• any man-made chemical taken into the body, (broadly) any chemical substance taken into the body;
  • but this would include nutrients;
  • chemicals which interfere with metabolism/physiology, ours or that of the pathogen;
  • (narrowly) chemicals which interfere with nervous system/behaviour/brain/.perception/mental function;
  • these are described as psychoactive;
  • any chemical used in medicine;
  • may be restricted to chemicals that cause harm/illicit chemicals/abused chemicals;


Distinguish between physical and psychological dependence on drugs

  • dependence is inability to stop use/addiction;
  • withdrawal symptoms if go without drug;
  • g. morning shakes with alcohol/cold turkey with heroin



  • drug necessary for continued functioning of the body (metabolism in the body);
  • prevents withdrawal/abstinence syndrome;
  • withdrawal results in physical (and psychological)
  • withdrawal symptoms e.g. opiates
  • caused by drug replacing/imitating natural chemicals;



  • occurs when drug is needed as a compulsive desire to continue to take a drug;
  • Reduces stress/anxiety/inhibitions;
  • only emotional dependence/no physical dependency;
  • withdrawal symptoms results in psychological symptoms
  • changes in lifestyle and behaviour;


Withdrawal symptoms

  • tremors;
  • cravings/irritability/restlessness/anxiety;
  • sweating;
  • depression;
  • sleep disturbance/insomnia;
  • altered time perception;
  • gastro interstitial problems/nausea/vomiting;


Drug tolerance and why it occurs with alcohol and heroin

  • progressive decrease in body‘s response/effects become less intense with time/usage;
  • user therefore uses larger and larger doses;



  • binds to pain receptor molecules at synapses;
  • mimics encephalins/natural neurotransmitters;
  • body adapts to presence of heroin and tries to restore original state;
  • more receptors made at post-synaptic membranes;
  • so more heroin needed to saturate them/have same effect;



  • alcohol tolerance due to liver adapting;
  • by producing more enzymes that break down alcohol;
  • oxidized by MEOS/microsomal ethanol oxidizing systems nerve cells in brain become less responsive;


How you might tell whether a drug is socially acceptable or not

  • survey of people‘s attitudes to the drug
  • legislation i.e. laws governing sale and use of drugs;
  • g. banned by law;
  • the number of people who use the drug/prevalence of drug taking;
  • the number of deaths from illegal drugs;
  • general acceptance or rejection of drug – takers;
  • g. it is socially acceptable to drink alcohol
  • but not acceptable to inject heroin;


Factors that contribute to drug dependence

  • to experience its psychic effect;
  • to avoid the discomfort caused by its absence/withdrawal;
  • the drug (or one of it metabolites) has become necessary for the continued function of the body; – trying the drug out of curiosity;
  • because of peer pressure/lack of self-identity;
  • boredom


Why the use of heroin can result in damage to health

  • use of unsterile needles to inject drug lead to blood poisoning/abscesses/skin infections at the sites of injection;
  • shared needles may lead to transfer of infective hepatitis B/HIV/AIDS;
  • long term use can lead to liver disease/failure;
  • can lead to blood poisoning;
  • transmission of disease e.g. HIV/AIDS/ hepatitis B;
  • deficiency diseases/malnutrition due to reduced secretion of digestive juices/money spent on drugs rather than food/loss of appetite
  • tend not to eat well therefore malnutrition;
  • tend not to maintain standards of hygiene;
  • may overdose as tolerance builds up;
  • respiratory/ cardiac centres of the brain can be fatally depressed;
  • constipation common;
  • street heroin may be impure and mixed with harmful substances, this can cause blood poisoning/damage to blood vessels;
  • damage to/collapse of blood vessels or veins due to injecting;
  • tolerance leads to high doses/physical dependence/addiction is likely;
  • associated life style has risks e.g. violence/crime/alcoholisms
  • withdrawal/abstinence symptoms may lead to vomiting/choking/diarrhoea/dehydration/fever/high blood [pressure;
  • users can become part of a drug subculture/loose contact with family and friends;
  • damage to foetus;
  • damage to mental health;


