Neurobiology

• The Perphiral nervous system is made up of the Autonomic nervous system and the Somatic nervous system.

  Autonomic is:

  • Sympathetic (fight or flight)
  • Parasympathetic (rest and digest)
• What affects does Sympathetic nervous system have on the body?

  • Increase heart rate
  • Increase breathing
  • Decrease parisalsis and intestinal secretions

  What affects does Parasympathetic nervous system have on the body?

  • Decrease heart rate
  • Decrease breathing
  • Increase parisalsis and intentinal secretions
• The main parts of the brain are the cerebrum which controls thoughts and memories, the cerebellum which controls balance and co-ordination, and the medulla which controls breathing and heart rate.
• The corpus callosum connects the two hemispheres of the brain together.

  The left hemisphere deals with information from the right visual field and controls the right side of the body.

  The right hemisphere deals with information from the left visual field and controls the left side of the body.
• The cerebral cortex is the outer layer of the cerebrum. It receives information, co-ordinates voluntary movement and makes decisions based on past experiences.

  There are localisation of the functions of the cerebral cortex. There are:

  • Sensory areas - deals with conintuous input form the senses
  • Motor areas - linked to different parts of the body to produce responses
  • Association areas - involved in language processing, personality, imagination and intelligence
• Memory incolves retaining, storage and retrieval of information. Memories include past experiences, knowledge and thoughts.

  Information goes from sensory memory to short term memory and is then either discarded or encoded into the long term memory.
• • Sensory memory is raw data which is received constantly from our sense organs. This is only retained for a few seconds before being discarded or encoded into the short term memory.
  • Short term memory has a limited capacity of around 7 pieces of information and only lasts a short period of time before being discarded or encoded into the long term memory.
  • Long term memory has an infinite capacity. Information from the STM is converted into a form which can be stored by encoding.
• To increase the capacity of the STM you can use:

  • Chunking - converting several pieces of information into one piece of information
  • Rehearsal - repeating information several times

  To encode information from STM to LTM you can use:

  • Rehearsal
  • Organisation - putting information into logical categories, making it easier to recall
  • Elaboration - an addition of further information or meaning which results in the information being more meaningful and interesting
• Retrieval on information from the LTM can be helped by information which is linked to the time or the place of when the information was encoded. This is called contextual cues.
• The direction of an impulse goes from the Dendrites to Cell body to Axon.
• The myelin sheath surrounds the axon. This insulates the axon and increases the speed of impulse transmission and prevents leakage of impulses which would weaken the conduction of signals.

  Glial cells produce the myelin sheath and surround the axons of nerve cells to provide physical support.
• Neurotransmitters relay impulses across the synaptic cleft. The impulse goes from the presynaptic neuron (axon) to the post synaptic neuron (dendrite).

  Neurotransmitters are stored in vesicles in the presynaptic neuron and are released into the synaptic cleft. Neurotransmitters will diffuse across the synaptic cleft and bind to receptors on the postsynaptic neuron.
• A minimum number of neurotransmitter molecules must attach to receptors on the post synaptic membrane in order for an impulse to be transmitted. This is the threshold value.
• The summation of a series of weak stimuli can realse enough neurotransmitter to reach the threshold value and transmit an impulse. Converging neural pathways can release enough neurotransmitter molecules.
• There are 3 types of neural pathways:

  1. Converging - impulses form several neurons travel to one neuron. This increases sensitivity.
  2. Diverging - impulses from one neuron travel to several neurons so the impulse affects more than one destination as the same time.
  3. Reverberating - neurons later in the pathway link with earlier neurons, sending the impulse back through the pathway.
• Endorphins are neurotransmitters that stimulate neurons involved in reducing the intensity of pain. Endorphins attack to neurons connected to pain receptors and act as inhibitors, making it less likely for the pain signals to be transmitted.

  Production is increased in response to:

  • Severe injury
  • Prolonged or continuous exercise
  • Stress
  • Certain foods
• Dopamine is a neurotransmitter that induces the feeling of pleasure and reinforces particular behaviour by activating the reward pathway in the brain.

  The reward pathway is activated when an individual engages in a behaviour that is beneficial to them.
• Neurotransmitters need to be removed to prevent continuous stimulation. The two ways to remove them are:

  • Degredation - broken down by enzymes
  • Reuptake - reabsorbed directly into the presynaptic membrane
• There are drugs which are used to treat neurotransmitter-related disorders. They are either:

  • Agonists - mimics the action of a neurotransmitter at a synapse
  • Antagonists - blocks the action of a neurotransmitter at a synapse
  • Enzyme inhibitors - cause an enhanced affect
• Reccreational drugs are taken either because they produce pleasurable sensations, enhance other experiences or help cope with pain. These are either agonists or antagonists and can affect an individuals:

  • mood
  • cognition
  • perception
  • behaviour
• Drug addication is caused by repeated use of drugs that act as antagonists. They block specific receptors causing the nervous system to increase both sensitivity and number of these receptors. This sensitisation leads to addiction.

  Drug tolerance is caused by repeated use of drugs that act as agonists. They stimulate specific receptors causing the nervous system to decrease sensitibity and number of these receptors. This desensitisation leads to drug tolerance where the individual must take more of the drug to get an affect.