Superior vena cava functions

The better main vein (SVC) is the better of the two cava veins, the great venous trunks that return oxygen-free blood from the systemic circulation to the right atrium of the heart. It is a large diameter (24 mm) vein, but short, which receives a venous return from the upper half of the body, above the diaphragm. (Venous return from the lower half, below the diaphragm, flows through the lower main vein). The SVC is located in the front right upper portion of the mediastinum. This is a typical central venous access (CVA) via a central venous catheter or central catheter placed peripherally. References to “cava” without further specification usually refer to SVC.

 


superior vena cava functions & structure

Superior vena cava formes with left and right brachiocephalic veins (also called veins). It also takes blood from the upper limbs, eyes, and neck, behind the lower limit of the first right bone cartilage. It flows vertically downstream of the first intercostal space and receives the azygos vein just before the puncture of fibrous pericardium opposite to the right cartilage of the hip, and its lower part is intramuscular. And then it ends in the upper and the rear part of the sine venarum right atrium, in the upper right front of the heart. It is also known as a cranial vein in other animals.

 

 

In superior vena cava functions, the lack of a valve divides the main vein from the right atrium. As a result, (right) vestibular spasms and (right) ventricles are carried to the internal jugular vein, and through the muscle can be perceived as cervical venous pressure. A better obstruction of the vena cava means a partial or complete obstruction of the superior vena cava, usually in the context of cancer, such as lung cancer, metastatic carcinoma or lymphoma.

 


Clogging can lead to enlarged veins in the head and neck, and can also cause shortness of breath, cough, chest pain and difficulty in swallowing. Pemberton’s sign may be positive. The obstruction-inducing tumors can be treated with chemotherapy and/or radiotherapy to reduce their effects, and corticosteroids may also be administered.[post_grid id=”473″]

fibrocartilage function

White fibrocartilage function consists of a mixture of white fibrous tissue and cartilage in various proportions. It owes its stiffness and durability to the first of these components and its flexibility to the latter. It is the only type of cartilage which, in addition to collagen type II, contains type I collagen. Fibrocartilage is found in the soft adjacent bone tissues, the pubic symphysis, the intervertebral disc, the meniscus, the triangular fibroblast, and the TMJ. During labor, it relaxes the pubic symphysis to help in childbirth, but this can lead to later problems in the joints.




Fibrocartilage function

If the vitreous cartilage is torn to the bone, the blood supply from the inside of the bone is sometimes enough to initiate treatment within the lesion. In such cases, the body creates a scar in the area, using a special type of cartilage called fibro-cartilaginous. Fibrocartilage is a hard, dense and fibrous material that helps fill the torn part of the cartilage; however, this is not a perfect replacement for smooth, glassy joint cartilage, which normally covers the surface of the joints.

Fibrocartilage callus

Fibrous callus is a temporary formation of fibroblasts and chondroblasts that forms at the point where the bone broke when the bone attempts to heal. The cells eventually dissipate and become dormant, lying in the resulting extracellular matrix, which is the new bone. Callus is the first symptom of the relationship saw on the X-ray, usually 3 weeks after the fracture. Callus formation is slower in adults than in children, as well as in cortical bone than spongy bones.

 


fibroblast

The fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, forms a structural skeleton (framework) in animal tissues and plays a key role in wound healing. Fibroblasts are the most common connective tissue cells in animals.

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Pleural effusion symptoms & Caues & diagnosis

Pleural effusion is an unusual amount of fluid in the lungs. This can lead to many conditions, so even if the effusion in the pleural cavity can be dehydrated, the doctor will probably manage treatment for anything caused. The pleura is a pencil-thin membrane that lines the surface of the lungs and the inside of the chest. When you have pleural effusion, the fluid accumulates in the space between the layers of the pleura. Usually, in the pleural space, there are only teaspoons of liquid fluid that allow the lungs to move smoothly in the chest cavity while breathing.




pleural effusion symptoms

You can not have them. Symptoms are more likely to occur when the pleural effusion is moderate or severe, or if there is also inflammation.

If you have symptoms, they may include:

Shortness of breath
Chest pain, especially in deep breathing (this is called pleurisy or pleural pain).
Fever
Cough

 

pleural effusion other symptoms (Causes)

A wide range of things can cause pleural effusion. Some of the more common ones are:

The spill from other organs. This usually happens in the case of congestive heart failure, when the heart does not pump blood properly into the body. But it can also come from the liver or kidney disease when fluid accumulates in your body and penetrates into the pleural space.

