Higher Human Biology Unit 3 Neurobiology and Immunology
Higher Human Biology Unit 3 – Neurobiology and Immunology Section 18 – The Cerebral Cortex
a) The Cerebral Cortex We will be learning… • To describe the cerebral cortex as the centre of conscious thought. • To explain how the cerebral cortex recalls memories and how it alters behaviour based on this knowledge • To state that there is localisation of brain functions in the cerebral cortex • To describe the functions of the sensory area, motor area, associated areas such as language, processing, personality, imagination and intelligence
The Cerebral Cortex • The cerebral cortex is the thin outer part of the cerebrum and is the centre of conscious thought and memories. The cerebrum is split into two halves called cerebral hemispheres. This is the largest and most complex part of the brain. • The cerebral cortex has three key functions: • receives sensory information • co-ordinates voluntary movement • making decisions based on experience.
Interconnections and Communication The cerebral cortex is the centre of conscious thought. Tiny nerve fibres link up all the different areas and messages are constantly passing between them from sensory areas to motor areas via association areas. This allows the brain to make an integrated response based on all the collective information. The cerebrum is also able to recall stored memories and then alter future decision based on the past experience. The cerebral cortex is also responsible for: • • • Intelligence Personality Creativity Imagination Conscience
How does the Cerebral Cortex Recall Memory? During recall, the brain "replays" a pattern of neural activity that was originally generated in response to a particular event, echoing the brain's perception of the real event. These replays are not quite identical to the original, though - otherwise we would not know the difference between the genuine experience and the memory. They are mixed with an awareness of the current situation. One corollary of this is that memories are not frozen in time, and new information and suggestions may become incorporated into old memories over time. Thus, remembering can be thought of as an act of creative reimagination.
How does the Cerebral Cortex alter Behaviour Based on Memory Poor cerebral cortex functions can lead to more impulsive behaviour. Study subjects in whom the activity of the prefrontal cortex was temporarily suppressed could control their emotional impulses less well than normal. If the front part of the cerebral cortex is less active then people have less control over their social behaviour and automatically follow their inclinations more.
The Cerebral Cortex – Localisation of function • Within the cerebral cortex, there are three main areas each of which deals with a particular function. • the sensory areas – receives information as sensory impulses from receptors (e. g. sense organs) • the association areas - analyse and interpret impulses received from the sensory areas and deals with thought processes, language, personality, imagination and intelligence. • the motor areas – act on information from association areas by sending motor impulses to effectors. • By this means, coordination of voluntary movement is achieved. https: //www. youtube. com/watch? v=sjb. Z 9 QGy. Bi 8
The Cerebral Cortex Frontal Lobe Motor Area Temporal Lobe Medulla Oblongata Sensory Area Sensory Association Area Cerebellum Spinal cord All these areas are duplicated in both hemispheres with the exception of the speech motor area which is found in the left hemisphere only for 90% of the population.
Function of the Sensory Area There is a major organisation of tissues to enable easy linkage of sensory messages from a specific area of the body with the motor impulses required to control these organs and tissues. The homunculus is a visual way of explaining this organisation. The somatosensory area receives information from cold, heat, pain, touch and kinaesthetic receptors in the skin. Thus, an impulse coming in from a leg is sensed by neurons in the somatosensory area adjacent to the neurons of the motor area which direct the movement of that leg.
Function of the Motor Area A large part of the motor area is devoted to the hands and lips. This allows a fine degree of motor control. For example, fingers can hold an egg without crushing it or manoeuvre a coin from finger to finger. Remember that the left motor cortex controls the right side of the body and vice versa. Large parts of the sensory area are devoted to the lips, fingers and sex organs, making them very sensitive. This explains why we kiss with the lips and why infants explore new toys with their lips. Similarly, large parts of the motor area are devoted to the tongue and lips, allowing speech, and to the fingers, allowing fine manipulation.
Function of the Associated Areas • At the simplest level, the association areas integrate sensory information from different sensory areas and relate it to past experience. A decision is then made and neuron impulses sent to the motor areas to give responses. • However, the association areas are also where the individual person resides, as they are the location of thought processes, personality, imagination, language and intelligence • Thought: mental activity of which we are aware and undertake deliberately, that generates ideas and underlies almost all human actions; • Personality: the sum of an individual's emotions, attitudes and behaviour; • Imagination: helps us to make sense of the world and learn, by allowing us to form visual or sensory images without actually experiencing them at the same time; • Language: a system of signs, gestures or sounds which convey particular meanings; • Intelligence: mental ability, either inborn or acquired, to pay attention, remember, process language, solve problems and make decisions; this is a very controversial topic
b) Information Transfer in the Brain We will be learning… • To state that there is a left and right hemisphere in the brain • To describe the right and left hemispheres and how they receive information from the right and left visual field respectively • To describe that the right and left hemispheres control the left and right side of the body respectively • To state that information is exchanged between the cerebral hemispheres through the corpus callosum
The Cerebral Cortex • The cerebrum is divided into two halves, the left and right cerebral hemispheres. • The left cerebral hemisphere receives information from the right visual field and controls the right side of the body. • The right cerebral hemisphere receives information from the left visual field and controls the left side of the body.
