THE BRAIN Biological Level of Analysis IB Psychology Taken from: Aamodt, S. & Wang, S.
Download ReportTranscript THE BRAIN Biological Level of Analysis IB Psychology Taken from: Aamodt, S. & Wang, S.
THE BRAIN Biological Level of Analysis IB Psychology Taken from: Aamodt, S. & Wang, S. (2008) Welcome to Your Brain Rider, Great Britain. THE NEURON BRAIN CELLS Your brain is made up of cells. Brain cells come in two types: neurons, which talk to one another and to the rest of the body, and glial cells, which provide essential support to keep the whole show going. There about 100 billion neurons and many more glial cells. USING PREVIOUS DIAGRAM & ONE IN TEXTBOOK (PG26) DRAW NEURON IN NOTES. Signals within a neuron are carried by electricity. To send electrical signals from one part of the neuron to another, the neuron opens channels that allow the ions to move across the membrane, creating a current that carries an electrical signal down the membrane. Neurons receive inputs through branched, treelike structures called dendrites, which put together information from a bunch of different sources. The neuron then sends an electrical signal down a long, wirelike structure, called an axon, which triggers a chemical signal to another neuron, and so on. Axons carry signals over long distances; your longest axons run from your spine to the tips of your toes. Each neuron in the brain receives chemical signals from some neurons and sends chemical signals to others. Communication between neurons relies on chemicals called neurotransmitters, which are released from small areas at the end of the axon when triggered by the arrival of a spike. Spikes are sudden increases in the electrical currents in a neuron. Every neuron makes and receives up to several hundred thousand chemical connections, called synapses, with other neurons. Neurotransmitters stick to synaptic receptors on the dendrites or cell bodies of another neuron, triggering further electrical and chemical signals. All of these steps, from release to detection, can take place in a thousandth of a second. For the brain to accomplish its many duties, neurons have to take on very specific tasks. Each neuron responds to a small number of events, such as hearing a particular sound, seeing someone’s face, carrying out a certain movement. At any given moment, only a small fraction of your neurons, distributed all over your brain, are active. This fraction is ever shifting; the whole game of thinking depends on which neurons are active and what they are saying to each other and to the world. SYNAPSES Synapses are the essential components of communication in your brain. Your thought patterns, basic abilities and functions, and individuality are determined by how strong these synapses are, how many of them you have, and where they are. Neurons use synapses to talk to each other within the brain. Only a small fraction of axons form their synapses outside the brain or spinal cord, sending signals to other organs of the body, including muscles. Draw! Pg26 NEUROTRANSMITTERS Each neuron has direct synaptic contact with several thousand other neurons. Neurons do not touch each other, instead contact is make through neurotransmitters. Neurotransmitters are the chemical messengers used by neurons to communicate with each other. It has been estimated that there are over 100 neurotransmitters. COMMON NEUROTRANSMITTERS Read Information Box in textbook, pg27. Monoamines: Acetylcholine (ACH) – involuntary muscle movement, learning memory and sleep Norepinephreine (NE) – controls sympathetic nervous system, involved in eating and alertness Dopamine (DA) – involved with movement, attention, learning and memory. Serotonin (5-HT) – involved in inducing sleep, sensory perception, temperature regulation, control of mood, appetite and aggressive behaviour Amino Acids: GABA – most common and is involved in most aspects of brain functioning – from memory to sleep. Peptides: there are over 50 peptide neurotransmitters EVIDENCE FOR WORKING OF BRAIN Scientists first learned about the functions of different parts of the brain by studying people with brain damage. Sadly, WWI was an especially rich source of data. Soldiers often survived head wounds because high-velocity bullets cauterized their wounds, preventing a fatal loss of blood or even infection. But the soldiers exhibited a baffling range of symptoms, which depended on the location in the brain that was damaged. Scientists can also figure out what a neuron does by tracking its activity under different conditions, by stimulating it, or by tracing its connections to other brain areas. For example, motor neurons in the spinal cord receive signals from neurons in the cortex that generate basic movement commands. In turn, these spinal cord neurons send signals to the muscles, causing them to contract. If scientists electrically stimulate only the spinal cord neurons, the same muscles contract. LOBES OF THE BRAIN LOBES OF THE BRAIN Occipital lobe: in the back of your brain, this is responsible for visual perception. Temporal lobe: just above your ears, this is involved in hearing and contains the area that understands speech. It also interacts closely with the amygdala and hippocampus and is important for learning, memory and emotional responses. LOBES OF THE BRAIN Parietal lobe: on the top and sides, receives information from the skin senses. It also puts together information from all the senses and figures out where to direct your attention. Frontal lobe: generates movement commands, contains the area that produces speech, and is responsible for selecting appropriate behaviour depending on your goals and your environment. PARTS OF THE BRAIN The brain is divided into three main regions, each with different functions. 1. The Forebrain: The cerebrum – largest part of brain, conscious thoughts and actions The thalamus – information relay system The hypothalamus – controls automatic body processes The basal ganglia – made up of smaller structures The limbic system – controls our feelings and emotions 2. The Midbrain: mainly involves the reticular activating system. 