Cancer. Usually, lung cancer is a problem, but other cancers that have spread in the lungs or pleura can also cause them.

Infections. Some diseases that lead to pleural effusion are pneumonia or tuberculosis.

Autoimmune conditions. Lupus or rheumatoid arthritis are some of the diseases that can cause it.

Pulmonary embolism. It is blockage of the artery in one of the lungs and can lead to pleural effusion.

 

Types of pleural effusions

There are several types of pleural effusion, each of which has different causes and treatment options. The first classification of pleural effusion is either permeated or exudative.

 

Transudational pleural effusion

This type is caused by fluid leakage into the pleural space due to a low number of blood proteins or increased blood pressure in the blood vessels. The most common cause is congestive heart failure.

Exudative effusion
This type is caused by blocked lymph or blood vessels, inflammation, tumors, lung damage
Typical conditions that can lead to this type of pleural infusion are a pulmonary embolism, pneumonia, and fungal infections.

 

Complicated and uncomplicated pleural effusion

There are also complicated and uncomplicated pleural effusions. Uncomplicated pleural effusions contain fluid without symptoms of infection or inflammation. They are much less likely to cause permanent lung problems.

Complicated pleural effusions, however, contain fluid with a significant infection or inflammation. They require immediate treatment, which often includes chest drainage.

 


Diagnosis

Your physician will ask you about your symptoms and give you a physical exam. He touches the chest and listens with a stethoscope.

To confirm that you have pleural effusion, you need to perform imaging tests, such as:

Chest X-ray. Pleural effusion appears white on the X-ray, while the air space looks black. If the pleural effusion is likely, you can get more X-ray films when you lie on your side. They can show if the fluid flows freely in the pleural space.

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Pleura function & Structure

The pleura is a raw membrane that folds together to form a bilayer membranous pleural sac. The external pleura (pleural wall) is attached to the chest wall but is separated from the fascia by the endotoxin. The internal pleura (visceral pleura) includes the lungs and adjacent structures, including blood vessels, bronchi, and nerves. The pleural cavity can be seen as a potential space because the two contaminants adhere to each other (through a thin film of serous liquid) under all normal conditions. Fetal pleura function develops up to 2.5 cm above the middle and middle junction of the third part of the clavicle.




Pleura function

The pleural cavity, together with the accompanying pleura, helps in the optimal functioning of the lungs during breathing. The pleural cavity also contains pleural fluid that acts as a lubricant and allows you to swell without effort on yourself during breathing movements. The surface tension of the pleural fluid also leads to a close application of the lung surface to the wall of the chest. This dependence allows greater filling of the alveoli during breathing. The pleural cavity transfers the muscle movements of the ribs to the lungs, especially during heavy breathing. During inhalation, the external interdental muscles contract, like the diaphragm. This enlarges the chest wall, which increases the volume of the lungs. This creates a negative pressure and inhales.

 

Pleural fluid

Pleural fluid is a serous fluid produced by the serous membrane that covers normal swelling. Most fluids are produced by parietal circulation (intercostal vessels) through mass flow and reabsorbed by the lymphatic system. In this way, the pleural fluid produces and reabsorb continuously. In a normal person weighing 70 kg, several milliliters of pleural fluid is always present in the intrapleural space. Larger amounts of fluid can accumulate in the pleural space only if the production rate exceeds the rate of reabsorption. Typically, the rate of reabsorption increases as a physiological reaction to the accumulating fluid, with the rate of reabsorption increasing to 40 times the normal rate before a significant amount of fluid accumulates in the pleural space. Thus, for the accumulation of fluid in the pleural space, a deep increase in pleural fluid production or some blocking of the reabsorptive lymphatic system requires.

 


Structure

In humans, there is no anatomical connection between the left and right pleural cavities. Therefore, in cases of pneumothorax, the second lung will continue to function normally unless there is a pneumothorax or bilateral pneumothorax that can collapse opposite the flesh, blood vessels and bronchi.

The visceral pleura function receives blood flow from the bronchial circulation, which also supplies the lungs. Parietal pleura gets its blood supply from the intercostal arteries, which also feed the body wall that is going through.

The cervical and cervical parts and the periphery of the membrane part of the pleura innervate with intercostal nerves. The mediastinal portion and the middle part of the diaphragm innervate with the diaphragm nerves. Visceral mold covering the lung itself receives the innervation of the autonomic nervous system and has no sensory innervation. Only the parietal pleura is sensitive to pain.

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Fibroblast function & Structure

A fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework (stroma) for animal tissues and plays a fundamental role in the healing of wounds. Fibroblast function is the most common connective tissue cells in animals.

 

fibroblast function

Fibroblasts produce collagen fibers, glycosaminoglycans, reticulate and elastic fibers, and fibroblasts of individual individuals divide and synthesize the ground substance. Tissue damage stimulates fibrocytes and induces fibroblast production.

 


Inflammation

In addition to the well-known role of structural components, fibroblasts play a key role in the immune response to tissue damage. They are early players in initiating inflammation in the presence of attacking microorganisms. They induce chemokine synthesis by displaying receptors on their surface. The immune cells then react and initiate a cascade of events to remove invasive microorganisms. Receptors on the surface of fibroblasts also allow the regulation of hematopoietic cells and provide pathways for immune cells that regulate fibroblast function.

 

Tumor meditation

fibroblast function, like tumor-associated host fibroblasts (TAFs), plays a key role in the regulation of immunity through extracellular matrix extracellular matrix (ECM) components and modulators. TAF is known to be significant in the inflammatory response as well as in immunological suppression in tumors. The ECM components originating from TAF cause changes in the ECM composition and start the ECM rebuild. ECM reconstruction describes as changes in ECM due to enzymatic activity that can lead to ECM degradation.

 

Immunological regulation of tumors is largely determined by ECM remodeling, because ECM is responsible for the regulation of many functions, such as proliferation, differentiation, and morphogenesis of vital organs. In many types of cancer, especially those associated with epithelial cells, ECM remodeling is common. Examples of TAF-based ECM derivatives include Tenascin and Thrombospondin-1 (TSP-1), which can be found in chronic inflammation and cancers, respectively.

 


The immune regulation of tumors can also be affected by TAF derived modulators. Although these modulators may sound similar to the ECM components of TAF derivatives, they differ in that they are responsible for the variability and rotation of the ECM. Split ECM molecules can play a key role in immune regulation. Proteases such as matrix metalloproteinases (MMPs) and the uPA system is cleav the ECM. These proteases derive with fibroblasts.

 

Secondary Actions

Murine embryonic fibroblasts (MEFs) use as “nutrient cells” in research on human embryonic stem cells. However, many researchers are gradually eliminating MEF factors in favor of breeding media with strictly defined components exclusively derived from humans. The source needed] In addition, the difficulty of using only human acquisition for dietary supplements is most often solved by means of “defined media”. where the supplements are synthetic and achieve the main goal, which is to eliminate the risk of contamination from derivative sources.

fibroblast function has a branched cytoplasm surrounding an elliptical, speckled nucleus with two or more nuclei. Active fibroblasts recognize after a thick rough endoplasmic reticulum. Inactive fibroblasts (called fibrocytes) are smaller in spindle shape and have a reduced amount of rough endoplasmic reticulum. Although they disjoint and disperse, when they need to cover a large space, fibroblasts, when crowded, often locally equalize in parallel clusters.

 


structures

Unlike epithelial cells lining the body structures, fibroblasts do not form flat single layers and are not limited by a polarizing connection to the basal lamina on the one hand, although in some situations they may contribute to the basic components of the leaf blade (eg, Sub-gut myofibroblasts can secrete the α-2 chain carrier component of laminin, which is not only present in the epithelial regions associated with the vesicle, which lacks the muscle lining). Fibroblasts can also migrate slowly over the substrate as single cells, again unlike epithelial cells. While epithelial cells from the lining of body structures, fibroblasts, and related connective tissues sculpt the “mass” of the body.[post_grid id=”473″]

Intervertebral disc function & structure, major injures

The intervertebral disc function acts as a shock absorber between each vertebra of the spine, keeping the circles separated when there is an effect of activity. They also serve to protect the nerves that run in the middle of the spine and intervertebral discs.

 

intervertebral disc function

Between the various vertebrae in the cervical, thoracic and lumbar vertebrae (not in the sacrum and caudal bone) there are oval pads made of fibrous insert called the intervertebral discs.

The discs have a hard outer shell of the cartilage that provides support (fibrous rings) and a soft, jelly-like center that provides cushioning (nucleus pulposus).

Intervertebral disc function have the following roles:




They provide cushioning of the vertebrae and reduce the stress caused by the impact. Keeping the vertebrae separated from each other, they act as a kind of shock absorber for the spine.

