biospych

• Cell body


  Contains the nucleus, other materials that help the cell to function like mitochondria, and dendrites that receive messages from other neurons in order to trigger an action potential (electrical impulse)
• Axon


  Carries the electrical impulse to the terminals, and the axon hillock connects the axon and cell body together
• Myelin sheath


  Fatty deposits around the axon that help to speed up the rate of message transmission
• Nodes of Ranvier


  Breaks along the cell in between the myelin sheath
• Axon terminal


  Where the nerve impulse becomes a chemical message that can pass onto the dendrites of another neuron
• Terminal buttons


  Where the nerve impulse becomes a chemical message that can pass onto the dendrites of another neuron
• Action Potential


  Nerve impulse travelling down the neuron in order to stimulate the release of neurotransmitters
• Resting membrane potential


  Usually around -70mV
• Excitatory postsynaptic potential


  Depolarises the neuron and reduces its charge
• Inhibitory postsynaptic potential


  Hyperpolarizes the neuron and increases its charge
• Threshold


  Usually happens at -55mV, and an impulse is sent along the neuron to the axon terminals at the end
• Synaptic Transmission


  Action potential starts off small but when it reaches the axon terminal it becomes a chemical message, which can be passed onto other neurons through the synaptic gap
• Presynaptic neuron


  The one giving the chemical message
• Postsynaptic neuron


  The one receiving the chemical message
• Synaptic Transmission


  1. Calcium channels open releasing calcium ions into the terminal buttons

  2. Vesicles that contain the neurotransmitter are released and move down to fuse with the membrane of the terminal buttons, to allow the neurotransmitter to move across the synaptic gap

  3. Receptors on the postsynaptic neuron bind to specific neurotransmitters

  4. Remaining molecules are either killed by enzymes in the synaptic gap, or are reabsorbed (uptake) and killed by enzymes in the neuron so they can be turned off to be used for the next action potential
• Common neurotransmitters


  • Acetylcholine
  • Noradrenaline
  • Dopamine
  • Serotonin
• Acetylcholine


  Stimulates muscle contractions, key function in motor control and movement, necessary for memory and other cognitive functions such as attention, involved in expressions of some emotions like anger and sexuality
• Noradrenaline


  Associated with emotion particularly mood control, involved in functions such as sleeping,dreaming and learning
• Dopamine


  Chemical precursor to noradrenaline, related to emotion and cognitive functions, associated with reinforcement of learning,as well as dependency(addictions), used in hormonal regulations (eg menstrual cycle)
• Serotonin


  Commonly associated with mood control, involved in many other functions (eg feeling pain and hunger)
• Drugs and their mode of action

  • Alcohol
  • Opioids (eg heroin,morphine)
  • Amphetamines (eg methamphetamines)
  • Nicotine
  • Cocaine
• Alcohol


  Depressant effect on nervous system, inhibits neural transmission by increasing action of GABA
• Opioids (eg heroin,morphine)


  Reduces GABA activity, leads to overactivity of dopaminergic neurotransmission
• Amphetamines (eg methamphetamines)


  Increases dopamine and noradrenaline in the synapse, can block reuptake and inhibit the breakdown of these neurotransmitters by enzymes
• Nicotine


  Increases the amount and transmission of dopamine, blocks the enzyme that breaks it down, mimics acetylcholine, binds to nicotinic receptors
• Cocaine


  Blocks the reuptake of dopamine, increases activity in the dopamine pathway
• Addiction


  Withdrawal starts when a drug is no longer in our system, which results in unpleasant and dangerous symptoms; it happens because our body has changed due to the drug and can no longer operate without it. Tolerance occurs where the user has to indulge in higher quantities of the drug to get a high as their body isn't affected by the drug anymore; the brain adapts to the high levels of dopamine and so reduces the amount being produced, so levels are now lower than before and they need to take even more of the drug to reach the same level of dopamine as before.
• Brain areas associated with aggression

  • Midbrain
  • Amygdala
  • Hypothalamus
  • Prefrontal Cortex
• Midbrain


  Coordinates and integrates behavioural responses to stressors (like pain), contains an area that links amygdala and hypothalamus with prefrontal cortex
• Amygdala


  Centre for emotion,emotional behaviour and motivation, connected with the prefrontal cortex ;this connection may lead to the expression of aggression
• Hypothalamus


  Role is to maintain homeostasis through the regulation of hormones, linked to aggressive behaviour in males via the production of testosterone
• Prefrontal Cortex


  Governs social interaction and regulates behaviour, can delay gratification of impulse, damage to this area can affect anger management and impulse control
• The case of Phineas Gage showed how damage to brain structure can affect a person's levels of aggression. He had a metal rod shot through his head and his behaviour changed from kind and polite to rude and aggressive.
• Lesion studies on animals suggest that there are parts of the brain that can control types of aggressive behaviour; for example, the dorsal hypothalamus produces defensive behaviour.
• The amygdala is thought to influence aggression in humans and other animals, as its the centre for emotions and emotional behaviour.
• The prefrontal cortex can also affect a person's aggression levels as damage to this area can lead to problems with anger management and impulse control.
• The hypothalamus also links to aggression through the production of testosterone which can cause aggressive behaviour.
• Evolution


  Happens by natural selection, a gene mutation is a variation in a gene which often happens unnaturally, mutation plays a part in natural selection as certain mutations call for an advantage in an organism's life
• Evolutionary explanation of aggression

  • Males have evolved to be more aggressive than females as it was an advantage for hunting and fighting, and they would be chosen by females more
  • Females being less aggressive was likely an advantage as their main role was child bearing so being aggressive would have put them in danger
  • Women have evolved to be more socially aggressive as this would not cause them harm but would make the other females seem less attractive so they'd easily find a mate to pass their genes onto their offspring
  • Many studies suggest that as we've evolved from shared ancestors that we can learn about aggression from non-human animals; the amygdala interprets threat and produces the fight or flight response and many animals possess an amygdala and studies show that it is linked to aggression
• Freud's psychodynamic explanation of aggression

  • Eros is the life instinct and Thanatos is the death instinct, Thanatos drives towards death and destruction, and Eros balances it out which is first directed at the self and then towards others, through aggression, in order to survive
  • The ID operates on the pleasure principle and immediate gratification, the ego operates on the reality principle so urges start to be controlled, and the superego operates on the morality principle
  • Aggressive urges can be reduced through catharsis
  • People may be unaware of their violent urges as they are in the unconscious mind; they influence our behaviour without us knowing it