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 .