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INNERVATION OF HEART HEART ANATOMY

The innervation of the heart is given by autonomic nerve fibers from the vagus and sympathetic trunks. Sympathetic innervation

preganglionic sympathetic fibers originate from dorsal levels I to IV (and sometimes the V and VI) of the spinal cord. Synapse in the cervical ganglia and dorsal.

Sympathetic Trunk Ganglia: formation of cardiac sympathetic branches to the heart
postganglionic sympathetic fibers to the heart, are driven by cardiac branches of the cervical and dorsal portions of the sympathetic trunk, these fibers end in sinoatrial and atrioventricular nodes in cardiac muscle fibers and dilation of the coronary arteries, including both atria and ventricles. The activation of these nerves results in: cardiac acceleration, increased strength of heart muscle contraction and dilation of the coronary arteries. Branches
heart: The cardiac branches are extremely variable in its topography and direction, and are grouped according to their level of origin as follows:
cervical cardiac branches, with higher frequency and a half originate in the cervical sympathetic trunk in ganglia, or both, and generally joined with branches of the vagus nerve, pharyngeal plexus, throat, carotid and thyroid. After all the branches down in front of or behind the aortic arch and enters the cardiac plexus. The superior cervical sympathetic nerve does not receive sensory input from the area.
cervicothoracic cardiac branches, also called lower cervical, originate from the cervicothoracic ganglion (stellate ganglion) and is usually joined by cervicothoracic cardiac branches of the vagus nerve (sometimes there is a branch of the phrenic nerve that joins.) Then the group of nerves goes ahead or behind the aortic arch to the cardiac plexus.
The thoracic cardiac branches: originate in the fourth or fifth upper thoracic sympathetic ganglion and together with the thoracic cardiac branches of vagus nerve (in relationship to the left recurrent laryngeal nerves), go directly to the cardiac plexus, especially the back walls of the atria .

parasympathetic innervation

Vagus Nerve: Primary visceral parasympathetic component, forming the cardiac plexus.
preganglionic parasympathetic fibers in the vagus nerves (originating in the medulla oblongata, the dorsal nucleus (parasympathetic) which receives input from the hypothalamus and the glossopharyngeal nerve) are conducted as cervical and thoracic cardiac branches to the ganglion cells in the cardiac plexus (below the tracheal bifurcation in the adventitia of the pulmonary trunk) or subepicardial, where they synapse.
parasimpátcias postganglionic fibers innervate the Keith and Flack node (node) of Aschoff and Tawara (atrioventricular) and coronary arteries. The activation of these nerves causes a reduction in the frequency and force of myocardial contraction and vasoconstriction of the coronary arteries.

afferent autonomic innervation

Most organs are innervated only by autonomic nerves. Therefore, it appears that visceral pain is driven by afferent autonomic nerves. Visceral pain is diffuse and poorly localized, while the somatic pain is intense and localized. Visceral pain is often referred to cutaneous areas innervated by the same segments of the spinal cord to the viscera painful. The explanation of referred pain is not known. One theory is that nerve fibers from the viscera and the dermatome ascend in the central nervous system along a common pathway and that the cortex is unable to distinguish between sites of origin. Another theory is that, under normal conditions, the bowel does not give rise to painful stimuli, while the area of \u200b\u200bskin repeatedly receives noxious stimuli. Since both afferents enter the spinal cord in the same segment, the brain interprets the information as coming from the skin rather than the viscera.

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Heart Physiology


Every heartbeat triggers a sequence of events called cardiac cycles, which consist mainly of three stages: atrial systole, ventricular systole and diastole. The cardiac cycle causes the heart alternate between contraction and relaxation about 75 times per minute, ie the cardiac cycle takes about 0.8 seconds.
During atrial systole, the atria contract and project the blood into the ventricles. Once the blood has been expelled from the atria, atrioventricular valves between the atria and ventricles are closed. This prevents the backflow of blood into the atrium. The closing of these valves produce the familiar sound of a heartbeat. Takes approx. 0.1 s.
ventricular systole involves the contraction of the ventricles to expel blood into the circulatory system. Once the blood is ejected, the two semilunar valves, valve right lung and left aortic valve is closed. Takes approx. 0.3 s. Lastly
diastole is the relaxation of all parts of the heart to allow the arrival of new blood. Takes approx. 0.4 s.
In the process you can hear two clicks:
The first heart sound caused the closure of two valves: tricuspid and bicuspid or mitral.
The second also by the closure of two valves: sigmoid aortic and pulmonary sigmoid.
This motion is about 70 times per minute.
rhythmic expulsion of blood causes the pulse can be felt in the radial artery, carotid, femoral, etc. If you look
the time of contraction and relaxation that the courts will be at rest approx. 0.7 s and ventricles about 0.5 s. That means that the heart spends more time at rest than at work.
In the physiology of the heart, it is noteworthy that the cells are depolarized by themselves give rise to an action potential, resulting in a contraction of heart muscle. In addition, heart muscle cells "talk" so that the action potential spreads through all of them, so that contraction of the heart occurs. The heart muscle never tetanize (cardiomyocytes have high refractoriness that's why no tetanus)
sinus node pacemaker operates, this means that slow waves generated in the rest of sinus tissue.



