PSY1EFP: EXPERIMENTAL FOUNDATIONS OF PSYCHOLOGICAL SCIENCE BRAIN-BEHAVIOUR RELATIONSHIPS SESSION 1: HOW DOES THE NERVOUS SYSTEM OPERATE? Session 1: How does the nervous system operate? Today’s big question: Myelin is like butter: what happens when it melts? In this face to face session we will: • Distinguish between the two basic divisions of the nervous system. • Distinguish between the functions of distinct types of neurons. • Describe the structure of the neuron. • Describe the electrical and chemical changes that occur when neurons communicate. • Identify the major neurotransmitters and their primary functions. • Clinical case example: Multiple Sclerosis. The nervous system has two basic divisions Central nervous system (CNS): brain and spinal cord Peripheral nervous system (PNS): all nerve cells in the body that are not part of the central nervous system. The peripheral nervous system includes the somatic and autonomic nervous systems. Neurons are specialized for communication Nerve cells are powered by electrical impulses and communicate with other nerve cells through chemical signals. Three basic phases - Reception: Chemical signals are received from neighbouring neurons. Integration: Incoming signals are assessed. Transmission: Signals are passed on to other receiving neurons. Types of neurons Sensory neurons: These neurons detect information from the physical world and pass that information to the brain. - Somatosensory nerves provide information from the skin and muscles. Motor neurons: These neurons direct muscles to contract or relax, thereby producing movement. Interneurons: These neurons communicate within local or short-distance circuits. Neuron Structure - Dendrite: detects chemical signals from neighbouring neurons Cell body (soma): collects and integrates information Axon: transmits electrical impulses Terminal buttons: bulbous end of an axon Synapse: supports chemical communication between neurons Synaptic cleft: narrow gap between terminal button (presynaptic membrane) and dendrite (postsynaptic membrane) of neighbouring neuron Myelin sheath: encases and insulates axons Composed of glial cells Nodes of Ranvier: Spaces between glial cells The resting membrane potential is negatively charged Resting membrane potential: the electrical charge of a neuron when it is not active - Polarized: when a neuron has more negative ions inside it than outside Polarization: creates the electrical energy necessary to power the firing of the neuron Action potentials cause neural communication Action potential (neural firing): the electrical signal that passes along the axon and subsequently causes the release of chemicals from the terminal buttons Case example: Multiple sclerosis (MS) is an autoimmune disease Symptoms of MS/ Loss of myelin and its consequences Neurotransmitters bind to receptors across the synapse Neurotransmitters: chemical substances that transmit signals from one neuron to another Receptors: In neurons, specialized protein molecules on the postsynaptic membrane; neurotransmitters bind to these molecules after passing across the synapse. - The binding of a neurotransmitter with a receptor produces an excitatory or inhibitory signal. Neurotransmitters Influence Mental Activity and Behaviour Drugs and toxins can alter neurotransmitter action. - Agonists: enhance the actions of neurotransmitters Antagonists: inhibit the actions of neurotransmitters Researchers often inject agonists or antagonists into animals’ brains to assess how neurotransmitters affect behaviour.