Red Eared Slider Lab Report

FIGURE 4: Effect of atrial extrastimulation on preexcitation. A: Manifest preexcitation during normal sinus rhythm (NSR) with HV interval value of -11 msec. Atrial extrastimulation (AES) increased the degree of preexcitation (HV interval value of -64 msec). B: An earlier coupled AES produced more pronounced preexcitation with HV interval value of -93 msec. C: A more premature AES produced full preexcitation with the His bundle activated retrogradely , with VA conduction over the AVN & an echo beat (atrioventricular reentry) (Issa et al, 2012).

In general, the heart receives continuous input from the autonomic nervous system (ANS) and/or endocrine system, which release chemicals that alter both the rate and force of heart muscle contraction. The ANS is composed of two antagonistic divisions, called the sympathetic and parasympathetic nervous systems; the sympathetic division, often referred to as the “fight or flight” system, speeds up heart rate through Norepinephrine release onto beta-1 adrenergic receptors on the heart. The parasympathetic division, referred to as the “rest or digest” system, slows heart rate through Acetylcholine release onto muscarinic receptors on the heart.

The myocardium contains the pacemaker cells that generate electrical impulses to create the heart’s movements. These impulses are triggered by action potentials in the pacemaker cells of the Sinoatrial Node. These are then transmitted to the atria and to the AV node. (Hull & Slegg, 2009)

Cardiac muscle has short branching fibers, is striated, and functions involuntary allow for the contraction of the heart to pump blood throughout the body (Castillo, 2018). The conduction system of the heart includes the Sinoatrial node, Atrioventricular node, left and right bundle branches, and Purkinje fibers and functions off of action potentials of nerve impulses. The Sinoatrial node is in the upper right atrium and is where the action potential begins and rhythm and pace of the heart is determined. The action potential will then travel to the Atrioventricular node in the lower right atrium where the impulse is delayed for a whole second so the left side of the heart can contract. After that the impulse travels to the Atrioventricular bundle, which connects the atria and ventricles. Once this is completed, the potential travels to the left and right bundle fibers that signal the septum and apex of the heart. Finally, the potential will reach the Purkinje fibers and stimulate the walls of both ventricles. This completes one cardiac cycle. A cardiac cycle is described as all the events associated with the blood flow through the heart during one complete heartbeat (McKinley, 2016). A heartbeat involves the contraction {systole} and relaxation {diastole} of the heart chambers. The most important driving force to continually move blood through the heart is the opening and closing of

A vasovagal response occurs when an individual is exposed to, or experiences a trigger. The response to the trigger results in a malfunction of components of the nervous system that regulate heart rate and blood pressure (5). The vagus nerve in conjunction with the thoracic ganglia, are responsible for the parasympathetic innervation of the heart, and therefore the lowering of the heart rate (E wiki vagus nerve).

The myogenic heart is composed of three types of muscles : atrial muscle, ventricular muscle, and specialized excitatory and conductive muscle fibers. Some cells show spontaneous depolarizations that cause a rythmical electrical activity from those cells. They are localised in specific area in the sinus venosus and ventricle. The pacemaker activity in the heart, providing an excitatory system that controls the rhythmical beating of the heart. This activity produce a rythmicity of contraction in the heart.

According to UC Davis Health Sports Medicine,” Heart rate refers to the number of times the heart beats per minute, and is directly related to the workload being placed on the heart.” (UC Davis Health,2017) Heart rate can be managed by two different branches of the autonomic nervous system that supply nerve impulses to the heart. The sympathetic nervous system is the fight or flight mechanism and releases hormones like epinephrine and norepinephrine to increase heart rate. The parasympathetic nervous system is the rest and digest mechanism and releases achetylcholine, which is a hormone that will decrease the heart rate. The vagus nerve is part of the autonomic nervous system, specifically the parasympathetic system. The autonomic nervous system

The autonomic nervous system is an integrated controlling system that is responsible for regulating and maintaining homeostasis for the optimal function of all internal organs. Along with other major systems, the autonomic nervous system dictates the status of the internal environment of the body and will make adjustments through feedback loops based on internal and external changes detected. Understanding the significance of manual autonomic regulation in a controlled setting will lay the groundwork for future therapies in cardiovascular disease and many other diverse diseases. We specifically wanted to test if unconscious stimulation of the vagus nerve will be less inhibited than conscious stimulation and will parasympathetic stimulation then

The cardiovascular system is the body’s way of circulating blood and the essential biomolecules that make living possible. Blood is pumped throughout the body by the heart, the heart receives oxygenated blood from the lungs via the pulmonary vein and distributes it using the various arteries and capillaries (Farley et al.). A main constituent for the cardiovascular system and a heavily relied upon factor for measuring the heart’s work is heart rate. Heart rate is a numerical value that quantifies the number of times the heart contracts which means opening and closing the valves that are responsible for the blood movement (Mariaconsuelo et al.). Contractions in terms of heart rate are referred to as “beats” thus the numerical value is beats per minute (BPM). Heart rate can be affected by numerous factors such as physical stress, chemicals introduced into the bloodstream through the environment, as well as naturally produced chemical compounds produced by the body in response to a need. To determine what exactly happens inside the body when these numerous factors come into play we set up various experiments that will give us a measurable outcome.

