Nicotinic Acetylcholine Essay Example | Topics and Well Written Essays - 1250 words

Nicotinic Acetylcholine - Essay Example Synthesized in the endoplasmic reticulum, a fraction of the subunits of this receptor assemble into homo and hetero-pentameric complexes. The only complexes that reach the cell surface, after exiting from endoplasmic reticulum are the pentameric complexes. nAChRs have been identified as crucial elements in central nervous system functions such as consciousness, attention, and memory; and participate in numerous cerebral circuits. (Bocquet, Carvalho, Cartaud, Neyton Poupon, Taly, Grutter, Changeux, Corringer 2007) The opening of the channels of these receptors is triggered by the neurotransmitter acetylcholine. Nicotine also has the same effect. A diagram of the chemical structure of acetylcholine is given below. Nicotinic acetylcholine receptors are located mainly in the postsynaptic membrane under the motor nerve terminal at the neuromuscular junction. Nicotinic receptors can also be found in different synaptic locations; e.g. the muscle nicotinic receptor always functions post-synaptically. The nerve cell forms of the receptor can be found both post-synaptically (performing classical neurotransmission) and pre-synaptically (causing the release of other neurotransmitters). In contrast to the muscarinic acetylcholine receptors, Nicotinic Acetylcholine receptors do not operate with the help of a second messenger. Instead they open themselves forming an ion channel. Curare causes inhibition of these receptors. Nicotinic acetylcholine receptors have a very wide distribution in the various body tissues. Nerve cell receptors are found in the central nervous system and also in the peripheral nervous system. The neuromuscular receptors, on the other hand are found in the neuromuscular junctions of somatic muscles. ... The neuromuscular receptors, on the other hand are found in the neuromuscular junctions of somatic muscles. The stimulation of these receptors causes muscular contraction.(Barrantes 1998) Structure and function of Nicotinic Acetylcholine Receptors The nicotinic acetylcholine receptor protein includes one or many sites which can bind the neurotransmitter ACh and also a specific channel for cat ions which is also known as the intrinsic cationic channel. These ions can be Na+, Ca2+ or K+ and the channel is specific in nature. The process of the opening of ion channel is linked to the binding of ACh. (Maelicke 1986) Protein chemistry and sequence analysis of polypeptide has revealed a general scheme for each subunit which consists of : 1. A globular extra cellular N-terminal domain (ECD); 2. A trans-membrane domain (TMD) 3. A cytoplasmic domain There are 2 to 5 Acetylcholine binding sites on the ECD. Nicotinic receptors have many subunits and these subunits belong There are 2 to 5 Acetylcholine binding sites on the ECD. Nicotinic receptors have many subunits and these subunits fit in a multigene family (seventeen members in the human being) When many of the subunits combine they form a great numbers of receptors. Every subunit gives three parts or "loops" to the site of binding. The sites which bind ACh are located on the outer side of the subunits. And as the agonist binds, the subunits happen to be more alike to the other subunits. And the channel gets more proportioned and a hole of about 0.65nm in diameter opens up. This channel helps the nicotinic acetylcholine receptor to adhere to its role by many ways. Firstly it encloses a mechanism of gating which is closed in the inactive states of the channel but it is open in the active

Indonesia Essay Example | Topics and Well Written Essays - 1000 words

Indonesia - Essay Example (FAO) The median age for males is 25.7 and for females 26.6, giving a total median age population of 26.1. (Country Reports 2006) The sex ratio (m/f) at birth is 1.05, at 15-64 is 1.0, and at 65 and over is 0.78. With 21 births and 6 deaths per 1,000 people, and 36 infant deaths per 1,000 live births, Indonesia has an annual growth rate of 1.4%. Life expectancy at birth is currently 69.6 years. The crude birth rate per 1000 people is 22.55 as per the 1998 census. (World Health Organization) The total fertility rate (per woman) is 2.4. The primary reasons for the decline in fertility rate in Indonesia are an increased use in contraception, which in turn is due to economic development, an increase in the education rate, and greater work force participation for women. (Shafiqul-Islam et. al 1995) Adult male and female literacy rates are at 93.4% and 85.5% respectively (WHO) The maternal mortality ratio, the infant mortality rate, and the under 5 mortality rate are all declining, due to several factors including increased immunization coverage, economic growth (particularly in rural areas), improvement in health facilities, and greater community awareness and participation. Constraints to reduction in mortality include increasing urbanization and poverty in remote island locations. (WHO) Ethnicity of Indonesia is Javanese 45%, Sudanese 14%, Madurese 7.5%, coastal Malays 7.5%, other 26%. Religious identity is Islam 88%, Protestant 5%, Roman Catholic 3%, Hindu 2%, Buddhist 1%, other 1%. (Country Reports: Indonesia) Indonesia has become a global source of contract migrant workers, who secure jobs in another country for a contracted period. The push factor is the demand for unskilled labor in Australia and Thailand, for example. The scarcity of skilled workers in Indonesia is a major pull factor for immigration into the country. (UN) Figure 3 - Religious Affiliation Resources Average daily protein intake is 65.74 as per the 1999 census. The people of Indonesia consume an average of around 2,800 calories per day. (FAO) Indonesia has faced serious problems with malnutrition due to inadequate production and availability of certain foods. Rice is the staple of the majority of Indonesians, due to availability and expense of meat protein. (FAO) Insufficient awareness of nutritional needs and poor eating habits are among other reasons for malnutrition. Other nutritional issues such as anemia, iodine deficiency, and vitamin A deficiency are also prevalent. (WHO) Forestry is a significant employer in Indonesia, supplying around 3.7 million jobs. An estimated 51-57% of the land area of the country is covered in forest land, equating to 98-109 million hectares. 34% is designated for protection and national parks. Secondary forest products such as plywood, sawn timber, rattan, and paper are among the most important non-oil exports of the country. Switching to sustainable forest resources is crucial because the population of Indonesia is increasing relatively rapidly. The government plans to decrease reliance on natural forest areas for such products, and increase reliance on plantations, with the goal of having