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Alcohol consumption effects on the nervous system (II)

The action potential is generated by the ionic channels and pumps located on the cellular membrane. The ionic channels are cellular molecular proteins that form pores on the cellular membrane, and adjust the electronic flow of different ions such as: sodium (Na+), potassium (K+), calcium (Ca++) or chlorine (Cl-) when the pores open and close. Each ionic channel is selective and allows only one type of ion to travel across. The ionic pumps maintain a normal balance between different types of ions assigning them on both sides of the cellular membrane.

In the majority of cases, the nervous impulse is transmitted by the neurotransmitters. Once the nervous impulse reaches the synaptic terminations of the axons, it stimulates the synaptic vesicles. A synaptic vesicle is a spheric or irregular structures that contains neurotransmitters and released them when the synaptic vesicle is stimulated.

The molecules of the released neurotransmitters spread out in the synaptic slit and combine with neuroreceptor molecules from synaptic membrane. Once the neurotransmitter is released and spread along the synaptic slit, it acts instantly.
There are two main mechanims that cause the neurotransmitter to act fast:
a) instant reabsorption of the neurotransmitter at synaptic level (the neurotransmitter is assimilated by the synaptic terminations which released it, stoping the neurotransmitter to act)
b) chemical degradation of the neurotransmitter (the neurotransmitter is destroyed by the enzymes of the receptor).

There is a lock-and-key type relation between the neurotransmitter and neuroreceptor molecules. When these two molecules come together, they modify the permeability of the receptor neuron's membrane. Some neurotrasmitters can increase the membrane permeability through a process called depolarization, while others decrease its permeability having a inhibitor effect.

The transmission speed of the action potential through dendrites to axon fluctuates between 3 and 320 km per hour. This speed fluctuation is caused by the axon's diameter (bigger diameter axons transmit the action potential faster) and by the presents or abstance of myelin sheath (because the myelin functions as an isolator, it causes the impulse to move forward by leaps increasing the speed of the action potential). The medical condition caused by impaired myelin layers are impaired is called multiple sclerosis. Multiple sclerosis is characterized by severe dysfunctions of the motor and sensorial nerves.

Up to now, there are known over 50 neurotransmitters and this number will grow in the near future. There are neurotransmitters with two different types of receptor molecules. Some can have an aroused effect in some areas of the nervous system and an inhibitor effect in others.

The most important neurotrasmitters are:

Acetylcholine (ACh) is a neurotransmitter that can be found in many synapses and, in general, has an arousal effect. It can also have an inhibitory effect. The effect of the acetylcholine depends on the types of the receptor molecules found in the membrane of the receptor neuron. This neurotransmitter is found especially in hypocamp, a cerebral structure that plays an important role when new memories are formed. Those cells that produce acetylcholine tend to degenerate in Alzheimer patients causing a decreased amount of acetylcholine. A lower-than-normal amount of ACh causes a sevete loss of memory. Some drugs that reduce the amount of acetylcholine produced cause muscular paralysis.

Norepinephrine (NE) is a neurotransmitter mostly produced by the neurons of the cerebral trunk.
Two well-known drugs, cocaine and amphetamines, extend the action of NE and slow down the reabsorption processes because the receptor neurons are activated longer than normal. This explains why cocain and amphetamine have psycho-stimulanting effects. By contrast, lithium cause an inverse process leading to depressive dispositions.

Gamma-aminobutyric acid (GABA) is one of the major inhibitors of the nervous system.
When the substance called pycrotoxine blocks the GABA receptors, the muscular movement connot be controled and the person displays convulsions.
Recent researches suggested that the alcohol inhibits the glutamate system stimulating the neurons, and activates the GABA system.

Two other substances that modify the moods by increasing or decreasing the neurotransmitter concentration are chlorpromazine and LSD. The chlorpromazine is a drug used in the treatment of schizophrenia, and it blocks the dopamine's receptors. A dopamine excess at synaptic level is found in schizophrenia and a dompamine restraint is found inParkinson disease. LSD has a similar chemical structure with serotonin - a substance that influences the emotions. Medical researches suggest that LSD accumulates in specific cerebral cells and imitates the serotonin.

Glutamate is a excitatory neurotransmitter that can be found in the neurons from the central nervous system. There are at least three types of glutamate receptors, one of them (the NMDA receptor) is playing an important role in learning and memorizing process. An increased number of NMDA receptors are located near the center of the brain. According to some medical trials, this brain area plays an important role in building new memories.

The alcohol progressively influences the central nervous system's function.

When a person start to drink excessively, the alcohol affects the cerebral hemispheres which represent the center of the conscienceness, reasoning and the central place where senzorial information arrive. When there is a 0,3-0,5%o alcohol blood concentration, the person experiences light dizziness, a relaxation feeling, and a light euphoria. People say things that usually they would not say, tend to become more communicative and sociable, and become less critical while their good mood increases. Their self-esteem increases while their motor reaction decrease. The intellectual efficaciousness also decreases, but the drinker over-estimates its efficaciousness. The person tends to take wrong and risky decisions because he/she don't assess correctly the potential danger and difficulties.

When the alcohol concetration increases to 1-2%o, the cerebellum is paralysed and the sensorial and motor functins are seriously impaired. Some people tend either to behave aggressively and get upset easely, or are quite and grouchy. They speak slow and have difficulties in coordonating their movements (cannot maintain the body's equilibrium). This explains why poeple in an advanced state of intoxication stagger, do not find the key hole and stumble.

When the alcohol concentration reaches 2-3%o, the medulla is anaesthetized. Meddula controls the reflexes of unconscious movements and the normal functioning of internal organs like urine bladder and rectum. The alcohol progressively causes a slow rate of reflexes activation until these reflexes numb and the bladder and intestin sphincters cannot be controled.

At an advanced state of intoxication (higher than 3-4%o), the cerebral trunk is paralyzed. This causes a slow breathing rhythm that can lead to a heart failure and even death. Silly bets, where drinking a bottle of strong liquor is considered a masculinity proof, lead to a high alcohol concentrations in the blood causing a serious alcohol intoxication and can be followed by death.

Unfortunately, an alcoholic does not pay attention to all these severe repercussions when he/she drinks. He/she only wants to release the interior tension and to relax, to change his/her mood, and achieve a better mood and to stop carring about porblems. However, in order to achieve all these, the alcoholic is paying the price of impairing his/her vital cerebral functions. In time his/her problems worsen and cannot be solved. When the mind is controlled by the alcohol's vapors, the alcoholic do not solves problems, but he/she is lossing those needed functions and abilities that can help him/her to find answers and solutions.

The information presented above show how thoughtless an acoholic acts paying for his "interior peace" the price of lossing his/her body normal function and nevetheless the normal functions of the brain.

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  »  Evolution of dependency
  »  Loss of control
  »  Consumption's effects
  »  Co-dependency
  »  Alcoholism treatment
  »  Avoid the consumption




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