3.1.1-3.1.2 the CNS and aggression Flashcards
What makes up the nervous system?
CNS and peripheral nervous system
What makes up the CNS?
brain and spinal cord
What is the role of the CNS?
-control body’s functions
-interpret sensory info and pass on to brain
-responsible for all voluntary and involuntary decisions
What are neurotransmitters?
Chemical messengers that operate between neurones and the brain in order to process thoughts/memories in the brain (across synapse)
What are neurones?
cells of the nervous system which carry electrochemical messages called nerve impulses
What are the 3 types of neuron?
motor, inter, sensory
function of a motor neuron
transmits messages from CNS to muscles
function of inter neuron
connect neurons to others, located in the brain
function of sensory neuron
carry info from senses to CNS
What is the link between neurons and nerves?
Nerves are bundles of neurons
Special elements of a neuron
-dendrites (finger like structures surrounding nucleus)
-axon (extends from nucleus and reaches to axon terminal)
What is a synapse?
A gap between the dendrite and axon terminal
What passes over a synapse?
Neurotransmitters/chemical messages
Benefit of synapses
allow each axon to communicate with a number of dendrites, forming a complex communication system
How does synaptic transmission work?
-process electrical signals and turn into chemical signals and back to electrical
-action potential causes neurotransmitter to be released into synapse
-neurotransmitter binds to receptor site of post synaptic neuron
What happens if neurotransmitters aren’t accepted?
-must be removed for next stimulation
-neurotransmitters broken down by enzymes
-reuptake occurs
What does action potential do?
the method by which the nerve impulse passes down the axon of the neuron to stimulate the release of neurotransmitters
How does action potential cause change?
-tiny electrical impulse triggered by change in electrical potential of neuron
How does the charge of a neuron change?
-inside of neuron has slight negative charge, outside is more positive at rest
-when stimulated, positive particles enter and the neuron is depolarised
-some positive particles are pushed back out and neuron returns to depolarised state
Define depolarization
when the resting potential of a neuron changes from negative to more positive
Define hyperpolarization
opposite to depolarization, change in a cells membrane potential that makes it more negative
What are the 3 hormones that are linked to drug taking?
serotonin, dopamine, glutamate
Effect of serotonin
-happiness and good mood
-low levels cause depression
-linked to an array of behaviours and mental disorders
Effect of dopamine
-pleasure feeling
-addiction
-linked to reward pathway which influences motivation, pleasure and attention
Effect of glutamine
-cognitive functioning, memory and learning
-too much is dangerous and leads to cellular death so is associated with some diseases and brain injuries eg. Alzheimer’s
What is an agonist drug
A drug with chemical properties similar to a neurotransmitter and mimics its effect by binding to receptors to excite the neuron so more of the natural NT us released
Example of agonist
cocaine and dopamine
What is an antagonist?
reduces/stops the effect of an NT as it binds to receptor site to stop/slow passage of message
Example of antagonist
Curare (poison) is antagonist for NT acetylcholine
What is another way that drugs work? (3)
-can block reuptake of NT from synapse so NT stays in gap which increases its action
-stops NT being synthesised
-stops NT being released
How does alcohol work?
blocks serotonin receptors which has calming effects, so we become merry
What parts of the brain are affected when alcohol wears off?
low mood caused: prefontal cortex (decision making), amygdala (controls emotions), can make us aggressive
How does nicotine work?
-affects dopamine receptors, causing a release of dopamine pleasure
-excess dopamine means the brain shuts off dopamine receptors in an attempt to balance
Why do people get addicted to nicotine?
low dopamine activity leads to nicotine craving to boost it
How does cocaine work?
-blocks dopamine reuptake
-therefore dopamine remains in synapse so can reattach to receptor and cause pleasure response again
How does cannabis work?
-ingredient THC binds to cannabinoid receptors
-THC inhibits release of neurotransmitter GABA, leading to increased dopamine levels
What is GABA?
NT that blocks receptors and inhibits release of dopamine (cannabis inhibits GABA which means dopamine is released)
How does heroin work?
-acts at opioid receptor sites in brain to release more dopamine
-morphine binds to receptors to reduce inhibitory effect of GABA on dopamine neurons
-higher dopamine activity and increased release into synapse
-continual stimulation of dopaminergic reward pathway results in feelings of euphoria
Short term effects of heroin
-calmed chill feeling as it floods endorphin receptors
-activates reward system and good feelings as dopamine is released
Long term effects of heroin
the brain adapts to high levels of dopamine and slows down its natural production, explaining why higher doses are needed
Symptoms of taking heroin
-small dose causes feelings of warmth
-large dose causes sleepiness and relaxation
-pleasure and pain reduction
-dry mouth, heavy limbs followed by slowing of mental functions, breathing and heart rate
How do amphetamines work?
-block reuptake of NTs, meaning euphoria lasts longer
-noradrenaline, serotonin and dopamine quickly released into brain
-dopamine neurons may be excited via glutamate neurons as the two are interlinked
describe amphetamines and dopamine
-increased release of dopamine from axon terminal
-blocks dopamine reuptake
-dopamine stored in vesicles in synapse or destroyed by enzymes
-causes euphoria
Short term effects of amphetamines
-the 3 neurotransmitters cause reward, pleasure, adrenaline all at once
-euphoric effects are intense eg, feeling powerful
-reduced fatigue
-high heart rate and blood pressure
Long term effects of amphetamines
-depression like symptoms when euphoria wears off which may cause and individual to become dependent
-dopamine receptors become damaged/desensitised which causes addiction as more dopamine is required to stimulate neuron
Physical long term effects of amphetamines
-extreme weight loss
-dental problems
-regular infections
-risk of stroke
Evaluate CNS as a good explanation Strengths
-high reliability as lab experiments can be replicated easily as they are artificial, eg. PET scans involve gamma rays being recorded on scanner
-high validity as objective methods were used-Diana Marinez et al used PET scans to demonstrate how heroin changed dopamine receptors in rats
Evaluate CNS as a good explanation Weaknesses
-limitation: reductionist because the effects of recreational drugs are reduced down to the release of a hormone
-comparison: social approach better explains situational and personal factors that cause on individual to first take/continue to take a drug
