The cns

• Central nervous system (CNS)


  Made up of the brain and spinal cord
• Functions of the CNS

  1. Receives sensory information

  2. Interprets sensory information

  3. Acts on sensory information
• Brain


  • Involved in many different physiological processes
  • Has three main functions: take information from the senses, interpret it, and act on it
  • Outer layer (cerebral cortex) is involved in higher order thinking, such as problem solving
  • Some parts are more primitive and concerned with vital functioning
• Spinal cord


  • Receives and transmits information to and from the brain to the peripheral nerves
  • Responsible for actions (which do not involve the brain), such as pulling your hand away from something hot
• Peripheral nervous system (PNS)


  • Relays information from the outside world, muscles and organs via neurons TO the CNS
  • Sends messages FROM the CNS to the muscles and glands in the body
• Parts of the PNS

  • Somatic nervous system
  • