Rat ileum consists of longitudinal and circular smooth muscle. The rat ileal smooth muscles express five isoforms of muscarinic acetylcholine receptor MAchR (M1-M5)(Yuan et al., 2011), and seven classes of 5-hydroxytryptamine (5-HT, serotonin) receptors (5-HT1-5-HT7)(Briejer et al., 1997). These receptors are major drug targets and belong to the family of G protein-coupled receptor (GPCR) consisting of seven transmembrane spanning domains (Hannon & Hoyer, 2008; Yuan et al., 2011). Both MAchR and 5-HT receptors are essential in the regulations of smooth muscle contraction in gastrointestinal tracts (Yuan et al., 2011). M2 receptors are more abundantly found in the ileal smooth muscle compared to M3 receptor (Tanahashi et al., 2013). Both M2 and M3 …show more content…
Atropine is a non-selective muscarinic cholinergic antagonist and it functions by directly blocking the M3 receptor (Bhattacharjee et al., 2013). This is an example of pharmacological antagonism whereby atropine competitively inhibits Ach, antagonizing the action of Ach at postganglionic muscarinic sites (Bhattacharjee et al., 2013). The inhibition effect of atropine is concentration-dependent (Wali et al., 1987). In high concentrations, atropine reduces Ach-induced contractions by blocking ion channels present at the postsynaptic membrane of the smooth muscle cells (Wali et al., 1987). Another antagonist, adrenaline, promotes longitudinal smooth muscle relaxation by interacting with B2-adrenergic receptor coupled to Gs protein (Kosterlitz et al., 1970). This is known as the physiological antagonism. Consequently, the binding of adrenaline depresses the Ach-induced contractions in the muscle (Kosterlitz et al., 1970) besides activating enzyme adenylyl cyclase which then leads to the production of cyclic adenosine monophosphate (cAMP), thus decreasing motility in smooth
In the beginning phases of muscle contraction, a “cocked” motor neuron in the spinal cord is activated to form a neuromuscular junction with each muscle fiber when it begins branching out to each cell. An action potential is passed down the nerve, releasing calcium, which simultaneously stimulates the release of acetylcholine onto the sarcolemma. As long as calcium and ATP are present, the contraction will continue. Acetylcholine then initiates the resting potential’s change under the motor end plate, stimulates the action potential, and passes along both directions on the surface of the muscle fiber. Sodium ions rush into the cell through the open channels to depolarize the sarcolemma. The depolarization spreads. The potassium channels open while the sodium channels close off, which repolarizes the entire cell. The action potential is dispersed throughout the cell through the transverse tubule, causing the sarcoplasmic reticulum to release
Nerve stimulation was induced for every fifteen seconds at an increment frequency of 0.5 pps (parts per seconds), 1.0 pps, 2.0 pps, 4.0 pps, 8.0 pps, 15 pps, and 25 pps. Every increment trial had a thirty-seconds waiting period. To witness the effects of tubocurare on muscle activity, the baseline was maintained between 20-30 grams and a control was established by turning the stimulator on repeat for 60-120 seconds. Then 0.25 ml of tubocurare was infused into the gastrocnemius muscle. The data was recorded for ten minutes.
Stimulation of 5HT1 receptors is associated with an inhibitory response while stimulation of the 5HT2 receptors is associated with an excitatory response. Soma of the serotonergic neurons are located in the midline raphe nuclei of the pons and in the medulla oblongata. Axons extend to the basal ganglia, hypothalamus, limbic forebrain, parts of the cerebral cortex, and to the spinal cord (Kruk and Pycock 1979). Functions believed to be moderated by serotonin include sleep, mood, arousal, control of motor activity, hunger, thermoregulation, and some neuroendocrine control mechanisms in the hypothalamus. (Powell 2004, Kruk and Pycock 1979).
Sympathetic nervous stimulation: This compensatory mechanism is the first one. Epinephrine (adrenaline) and norepinephrine (noradrenaline) are released which causes an increase in BP and the heart to pump faster and more powerfully. They also increase cardiac output in this way it temporally helps compensate for the hearts reduced ability to pump blood. This is not good long term as it increased the amount of oxygen the myocardium needs.
...s to interfere with bonding to the receptors. The final possibility uses CNP, which downregulates the activation in MAP kinase pathways in the chondrocytes (4).
Myasthenia Gravis is an autoimmune disease in which the lymphocytes in the blood produce antibodies that destroy muscle-cell sites for the reception of acetylcholine molecules. Normally, acetylcholine is used in signal transmission between nerves and muscles, its goal is to provide muscle contractions.
Muscle fatigue is a decline in ability of a muscle to generate force within any part of the body. Muscular fatigue is a particular response when it comes to an untrained athlete that is starting an intense workout program, and the muscles of the body is not able to respond in an orderly manner as it would respond to an elite athlete. This paper will focus and provide general information about recent studies on peripheral fatigue. Peripheral fatigue is one of the sites for possible fatigue and its where neural, mechanical, or energetic events can hamper tension development. Neural fatigue is a factor of peripheral fatigue, which occurs when the nerves are unable to generate a signal and this reduces the ability of the muscle fiber to contract which is considered to be metabolic fatigue. Neural factors deals with the movement of action potential going through a process to produce a muscle contraction and when this process does not go through the proper steps then fatigue set in because the muscles will not be able to contract. Neural fatigue has two main factors which is, a shortage of...
Adenosine is a natural chemical found in the body which binds to respective adenosine receptors in the sinoatrial node and slows down the activity of the nerve cells. Caffeine also binds to these receptors which results in the activity of these nerve cells to increase.
Acetylcholine (Ach) is a major transmitter found in the autonomic ganglia that allows neurons to communicate for sensory input and muscle control. Muscarinic receptors are vital in the control of the central nervous system (CNS) and also parasympathetic control of the heart, lungs, and gastrointestinal processes. By blocking the action of these receptors, a result is possible impaired central and peripheral nervous system functioning. Inhibiting this function could also cause tachycardia, which can lead to myocardial infarction (heart attack) or angina (chest pain). Scopolamine is also used as a pupil dilator, in pain management, and to treat symptoms associated with chemotherapy.... ...
Irritable bowel syndrome (IBS) is a functional GI disorder (FGID) characterized by abdominal pain in association with altered bowel habits in the absence of any identifiable structural or biochemical abnormalities. It is a very common disorder that can have a profound negative impact on a patient’s quality of life and constitutes a considerable social and economic burden on society. Extensive research over the last few decades has led to a better understanding of this complex syndrome and improvements in treatment. After a brief review of the clinical manifestations and diagnosis of IBS, the current understanding of the complex physiological mechanisms contributing to the syndrome will be addressed. The remainder of this paper will focus on a number of important topics at the interface of IBS and psychiatry, including psychiatric comorbidity in IBS, the complex role of psychosocial stressors in the onset and perpetuation of symptoms in IBS, and various considerations in the management of IBS from the perspective of psychiatry.
Muscle contraction is a long process. It goes through many different steps. First, an electrical signal, action potential, travels down a nerve cell, causing it to release a chemical message, known as neurotransmitter,into a small gap between the nerve cell and muscle cell. This gap is called the synapse.The chemical message, neurotransmitter, crosses the gap, and attaches to a protein called a receptor on the muscle-cell membrane and causes an electrical signal, action potential, in the muscle cell.The chemical signal, action potential, spreads quickly along the muscle cel...
Irritable Bowel Syndrome (IBS) is a gastrointestinal syndrome characterized by chronic pain and irregular bowl movement with the absence of organ cause. IBS could be diarrhea-predominate or constipation-predominate. One of the pathophysiology that thought to cause IBS diarrhea-predominate (IBS-D) is a high level of serotonin especially after the meals. There are two type of serotonin that involve in the gastrointestinal system, type 3 (HT3) and type 4 (HT4). The purpose of this study is to evaluate the efficacy of ondansetron, which is a selective 5-HT3-receptor antagonist that have been used as antiemitc agent, in the treatment IBS-D.
For many years, the mechanism of caffeine was not yet clear. However, it was thought that the mechanism involves the re...
Gastrin hormone has a role in controlling gastric secretion. Gastrin hormone functions by binding on the secretory cells ...
Exercise may serve as an effective tranquilizer. Studies in adults indicate that 30 min of aerobic exercise reduces muscle tension by as much as does a dose of 400 mg o...