They help to protect the nerves that run along the spine and between the vertebrae.
They increase the flexibility of the spine and allow us to bend at the waist without pushing the vertebrae towards each other.

 

injures

Intervertebral discs are susceptible to many injuries. Most often it is called <b> disk hernia </ b> (a.k.a., bulging disc or slipped disk). Convex discs usually appear later in life. When discs age, they begin to break down, and when someone exerts excessive pressure on them, eg. Lifting something heavy around the waist instead of on the legs, they can break, break, and the gelatinous medium leaks. The jelly can irritate the surrounding nerves and cause their inflammation. This inflammation can put pressure on the nerves, causing back pain. The disc herniation diagnoses in several ways, including palpitations (spinal sensation) or X-rays and MRI imaging. Treatment of disc herniation as simple as resting and allowing healing, taking anti-inflammatory medications to reduce swelling, and in some extreme cases, surgery performed to repair the damage.

 

structure

Intervertebral disks consist of an outer fibrous ring, an intervertebral fibrous ring that surrounds the inner, gel-like center, the nucleus pulposus. The fibrous core consists of several layers (plaques) of fibrous-cartilage composed of both collagen type I and types II. Type I concentrates towards the edge of the ring, where it provides more strength. Stiff lamina can withstand compressive forces. Fibrous intervertebral discs contain the crush nucleus, which helps to evenly distribute the pressure on the disc. This prevents the formation of stress concentrations that could damage the underlying vertebrae or their end plates. The nucleus pulp contains loose fibers suspended in a mucoprotein gel. The disk kernel acts as a shock absorber, absorbing the effects of body activity and separating two vertebrae. It is a remnant of a notochord.

 


There is one plate between each pair of vertebrae, with the exception of the first cervical segment, the atlas. Atlas is a ring around a roughly conical axis extension (second cervical segment). The axis acts as a pole around which the atlas can rotate, allowing the neck to rotate. There are 23 discs in the human spine: 6 in the neck (cervical region), 12 in the middle ridge (thoracic region) and 5 in the lower back (lumbar region). For example, the circle between the fifth and sixth cervical vertebrae is referred to as “C5-6

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Mediastinum function & Structure

Lymph nodes (mediastinum) are small round organs of the lymphatic system that support the proper functioning of the immune system. They help the body fight infection by filtering foreign lymphatic particles, a transparent or whitish fluid that consists of white blood cells. Lymphrate also contains a type of white blood cells called lymphocytes that help attack bacteria in the blood. Intra-articular lymph nodes are glands that are located in the part of the chest that lies between the breastbone and the spine. Read below mediastinum function.




mediastinum function

This region is called mediastinum and contains the heart, thymus, trachea and large blood vessels. Mediastinal lymph nodes are responsible for bone marrow support and the thymus for the production of mature lymphocytes. Lymph nodes differ in size from the size of the head to the size of lima beans. They enclose in a fibrous capsule. The lymph nodes are connected with each other by various lymph vessels and are drainage vessels (ie away from the center or away from the central nervous system).

The mediastinum locates in the chest and is close on the right and left through the pleura. It surrounds with the chest at the front, the lungs at the sides and the spine at the back and stretches from the sternum to the front of the spine at the back and contains all the organs of the chest except the lungs. It is continuous with a loose connective tissue of the neck.

 

mediastinum structure

Mediastinum can be divided into upper (or upper) and lower (or worse) parts:

The mediastinal mediastinum begins at the top of the chest and ends in the plane of the chest.
The chest surface separates the upper and lower mediastinum. This is the plane at the angle of the sternum and the intervertebral disc T4-T5. 



Inferior mediastinum from this level to the diaphragm. This lower part divides into three areas, all referring to the pericardium – the front part of the mediastinum located in front of the pericardium, the middle mediastinum contains the pericardium and its contents, and the posterior mediastinum is located behind the pericardium.

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Somatic Nervous System function & parts

The somatic nervous system is part of the peripheral nervous system, which is the entire nervous system outside the brain and spinal cord. In particular, the somatic nervous system is responsible for the movements of voluntary muscles and a process name is a reflex arc. This system transfers nerve impulses back and forth between the central nervous system, which is the brain and spinal cord as well as skeletal muscles, skin and sensory organs. One of the most composite systems in the body is the nervous system. In this lesson you will learn about the somatic nervous system and how important the body’s functions are. Examples and illustrations will provide to facilitate the understanding Somatic Nervous System function. The somatic nervous system plays a very important role in bringing the ball to the alley – especially if you want to strike.




