Here are the physiological explanations for why your body parts feel as they do the day after.
Eyes: You can´t fool your eyes.
Only a few people don´t have the classical red eyes the day after.
The reason is,that alcohol is widening the blood vessels in the eyes.
The eyes can also become dehydrated,and felt dry beacuse of the booze.
Mouth: Dry mouth and throat even drier.
The reason is dehydration.And the feeling becomes much worse if you mix together alcohol and tobacco.
Heart: When the nervous system are artificially active (in alcohol emigration from the body),the heart pumps on.
Beacuse of that,you can get a higher pulse and palpitations during the night and the day after.
The liver: The body refuses to store alcohol.Instead,it allows to break down the alcohol.
But oxidation in the liver becomes the alcohol to acetaldehyde,and the next step is acetic acid.
Pancreas: When you´ve been drinking alcohol,begins an unnatural high production of gastric juice running.
The next day,this can result in abdominal pain in the upper and vomiting.
Gut: The gut works faster with alcohol in the circulation.
Therefore will also absorption be more sloppy and it may result in diarrhea.
Head: The headaches have a specific explanation.
The blood vessels in the head are small and sensitive.And alcohol widen blood vessels.
That together with dehydration,makes the headache.
Nervous system: Alcohol is soporific,but for that we should not become unconscious,our nervous systems are alert when we drink.
When the alcohol leaves the body,which it may do over the hangover,the nerves are hyperactive,and can cause sweating,trembling and palpitations.Failure to sleep fueling these symptoms.
Muscles: The muscles are tired and exhausted the day after,beacuse of low blood sugar and dehydration.
Worse metabolism contribute to lactic acid,which can cause seizures.
Kidneys: Hormone that controlls the kidney´s dehydration becomes sloppy of alcohol.
That leads to that the kidney doesn´t help to retain water as normal.This leads to dehydration.