This website uses cookies to ensure you have the best experience. Learn more

Primary Pacemaker Cells Essay

577 words - 2 pages

Primary pacemaker cells located in the central region of the sinoatrial node (SA node) undergo spontaneous diastolic depolarization, which ultimately triggers the action potential (AP) upstroke. The excitatory AP wave front subsequently spreads through adjacent areas of the perinodal region to reach the crista terminalis and atrium. Repolarization of the pacemaker cells allows the cycle to repeat. This inherent cyclic behavior enables the SA node to serve as the normal pacemaker of the heart (7; 12; 14; 26; 57).
In both central nodal and adjacent perinodal cells, the ionic basis of spontaneous diastolic depolarization and different phases of the AP have been attributed to numerous overlapping currents (7; 8; 14; 27; 36; 37; 42; 47; 59; 64; 72). Studies conducted on different mammalian species have identified the following voltage sensitive cation currents: a hyperpolarization-activated non-selective cation current (If), two calcium currents (ICa,L (L-type) and ICa,T (T-type)), a sodium current (INa), and at least four voltage-dependent potassium currents (IKur, IKr, IKs and Ito). There also appears to be a relatively small (compared to ventricular myocytes) inwardly rectifying K+ current (IK1)(17; 24; 33; 35-37; 47; 52; 54; 64; 72). However, SA node anatomy as well as its physiology are complex and vary considerably between species (3; 5-7; 16; 18; 29; 30; 41; 42; 68). This suggests that patterns of ion channel expression may also be highly complex and variable between species.
The basic characteristics of cardiac pacemaker activity were elucidated by electrophysiological studies of multicellular SA node preparations. Such studies demonstrated clear gradations in AP characteristics (voltage range and time course) recorded from primary pacemaker cells (central region) versus cells located in adjacent perinodal regions (5; 7; 32; 66). Subsequent voltage clamp studies of single SA node cells...

Find Another Essay On Primary Pacemaker Cells

Biological Aging-Effects on Body Systems Essay

1621 words - 6 pages pacemaker cells. Fourth, the amounts of elastin, cologne, and fat in the walls of the heart increase while the amount of muscle decreases (Schaie & Willis, 2002). The alveoli in the lungs thicken, causing less effective oxygen exchange. Subsequently, reduced oxygenation of the blood occurs. Absent disease, there is a gradual change in the efficiency of the respiratory system due to aging combined with accumulated damage to the lungs from air

A brief description of cardiac myxomas and the anesthetic implications for anestesia providers. Some of the formatting of this paper has been lost....the superscripts for references lost their format

1973 words - 8 pages MYXOMACardiac myxomas are rare, benign, slow growing primary cardiac tumors found most commonly in the septum of the left atrium, although they can occur in any chamber of the heart.1,2,3,4 Myxomas account for about 50% of all benign intercardiac tumors making them the most common.14,15,16,17,18 Approximately 70-85% of myxomas occur in the left atrium and the remainder in the right atrium.1,2,5,7,9,10,11,12,13,14,16,17 Very rarely one will occur

Symptoms and Modes of Infection of Bacillus Anthracis

1937 words - 8 pages substantial extravasation of fluid in the body. Vasodilation is stimulated by intracellular cAMP which is increased due to edema factors. When scientists induced canines with ET; ET promptly reduced blood pressure and central venous arterial pressure. Vasodilation caused by edema factors is said to cause hypotension and declines of central venous arterial pressure. Increased cAMP in cardiac pacemaker cells and tachycardia; tachycardia is the increase

General Studies and research of Cardiology

1884 words - 8 pages pulmonary circulation, the heart pumps blood through the lungs. It takes the de-oxygenated blood away from the heart, to the lungs, and back to the heart with oxygen-rich blood. Because the heart is an intricate organ it has many parts that can fail due to disease or dysfunction. The electrical portion of the heart is caused by muscle cells that are charged by the cardiac pacemaker in the sinoatrial node. These electrical charges and beats can

The aetiology, current and potential treatments of multiple sclerosis

7567 words - 30 pages nerve, brainstem, spinal cord, and periventricular regions, have been identified as particularly vulnerable. These lesions may be broadly divided into two groups, acute and chronic.Acute lesions by their very nature are inflammatory, and exhibit infiltration of cells associated with inflammation, namely T- and B-lymphocytes, and macrophages. The macrophages will often contain the debris of the myelin broken down from the sheaths. The degree of