Somatic Nervous System function

The basic role of the somatic nervous system is to connect the central nervous system with organs, muscles and the skin. This enables you to perform compound movements and behaviors. Somatic neurons carry messages from external areas of the body that are related to the senses. It’s like moving from the environment to the central nervous system. Sensory/afferent neurons carry impulses to the central nervous system and the brain. After processing by the central nervous system, the somatic motor or efferent neurons receive a signal to the muscles and organs of the senses.

 

Remember the pairs of nerves described above under the parts of the somatic nervous system. Some of the nerve pairs only have sensory neurons, such as those that involve in sense of smell and vision. Others have only motor neurons, such as those involved in the movement of the eyeball (not seeing) and hearing. In somatic nervous system function, some pairs of nerves have both sensory and motor neurons, such as those associated with taste and some aspects of swallowing.

 

Parts of the somatic nervous system

The somatic system consists of two different types of neurons, which are also called nerve cells. Two types of neurons are sensory neurons or afferent neurons that transmit messages to the central nervous system and motor neurons, also called outgoing neurons that transmit information from the central nervous system to additional zone of the body. The neuron has a body and axon; The body of the neuron is located in the central nervous system. The axon is embedded in the skeletal muscles, sensory organs or skin.

 


Now we will talk about how the somatic nervous system fits the peripheral nervous system. In the peripheral nervous system there are 12 pairs of cranial nerves and 31 pairs of spinal nerves, which are composed of sensory neurons and motor neurons. Some pairs of nerves have only sensory cells, some have only motor cells, and still, others have both sensory and motor cells. Cellular nerve cells are somatic or autonomous. Because this lesson is about the somatic nervous system, we will not discuss autonomic nerve cells in detail.

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Parasympathetic nervous system functions & structure

The parasympathetic nervous system function is responsible for stimulating “rest and digestion. The feeding and reproduction” activities that occur when the body is resting, especially after eating, including sexual arousal, drooling, tearing (tears), urination and defecation.

 

The nerve fibers of the parasympathetic nervous system arise from the central nervous system. Specific nerves include several cranial nerves, in particular, the oculomotor nerve, the facial nerve, the laryngopharyngeal nerve, and the vagus nerve.


The three spinal nerves in the sacrum (S2-4), commonly referred to as pelvic span nerves, also act as parasympathetic nerves.

 

 

The parasympathetic nervous system function

Feeling

Intravital nerve supply fibers that transmit sensory information from the internal organs of the body back to the central nervous system. These are not divided into parasympathetic and sympathetic fibers as drainage fibers: 34-35 Instead, autonomic sensory information is carried out by visceral afferents generally.

 

Parasympathetic nervous system function

 

General visceral sensations are mostly unconscious visceral motor reflexes from the hollow organs and glands that are transmitted to the CNS. While unconscious reflex arcs are usually undetectable. In some cases, they can send pain sensations to the CNS masked, like the mentioned pain. If the peritoneal cavity becomes inflamed or if the gut suddenly expands, the body will interpret the effective stimulus of pain as being somatic at first. This pain is usually not located.

 

 

Vascular effects

Heart rate is largely controlled by the action of an internal pacemaker. Cardiac cells exhibit automatism because it has the ability to generate electrical activity independent of external stimulation.

 

In the parasympathetic nervous system function, the absence of any external stimuli, peripheral stimulation contributes to maintaining heart rate in the range of 60-100 beats per minute (bpm). At the same time, the two branches of the autonomic nervous system activity in a complementary way. It increases or slowing down the heart rate. In this context, the vagus nerve acts on the sinoatrial node, slowing its conduction, actively modulating the vagus nerve tension, respectively.

 

The vagus nerve plays a key role in regulating the heart rate by modulating the sinus node response, the vagus nerve tone can be quantified by examining the modulation of the heart rate caused by changes in the vagus tone.  The main mechanism of the parasympathetic nervous system for vascular and cardiac control is the so-called nasal sinus arrhythmia (RSA).




Sexual activity

Another role played by the parasympathetic nervous system is sexual activity. In males, cavernous nerves from the prostate plexus stimulate smooth muscles in fibrous tufts of rolled penile arteries to loosen. It allows the blood to fill the two corpus cavernosum and the penile spongy body.

