heart anaphys review

The Cardiovascular System : 

The Cardiovascular System A Review: The Heart

Heart : 

Heart A hollow muscular organ Located in thorax between 2 lungs 4 chambers 4 valves 2 atria (atrium) & 2 ventricles 2 separate pumps (R & L sides) Right side receives blood from the body and sends it to the lungs (pulmonary) Left side receives blood from lungs and sends it to the body (systemic)

Slide 3: 

The heart lies between the lungs in a region called the mediastinum.  You can also see that the heart is wrapped by some membranes that also hold the heart in its position relative to the diaphragm and lungs.

Position of Heart : 

Position of Heart

2 Pumps : 

2 Pumps

Slide 7: 

The Pericardium The pericardium is the set of membranes around the heart.  It is actually composed of three layers of membranes. visceral pericardium - the innermost parietal pericardium - the middle, fibrous pericardium - the outer one is the extra one, and  is tough. Pericardial Cavity- tiny space between the visceral pericardium and the parietal pericardium

Layers of the Heart : 

Layers of the Heart Pericardium Myocardium Fibrous pericardium Serous pericardium (parietal layer) Pericardial space Serous pericardium (visceral layer - Epicardium) Endocardium

Chambers of the Heart : 

Chambers of the Heart

Valves of the Heart : 

Valves of the Heart 4 valves One way flow Leaky valve = heart murmur 2 atrioventricular valves Left AV valve- bicuspid or mitral Right AV valve- tricuspid 2 semilunar valves Pulmonic semilunar valve Aortic semilunar valve

Valves of the Heart : 

Valves of the Heart Tricuspid Valve Mitral Valve Pulmonic Valve Aortic Valve

Atrioventricular Valves : 

Atrioventricular Valves Right AV valve Between right atrium and right ventricle Also called the tricuspid valve because it has three cusps. Cusps close when right ventricle contracts….preventing blood from going back up into the right atrium Left AV valve Between the left atrium and the left ventricle Also called the bicuspid valve because it only has two cusps Also called the mitral valve Cusps close when left ventricle contracts….preventing blood from back up into the left atrium

Semilunar Valves : 

Semilunar Valves Pulmonary semilunar valve When right ventricle contracts, blood is forced through this valve to enter pulmonary trunk Aortic semilunar valve When left ventricle contracts, blood is forced through this valve to enter the aorta

Cardiac Conduction System : 

Cardiac Conduction System The cardiac conduction system generates and transmits impulses that stimulate contraction of the myocardium. Under normal circumstances, the conduction system first stimulate the contraction of the atria and then the ventricles.

Slide 15: 

Electrophysiologic Properties of the Heart Excitability. The ability of the heart to depolarize in response to a stimulus. Once stimulated, the whole heart muscle contracts. It is influenced by hormones, electrolytes, nutrition, oxygen supply, medications, infection, and nerve characteristics. Automaticity/Rhythmicity. The ability of cardiac cells to initiate an impulse spontaneously and repetitively, without external neurohormonal control. Conductivity. The ability of the heart muscle fibers to propagate electrical impulses along and across cell membranes.

Conduction System of the Heart : 

Conduction System of the Heart

Coronary Arteries : 

Coronary Arteries Atherosclerosis is an accumulation of fat on the inner walls of arteries. When coronary arteries become partially blocked….angina When coronary arteries become significantly blocked….myocardial infarction

Cardiac Cycle- refers to the events of one complete heart beat. The length of the cardiac cycle is usually about 0.8 sec. : 

Cardiac Cycle- refers to the events of one complete heart beat. The length of the cardiac cycle is usually about 0.8 sec. Systole (contraction of the muscle)- there is ventricular pumping, the chambers of the heart become smaller as the blood is ejected. Occurs secondary to depolarization of cells Diastole (relaxation of the muscle)- there is ventricular filling, the heart chambers fill with blood in preparation for subsequent ejection.

Cardiac Output : 

Cardiac Output Volume of blood ejected per minute Each ventricle ejects approximately 70mL of blood/ beat Averages between 4-8L/min CO = Stroke volume X heart rate =70 ml X 60 beats/min =4,200 ml/min

Stroke Volume Is Determined By Three Factors : 

Stroke Volume Is Determined By Three Factors Preload Afterload Contractility

Preload : 

Preload Degree of stretch of myocardial fibers Determined by the volume of blood in left ventricle (LV) at end of diastole Increased volume – increased preload- increased cardiac output (CO) Decreased volume – decreased preload – decreased cardiac output (CO) Frank- Starling Law-the critical factor controlling stroke volume is how much the cardiac muscle cells are stretched just before the contract. The more they are stretched, the stronger the contraction will be. The important factor stretching the heart muscles is the venous return.

Factors Which Increase Preload : 

Factors Which Increase Preload IV fluids Blood Vasoconstriction

Factors Which Decrease Preload : 

Factors Which Decrease Preload Diuretics Dehydration Hemorrhage Vasodilation

Afterload : 

Afterload Resistance or pressure the ventricles must overcome to pump blood out Left ventricle (LV) affected by systemic vascular resistance (SVR) Right ventricle (RV) affected by pulmonary vascular resistance (PVR) Related to arterial pressure or diameter of arteries As pressure increases, resistance increases, afterload increases As pressure decreases, resistance decreases, afterload decreases

Contractility : 

Contractility Force generated by the myocardium when it contracts – inotropic property Ejection fraction (EF) - percentage of LV end-diastolic volume that is ejected with each contraction

Autonomic Nervous System (ANS) Regulation of Cardiovascular System : 

Autonomic Nervous System (ANS) Regulation of Cardiovascular System Heart rate – chronotropic effect Contractility – inotropic effect Conduction velocity at AV node – dromotropic effect Afterload - vascular resistance – arterial vasoconstriction and dilation Preload – venous constriction and dilation

Subdivisions of ANS : 

Subdivisions of ANS Parasympathetic – acetylcholine produces inhibitory response Sympathetic – catecholamines stimulate Increase heart rate – Beta 1 receptors Dilate smooth muscles – Beta 2 receptors Vasoconstrict vessels – Alpha receptors

Slide 29: 

The Fetal Circulation