substance abuse + addictions Flashcards
(25 cards)
what neurotransmitter does the mesocorticolimbic pathway relsease
dopamine
what is mesocorticolimbic pathway responsible for
feelings of pleasure, reward and motivation.
how does mesocorticolimbic pathway dopamine release work
when doing happy activities eg eating,sex dopamine is released within this system-particularly within an area called the nucleus accumbens-
results in feelings of calm, relaxation, pleasure and/or satisfaction, and this motivates us to engage in such behaviors again and again and again.
describe addiction
and examples
obsession, compulsion or excessive physical and/or psychological dependence eg substance abuse, gambling, sex, eating
drug and alcohol dopamine release
alcohol/drugs result in the release of dopamine within the nucleus accumbens of the mesocorticolimbic pathway.
results in a more immediate (within seconds to minutes) and intense release and response to dopamine than occurs with more ‘natural’ means of stimulating this system.
drug that induce pleasure and reward system of brain
amphetamines
hallucigens
MDMA
PCP
addictive substance affect on dopamine
increased dopamine release
preventing or reducing dopamine reuptake or breakdown (from the synaptic cleft)
enhancing the effects of dopamine binding on the postsynaptic receptors
properties of fat soluble chemicals eg drugs
pass through the plasma membrane easily, so they are absorbed more quickly
pass through the blood-brain barrier and more quickly affect the brain
stored in adipose tissue (fat), so they can be released over a longer time for a longer effect
effects of dopamine stimuated by substance abuse
downregulation of dopamine receptors
dimished drug effects with continued use
requirement for more drug to achieve same level of pleasureable feelings
dimished pleasure in other behaviours
whats downregulation and what does it do
Downregulation is a reduction in the number of dopamine receptors on postsynaptic neurons.
When downregulation occurs, the same level of ‘pleasure & reward’ will not be achieve with the same level of drug; thus resulting in a need to increase the amount of substance consumed to achieve the same ‘high’
whats withdrawal
The changes in the brain/te roro and body due to stopping a drug/substance
affecting a different area of the mesocorticolimbic pathway- the amygdala of the limbic system
whats amygdala responsible for
registers fear and anxiety, but processing by our prefrontal cortex allows us to contextualize new experiences to regulate our responses of fear and anxiety appropriately.
withdrawal causes….
dopamine levels to drop incredibly low below the baseline, leaving a person feeling very sad and miserable. This is then interpreted by the amygdala as anxiety and there is initially reduced regulation of this anxiety by the prefrontal cortex.
Thus there is a perception of danger with this enhanced ‘fear/anxiety’ response.
to deal with this, the amygdala releases other neurotransmitters, including noradrenaline.
The symptoms of withdrawal will largely relate to these two phenomenon:
the terribly low mood and anxiety perceived via the amygdala
the hyperactive response of the sympathetic nervous system
alcohol addiction consequences
ncreased risk of cancer (particularly of the GI tract and accessory organs)
subfertility
liver cirrhosis
impaired immunity
brain damage
teratogenicity
increased risk of accidental injury, including vehicle related or otherwise
psychosocial impacts
what does alcohol act as an agonist on
GABA neurotransmitter
alcohol metabolism
Ethanol is broken down into acetaldehyde by the enzyme alcohol dehydrogenase. Acetaldehyde is a toxic substance that is a known carcinogen, but is relatively short-lived.
Acetaldehyde is further broken down by the enzyme aldehyde dehydrogenase into the non-toxic acetate.
Acetate can then be broken down into carbon dioxide and water which can be eliminated from the body.
factors impacting alcohol metabolism
Amount of alcohol in the drink
Amount of food in the stomach - Food will lower the rate of absorption, which then reduces the amount of alcohol that the liver has to metabolize at any one time.
Biological sex – Males generally produce more alcohol dehydrogenase than females. So, given the same amount of
ohol, females are more likely to become intoxicated compared to males.
Personal genetics – Each of us will have different metabolic rates, and some people may have genes that produce alcohol dehydrogenase at different rates.
Rate alcohol is consumed
Age – livers s ability to metabolize alcohol at a particular rate decreases with increasing age.
alcohol affects on GABA
Loss of inhibition – this can lead to potentially harmful behaviours
Decreased sensation, including pain and visual acuity
Decreased concentration
Decreased memory
Improved self confidence –
Decreased judgment and social functioning
Unstable emotions
Stupor, unconsciousness, coma
Respiratory depression and possible death
affect of intoxication on GI
Alcohol irritates the stomach, possibly leading to:
nausea and vomiting
inflammation resulting in gastritis
affect of intoxication on renal system
Alcohol causes the inhibition of Anti-diuretic Hormone (ADH). thus when ADH is inhibited there is increased water loss in urine (urination occurs more frequently and in larger, more dilute (pale) volumes).
This increased water loss results in dehydration, which further affects the functionality of body cells, including neurons in the brain!
affect of intoxication on cardiovascular
Alcohol stimulates vasodilation, hypovolemia and hypotension. In an attempt to compensate for the hypotension, heart rate increases causing tachycardia; a
Additionally, the vasodilation causes increased heat loss from the body (while also causing a perception of increased warmth at the body surface). This can potentially lead to hypothermia if exposed to cold temperature for too long.
intoxication affect on respiratory
Alcohol has a depressive effect on the mucosa of the respiratory tract, reducing cilia movement and thus leading to a reduced ability to move mucous and debris out of the respiratory tract.
and depressed ventilation and respiration.
chronic implicstions of alcohol
skin, muscles, cardio, resp, renal, GI, endocrine, nutrition, NS
Skin/Integumentary system
Facial puffiness & parotid gland hyperplasia
Alterations in vascularity, including vasodilation, telangiectasia, bloodshot eyes, corkscrew vessels in sclera & palmar erythema
Increased sweating
Musculoskeletal systems
Osteoporosis
Osteonecrosis
Gout
Muscle wasting
Immune system
Enhanced inflammation, particularly within alcohol affected tissues
Overall suppressed immunity- increasing risk of infections associated with many body systems (e.g. respiratory, reproductive, GI)
Cardiovascular system
Cardiac dysrythmias
Cardiomyopathy
Hypertension
Respiratory system
Oedema of vocal cords (‘hoarseness’ of voice)
Obstructive sleep apnoea
Acute respiratory distress syndrome
Enhances damage associated with smoking (e.g. infections, cancer)
GI
fatty liver (steatosis)
steatohepatitis
liver cirrhosis
fibrosis
portal hypertension
hepatic carcinoma
Nutrition & metabolism
Malnutrition & nutrient deficiencies (enhanced by malabsorption)
Lactic acidosis and ketoacidosis
Glucose intolerance and insulin resistance
Hypertriglyceridemia & increased lipolysis
Increased risk of metabolic syndrome & possibly type 2 diabetes
Endocrine system
Inhibition of ADH
Elevated ACTH (‘pseudo’ Cushing’s syndrome)
Increased SNS activity
Hypothyroidism
Nervous system
Addiction (and subsequent withdrawal)
Alterations to stress response pathways
Neuronal depression/decreased neurotransmission (can lead to loss of consciousness & coma)
Tissue damage resulting in:
Peripheral neuropathy
Cerebellar degeneration
Wernicke-Korsakoff syndrome (more details below)
Alcoholic dementia
