The Brain

• the cerebrum is the largest part of the brain, accounting for 80% of the total mass of the brain
• the cerebrum is responsible for voluntary actions (conscious activites), thought, vision , speech, memory, problem solving
• the cerebrum is divided into two cerebral hemispheres which are joined together by a band of nerve fibres known as the corpus callosum; the left and right
• the cerebrum has a thin outer layer known as the cerebral cortex or 'grey matter'
• the cerebral cortex consists of the cell bodies of neurones (with more neurones in the brain, more neurone connections can be made - increases the ability for the brain to carry out more complex behaviours)
• beneath the cerebral cortex, is the 'white matter' which consists of the myelinated axons of neurones
• the hypothalamus is responsible for regulating body temperature, regulating digestive activity, osmoregulation, and controlling endocrine functions - it monitors the blood as it flows through the brain and, in response, releases hormones or stimulates the pituitary gland to release hormones (important role in homeostasis)
• hypothalamus - regulation body temperature:

  monitors blood temperature and initiates a homeostatic response if this temperature gets too low or too high
• hypothalamus - osmoregulation:

  cells in the hypothalamus monitor the water balance of the blood and releases the hormone ADH if the blood becomes too concentrated (ADH increases absorption of water in the kidneys)
• hypothalamus - regulating digestive activity:

  the hypothalamus regulates the hormones that control appetite as well as the secretion of digestive enzymes
• hypothalamus - controlling endocrine functions:

  the hypothalamus causes the pituitary gland to release hormones that control a variety processes (e.g. metabolism, sexual functions, sleep, and mood)
• the cerebellum coordinates movement (i.e. balance)
• the medulla oblongata contains co-ordination centres that control different functions (e.g. the cardiac centre controls heart rate, the respiratory centre controls breathing rate)
• the brain can't be studied in isolation as different regions work together to bring about brain function
• CT scans produce cross-section images of the brain using x-ray radiation;

  a beam of rays are aimed at a patient from all angles around the body, detectors are used to pick up the x-rays as they exit the patients body, denser tissue absorbs more of the x-ray radiation so shows up lighter region on a scan.
• a CT scan shows physical structures of the brain and allows visualisation of any tissue damage and damaged blood vessels
• CT scans are not recommended for pregnant patients or children due to the risks of exposure to the x-ray radiation (a CT scan uses high levels of x-ray radiation)
• an MRI uses a combination of magnetic field and radio waves to generate images through the body
• soft tissues can be seen clearly using MRI, and images produced are at a higher resolution than those produced from CT scanning
• MRI is useful for identifying areas of abnormal or damaged tissue, but only enables brain function to be analysed by linking damage on a scan with visible symptoms in a patient
• MRI scans can be used to identify and locate tumours in the brain
• MRI scans do not carry the risk associated with the use of potentially harmful x-rays, but can interfere with medical devices like pacemakers due to the use of magnets
• fMRI scans work similarly to MRI scans, however, fMRI scans allow brain function to be studied in real time
• fMRI scans show the location of oxygenated blood in the brain, therefore indicating which brain regions are active at any one time - the scanner measures the ratio of oxygenated to deoxygenated haemoglobin
• PET scans use radioactive tracers (like radioactively labelled glucose) which collect in areas where there is increased blood flow, metabolism, or neurotransmitter activity
• The PET scanner can detect areas of high radioactivity, so the movement of the tracer through the body and any accumulation of the tracer in the brain can be seen. The amount of radioactive tracer present in a brain region can indicate whether that region is active or inactive.
• the visual cortex is the region of the cerebral cortex where visual information is processed
• soon after birth, the neurones in the visual cortex of baby mammals begin to form connections, or synapses, allowing visual information to be transferred and processed by the visual cortex.
• Both eyes need to be stimulated in order for the visual cortex to be organised correctly during the critical period in early development
• Synapses that pass on impulses during the critical period are strengthened and become permanent parts of the structure of the visual cortex. Synapses that do not receive nerve impulses during the critical period are lost and cannot be re-formed later on (this can result in blindness)
• Hubel and Wiesel carried out a study using animal models (kittens) to evidence the critical period of development by depriving the animals models of vision in one eye
• animal models have been used in brain research due to some animals having similar brain structure to humans, and as many consider experimenting on animals for medical reasons to be more ethically acceptable than experimenting on humans