Metabolism of alcohol

  • alcohol dehydrogenase;
  • alcohol converted to acetaldehyde/ethanol;
  • NAD – hydrogen carrier;
  • ethane dehydrogenase;
  • ethanol to acetic acid/acetate/ethanoic acid;
  • acetate converted to acetyl coA;
  • enters Krebs Cycle;
  • respired to carbon dioxide and water;
  • liver metabolises alcohol as an energy source rather than fat;
  • catalase may also oxidize alcohol;
  • MEOS used when blood alcohol concentration (BAC) is higher;


Long term consequences of alcohol consumption on the liver, brain and peripheral nervous system


  • inflammation;
  • scarring/fibrous tissue;
  • cirrhosis/hepatitis/jaundice/cancer;
  • fatty liver;
  • compression of blood vessels in liver (blood forced from portal veins into veins from oesophagus and rectum);



  • loss of short term memory
  • impaired judgement;
  • confusion/disorientation/anxiety/hallucinations;
  • impaired motor control;
  • dementia;
  • sleep disturbance/reduced REM sleep;
  • shrinkage of brain cells;
  • by alcohol induced dehydration;
  • inhibits secretion of AHD so kidneys remove more water than normal ;
  • hypoxia – low blood oxygen causes death of brain cells;
  • low blood glucose levels cause death of brain cells
  • blockage of brain capillaries;
  • loss of intellectual functions e.g. calculations, learning;
  • Korsakoff‘s psychosis, leading to loss of short term memory and learning ;
  • Wernicke‘s encephalopathy leading to comma, disturbance of speech/walking, confusion;
  • Neglecting of diet leading to Vitamin B1 deficiency – Leads to long term brain damage


Peripheral nervous system

  • (poly) neuropathy (neurological disorder that occurs when many PNS throughout the body malfunction simultaneously);
  • damage to sensory nerves;
  • feeling cold, pains/cramps/numbness(partial/total lack of sensation)/tingling;
  • starts in hands and spread to centre of body;
  • damage to motor neurones;
  • muscle wasting/weakness;
  • damage to autonomic nerves;
  • related to faintness/incontinence(involuntary urination/defecation)/impotence(powerlessness/feeble/weak)/blurred vision/poor control of gut;
  • caused by Vitamin B1/thiamine deficiency;
  • poor diet/all or most energy needs from alcohol so no balanced diet; – damage to axons;


Short term effects of alcohol consumption on the brain

  • depressant;
  • effects depends on blood alcohol concentration;
  • depresses brain function;
  • by inhibiting reticular activating system (RAS);
  • therefore activity of cerebral cortex
  • intellectual faculties diminished;
  • loss of coordination/judgement/control over fine movement;
  • g. slurred speech/staggering walking;
  • depression of respiratory centres/death;
  • relaxed feeling/increased confidence/reduced tension;
  • loss of inhibitions;
  • slower reaction time;
  • loss of balance;
  • at higher levels, comma;


Social problems associated with heavy alcohol drinking

  • personal relationship affected/considerable stress caused to the family;
  • social isolation from friends/neighbours/embarrassment;
  • violence in marriage + marital breakdown;
  • correlated with wife battering (half husbands involved frequently drink);
  • aggressiveness + destruction of property;
  • crime as means to finance drinking;
  • drink-driving + traffic accidents;
  • neglect of food intake;
  • frequent changes of jobs/loss of employment;
  • uncontrollable anger;
  • sexual assault;
  • grandiose behaviour;
  • young single women getting pregnant;
  • conflict between parents affect children;
  • sexual abuse of children;
  • child neglect/children more likely to need child guidance/help from social services;
  • children left unattended more likely to have accidents;
  • poverty resulting from money spent on alcohol;
  • poverty resulting from loss of job;
  • poor health leading to loss of income/premature death;
  • g. repossession of home, default on hire purchase/mortgage repayment;


Effects of heroin on the nervous system

  • heroin is an opiate/depressant;
  • does not stimulate vomit and nausea centres;
  • psychoactive;
  • binds (with high affinity and specificity) to pain receptors on the synapses;
  • mimics encephalins;
  • inhibits activities of the neurones concerned with pain;
  • inhibits activities of cardiac and respiratory systems;
  • gives a sense of warmth/rush;

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