Biological psychology

• Central Nervous System (CNS)


  Consists of the brain and spinal cord. It is the central processing and control point for all human behaviour.
• Neurons


  Cells in the central nervous system that communicate with around 1000 other cells at a time in huge networks
• Neuron


  • Cell body contains the cell nucleus and other materials that allow the cell to function
  • Dendrites receive messages from other neurons to trigger an action potential
  • Axon passes the electrical impulse towards the axon terminals
  • Axon hillock is where the nerve impulse is triggered from
  • Myelin sheath provides an insulating layer to the axon and helps speed up message transmission
  • Nodes of Ranvier are breaks between the cells along the myelin sheath
  • Axon terminals pass nerve impulses to other neurons, muscles or glands
• Action potential


  A tiny electrical impulse that is triggered by a change in the electrical 'potential' of the neuron itself
• Action potential process


  1. Neuron is at rest with negative charge inside

  2. Positively charged particles enter neuron, depolarising it

  3. Positively charged particles pushed outside, neuron moves back to polarised state

  4. Neuron returns to initial polarised resting state
• Synaptic transmission process


  1. Electrical impulse reaches axon terminal

  2. Calcium channels open, releasing neurotransmitters into synaptic cleft

  3. Neurotransmitters bind to receptors on postsynaptic neuron

  4. Unused neurotransmitters are destroyed or reabsorbed
• Acetylcholine


  Stimulates muscle contractions, key for motor control and movement. Necessary for memory and cognitive functions like attention and alertness.
• Dopamine


  A precursor to noradrenaline, so has similar functions. Associated with reinforcement in learning as well as addiction and dependency.
• The right balance of neurotransmitters is important for good moods and clear thinking
• How recreational drugs affect neurotransmission


  1. Drugs act by changing the way neurotransmitters operate in the brain

  2. Most psychoactive drugs of addiction work on the dopamine system, boosting activation of dopaminergic synapses

  3. Brain naturally reacts by reducing its own dopamine production
• Reward system


  When something leads to the activation of this pathway, we feel good and are likely to do it again
• Reward or enjoyment from eating high-calorie foods ensures we store enough fat on our bodies, in preparation for periods of famine
• Drugs hijack the reward system and produce pleasurable feelings without any adaptive function
• Drugs


  Act by changing the way neurotransmitters operate in the brain
• Psychoactive drugs of addiction

  Work on the dopamine system
• How drugs affect the dopamine system

  1. Increase the amount of dopamine in the reward pathways of the brain

  2. Cause an intensely pleasurable experience or feeling of euphoria

  3. Brain reacts by reducing its own natural production of dopamine

  4. Person experiences an unpleasurable experience (dysphoria)

  5. Motivates the person to take more of the drug
• Repeated use of the drug causes further down-regulation of dopamine production, leading to physical dependence on the drug to avoid withdrawal
• Drugs and their modes of action


  • Alcohol: Depressant effect, increases GABA activity
  • Opioids: Reduces GABA activity, increases dopaminergic neurotransmission
  • Amphetamines: Increases dopamine and noradrenaline
  • Cocaine: Increases activity in the dopamine pathway
  • Nicotine: Targets aspects of the dopamine pathway, mimics acetylcholine
• Withdrawal


  Occurs when a drug is no longer active in our system, can result in unpleasant and dangerous symptoms
• Tolerance


  User has to take ever-greater doses of the drug to get the same effect
• The brain adapts to the high level of dopamine caused by the drug and down regulates its own natural production of it
• 10,000 years ago, humans had some ideas about brain functioning, as evidenced by the use of trepanning to treat migraines and epilepsy
• Hippocrates put forward the idea that each side, or hemisphere, of the brain served a distinct function
• Phrenology, the 'science' of mapping character traits to bumps on the head, reflected the idea that behaviour was linked to the brain
• Phineas Gage


  A railway worker who suffered brain damage, leading to a fundamental change in his personality
• Broca's area


  Part of the brain responsible for the motor control involved in speech production
• Wernicke's area


  Part of the brain involved with the understanding of speech
• Lesions/stimulation to different areas of the brain in animals has been shown to activate specific types of aggressive behaviour
• Types of aggressive behaviour in animals

  • Offensive behaviour
  • Defensive behaviour
  • Predatory aggression
• Periaqueductal grey matter (PAG)


  Links the amygdala and hypothalamus with the prefrontal cortex, plays a role in coordinating and integrating behavioural responses to perceived internal and external stressors
• Amygdala


  Centre for emotions, emotional behaviour and motivation, integrates internal and external stimuli
• Hypothalamus


  Maintains homeostasis through the regulation of hormones, including those that regulate sexual function, linked to aggressive behaviour in males via the production of testosterone
• Prefrontal cortex


  Influential in governing social interaction and regulation of behaviour, associated with the ability to delay gratification of an impulse
• Damage to the prefrontal cortex often leads to problems with anger management, irritability and impulse control
• There are issues with the generalisability of findings from animal research to humans, as human brains are much more complex
• There are ethical considerations in the use of animals in research into human psychology, as the animals can be harmed
• Brain imaging studies have found lower activity in the prefrontal cortex and differences in the functioning of the limbic system in impulsive murderers and reoffenders
• The idea of a biological basis for aggression is consistent with the genetic explanation, as our genetic blueprint builds our brain structures
• Cerebral cortex


  The outer layer of cerebral tissue in the brain, divided into two hemispheres (left and right)
• Cerebral cortex


  • Contains between 14-16 billion neurons
  • Left hemisphere processes verbal information, right hemisphere processes nonverbal information
  • Folded to allow a larger surface area, enabling more brain activity