Unit 5: Section 4- The Brain and Behaviour

A summary of the Brain and Behaviour subtopic of Grey Matter from Edexcel A2 biology

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Brain Structure and Function 1

  • Cerebrum- divided into 2 cerebral hemispheres. Has a thin outer layer called the cerebral cortex which is highly folded (so it can fit into the skull). Involved in vision, learning, thinking and emotions
  • Hypothalamus- Found beneath middle part of the brain. Automatically maintains body temperature at the normal level. Produces the hormones which control the pituitary gland
  • Medulla- At the base of the spinal cord. Automatically controls breathing and heart rate
  • Cerebellum- Underneath the cerebrum, also has a folded cortex. Coordinates movement and balance
  • Scanners are used to visualise the brain in an unintrusive way
  • Computerised Tomography (CT)- Produce cross-sectional images using many x-rays. Dense tissues absorb more radiation, so show up as being lighter. Show the major structures in the brain, but doesn't show function. Can show damaged/diseased areas eg. strokes. Blood has a different density, so will show up as a lighter colour. Scan will show extent and position
  • Magnetic Resonance Imaging (MRI)- Uses a strong magnetic field and radio waves. Can see a lot of detail of the structure (more than CT), but doesn't show function. Good for showing tumours, as they respond differently to the magnetic field and show up white. Shows the exact size of the tumour and its location. Can work out what functions are affected by the tumour
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Brain Structure and Function 2

  • Functional Magnetic Resonance Imaging (fMRI)- Show changes in brain activity. More oxygenated blood flows to active areas, and molecules of oxy. blood respond differently to magnetic fields than deoxy. blood.
  • An fMRI scan gives a detailed picture of the structure and can be used to research the function of the brain as well. If a task is carried out whilst in the scanner, the part of the brain that's involved will become more active.
  • Useful in diagnosing medical problems as they show damaged/diseased areas. Eg. an fMRI scan can be taken before and after a seizure to pinpoint which part of the brain's not working properly and find the cause of the seizure. The patient can receive the most effective treatment
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Brain Development and Habituation 1

  • Brain development- How the brain grows and how the neurones connect. Nature and nurture both have an effect, but disagreements over which influences development the most. In order to do an accurate experiment, need to cancel out one factor to investigate the other.
  • 1. Animal experiments- Study the effect on different environments on animals of the same species (differences due to nurture) eg. rats in a stimulating environment get better scores on problem-solving tasks than those in isolation. Also study the effect of genes (nature) on animals in similar environments, through genetic engineering mice to lack a certain gene
  • 2. Newborn studies- Study brains of newborn babies to see which functions they are born with and how developed the parts are. What they're born with is due to nature. Studies show crying, feeding and face recognition are nature (born with), and speaking is nurture (not born)
  • 3.Twin studies- Twins are genetically identical, so if they are separated into different environments any differences are due to nurture eg. identical twins have similar IQ scores, so nature plays a big role in intelligence. Identical twins in the same environment are compared to non-identical twins in the same environment. Stuttering more common in identical twins-nature, no difference in reading ability between identical and non-identical- nurture
  • 4. Brain damage studies- Compare development of function in children with and without brain damage. Children aged 1-3 with damaged language area show delayed development, but catch up with 'normal' children by age 5, showing nurture plays a big role in language development
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Brain Development and Habituation 2

  • 5.Cross-cultural studies- Children brought up in difference cultures have environmental differences. Study the effects of a different upbringing on brain development by studying large groups of children from different cultures. Look for major differences in characteristics- likely to be due to nurture. Eg. Kenyan children with high protein diets have higher IQs than children with poor diets with limited proteins, suggesting nurture plays a big role in intelligence
  • Habituation is the reduced response to an unimportant stimulus after repeated exposure over time. Means animals don't waste time and energy responding to unimportant stimuli, but still remain alert to important stimuli which might threaten their survival
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Development of Visual Cortex

  • The visual cortex is an area of the cerebral cortex which receives and processes visual information. Neurones receive info from the left or right eye. Neurones are grouped in ocular dominance columns, which are the same size and arranged in an alternating pattern (if receive info from right eye- right ocular dominance columns).
  • Hubel and Wiesel investigated the structure of the visual cortex, and found that left ocular dominance columns were stimulated when an animal uses its left eye and vice versa
  • The experimented on newly-born kittens. They stitched shut one eye of each kitten so they could only see out of the other eye. The kittens were left like this for several months, before being unstitched and finding that the kitten was blind in the stitched eye. The ocular dominance column in the stitched eye were smaller than normal, and the odc in the open eye were bigger than normal.
  • The odc for the open eye had to expand to take over the columns which weren't stimulated- switched dominance. 
  • When repeated on cats, the stitched eyes hadn't gone blind, and the cats fully recovered their vision. Experiments showed that the visual cortex only develops normally if both eyes are stimulated in the early stages of life. Shows there is a 'critical window'
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