20. Impulses are from different synapses, usually from different neurones. The number of different sensory cells stimulated can be reflected in the control of the response
26. Temporal lobeComponentFunctionFrontal lobeConcerned with the higher brain functions like decision making, reasoning, planning and consciousness of emotions. It is responsible for the formation of associations and ideas.Parietal lobeConcerned with orientation, movement, sensation, calculation, recognition and memoryOccipital lobeConcerned with vision, colour, shape recognition and perspectiveTemporal lobeConcerned with hearing, sound recognition, speech and memory ThalamusResponsible for routing incoming sensory information to the correct part of the brainHypothalamusMonitors core body temperature and skin temperature. Controls sleep, thirst and hunger. Also acts as an endocrine gland (antidiuretic hormone) and links to the pituitary glandHippocampusLong-term memoryCerebellumResponsible for balance, co-ordinating movements, receiving information from the primary motor cortex, muscles and joint, checks motor programmesMidbrainRelays information to the hemispheresMedulla oblongataRegulates body processes like heart rate, breathing and blood pressureBasal gangliaResponsible for selecting and initiating stored programmes for movement<br />Discovering the function of each brain region<br />Until recently, neuroscientists were only able to study the brain by looking at pathological specimens, by examining the effect of damage to particular areas of the brain, using animal models and studying human patients during surgery. Individuals with brain damage still provide valuable information but neuroscientists now have a wide range of non-invasive imagining techniques.<br />Studies of individuals with damaged brain regions<br />Studying the consequences of accidental brain damage can determine the functions of certain regions of the brain. Researchers have also studied the consequences of injuring or destroying neurones to produce lesions in non-human animal ‘models,’ and the consequences of the removal of brain tissue.<br />The story of Phineas Gage<br />Gage was the foreman of a railway construction company who was popular and responsible. He was working with dynamite when an explosion propelled a three and a half foot long iron bar through his head. He did not die but most of the front part of the left hand side of his brain was destroyed. After the accident, his personality changed where he became nasty, foul-mouthed and irresponsible. He was impatient and obstinate, unable to complete any plans for future action. He died 12 years later.<br />Harvard University have used photographs and X-rays to come up with computer graphics showing that it is highly probable that the accident severed connections between the midbrain and frontal lobes. Thus, the reduced ability to control his emotional behaviour was related to damage at this site.<br />The strange case of Lincoln Holmes<br />A car crash left Holmes with damage to an isolated part of his temporal lobe and now he cannot recognise a face. He can see facial features but they all appear as a jumble, which he is unable to put all the component parts together. He cannot even recognise a photograph of himself. This has revealed that recognition of faces is at least partly carried out by a specific face recognition unit in the temporal lobe.<br />The effects of strokes<br />Brain damage caused by a stroke can cause problems with speaking, understanding speech, reading and writing. Paul Broca concluded that lesions in a small cortical area in the left frontal lobe were responsible for deficits in language production.<br />Some patients can recover some abilities after a stroke, showing that neurones have the potential to change in structure and function, known as neural plasticity. The brain’s structure and functioning is affected by both nature and nurture, remaining flexible even later in life.<br />Brain imaging<br />CT scans<br />Computerised Axial Tomography was developed in the 1970’s in order to view images of soft tissue. CT scans use thousands of narrow-beam X-rays to pass through the tissue from different angles. Each narrow bean is attenuated according to the density of the tissue in its path. The X-rays are detected and used to make a picture of slices of the brain.<br />CT scans only give a still image meaning that it is used to look at structures rather than functions of the brain. They can be used to detect brain disease but small structures cannot be distinguished.<br />MRI<br />Magnetic resonance imaging uses a magnetic field and radio waves to detect soft tissues. The atoms line up with the direction of the magnetic field. Hydrogen atoms in water are monitored as they have the strong tendency to line up with the magnetic field and there is a high water content.<br />A magnetic component of high frequency radio waves is superimposed onto a magnetic field causing the direction and frequency of spin of the hydrogen nuclei to change. The nuclei take energy from the radio waves, so when there are no more radio waves, the hydrogen nuclei return to their original alignment and release energy. The energy is detected and sent to a computer, which produces image slices. Different tissues respond differently, producing contrasting signals and distinct regions in the image. MRI is used to diagnose tumours, strokes, brain injuries and infections of the brain and spine. It can produce much more detailed images than CT scans can.<br />fMRI<br />Functional Magnetic Resonance Imaging can provide information about the brain in action. It is used to study human activities like memory, emotion, language and consciousness.<br />fMRI records the uptake of oxygen in active brain areas as deoxyhaemoglobin absorbs the radio wave signal but oxyhaemoglobin does not. Increased neural activity in the brain results in an increase in blood flow for oxygen, so there is an increase in oxygaemoglobin. The less radio signal there is absorbed, the higher the level of activity.<br />From the eye to the brain<br />The axons of the ganglion cells that make up the optic nerve pass out of the eye and extend to several areas of the brain, including the thalamus. Before reaching the thalamus, some neurones in each optic nerve branch off to the midbrain to connect to motor neurones involved in controlling the pupil reflex and movement of the eye. Audio signal arrive at the midbrain to turn our eyes in the direction of a visual or auditory stimulus.<br />Visual Development<br />The human nervous system begins to develop soon after conception. By the 21st day, the neural tube had formed, developing into the spinal cord while the front part of the tube develops into the brain. The rate of brain growth can be 250,000 neurones per minute to reach a total of about 100,000 million neurones. There is not a huge increase in the number of brain cells after birth but the brain increases in size because of several factors. These factors are mainly the elongation of axons, myelination and the development of synapses. <br />Axon growth<br /> Axons of the neurones from the retina grow to the thalamus where they form synapses with neurones in the thalamus in a very ordered arrangement. Axons from these thalamus neurones grow towards the visual cortex in the occipital lobe.<br />The visual cortex is made of columns of cells, proven in staining techniques and by using electrical stimulation. Axons from the thalamus synapse within these columns while adjacent columns receive stimulation.<br />The columns were thought to be a result of nurture rather than nature but Crowley and Katz proved that it is not the case. They saw, by using labelled tracers, that ferrets and newborn monkeys both have these columns, suggesting that their formation was genetic. However, periods during postnatal development have been identified when the nervous system must gain specific experiences to develop properly, known as critical windows or sensitive periods.<br />Radioactive label moves from one eye and is concentrated into distinct bands in the visual cortex, showing the columns of cells that receive input from that eye. These banding patterns have been observed in animals that have received no visual stimulation.287655047625<br />Evidence for a critical period in visual development<br />Medical observations<br />One case is that of a young Italian boy who had a minor eye infection, it was bandaged up for two weeks. Afterwards, he was left with permanently impaired vision.<br />People born with cataracts contributed to the understanding of critical periods in development. Cataract is the clouding of the lens of the eye, affecting the amount of light to the retina. If it is not removed by the age of 10, it can cause permanent impairment of the person’s ability to perceive shape. However, elderly people report normal vision if the cataract is removed despite having them for years. This suggests that there is a specific time in development when it is crucial for a full range of light stimuli to enter the eye. <br />PowerPoint’s include:<br />Nerve Impulses - Over all story<br />The Brain - scans and imaging<br />