Os Efeitos do Álcool no Organismo Humano

O álcool é um depressor de muitas ações no Sistema Nervoso Central, e esta depressão é dose-dependente. Apesar de ser consumido especialmente pela sua ação estimulante, esta é apenas aparente e ocorre com doses moderadas, resultando da depressão de mecanismos controladores inibitórios. O córtex, que tem um papel integrador, sob o efeito do álcool é liberado desta função, resultando em pensamento desorganizado e confuso, bem como interrupção adequada do controle motor.

O etanol se difunde pelos lipídios, alterando a fluidez e a função das proteinas. Altas concentrações de álcool pode diminuir as funções da bomba Na⁺ K⁺/ATPase no transporte de elétrons, este efeito compromete a condução elétrica. O álcool parece atuar sobre canais existentes nas membranas dos neurônios, através dos quais estas células trocam íons com o meio circundante. Por meio deles, íons positivos ou negativos entram e saem dos neurônios, aumentando ou diminuindo sua atividade elétrica.

O procedimento, por sua vez, afeta todas as funções cerebrais. Normalmente, os canais iônicos são abertos ou fechados pela ação de neurotransmissores ou por variações na diferença de potencial elétrico entre o interior e o exterior dos neurônios.

Quando o etanol se liga ao receptor GABAérgico, ele promove uma facilitação da inibição GABAérgica. O resultado é um efeito muito mais inibitório no cérebro, levando ao relaxamento e sedação do organismo. Diversas partes do cérebro são afetadas pelo efeito sedativo do álcool tais como aquelas responsáveis pelo movimento, memória, julgamento, respiração, etc. porque existem receptores GABA em muitas partes do cérebro. “No cerebelo e no sistema vestibular, o álcool provoca a disartria que são os problemas na articulação de palavras que levam àquela fala enrolada. Já ataxia é o nome dado para a perda da coordenação dos movimentos. E existem ainda os problemas da visão dupla e do nistagmo, que são oscilações involuntárias dos olhos”.

Em níveis mais altos de álcool no sangue, a cognição e a coordenação motora são tão afetadas que multiplicam os riscos de dirigir veículos e operar máquinas perigosas, e até mesmo um simples passeio de bicicleta pode causar um acidente grave. O uso prolongado e abusivo do álcool pode causar dependência. Então, se a pessoa para de beber, ela experimenta o fenômeno de abstinência alcoólica, levando o indivíduo a um estado de desconforto emocional, ansiedade, tremores, insônia.

How Alcohol Affects the Brain

General Effects of Alcohol on the Brain

Alcohol can affect several parts of the brain, but in general, alcohol contracts brain tissue and depresses the central nervous system. Also, alcohol destroys brain cells and unlike many other types of cells in the body, brain cells do not regenerate. Excessive drinking over a prolonged period of time can cause serious problems with cognition and memory.

When alcohol reaches the brain, it interferes with communication between nerve cells, by interacting with the receptors on some cells. The alcohol suppresses excitatory nerve pathway activity and increases inhibitory nerve pathway activity. Among other actions, alcohol enhances the effects of the inhibitory neurotransmitter GABA. Enhancing an inhibitor has the effect of making a person sluggish. Also, alcohol weakens the excitatory neurotransmitter glutamine, which enhances the sluggishness even farther.

Chemical Effects of Alcohol on the Brain

To understand how alcohol interferes with brain function, it is necessary to know a little bit about normal brain function. The brain is the control center of the body - it controls all the systems in your body including your muscular system, your respiratory system and your digestive system. But how does the brain control these functions? It does so by using a series of chemical, electrical and physical signals from cell to cell. Within the cell, electrical signals are used for transmission, but between cells, chemical signals are used - these chemical signals are called neurotransmitters.

The gap between cells where neurotransmitters are active is called the synapse. The expelled neurotransmitter travels across the synapse and binds to a protein on the receiving cell membrane called a receptor, which is specific for that neurotransmitter. This action causes some change in the receiving cell, either chemical, electrical or physical, which can excite the receiving cell to perform an action or inhibit the receiving cell from performing an action.

When alcohol is introduced to the synapse, the normal neurotransmission may be affected.

Effects of Alcohol on Brain Parts

Alcohol affects different parts of the brain in different ways.
The Cerebral Cortex and Alcohol | The Limbic System and Alcohol | The Cerebellum and Alcohol | The Hypothalamus, Pituitary Gland and Alcohol | The Medulla and Alcohol

The cerebral cortex and alcohol

The cerebral cortex processes information from your senses, processes thoughts, initiates the majority of voluntary muscle movements and has some control over lower-order brain centers. In the cerebral cortex, alcohol can:

• Affect thought processes, leading to potentially poor judgement.
• Depresses inhibition, leading one to become more talkative and more confident.
• Blunts the senses and increases the threshold for pain.

As the BAC increases, these effects get more pronounced.

The limbic system and alcohol

The limbic system, which consists of the hippocampus and septal area of the brain, controls memory and emotions. The affect of alcohol on this sytem is that the person may experience some memory loss and may have exaggerated states of emotion.

The cerebellum and alcohol

The cerebellum coordinates muscle movement. The cerebral cortex initiates the muscular movement by sending a signal through the medulla and spinal cord to the muscles. As the nerve signals pass through the medulla, they are influenced by nerve impulses from the cerebellum, which controls the fine movements, including those necessary for balance. When alcohol affects the cerebellum, muscle movements become uncoordinated.

The hypothalamus, pituitary gland and alcohol

The hypothalamus controls and influences many automatic functions of the brain (through the medulla), and coordinates hormonal release (through the pituitary gland). Alcohol depresses nerve centers in the hypothalamus that control sexual arousal and performance. With increased alcohol consumption, sexual desire increases - but sexual performance declines.

By inhibiting the pituitary secretion of anti-diuretic hormone (ADH), alcohol also affects urine excretion. ADH acts on the kidney to reabsorb water, so when it is inhibitted, ADH levels drop, the kidneys don't reabsorb as much water and the kidneys produce more urine.

The medulla and alcohol

The medulla (brain stem) influences or controls body functions that occur automatically, such as your heart rate, temperature and breathing. When alcohol affects the medulla, a person will start to feel sleepy. Increased consumption can lead to unconscious. Needless to say, alcohol's effect on the medulla can be fatal if it is excessive.

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