B6 All will know that a stimulus is a change in the environment of an organism -D Most will describe how animals respond to stimuli in order to keep themselves in favorable conditions -C Some will explain how the central nervous system (CNS) coordinates an animal’s responses -B

B6 Foundation Brain and Mind

How organisms respond to change in the environment The nervous system allows the body to respond to changes in the environment. This is a process usually coordinated by the brain. Reflex actions are extra-rapid responses to stimuli, and this process also involves the nervous system, but bypasses the brain.

The information pathway Receptor Sensory Neurones Relay neurone Spinal cord/Brain Motor neurone Effector

A stimulus is a change in the environment of an organism. An animal’s response to a stimulus is coordinated by their central nervous system (CNS). The CNS consists of the brain and the spinal cord. It gathers information about, and responds to, changes in the environment.

Receptors respond to a stimulus and send impulses along sensory neurons to the CNS. The CNS coordinates the information and sends impulses along motor neurons to the effectors, which bring about a response.

Stimulus Receptor Sensory neuron Central nervous system Motor neuron Effector Response

The peripheral nervous system (PNS) consists of motor and sensory neurons that carry information from the receptors to the CNS, as well as instructions from the CNS to the effectors.

Pressure and temperature Receptors Smell Touch Pressure and temperature Hearing Sound and Balance Sight Light Taste

Types of nerve Cell Neurones are highly specialised cells Sensory neurone Gathers and sends information from the senses such as touch, smell, sight etc Relay neurone Communicates between sections of the central nervous system Motor neurone Sends signals to effector cells such as muscles, glands etc. http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemact.shtml -

Receptors and Effectors Receptors send information to the brains via the sensory neurones. These are relayed to the correct part of the Brain or spinal cord. (CNS) The response is transmitted along the motor neurones. This makes muscle cells contract (movement) or glands secrete chemicals ( hormone secretion)

Synapses Neurones do not actually touch each other This allows a co-ordinated response to a stimuli

What is a synapse? A synapse is a junction between two neurones across which electrical signals pass. The human body contains up to 500 trillion synapses. presynaptic cell postsynaptic cell

The release of neurotransmitters When a nerve impulse arrives at the end of one neurone it triggers the release of neurotransmitter molecules from synaptic vesicles. synaptic vesicle neurotransmitter molecules

Continuing the impulse The neurotransmitters diffuse across the synaptic cleft and bind with receptors on the next neurone, triggering another impulse. synaptic cleft nerve impulse receptor

Watch this animation http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/human/thenervoussystemrev2.shtml

Reflex All will recall that neurons transmit electrical impulses when stimulated D Most will describe how a reflex arc works-C Some will describe how simple reflexes ensure that an animal will respond to a stimulus in a way that is most likely to result in its survival -B

Recap… What are the 3 types of neurone? What do they do? 1 minute to write them down!

What are Reflex Actions? Reflexes are involuntary actions They are predominantly controlled by the spinal cord Some reflexes can be modified by conscious control from the brain.

Why are reflexes important? Simple reflexes are important for self preservation, they are automatic responses to ensure survival and avoid damage. However animals that only have reflexes cannot adapt their behaviour so if their environment changes or a new situation arises they may be at a disadvantage.

Simple reflexes in new born babies include Grasping Startle Steppping Sucking Rooting

Turn to page 181: Complete questions 1-3 On page 182: Draw and annotate the diagram of a reflex arc

Reflexes part 2 All will be able to identify the components of the nervous system D Most will describe the structure of a neuron C Some will describe the pathway of nerve impulse B

Task 1: Complete w/s ab6.4- page 183 helps Task 4: Practical: Testing reactions

The Brain What can you say about the brain?

The Brain The human brain has billions of neurones New neurone pathways develop in our early years New experiences lay down new pathways When we learn, certain pathways are more likely to transmit certain impulses The variety of potential pathways means that we are very adaptable.

How do we develop more complex behaviour Conditioned reflexes help us survive. Conditioning is a learned behaviour If we learn that an oven is hot we will not touch it and burn ourselves.

Memory Scientists describe memory as the ability to store and retrieve information. You have a SHORT term and LONG term memory

Memory All will know how memory is developed Most will describe how we learn Some will explain how we learn

Short term memory Short term memory lasts about 30 seconds. To read this slide you are using your short term memory. If your brain is damaged in this area you would not be able to make sense of the sentence as you would forget the beginning before you got to the end.

Each new experience changes our behaviour - this is called learning. If the experience is repeated, or the stimulus is very strong, more nerve impulses are sent along the new pathway. This reinforces the learning process and explains why repetition helps us to learn new things.

Repetition strengthens the connections between neurons and makes it easier for impulses to travel along the pathway. Skills can also be learnt through repetition. For example learning to ride a bike requires practice and repetition to learn a new set of skills.

How much can you store! Look at page 198. In pairs do the activity in the blue box. How many letters can you remember? Anything over 7 letters means you have an excellent short term memory (despite what you think!) Short term memory also depends on your level of attention

Long term memory Long term memory is a lasting store There seems to be no limit to how much we can store in long term memory We remember things better if we can see a pattern in them

Memory models Explanations of how memory happens are called models of memory None of the models completely explain memory. Read about these on page 198-201 Multi-store model Working memory model

Brain and drugs 1. recall that some drugs and toxins affect the transmission of impulses across synapses; 2. describe how Ecstasy (MDMA) affects the brain 3. describe the mood-enhancing effects of Ecstasy.

Some drugs stop the impulse from passing across the synapse. Other drugs stimulate the synapse so that once an impulse crosses the gap the impulse is repeated over and over again.

Using page 188. Outline the stages in How a synapse works On p189: What is serotonin? How does it work? What is prozac?

Serotonin is a chemical that is released into synapses in the brain Serotonin is a chemical that is released into synapses in the brain. An increase in serotonin levels in the synapses makes us feel happier. However, serotonin is normally absorbed by receptor molecules on the other side of the synapse. This prevents the levels of serotonin from increasing.

Ecstasy (also called MDMA) is a drug that blocks the serotonin receptor sites in the synapses in the brain. This prevents the serotonin from being absorbed by the receptor molecules. As a result, the level of serotonin in the synapse increases. This produces a feeling of wellbeing.

Helping you with revision Repetition – if you cannot remember something easily read it several times. Rehearsal – Read short sections of work, and then make notes from memory to transfer it into your long term memory. Active memory – Use highlighter pens to pick out the main points.

How do we know what the brain does? Studying damage to the different parts of the brain allows us to see what they do. We can look at the electrical activity using an EEG ( electroencephalogram) This gives a trace showing brainwaves. MRI ( Magnetic Resonance Imaging) Allows us to look at cross sections of the brain. The brighter the colour the more electrical activity.

How drugs affect our nervous system Drugs can change the speed at which impulses are sent. They can also send false signals. They can interfere with the synapses stopping the neurotransmitters or mimic them and overload the CNS with too many signals.