What are the phases of the cardiac cycle?
There are two phases of the cardiac cycle. In the diastole phase, the heart ventricles are relaxed and the heart fills with blood. In the systole phase, the ventricles contract and pump blood out of the heart and to arteries. One cardiac cycle is completed when the heart chambers fill with blood and blood is then pumped out of the heart.
What happens during the relaxation phase of the heart cycle?
Relaxation phase: During the relaxation phase, all 4 chambers of the heart are in diastole as blood pours into the heart from the veins. The ventricles fill to about 75% capacity during this phase and will be completely filled only after the atria enter systole.
What are the phases of cardiac action potentials?
There are five cardiac action potential phases, numbered 0 through 4 (scientists get strange ideas sometimes). Phase 0is depolarization of the membrane and the opening of "fast" (i.e., high-flow) sodium channels.
What happens in the second phase of the cardiac cycle?
In the second phase of the cardiac cycle both the atrioventricular and semilunar valves of the heart remain closed. At this point, the ventricles begin to contract and although the ventricular myocardial muscle fibers only shorten a little, the intraventricular pressure rises rapidly.
What are the phases of the heart?
There are two phases of the cardiac cycle: The diastole phase and the systole phase. In the diastole phase, heart ventricles relax and the heart fills with blood. In the systole phase, the ventricles contract and pump blood out of the heart to arteries.
What phase is the heart at rest?
This process is called the cardiac cycle. The period of relaxation is called diastole. The period of contraction is called systole. Diastole is the longer of the two phases so that the heart can rest between contractions.
What are the three phases of your heart contraction?
Every single beat of the heart involves three major stages: cardiac diastole, when chambers are relaxed and filling passively; atrial systole when the atria contract leading to ventricular filling; and ventricular systole when blood is ejected into both the pulmonary artery and aorta.
What are the 2 phases in heart function?
This stimulus causes a series of events in the atria and the ventricles. All these events are “organized” in two phases: diastole (when the heart fills with blood) and systole (when the heart pumps the blood)
Which is the working phase of the heart quizlet?
For any one chamber in the heart, the cardiac cycle can be divided into two phases. During contraction, or systole, A chamber attract blood either into the heart chambers or into an arterial trunk. Systole is followed by the second phase: relaxation, or diastole.
Is the relaxation phase of the heart?
Systole is the contraction phase of the cardiac cycle, and diastole is the relaxation phase.
What are the 4 phases of diastole?
LV filling occurs during diastole, which has 4 phases: (1) isovolumic relaxation; (2) rapid filling phase; (3) slow filling, or diastasis; and (4) final filling during atrial systole (atrial kick.) Isovolumic relaxation – this phase occurs after the aortic valve closes and the mitral valve is still closed.
What happens in diastole phase?
diastole, in the cardiac cycle, period of relaxation of the heart muscle, accompanied by the filling of the chambers with blood. Diastole is followed in the cardiac cycle by a period of contraction, or systole (q.v.), of the heart muscle.
What are the 7 phases of the cardiac cycle?
The different phases of the cardiac cycle involve:Atrial diastole.Atrial systole.Isovolumic contraction.Ventricular ejection.Isovolumic relaxation.Ventricular filling.
What is systole and diastole?
Summary. Diastole and systole are two phases of the cardiac cycle. They occur as the heart beats, pumping blood through a system of blood vessels that carry blood to every part of the body. Systole occurs when the heart contracts to pump blood out, and diastole occurs when the heart relaxes after contraction.
What are the two phases of the heart?
All these events are “organized” in two phases: diastole (when the heart fills with blood) and systole (when the heart pumps the blood) During these two phases, many different events are observed and we will describe them in the following paragraphs.
What are the two phases of the cardiac cycle?
This stimulus causes a series of events in the atria and the ventricles. All these events are “organized” in two phases: diastole (when the heart fills with blood)
What is the first event of the cardiac cycle?
Atrial diastole is the very first event of the cardiac cycle. It occurs some milliseconds before the electrical signal from the SA node arrives at the atria. The atria function as conduits that facilitate the passage of blood into the ipsilateral ventricle.
What happens at the beginning of systole?
At the beginning of systole, the atrioventricular valves are closed and the ventricle is in isovolumetric contraction. So there is a sharp increase in pressure but the volume remains the same.
What is the atrial pressure wave?