BLOCKERS - TTX "Tetrodotoxin is a channel blocker of voltage-dependent Na +, so if I apply generaré a slow wave and there is no contraction. - Nifedipine, diltiazem and verapamil are calcium channel blockers of voltage-dependent, affecting the amplitude of slow waves. - Atropine is a muscarinic receptor blocker thus increases the heart rate due to activation of the sympathetic nervous S - Propranolol is a beta blocker-adrenoceptor sinus node, its action is to decrease the heart rate.

CARDIAC EXCITATION:
Cardiac muscle is myogenic. This means that, unlike skeletal muscle, which requires a conscious or reflex stimulation, the heart muscle itself is excited. The rhythmic contractions occur spontaneously, and their frequency may be affected by nervous or hormonal influences such as exercise or the perception of danger.
stimulation of the heart is coordinated by the autonomic nervous system, both by the sympathetic nervous system (Increasing the pace and force of contraction) and the parasympathetic (reduces heart rate and strength).
The sequence of contractions is caused by depolarization (electrical polarity reversal of the membrane due to active ions pass through it) or sinus node of Keith-Flack node (nodus sinuatrialis), located on the top of the right atrium. The electrical current produced in the order of microvolts, is transmitted throughout the atria and passes to the ventricles by the atrioventricular node (AV node) located at the junction between the two ventricles, consisting of specialized fibers. The AV node serves to filter the activity too rápida de las aurículas. Del nodo AV se transmite la corriente al fascículo de His, que la distribuye a los dos ventrículos, terminando como red de Purkinje.
Este sistema de conducción eléctrico explica la regularidad del ritmo cardíaco y asegura la coordinación de las contracciones auriculoventriculares. Esta actividad eléctrica puede ser analizada con electrodos situados en la superficie de la piel, llamándose a esta prueba electrocardiograma o ECG.
Batmotropismo: el corazón puede ser estimulado, manteniendo un umbral.
Inotropismo: el corazón se contrae bajo ciertos estímulos. El sistema nervioso simp+atico tiene un efecto inotrópico positivo, por lo tanto aumenta la contractilidad heart.
chronotropism: refers to the slope of the action potential. Sympathetic NS increases the slope, thus producing tachycardia. In contrast, the parasympathetic SN decreases. Dromotropic
is the speed of cardiac impulse conduction by excito-conductor system. Sympathetic NS has a positive dromotropic effect therefore increases the driving speed. Parasympathetic Sn is the opposite effect.
lusitropism: the relaxation of the heart under certain stimuli.

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cardiac morphology

CAVITIES CARDIAC
The heart has four chambers, two atria or upper (or atria) and two lower ventricles. The atria receive blood from the venous system, pass to the ventricles and from there out to the arterial circulation.
The right atrium and right ventricle forming what traditionally is called the right heart. Receives blood coming from all over the body, which flows into the right atrium through the superior and inferior vena cava. This blood is low in oxygen, reaches the right ventricle, where it is sent to the pulmonary circulation through the pulmonary artery. Since the resistance movement lung is smaller than the systemic, the force that the ventricle must do is lower, which is why its size is considerably smaller than the left ventricle.
The left atrium and left ventricle are called the left heart. Receives blood from the pulmonary circulation, which flows through four pulmonary veins to the upper portion of the left atrium. This oxygenated blood from the lungs. The left ventricle sends it through the aorta for distribution throughout the body.
tissue separating the right heart called the left septum. Functionally, it is divided into two separate parties: the upper or atrial septum, and interventricular septum or less. The latter is especially important because he runs the bundle of His, that allows to boost the lower parts of the heart.

HEART VALVE
heart valves are the structures that separate cavities of other, preventing retrograde reflux exists. Are located around the atrioventricular orifices (or atrioventricular) and between the ventricles and arteries out. They are four:
The tricuspid valve separates the right atrium of the right ventricle.
valve lung, which separates the right ventricle to the pulmonary artery.
mitral valve, which separates the left atrium of the left ventricle.
aortic valve, which separates the left ventricle to the aorta.

STRUCTURE OF THE HEART
From inside to outside the heart has the following layers:
The endocardium, a layer of endothelial lining, with which contact blood.
myocardium, the heart muscle itself, that pushes blood through the body.
The pericardium is a fibroserosa layer that surrounds the heart and divides into two parts:
fibrous pericardium, is the outermost part of the pericardium and rugged, composed of dense connective tissue.
Serous Pericardium: It is internal and is composed of two layers (parietal and visceral) and has a lubricating function.