the nervous system

• Definition: Nervous system?

  a specialised network of cells that is our primary internal communication system
• What is the central nervous system?

  the part of the nervous system that includes the brain and spinal cord, it's the origin of complex commands and decisions
• how is the brain involved in the CNS?

  the brain is our centre of conscious awareness and is divided into 2 hemispheres (left and right) which are separated by the corpus collosum
• how is the spinal cord involved in the nervous system?

  the spinal cord is an extension of the brain that is responsible for reflex actions
• what is the function of the CNS?

  to pass messages to and from the brain, and to connect nerves to the PNS
• what is the function of the peripheral nervous system?

  contains all the nerves that lie outside the CNS, that connect the CNS to organs
• What are the 2 subdivisions of the PNS?

  the autonomic nervous system and the somatic nervous system
• what is the function of the ANS?

  Communicates with internal organs and glands, and governs involuntary functions, such as breathing and heart rate
• what is the function of the SNS?

  controls muscle and voluntary movement after receiving info from sensory receptors
• what are the 2 subdivisions of the ANS?

  Sympathetic and parasympathetic.
• what is the function of the sympathetic nervous system?

  to regulate the flight or fight response
• how does the sympathetic system regulate flight or fight?

  by preparing the body to deal with potential threats and triggering a response of increased breathing, heart rate, blood flow to the muscles
• what is the function of the parasympathetic system?

  to maintain normal body function, such as slowing heart and breathing rate after threats have passed
• What are the structures in a neuron?

  Cell body (soma), nucleus, describes, axon, myelin sheath, nodes of Ranvier, axon terminals
• Where are sensory neurones found?

  Receptors in the PNS and carrying nerves between the spinal cord and brain
• What is the function of sensory neurones?

  • To take nerve impulses to the brain (are translated into sensations of vision, hearing etc)
  • Nerve impulses to the spinal cord for fast reflexes
• What is the location of relay neurons?

  • Between sensory input and motor responses
  • In the brain and spinal cord
• What is the function of relay neurons?

  To allow sensory and motor neurons to communicate on the action taken to a stimuli
• What is the location of motor neurons?

  Connecting CNS and muscle movement
• What is the function of motor neurons?

  Releases a transmitter (acetylcholine) to trigger a response at an effector
• What are the stages of synaptic transmission?

  1. activation of a neuron creates a positive charge in the cell, creating an action potential
  2. arrival of AP at pre-synaptic neuron released neurotransmitters from the synaptic vesicle
  3. neurotransmitter diffuses across the synaptic cleft
  4. neurotransmitters bind to the post-synaptic receptors
  5. signal transmitted at post-synaptic dendrites
• what systems work during fight or flight response?

  the endocrine and autonomic nervous system
• what do the sympathetic and parasympathetic systems affect?

  • Salivation
  • Lacrimation
  • Urination
  • Digestion
  • Defection
• What is the reflex arc?

  Stimulus -> receptor -> sensory neuron -> relay neuron (in CNS) -> motor neuron -> effector -> response
• what is the process of synaptic transmission?

  1. neuron activated, so inside cell becomes positively charged and creates an action potential
  2. arrival of action potential at pre-synaptic neuron releases neurotransmitter from synaptic vesicle
  3. neurotransmitter diffuses across synaptic cleft
  4. neurotransmitter binds to post-synaptic receptors
  5. signal is transmitted
• what are neurotransmitters?


  chemicals that diffuse across synapses, each have own specific molecular shapes
• what is acetylcholine?


  neurotransmitter found at end of motor neurone that cause muscles to contract when released
• what is excitation?

  Activation or stimulation of a neuron or muscle cell. e.g: adrenaline makes neurone more positive, so more likely to fire
• what is inhibition?

  suppression of a neuron, eg: serotonin makes neuron more negative so less likely to fire
• what is summation?

  • whether or not a neuron is likely to fire
  • more excitatory neurotransmitters, more positively charged neuron so the neuron fires the impulse
  • and visa versa