The atrial pressure wave shows the change in the atrial pressure during systole and diastole. There are three significant pressure changes represented by the letters a, v, and c. The pressure change generated as the atria fill with blood is represented by the ‘v’ wave towards the end of the atrial pressure wave. There is a slight decline in the atrial pressure that corresponds with the opening of the atrioventricular valve. This is followed by the ‘a’ wave which represents the contraction of the atria. The ‘a’ wave is followed by a downward slope as the atrioventricular valves close. This is followed by another increase labeled as the ‘c’ wave. This represents bulging of the atrioventricular valves into the atria during ventricular contraction.
What is the term for the period of contraction of the ventricles?
Ventricular systole refers to the period of contraction of the ventricles. The electrical impulse arrives at the atrioventricular node (AV node) shortly after the atria are depolarized. There is a small delay at the AV node, which allows the atria to complete contracting before the ventricles are depolarized.
What is the alternating state of the atria and ventricles?
Both the atria and the ventricles undergo alternating states of systole and diastole. In other words, when the atria are in diastole, the ventricles are in systole and vice versa. This article will discuss the phases of the cardiac cycle and the underlying physiological principles that govern the process.
What are the phases of cardiac action potential?
Two of these, phase 2 (the plateau phase) and phase 4 (the diastolic interval) are marked by little to no change in voltage. Sodium, potassium and calcium are the primary ions.
What happens during phase 2 of the cardiac cell?
Phase 2 ends when the inward flow of calcium and sodium cease while the outward flow of potassium (the rectifier current) continues, pushing the cell toward repolarization. Quirks of the Cardiac Cell Action Potential. The cardiac cell action potential differs from the action potentials in nerves in a variety of ways.
What phase of the cell is repolarized?
Phase 1is partial repolarization of the membrane thanks to a rapid decrease in sodium-ion passage as the fast sodium channels close. Phase 2is the plateau phase, in which the movement of calcium ions out of the cell maintains depolarization.
What cells control the beating of the heart?
For one thing, the initiation of the "beating" of the heart is controlled by special cardiac myocytes, or heart-muscle cells, called pacemaker cell s. These cells control the pace of the heartbeat even in the absence of outside nerve input, a property called autorhythmicity.
What is the heart muscle called?
Heart muscle is also called myocardium.
How many times does the heart pump blood?
Like so many things in the biology world, however, the precise and coordinated way that electrical activity powers the heart to pump vital blood toward the body's tissues, 70 or so times a minute, 100,000 times a day for decades on end, is wondrously elegant in its operation.
Is the beating of the heart a phenomenon?
The beating of the heart is probably associated with the phenomenon of life more strongly than any other single concept or process, both medically and metaphorically.
What are the two phases of the cardiac cycle?
The Cardiac cycle is the sequence of events that occurs when the heart beats. Below are the two phases of the cardiac cycle: Diastole phase: The heart ventricles are relaxed and the heart fills with blood. Systole phase: The ventricles contract and pump blood to the arteries.
What are the layers of the heart?
The heart wall consists of three layers: Epicardium: The outer layer of the wall of the heart. Myocardium: The muscular middle layer of the wall of the heart. Endocardium: The inner layer of the heart.
Which arteries carry oxygenated blood to the head and neck?
Carotid arteries: Supply oxygenated blood to the head and neck regions of the body. Common iliac arteries: Carry oxygenated blood from the abdominal aorta to the legs and feet. Coronary arteries: Carry oxygenated and nutrient-filled blood to the heart muscle. Pulmonary artery: Carries deoxygenated blood from the right ventricle to the lungs.
What is the section of nodal tissue that delays and relays cardiac impulses?
Atrioventricular Node: A section of nodal tissue that delays and relays cardiac impulses. Purkinje Fibers: Fiber branches that extend from the atrioventricular bundle. Sinoatrial Nod e: A section of nodal tissue that sets the rate of contraction for the heart.
Which artery supplies oxygenated blood to the head and neck regions of the body?
Brachiocephalic artery: Carries oxygenated blood from the aorta to the head, neck, and arm regions of the body. Carotid arteries: Supply oxygenated blood to the head and neck regions of the body.
What is the role of the heart in conduction?
Cardiac conduction is the rate at which the heart conducts electrical impulses. Heart nodes and nerve fibers play an important role in causing the heart to contract. Atrioventricular Bundle: A bundle of fibers that carry cardiac impulses. Atrioventricular Node: A section of nodal tissue that delays and relays cardiac impulses.
What is the heart surrounded by?
The heart is situated within the chest cavity and surrounded by a fluid-filled sac called the pericardium. This amazing muscle produces electrical impulses that cause the heart to contract, pumping blood throughout the body. The heart and the circulatory system together form the cardiovascular system.
