Investigation of inheritacne:

  • Twin studies provide genetecists with a natural experiment. If genetics affect a trait then identical twins (MZ) should show greater similarity for that trait than fraternal twins (DZ).
  • Reseacrh looks for degrees of concordance. Twins are concordant if both or neither have a trait. They are disconcordant if one has it and the other doesn't.
  • MZ twins have the samae genes and DZ twins share 50% of genes. If concordance rates are significantly higher for MZ twins this is evidence that genetics play an important role in the expression of that trait. 
  • Twin studies have been criticised as twins are raised in the same environment adn trated the same way adn this could be whta causes a trait to be exhibited rather than genes.
  • Genotype - the genetic makeup of an individual. 
  • Phenotype - the characteristics expressed by an individual.

Methods of studying the brain:

  • Neuro surgery - used as a last resort. 
  • Electroencephalogram (EEG) - recording electrical activity in the brain. Have been used to study sleep. One stage of sleep is REM (Rapid Eye Movement). Our waves begin resembling those of when we are awake and it seems that it is when we dream.
  • CAT scans (Computerised Axiel Tomography) - a moving X-ray that can take 3D pictures of damaged areas of teh brain.
  • PET scans (Positron Emission Tomography) - uses a radioactive marker to study teh way teh brain works. The region being used most needs most energy so the scan will show which areas of the brain are using the most. 
  • fMRI (Functional Magnetic Resonance Imaging) - measures brain activity by detecting changes associated with blood flow. Cerebral blood flow and neuronal activity are coupled. The area being used most has teh most blood flow.


  • Neurons are nerve cells that exist through out the body and make up the nervous system.
  • There are sensory (informtion comes from senses), relay (connects other neurons) and motor (carries message from CNS to muscles) neurons.
  • Structure of a neuron - dendrite (branched structures receive messages from other neurons and allow those messages to travel through the cell body), cell body (contains nucleus, SER, RER and otehr cellular components), axon (carries an electrical impulse from the cell body to the axon terminals on the other sidewhich then pass the impulse to another neuron), synapse (chemical junction between axon terminals of one and dendrites of another, a gap where chemical interactions acn occur), myelin sheath (insulating fat).
  • Synaptic transmission - information passed as an electrical impulse. Nuerotransmitters are chemical messengers which are contained in the synaptic vessels in the axon terminals. Can have an excitatory on inhibitory effect once they cross the synaptic gap. Excitatory neurotransmitters make the post-synaptic cell more likely to fire and inhibitory neurotransmitters make it less likely to fire. When the neurotransmitter binds to the post-synaptic receptors they can result in an excitatory post-synpatic potential (EPSP) which makes the cell more likely to fire or an inhibitory post-synaptic potential (IPSP) which makes the


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