For starters the SA node is set in the posterior wall of the right atrium that is close to the entrance of the superior vena cave. Then with the SA node it contains many pacemaker cells, which establishes the person’s heart rate. Also it is known as the cardiac pacemaker (natural pacemaker). It is connected to the ‘large AV node which is by the internodal pathways within the arterial walls. Also it shows the action takes just about 230 msec to pass through the SA node to AV node the length of these pathways. Once it passes by the conduction cells exceed the motivation of contractile cells of mutually atria. After this action it spreads from one side to the other to the atrial surfaces by cell-to-cell contact. As the stimulus only affects

The heart is made up of cardiac muscles that are striated, involuntary, and contains intercalated disks which consist of gap junctions that send electrical signals to the heart. In order for contraction to occur in the heart, action potentials have to first move through the T-tubules to the L-type calcium channels. The calcium used here is not used for contraction. From there, more calcium comes in from outside the cell and binds with ryanodine receptor which causes the actual contraction of the heart. Next, cross bridge cycling occurs and in order for contraction to end, calcium is decreased by using ATP pumps to pump the calcium to the sarcoplasmic reticulum. In the heart, the heartbeat is maintained by the pacemaker cells in the SA node. For it to maintain its heart rate, the SA node is stimulated which causes an action potential to happen. The action potential goes quickly from the top-down and it continues through the AV node. The AV node is another pacemaker in the cell but is slower than the SA node. It is also the only pathway where action potential can move from the atria to the ventricle. From the AV node, it goes to the Bundle of His which then branches

We hope that you will consider the submitted manuscript for publication in Circulation: Arrhythmia and Electrophysiology.

The cardiac cycle is associated with the blood flow through the heart (Saladin, 2015). The heart rate is a term describing the regularity of the cardiac cycle (Marieb,2007). The heart rate is the amount of times it contracts or also known as beats in a unit of time, nearly always per minute. The normal pulse rate for healthy adults ranges from 60-100 bpm(beats per minute), approximately the adult heart rate regulates 75 bpm but this varies from person to person (Saladin, 2015). The heart rate generally slows down through childhood, as you develop (MacGill, 2015). Abnormal heart rates have medical names and harmless for some (MacGill, 2015). Tachycardia refers to the heart beating too fast at rest being over 100 beats per minute and Bradycardia refers to the heart beating too slow, usually below 60 beats per minute ( MacGill, 2015). The nervous system monitors the body and signals your heart to beat faster in response to increased activity. The normal heart rate undergoes healthy variation, going up in response to some conditions, including exercise, body temperature, body position, and emotion (MacGill, 2015). The blood is rushing around the heart to get rid of deoxygenated blood and carries back oxygenated blood from the lungs (Saladin, 2015) Sounds heard in the cardiovascular system result from the turbulent blood flow (Marieb, 2007). Two sounds can be heard during each cardiac cycle; these sounds are commonly known as "lub" and "dub". The sequence is

The autonomic nervous system is composed of nerves leading from the central nervous system (CNS) that innervate and control smooth muscle cardiac muscle, and glands it controls many organs systems automatically its actions are not generally under voluntary control( Quizlet,2017). The autonomic nervous system is divided into two parts the sympathetic nervous system and the parasympathetic nervous system. Usually, if one system stimulates a function, the other inhibits it. The policies oppose one another in governing the functions of smooth muscle and glands in many parts of the body. Some of the significant effects of the two systems are compared.

Heart rate variability is defined as the variation in the interval between normal heart beats and provides an important non-invasive assessment of cardiac autonomic control. It is postulated to be the effect of the interplay between the sympathetic and the parasympathetic components of the autonomic nervous system. The SA node receives different inputs from the SNS, PSNS and the humoral factors which cause the beat to beat variation in the heart rate. Heart rate variability is thus an important indicator of autonomic tonal variations. It has also been postulated to be the mediator of the effects of cognitive and mind-body therapies on cardiovascular conditions.