Biopsychology Overall learning outcomes: You should be able to: Develop understanding of the basic structure and function of neurons. You should be able to: Use technical terminology correctly Label diagrams of neuron and synapse Explain how neurons communicate the process of neuronal transmission the process of synaptic transmission Explain the role of neurotransmitters the effects of drugs on transmission and behaviour agonists and antagonists

Lesson Objectives By the end of the lesson you … Must be able to define (AO1) the central nervous system, synapse, neurons and neurotransmitters.

Synapses Neurons transmit signals electrically along their axons. The synapses (junctions between neurons) transmit signals chemically.

Synapse Vesicles filled with neurotransmitter Synaptic cleft Go to human body Location of receptors (post-synaptic density)

Neurotransmitters Information is carried by biochemical substances called neurotransmitters. The terminal buttons and the dendrites of other neurons do not touch, but instead pass the information containing neurotransmitters through a synapse.

1. Synapses: 2. Myelin sheaths: 3. Axon: 4. Soma: 5. Nucleus: Send electrical impulses to neighbouring neurons. 2. Myelin sheaths: Cover the axon and work like insulation to help keep electrical signals inside the cell, which allows them to move more quickly. 3. Axon: Transfers electrical impulse signals from the cell body to the synapse. 4. Soma: The cell body which contains most of the cell’s organelles 5. Nucleus: Contains the cell’s DNA 6. Dendrites: Receive electrical impulses from neighbouring neurons.

Must be able to define (AO1) the biological approach. Must be able to define (AO1) the central nervous system, synapse, neurons and neurotransmitters.

Define (without notes) neuron neurotransmitter gene synapse CNS

Define (without notes) neuron a nerve cell that sends electrical impulses neurotransmitter a chemical released at the end of the neuron to pass a message on to another neuron. gene units of information that are inherited. synapse the space between two neurons which is crossed by neurotransmitters. CNS central nervous system – the brain and spinal cord which organise communication around the body.

Lesson Objectives By the end of the lesson you … Must be able to describe (AO1) how the synapse, receptors, neurons and neurotransmitters pass ‘messages’ Must be able to describe (AO1) the components of a neuron.

The neuron Draw and complete by going to and from computer at the front.

The Synapse

1 Vesicles release neurotransmitter into synaptic cleft

2 Neurotransmitter binds to receptors & activates them

3 Excess neurotransmitter is taken up by the pre-synaptic neuron

4 Enzymes are released to break down the remaining neurotransmitter

5 Vesicles are replenished with new & reused neurotransmitter

Synaptic transmission Sort the cards into the correct order and then write the details up on the flow diagram to show the process of synaptic transmission

Synaptic transmission - answers nerve impulse travels down an axon nerve impulse reaches synaptic terminal this triggers the release of neurotransmitters the neurotransmitters are fired into the synaptic gap neurotransmitter binds with receptors on the dendrite of the adjacent neuron if successfully transmitted the neurotransmitter is taken up by the post-synaptic neuron the message will continue to be passed in this way via electrical impulses

Prozac Selective Serotonin Reuptake Inhibitor In the brain, messages are passed between two nerve cells via a chemical synapse, a small gap between the cells. The (presynaptic) cell that sends the information releases neurotransmitters (including serotonin) into that gap. The neurotransmitters are then recognized by receptors on the surface of the recipient (postsynaptic) cell, which upon this stimulation, in turn, relays the signal. About 10% of the neurotransmitters are lost in this process; the other 90% are released from the receptors and taken up again by monoamine transporters into the sending (presynaptic) cell (a process called reuptake). To stimulate the recipient cell, SSRIs inhibit the reuptake of serotonin. As a result, the serotonin stays in the synaptic gap longer than it normally would, and may repeatedly stimulate the receptors of the recipient cell. The current model of SSRIs (the Monoamine Hypothesis) assumes that a lower homeostatic level of serotonin is primarily responsible for depression. While this holds in cases of major depression, minor to moderate cases are not as clear cut, and may in fact be caused by excess serotonin in specific areas of the brain. Selective Serotonin Reuptake Inhibitor

Illustration 1 shows how this works in a healthy nerve transmission process

Illustration 2 shows the process when Major Depression is present Illustration 2 shows the process when Major Depression is present. Note that fewer Serotonin molecules are present in the synaptic cleft and hence fewer make it to the next neuron to make it "fire."

Illustration 3 shows how an SSRI drug blocks the reuptake of Serotonin thus causing the concentration in the synaptic cleft to be increased. Consequently more serotonin makes it to the receptor sites on the next nerve cell and the functioning returns to normal.

http://www.youtube.com/watch?v=BfNU_FPDa98

Neuronal transmission Neurons transmit electrical signals called action potentials. Action potentials work a bit like a ‘Mexican wave’. The presence of a myelin sheath on a neuron changes the rate of transmission.

Multiple sclerosis is caused by a process called demyelination. What do you think this might be? How do you think it might cause MS symptoms? A demyelinating disease is any disease of the nervous system in which the myelin sheath of neurons is damaged.[1] This damage impairs the conduction of signals in the affected nerves. In turn, the reduction in conduction ability causes deficiency in sensation, movement, cognition, or other functions depending on which nerves are involved. Some demyelinating diseases are caused by genetics, some by infectious agents, some by autoimmune reactions, and some by unknown factors. Organophosphates, a class of chemicals which are the active ingredients in commercial insecticides such as sheep dip, weed-killers, and flea treatment preparations for pets, etc., will also demyelinate nerves. Neuroleptics can also cause demyelination.[2] Demyelinating diseases are traditionally classified in two kinds: demyelinating myelinoclastic diseases and demyelinating leukodystrophic diseases. In the first group a normal and healthy myelin is destroyed by a toxic, chemical or autoimmune substance. In the second group, myelin is abnormal and degenerates.[3] The second group was denominated dysmyelinating diseases by Poser[4] In the most known example, multiple sclerosis, there is good evidence that the body's own immune system is at least partially responsible. Acquired immune system cells called T-cells are known to be present at the site of lesions. Other immune system cells called Macrophages (and possibly Mast cells as well) also contribute to the damage.[5] Some demyelinating diseases are caused by genetics, some by infectious agents, some by autoimmune reactions, some by exposure to chemical agents, and some by unknown factors.

Myelinated Axon - + + - + - - + + - + - - + + - + - + - + - - + + - + Dendrites Axon Terminal

Unmyelinated Axon - + + - + - + - + - - + - + + - + - + - - + + - + - Dendrites Axon Terminal

Can you? Explain what is meant by sensory, relay and motor neurons (2 marks each) With reference to neurotransmitters, explain what is meant by both excitation and inhibition (4 marks) With reference to sensory, relay and motor neurons, explain the knee-jerk reflex (4 marks) Explain the difference between excitatory or inhibitory synaptic connections (4 marks) Answer the ‘Check it’ questions on page 117

Must be able to describe (AO1) how the synapse, receptors, neurons and neurotransmitters pass ‘messages’ Must be able to describe (AO1) the components of a neuron.