 

It made them stiff to prepare for sex. action. After separating the ejaculate, sympathetic people interact with each other and cause peristalsis of the auditory canal and closure of the internal urethral sphincter to prevent sperm from entering the bladder. At the same time, Paralympics cause peristalsis of the urethral muscle.

 

In the parasympathetic nervous system function, the pudendal nerves cause a contraction of the tuberculous to secrete the strength of the semen. During remission, the penis becomes flabby again. In females, there is erection tissue analogous to male, but less important, which plays a large role in sexual stimulation.

 

PN causes secretion in the female, which reduces friction. Also in women, the parasympathetic innervate the fallopian tubes. It helps peristaltic cramps and the movement of the oocyte to the uterus for implantation. Secrets from the female genital system help in the migration of sperm. PN (and SN to a lesser extent) play an important role in reproduction.

 

 

Other parasympathetic nervous system function (receptors)

The parasympathetic nervous system mainly uses acetylcholine (ACh) as a neurotransmitter, although peptides (such as cholecystokinin) may be used. ACh acts on two types of receptors, muscarinic and nicotinic cholinergic receptors.

 

Most of the transmission proceeds in two stages: after stimulation. The neurotransmitter releases ACh in a ganglion that acts on the nicotinic receptors of postganglionic neurons. The postganglionic neuron then releases ACh to stimulate muscarinic receptors on the target organ.

 

 

Parasympathetic nervous system structure

The parasympathetic nerves are autonomic or sensory branches of the peripheral nervous system (PNS). Restoration of the parasympathetic nerve arises in three main areas.

 

Parasympathetic

 

Certain cranial nerves in the skull, namely the parasympathetic nerves usually arise from specific nuclei in the central nervous system. (CNS) and synapse in one of the four parasympathetic ganglia: cilia, pterygopalatine, or submandibular. These four ganglia, the parasympathetic nerves end their journey to target tissues through the trigeminal branches (optic nerve, maxillary nerve, mandibular nerve).

 

The vagus nerve does not participate in these cranial ganglia, because most parasympathetic fibers are intended for a wide range of ganglia on or near the torso (esophagus, trachea, heart, lungs) and abdominal viscera (stomach, pancreas, liver, kidney, small intestine, and about half large intestine). The vicious labyrinth ends at the intersection between the medial and posterior mediastinum. It just before the bending of the lateral spleen of the colon.

SA node function & their phase & understanding sinus node

The SA node, also known as the sinus node. It is a group of cells located in the wall of the right atrium of the heart. These cells have the ability to spontaneously produce an electrical impulse (action potential, see below for more details) that travels through the heart via the electrical conduction system, causing it to contract. Read below SA node function.

 


 

SA node function

The main role of sinus node cells is to initiate functional potentials. They can pass through the heart and cause spasms. The functional potential is the change in the voltage (membrane potential) across the cell membrane, produced by the movement of charged atoms (ions).

 

Cells without a pacemaker (including ventricular and atrial cells) have a period immediately following the action potential where the potential of the membrane remains relatively constant; this also knows as the potential of resting membrane.

 

In the SA node function, this gives a positive change in membrane potential (known as depolarization), which initiates the beginning of the next action potential. However, cancer cells do not have this resting phase. Instead, immediately after one potential action, the membrane potential of these cells automatically begins to depolarize again.

 

This knows as the potential of the stimulator. When the pacemaker potential reaches a predetermined value, known as a threshold value, then it produces a functional potential. Other cells within the heart (including Purkinje fibers and atrioventricular node, AVN) can also initiate functional potentials. However, they do so slowly, and therefore, if the SA node is working, it usually pierces from AVN.

 


phase 4

This phase is also known as the stimulator potential. Immediately after the action of potential, when the membrane potential is very negative (hyperpolarized), the voltage slowly begins to increase. This is initially caused by the closure of potassium channels, which reduces the flow of potassium ions.

 

Phase 0

This is the depolarization phase. When the membrane potential reaches the threshold (about -20 to -50 mV), it begins to depolarise rapidly (it becomes more positive). This is mainly due to the Ca2 + flow through the L-type calcium channels, which are now completely open. The calcium channels and HCN channels deactivate during this stage, T-type.

 

Phase 3

This phase is the phase of repolarization. This is due to the inactivation of L-type calcium channels (preventing Ca2 + from moving to the cell) and activation of potassium channels, which allows K + outflow from the cell, making the membrane potential more negative.