Brain and Mind

Reflexes A reflex is an automatic response to a stimulus. Reflexes are very fast Simple reflexes help an animal to survive. Examples include hiding from predators, finding food / shelter / mates The big disadvantage with relying on simple reflexes is that the animal can’t adapt its behaviour if the environment changes. Complex animals like humans can make conscious decisions to aid survival (like putting a coat on if we’re cold). Sometimes our reflexes can also be modified due to experience.

Reflexes Simple reflexes:- A newborn baby shows reflexes such as sucking, gasping, the startle reflex and swimming. These help the baby to survive. Conditioned reflexes:- These are reflexes that we learn in response to a stimulus. For example, Pavlov rang a bell whenever he gave his dog food. After a while, the dog would produce saliva when he heard a bell even though there was no food present – he had learned to associate the sound of the bell with food. Modifying reflexes:- we can modify certain reflexes as we get older. For example we can overcome the reflex telling us to empty our bladder as soon as its full. We can also overcome the reflex telling us to drop a hot plate. Impulses travel from our brain to the effectors involved, preventing the simple reflex from taking place.

Reflex arc Receptors detect a stimulus Electrical impulse sent along sensory neuron Impulses move through spinal cord Impulses sent along motor neuron to effector

Nervous system Imagine you put your hand on a pin. This is detected by special cells in the skin which send an electrical impulse along sensory neurones to your spinal cord. Impulses are then sent via your motor neurons to the muscles in your arm. The muscles contract and you pull your hand away. stimulus receptors processing centre effector response

Nervous system Central nervous system (CNS) – brain and spinal cord Peripheral nervous system – includes sensory and motor neurons that carry impulses all around the body

Motor neuron (makes connections with other neurons) Motor neurons carry electrical impulses from the CNS to effectors (muscles or glands) The axon of a motor neuron is covered with a fatty layer called a myelin sheath. This speeds up the rate at which an impulse can travel along the neuron.

Synapses Mitochondrion (provides energy) Neurotransmitter released into synapse Neurotransmitter diffuses across Neurotransmitter binds to receptors on motor neuron Direction of electrical impulse A synapse is a small gap between 2 neurons. When an impulse arrives at the synapse, a chemical called a neurotransmitter is released. This chemical diffuses across the synapse and binds to receptors on the other side. This triggers an electrical impulse in the second neuron. The neurotransmitter then binds to uptake receptors on the first neuron, and is reabsorbed.

Drugs and synapses Some synapses release a neurotransmitter called serotonin. Some drugs like ecstasy or prozac bind to the uptake channels at these synapses. This means that when serotonin is released, it stimulates the neurons but can’t be reabsorbed. Therefore, serotonin becomes concentrated in the synapse and keeps binding to receptors, overstimulating the neurons. This results in enhancing someone’s mood, or making them feel happy. (other drugs may work by preventing neurotransmitters being released, or preventing them from binding to the receptors on motor neurones. These drugs prevent electrical impulses being generated in certain neurons - eg pain killers.)

The brain The folded part of the brain is called the cerebral cortex. This is responsible for our language, learning and memory. It contains billions of neurons. In this diagram, the size of the body part represents the surface area of the sensory region of the cerebral cortex associated with it. Eg, fingertips are very sensitive, so have a large sensory region of the brain linked to them.

Learning When we have a new experience, new neuron pathways are created. When we repeat the experience, these new pathways are strengthened. This means that electrical impulses are more likely to pass along these new pathways. So repetition helps you learn because it strengthens neural pathways.

Age and learning Children can form new neuron pathways very easily. Therefore children learn from experience very quickly. As we get older, it becomes harder to form new neuron pathways. Feral children have been isolated from other humans, and survived in the wild. They have had no experience with human language. If a feral child is brought back into society after the age of about 8, it is very difficult to teach them language. This is because the time when it is easy to lean language had already passed.

Memory As you read a sentence you are using your short term memory. This lasts only a short while, and can only remember about 7 items. To remember something like the words of a song, you need to move information into your long term memory. Rehearsal can help you remember by moving info into your long term memory. Associating information with some kind of pattern, or with a smell, colour or sound also helps you remember. This is because if you process information, you move it into your long term memory. We don’t fully understand how memory works, but there are different ‘models of memory’ which suggest different theories – like the multi-store model and working memory model.