4060 words - 16 pages techniques are particularly useful for identifying cortical lesions, which can manifest as dysplasias, neoplasms, vascular malformations, and traumatic scars, all of which are recognized causes of epilepsy (Cook & Stevens, 1995). The detection rate of abnormalities varies tremendously, however, and can range anywhere from less than 10% to 70% (Cook & Stevens, 1995). The seizures precipitated by epilepsy are classified by two main types: primary

When the Bubble Burst

1539 words - 6 pages By the time I arrived state side from my second tour in the Middle East the housing bubble had already burst. I noticed a drastic change in the way that many of my friends and family were living. Several of my friends that worked in real estate had sold their boats and seconds houses. My own stock portfolio had lost a third of its value. My sister and her husband had defaulted on their home mortgage leaving them scrambling for a place to live. I

phase diagram

4456 words - 18 pages Introduction: Chemical equilibrium is a crucial topic in Chemistry. To represent and model equilibrium, the thermodynamic concept of Free energy is usually used. For a multi-component system the Gibbs free energy is a function of Pressure, Temperature and quantity (mass, moles) of each component. If one of these parameters is changed, a state change to a more energetically favorable state will occur. This state has the lowest free energy

Revolutionary Work of Art

1890 words - 8 pages Walter Benjamin emphasizes in his essay, “The Work of Art in the Age of its Technological Reproducibility” that technology used to make an artwork has changed the way it was received, and its “aura”. Aura represents the originality and authenticity of a work of art that has not been reproduced. The Sistine Chapel in the Vatican is an example of a work that has been and truly a beacon of art. It has brought a benefit and enlightenment to the art

Enlightenment Thought in New Zealand Schools

1594 words - 6 pages [1784]). What is Enlightenment? In I. Kramnick (Ed.), The Portable Enlightenment Reader (pp. 1-7). New York: Penguin. Kramnick, I. (1995). Introduction. In The Portable Enlightenment Reader. (pp. ix-xxiv). New York: Penguin. Kramnick, I. (1995). The American Declaration of Independence. In. The Portable Enlightenment Reader, (pp. 448-452). New York: Penguin. Mallard, T. (2001). Speech to Auckland Primary Principals’ Association. http

Psychological Egoism Theory

2240 words - 9 pages The theory of psychological egoism is indeed plausible. The meaning of plausible in the context of this paper refers to the validity or the conceivability of the theory in question, to explain the nature and motivation of human behavior (Hinman, 2007). Human actions are motivated by the satisfaction obtained after completing a task that they are involved in. For example, Mother Teresa was satisfied by her benevolent actions and

Similar Essays

A Good Essay On Parkinsons Disease. Written For A Medical Class

1246 words - 5 pages midbrain, ventral to the tegmentum. It is controlled of apigment-rich section called the "zona compacta" and a somewhat cell-poor region calledthe "zona reticulata". Neurons in the zona compacta are accountable for the making ofdopamine, while the zona reticulata primarily creates GABA (gamma amino-butyric acid).Symptoms of PD are many and often occur in Primary and Secondary symptoms.The following symptoms are Primary. Tremors are the most

Parkinson’s Disease And Medical Treatment Options

1549 words - 6 pages degeneration of a cluster of cells in the part of the brain known as the substantia nigra. The substantia nigra is associated with the production and distribution of dopamine, a chemical messenger to the basal ganglia. The basal ganglia is responsible for controlling motor movements. However, due to this degeneration within the substantia nigra, less dopamine is produced and therefore, motor movements which depend on receiving dopamine to be

Parkinson's Disease Essay

689 words - 3 pages , poor coordination, and faulty balance. A shortening of muscles along the front of the neck tends to bend the head and spine forward, while the lack of animation in the face creates a mask like expression. As these symptoms worsen, chronic fatigue, mental confusion, and speech impairment may develop and the person with Parkinson's may find it impossible to walk unassisted. The symptoms of Parkinson's disease appear when neurons (nerve cells

Symtomps And Causes Of Bacillus Anthracis

1260 words - 5 pages extravasation of fluid in the body. Vasodilation is stimulated by intracellular cAMP which is increased due to edema factors. When scientists induced canines with ET; ET promptly reduced blood pressure and central venous arterial pressure. Vasodilation caused by edema factors is said to cause hypotension and declines of central venous arterial pressure. Increased cAMP in cardiac pacemaker cells and tachycardia; tachycardia is the increase of