b6 brain and mind
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B6 Brain and MindW Richards
The Weald SchoolOCR 21st Century Additional Science
B6.1 How do animals respond to changes in their environment?
The Nervous SystemThe CENTRAL NERVOUS SYSTEM (CNS) enables us to react to changes in our surroundings (stimuli). It consists mainly of the brain, the spinal chord, nerve cells (neurones) and receptors.Types of receptor:Light receptors in the eyesSound receptors in the earsTaste receptors on the tongueSmell receptors in the noseTouch, pressure and temperature receptors in the skinChanges of position receptors in the ears (balance)
Nervous ReactionsWhen we react to a stimulus our bodies use the following pattern and these signals are sent using electrical impulses:For example, consider a man and a camel:Oh No!What are the stimulus, receptor, coordinator, effector and response in this situation?
Examples of reactions
StimulusReceptor (i.e. the thing that detects the stimulus)Effector (i.e. the thing that will do the reaction)Response (i.e. action taken)Bright lightSour tasteLosing balanceSit on a drawing pin
Simple reflexes in humansBabies can demonstrate simple reflexes:
Stepping reflexStartle (or moro) reflexGrasping reflexRooting reflexSucking reflex
The Iris ReflexWhen the light is bright the radial muscles relax, the circular muscles contract and the pupil increases in size.When the light is bright the radial muscles _____, the circular muscles _______ and the pupil ________ in size.
Reflex Actions in AnimalsSimple animals rely on reflex actions for most of their behaviour:
Slower responses - hormonesNervous impulses are electrical signals and are transmitted quickly through the body. The body can also produce a slower response using chemical messengers called hormones.Examples of bodily processes that use hormones:The development of nervous and hormonal communication systems depended on the evolution of multicellular organisms.
B6.2 How is information passed through the nervous system?
Conscious actionsA conscious action is one where the brain makes a considered response. Heres what happens:
Reflex actionsSometimes conscious action is too slow to prevent harm, e.gIn situations like this the body bypasses the brain to produce a quicker response. Heres how it works
Types of nerve cell (neuron)Nerve cells (neurons) are elongated with branched endings to connect to many muscles fibres and aid the transmission of electrical impulses:
The CNS and the PNSThere are two types of neurone we need to consider:
SynapsesNeurones never ____ each other there is a small gap between them called a _____. A signal is sent from one _______ to the next by a _______ transmitter across the synapse (called a neurotransmitter). These transmitters are then ________ back into the sensory neurone to be used again. This process only reacts with specific chemicals that bind to the receptor molecules.Words chemical, synapse, neurone, touch, reabsorbed
Drugs and the Nervous System Drugs are classed as a substance that affects the central nervous system, causing changes in psychological behaviour and possibly addiction. They do this by affecting the transmission of impulses. Consider Ecstasy for example:Beta blockers and Prozac can also affect the transmission of impulses.
The Cerebral CortexThe cerebral cortex is the part of our brain most concerned with intelligence, memory and consciousness. By studying the effects (e.g. memory/sight loss) when different parts of the brain are damaged scientists have been able to identify which parts of the brain control which functions.
Other techniques of studying the brain1) An electroencephalogram (EEG) is a visual record of the electrical activity generated by neurons in the brain. It works by amplifying and detecting the electrical signals from the brain.2) Magnetic resonance imaging (MRI) scanning is a new technique that produces images of different cross sections of the brain and uses colours to represent activity.
Conditioned reflexes - Pavlovs DogI won the Nobel Prize in 1904 and am most famous for investigating conditioned responses:Steak + dog = salivaSteak + bell + dog = salivaBell + dog = salivaNotice that the final response (saliva) has no direct relation to the stimulus (the bell). Conditioned reflexes can increase an animals chance of survival!
Reflex actionsSometimes the brain can modify a reflex response via a neuron to the motor neuron of the reflex arc, meaning that you could keep hold of a hot object:
B6.4 How do humans develop more complex behaviour?
Human BrainsUg. My chances of survival were made a lot better when my brain got bigger. Notice I can now use simple tools!Mammals have complex brains with billions of neurons. The interaction between our ancestors and their environment caused neuron pathways to form in the brain.
Learning Complex BehaviourWhen the brain is asked to do certain tasks different areas are activated. New experiences cause new neuron pathways to develop, while pathways that are not used are eventually destroyed. This is why we become better at certain tasks when we practice them more often.
Feral childrenTask: to find out what feral children are, what has caused their condition and what the consequences are.
MemoryOur memory is divided into two types: short term and long term.Short term memory is capable of storing a limited amount of information for a limited amount of time. Long term memory is when more information is stored over a much longer time.Ways of improving short term memory, e.g. a phone numberWays of improving long term memorye.g. exam revision
Using Models to Explain MemoryWe can understand memory better by using models to explain it, for example:What could cause a model to be limited in explaining how memory works?