as nervous tone.


23/23

Blood Circulation System and It Regulation. Blood Circulation in Facial Region

Documents

Transcript of Blood Circulation System and It Regulation. Blood Circulation in Facial Region