HOW DOES ALCOHOL AFFECT US?
With the first drink and with blood alcohol levels remaining fairly low, stimulation is the first effect. At these low levels, alcohol sensitises one the brain’ s major excitatory message pathways, the N- methyl-D-aspartate( NMDA) system( not to be confused with ecstasy). This makes certain NMDA receptors more readily activated by the brain’ s main neurotransmitter, glutamate. Some of the most sensitised brain regions are the cortex( thinking), hippocampus( remembering) and nucleus accumbens( NA)( pleasure-seeking), and our inhabitation begin to decrease.
After two or three drinks, alpha rhythms increase, extra blood flows to the prefrontal cortex and to the right temporal cortex. Mood is heightened and may feel even more euphoric.
After three of four drinks, a turning point is reached, reflecting the complex‘ biphasic’ relationship with alcohol. With our blood now awash with alcohol, the very NMDA receptors that helped to perk us up after just one drink are refusing to respond, also the brain’ s gamma-aminobutyric acid( GABA) system becomes activated. GABA is an inhibitory neurotransmitter, which dulls activity( it’ s the system activated by benzodiazepines, such as Valium). From this point, alcohol begins to act more like a depressant / sedative. The hippocampus and thalamus are both slowed down.
Any more drinks, and our speech and other motor functions begin to fail us. The cerebellum seems to be most affected by this stage. A common experience is that the room is spinning. This is called positional alcohol nystagmus, a booze-induced version of an eye reflex normally triggered by the inner ear’ s balance organs when they detect head rotation( Motluk 1999).
A blood alcohol concentration of 500mg per 100ml is considered lethal. At this concentration, the brain centres that keep us breathing shut down.
PHYSIOLOGICAL EFFECTS OF ALCOHOL
Ethanol is a diuretic, so you end up expelling more water thank you drink. It acts on the pituitary gland, blocking production of the hormone vasopressin, which directs the kidneys to re-absorb water that would otherwise end up in the bladder so, the body borrows water from other places, including the brain, which shrinks temporarily though the brain itself cannot experience pain, it’ s thought that dehydration shrivels the dura( a membrane covering the brain). As this happens, it tugs at pain-sensitive filaments connecting it to the skull. Water loss may also account for pains elsewhere in the body.
Frequent trips to the toilet also result in loss of essential sodium and potassium ions, which are central to how nerves and muscles work. Subtle chemical imbalances caused by ion depletion could account for a cluster of symptoms including headaches, nausea and fatigue.
Alcohol also depletes over reserves of sugar, leading to hypoglycaemia. The body’ s store of energy-rich glycogen in the liver is broken down into glucose; this quickly becomes another constituent of urine. This can account for feelings of weakness and unsteadiness the morning after.
Heavy drinkers suffer malnutrition. Since alcohol is high in calories, appetite is suppressed. It also causes vitamin deficiency, by interfering with absorption of vitamin B from the intestines long term, this causes brain damage. Other physical effects include liver damage, heart disease, increased risk of a stroke and susceptibility to infections due to a suppressed immune system. Women who drink while pregnant can produce babies with foetal alcohol syndrome.