The Central Nervous System and Neurons in Human Behaviour

• Central nervous system


  Made up of brain and spinal cord, and the neurons within these structures
• Central nervous system


  • Organises communication within the body
  • Co-ordinates activities
• Brain


  Centre of the nervous system which controls all the organs and systems of the body
• Spinal cord


  Collection of neurons that communicates between the brain and the body, sending information inwards to the brain and outwards to the body
• Neurons


  Specialized nerve cells transmitting nerve impulses around the body
• Parts of a neuron

  • Cell body
  • Dendrites
  • Axon
  • Nodes of Ranvier
  • Axon terminals
  • Terminal buttons
• Cell body


  • Main part of the cell where the nucleus is
  • Energy is made here
• Dendrites


  • Branches attached to the cell body
  • Found at the top end / the "beginning" of the neuron
• Axon


  • Long thin structure
  • Coated in a myelin sheath: a layer of electrical insulation made of fatty tissue
• Nodes of Ranvier


  • Gaps in the myelin sheath around the axon
• Axon terminals


  • Branches at the end of the axon
  • The "end" of the neuron
• Terminal buttons


  • Bulb like structures at the very end of the neurons
  • They contain neurotransmitters
• Neurotransmitters


  Tiny chemicals that pass messages in the synapses between neurons
• Neuron


  Transmits messages around the body
• There are networks of millions of neurons in your brain and body that are all connected and communicate with each other
• Communication along neurons

  1. Dendrite receives a message, often from another neuron

  2. Triggers an action potential: an electronic message within the cell body

  3. Action potential travels down the axon

  4. Action potential reaches the axon terminals, and the terminal buttons at the end of the axon terminals

  5. Terminal buttons will pass this message to the next part of the body
• Axon


  • Myelin sheath and nodes of Ranvier help to make the process of action potential travel very fast
• If the message is passed to another neuron, then stages 1-5 will happen again
• Synaptic transmission


  Communication between neurons
• Synapses


  • Gaps in between neurons
  • Electrical messages cannot travel in these spaces
  • A different type of message is sent using neurotransmitters (a chemical message)
• Action potential


  • The electrical impulse that travels along the axon and acts as a form of message
  • Created as a result of neurotransmitters attaching to receptors on the dendrite of the neuron
  • Causes the terminal buttons to release neurotransmitters into the next synapse
• Synaptic gap / cleft


  The tiny space between the terminal buttons of one neuron and the dendrite of the next neuron
• Presynaptic neuron


  The neuron where a chemical message starts (the neuron that releases the neurotransmitters)
• Postsynaptic neuron


  The neuron where a chemical message travels to (the neuron that receives the neurotransmitters)
• Receptors


  Sites on the dendrites of the neuron that are designed to bond to and receive particular neurotransmitters
• Reuptake


  • The process in which neurotransmitters are absorbed back into the presynaptic neuron and recycled once the action potential has been created on the post synaptic neurone
  • Stops the message and turns off the neuron in preparation for the next action potential
• Neurotransmitters


  Allow for communication between neurons in the synaptic gap
• Functions of different neurotransmitters


  • Regulate different feelings and behaviours
  • Dopamine is associated with pleasure, reward and reinforcement, involved in addictive behaviours, posture and control of movement
  • Serotonin is involved with mood control and feelings such as happiness, also involved in pain, sleep, temperature and hunger
  • Norepinephrine (noradrenaline) is associated with the fight and flight response, with attention, and being ready for action
  • Acetylcholine stimulates muscle contraction and is involved in motor control and movement, linked to memory, thinking and learning, also involved in expressions of some emotions e.g. anger and sexuality
• Recreational drugs


  Drugs taken for pleasure and enjoyment, different from medicinal drugs prescribed to treat conditions or mental disorders
• Psychoactive drugs


  Recreational drugs that alter brain function and change mood, perception or conscious experience
• Recreational drugs have been used by humans of many different cultures for centuries, in order to achieve a different state of consciousness
• Mode of action of drugs

  How drugs affect the brain and synapses through their effects on neurotransmitters
• Addictive drugs


  • Nicotine
  • Alcohol
  • Cocaine
• Reward pathways


  Chains of neurons stimulated by behaviours needed for species survival, e.g. eating food and having sex, often involving dopamine
• Stimulation of reward pathways


  Makes us feel good and encourages us to repeat these behaviours
• Addictive drugs


  Hi-jack reward pathways and can rewire the brain, so that it makes the individual seek out the addictive substance (sometimes instead of food or sex)
• Different drugs have different modes of action, involving increasing particular neurotransmitters
• Drug


  Substance that has a physiological effect on the body
• Drugs covered

  • Alcohol
  • Cocaine
  • Nicotine
  • MDMA
• Alcohol


  • Short term effects: Varies depending on individual, mood and environment. Can reduce anxiety and inhibitions or make individual more aggressive
  • Long term effects: Can be addictive, lead to liver failure and damage brain and nervous system