3. The Hindbrain: has 3 main structures: The cerebellum – controls co-ordination of movement Pons – connects two halves of cerebellum Medulla Oblongata – controls basic functions THE CEREBRUM The cerebrum is divided into left and right halves or hemispheres. Split down the middle by deep rift: longitudinal fissure. The surface of each hemisphere is heavily folded like the surface of a walnut. The brain consists of grey matter (outside) and white matter (inside). The outer layer of grey matter, called the cerebral cortex, is just 4 millimetres thick. THE CORPUS CALLOSUM The two halves or hemispheres that make up the cerebrum are linked by a ‘bridge’ called the corpus callosum. This is a dense mass of joining fibres that is four inches long and joins the two hemispheres. Allows the exchange of information from one hemisphere to another. THE CEREBRAL CORTEX The largest part (due to its folds and grooves) of the human brain, making up a little over threefourths of its weight. Shaped like a large crumpled-up comforter that wraps the top and sides of the brain. Scientists divide up the cortex into four parts called lobes; the occipital lobe, temporal lobe, parietal lobe and frontal lobe. ASSOCIATION CORTEX About ¾ of the cortex remains a mystery and it is known as the association cortex. This is where higher mental functions such as thinking, reasoning, learning probably take place but nobody has yet been able to localise these functions. WHAT IS THE AREA THAT PRODUCES SPEECH CALLED? WHAT IS THE AREA THAT UNDERSTANDS SPEECH CALLED? LIMBIC SYSTEM AND BASAL GANGLIA THE THALAMUS Relays sensory information (except smell) from the spinal cord, brain stem, cerebellum and parts of the cerebrum to the cerebral cortex. Sensory information entering the body through the eyes, ears, or skin travels in the form of spikes to the thalamus, in the centre of the brain. Filters information and passes it along, as more spikes, to the cortex. Functions include being the interpretation centre for pain, temperature, light touch and pressure. Plays a role in emotion and memory. THE HYPOTHALAMUS Small region of the brain that has many important functions. Main function is homeostasis or maintaining the body’s temperature and balance. It assists in the regulation of hunger and thirst. It also dictates daily sleep cycles. If it detects a problem it can send a neural or chemical message. Therefore, it controls endocrine system and release of hormones. THE LIMBIC SYSTEM The limbic system is located on the middle surface of the temporal lobe. It is composed of the thalamus, hypothalamus, the olfactory cortex, the amygdala and the hippocampus. It is the centre of our emotions and is responsible for emotion production and storing of emotional memory. It also controls appetite and sleep patterns, and plays an important part in motivation. BASAL GANGLIA The basal ganglia are a collection of nuclei found on both sides of the thalamus, outside and above the limbic system, within the temporal lobes. Made up of a number of smaller structures that involve muscle tone and posture. Interconnected with the cerebral cortex, thalamus and brainstem. THE AMYGDALA Almond-shaped brain area located above each ear and near the hippocampus. Responsible for emotions, particularly fear and anxiety. Triggers fight or flight response. Appears to be involved in the memory process. THE HIPPOCAMPUS Responsible for declarative memory, or things we know such as facts and figures. It places information and is necessary for our long-term memory. THE MIDBRAIN & THE RF Connects the forebrain and hindbrain. There is only really one main structure in the midbrain and that is the reticular formation (RF). Reticular formation is a network of neurones that regulates alertness and muscle movement. Reticular activating system stimulates the upper part of the brain, keeping people awake and alert. Carries mainly sensory information to brain and motor information to spinal cord. At the centre of arousal and motivation as it helps us focus attention and acts as a filter between your conscious and unconscious mind. THE HINDBRAIN OR BRAINSTEM At the very bottom of the brain where it attaches to your spinal cord. Region controls basic functions that are critical for life, such as: breathing, heart rate, sleep, arousal, digestion, reflexive movements of the head and the eyes. Acts as a relay station, passing messages back and forth. If the brain stem is damaged, this can be fatal and can cause ‘brain death’. Consists of the cerebellum, pons and medulla. THE CEREBELLUM A large region at the back of the brain that is often referred to as ‘little brain’. Controls subconscious movements of the skeletal muscles that maintain balance and posture. Integrates sensory information to help guide movement. Contains cardiac, respiratory and vasomotor control centres. PONS The pons is the larger ‘swelling’ just above the medulla that acts as a bridge between the lower parts of the brain and the upper sections. It is vital in co-ordinating the movements of the two halves of the body. Involved in the regulation of sleep, arousal and movement. Influences dreaming. MEDULLA Located at the top of the spinal column. This is the part of the brain that a person would least want to have damaged, as it controls lifesustaining functions such as heartbeat, breathing and swallowing. It is in the medulla that nerves coming from and going to the left and right sides of the body cross over, so that the left side of the brain controls the right side of the body and vice versa. THE ENDOCRINE SYSTEM Our body is not solely influenced by our nervous system, The endocrine system is the body’s second communication system. It contains glands that secrete chemicals directly into the blood stream or lymph system. These chemicals, or hormones, are carried throughout the body where they affect both internal processes and visible behaviour. THE PITUITARY GLAND The most influential endocrine gland. Located at the base of the brain and is controlled by the hypothalamus. The pituitary releases hormones that affect growth, and also influences the release of hormones by other endocrine glands. Also influences our response to stress. RIGHT VS. LEFT HEMISPHERE ARE WE IN OUR RIGHT MINDS? When people talk about the “right brain” and the “left brain,” they’re referring to the two sides of the cortex. While there are some real differences in function between them, the distinctions are often misunderstood. Most people’s speech is controlled by the left side of the brain, which is also responsible for mathematics and other forms of logical problem solving. Curiously, it is also the source of many misremembered or confabulated details. ARE WE IN OUR RIGHT MINDS? All in all, the left side of the brain seems to have an intense need for logic and order, so intense that if something doesn’t make sense, it usually responds by inventing some plausible explanation. The right side is much more literal and truthful when it reports what happened. It controls spatial perception and the analysis of objects by touch, and excels at visual-motor tasks. Rather than being “artistic” or “emotional”, the right brain is simply more grounded. SPERRY (1968)