How does the heart work?
The heart functions by pumping blood both to the lungs and to the systems of the body. To prevent blood from flowing backwards or “regurgitating” back into the heart, a system of one-way valves are present in the heart. The heart valves can be broken down into two types: atrioventricular and semilunar valves.
What is the second layer of the heart wall?
Thus, the epicardium is a thin layer of serous membrane that helps to lubricate and protect the outside of the heart. Below the epicardium is the second, thicker layer of the heart wall: the myocardium. Myocardium. The myocardium is the muscular middle layer of the heart wall that contains the cardiac muscle tissue.
What are the two types of heart valves?
The heart valves can be broken down into two types: atrioventricular and semilunar valves. Atrioventricular valves. The atrioventricular (AV) valves are located in the middle of the heart between the atria and ventricles and only allow blood to flow from the atria into the ventricles.
What are the two chambers of the heart?
At any given time the chambers of the heart may found in one of two states: 1 Systole. During systole, cardiac muscle tissue is contracting to push blood out of the chamber. 2 Diastole. During diastole, the cardiac muscle cells relax to allow the chamber to fill with blood. Blood pressure increases in the major arteries during ventricular systole and decreases during ventricular diastole. This leads to the 2 numbers associated with blood pressure—systolic blood pressure is the higher number and diastolic blood pressure is the lower number. For example, a blood pressure of 120/80 describes the systolic pressure (120) and the diastolic pressure (80).
What is the layer of the heart that keeps blood from sticking to the inside of the heart?
Endocardium is the simple squamous endothelium layer that lines the inside of the heart. The endocardium is very smooth and is responsible for keeping blood from sticking to the inside of the heart and forming potentially deadly blood clots. The thickness of the heart wall varies in different parts of the heart.
Which layer of the heart contains the heart muscle tissue?
The myocardium is the muscular middle layer of the heart wall that contains the cardiac muscle tissue. Myocardium makes up the majority of the thickness and mass of the heart wall and is the part of the heart responsible for pumping blood. Below the myocardium is the thin endocardium layer. Endocardium.
What is the purpose of the pericardium?
Pericardium is a type of serous membrane that produces serous fluid to lubricate the heart and prevent friction between the ever beating heart and its surrounding organs. Besides lubrication, the pericardium serves to hold the heart in position and maintain a hollow space for the heart to expand into when it is full.
What is the name of the electrical signal that the heart produces?
Encyclopaedia Britannica/UIG/Getty Images. The heart generates its own electrical signal (also called an electrical impulse), which can be recorded by placing electrodes on the chest. This is called an electrocardiogram (ECG, or EKG). The cardiac electrical signal controls the heartbeat in two ways.
What causes the heart to contract in a coordinated manner?
From the initiation of a heartbeat in the SA node, through contraction of the ventricles, the cardiac electrical system causes the heart to contract in a coordinated manner, maximizing the efficiency of the beating heart.
What is the AV node?
Figure 4: The specialized AV conduction system consists of the AV node (AVN), the "His bundle," and the right and left bundle branches (RBB and LBB). The AV node conducts the electrical impulse to the His bundle (pronounced "hiss"). 1 The His bundle passes the signal to the right and left bundle branches. The right and left bundle branches, in turn, send the electrical impulse to the right and left ventricles, respectively. The figure also shows that the LBB itself splits into the left anterior fascicle (LAF) and the left posterior fascicle (LPF).
What are the two parts of the heart?
From an electrical standpoint, the heart can be thought of as being divided into two portions: the atria (upper chambers) and the ventricles (lower chambers). Separating the atria from the ventricles is an area of fibrous tissue (labeled AV disc in the figure).
How does the number of electrical impulses affect the heart rate?
First, since each electrical impulse generates one heartbeat, the number of electrical impulses determines the heart rate. And second, as the electrical signal "spreads" across the heart, it triggers the heart muscle to contract in the correct sequence, thus coordinating each heartbeat and assuring that the heart works as efficiently as possible.
Where does the electrical impulse originate?
Figure 2: The electrical impulse originates in the sinus node. From there, it spreads across both atria (indicated by the blue lines in the picture), causing the atria to contract. This is referred to as "atrial depolarization."
Where is the electrical signal produced in the heart?
The heart's electrical signal is produced by a tiny structure known as the sinus node, which is located in the upper portion of the right atrium. (The anatomy of the heart's chambers and valves includes two atria at the top of the heart with two ventricles at the bottom.)