The Corpus Callosum • The cerebral hemispheres are not entirely separate, they are connected by a large bundle of nerve fibres known as the corpus callosum. • The corpus callosum allows the transfer of information between the cerebral hemispheres and so allows the coordination of brain function, thus enabling the brain to act as an integrated whole.
The Cerebral Cortex • The cerebral cortex is highly folded (convoluted) which greatly increases its surface area, this • provides greater space for more neurons • allows for more interconnections between neurons cerebral cortex
Einstein's Brain Einstein died in April 1955 from an abdominal aortic aneurysm. He had requested that his body be cremated, but in a bizarre incident, Princeton pathologist Thomas Harvey removed his famous brain during his autopsy and kept it in the hope of unlocking the secrets of his genius.
Electroencephalograms – EEG’s • EEG’s record the electrical activity of the cerebrum. • EEG’s can indicate different levels of brain activity but are not precise enough to locate the areas of the brain which are active.
Brain Scans • Brain scans, such as Computed Tomography CT/CAT, Magnetic Resonance Imaging MRI or Positron Emission Tomography PET scans, provide a more detailed images of the brain. • They can detect activity through changes in blood flow or uptake of glucose and can allow localisation of function to be identified by showing which areas are most active whilst carrying out a particular function. CAT – X-Ray MRI – Powerful magnetic fields PET - special dye containing radioactive tracers
CAT - Brain Scan These show metabolic activity, providing better evidence for localisation of function. For example, while listening, metabolic activity in the areas of the brain involved in hearing can be traced. Stroke Brain Injury
MRI - Brain Scan Brain Tumour
PET Brain Scan PET scan of normal brain PET scan Alzheimer’s brain
Split Brain Syndrome • In rare cases, a person can be born without a corpus callosum or may have it cut due to serious epilepsy, this results in split brain syndrome. • The cerebral hemispheres do not share information and each processes information separately.
https: //www. youtube. com/watch? v=ZMLz. P 1 VCANo
Changes in behaviour • The subsequent behaviour of such split-brain patients, in whom the two hemispheres cannot communicate properly, shows that tasks are not evenly divided between the two hemispheres. • Images appear to be processed by the left hemisphere in most people. Language and analytical skills are also processed here. • Damage to a discrete part of the brain in the left frontal lobe of the languagedominant hemisphere has been shown to significantly affect the use of spontaneous speech and motor speech control.
Phineas Gauge
Questions 1. Describe the functions of the medulla and cerebellum in the central core of the brain. 2. Describe the functions of the limbic system. 3. Describe the functions of the cerebral cortex. 4. Describe the localisation of functions within the brain 5. Describe where information from one side of the brain is processed. 6. State the function of the corpus callosum
Answers 1. Describe the functions of the medulla and cerebellum in the central core of the brain. medulla – regulates breathing, heart rate, sleeping and arousal cerebellum –responsible for controlling balance, posture and movement 2. Describe the functions of the limbic system. Processing information for memories, regulating emotional states, e. g. fear, aggression and anxiety, regulating biological motivation, e. g. hunger, thirst and sex drive.
Answers 3. Describe the functions of the cerebral cortex. Receives sensory information, co-ordinates voluntary movement, making decisions based on experience 4. Describe the localisation of functions within the brain • the sensory areas • the association areas • the motor areas 5. Describe where information from one side of the brain is processed. In the opposite cerebral hemisphere e. g. Information from the right side is processed in the left cerebral hemisphere 6. State the function of the corpus callosum It allows the transfer of information between the cerebral hemispheres
a) The Cerebral Cortex Now I can…. . • Describe the cerebral cortex as the centre of conscious thought. • Explain how the cerebral cortex recalls memories and how it alters behaviour based on this knowledge • State that there is localisation of brain functions in the cerebral cortex • Describe the functions of the sensory area, motor area, associated areas such as language, processing, personality, imagination and intelligence
b) Information Transfer in the Brain Now I can…. . • State that there is a left and right hemisphere in the brain • Describe the right and left hemispheres and how they receive information from the right and left visual field respectively • Describe that the right and left hemispheres control the left and right side of the body respectively • State that information is exchanged between the cerebral hemispheres through the corpus callosum
Word Definition Cerebral hemispheres Corpus Callosum two regions into which the cerebrum is divided Limbic system band of tissue in the brain that connects the two cerebral hemispheres area of the brain that contains LTM and other
Suggested activities • David Eagleman the brain documentary • Study brain injuries,
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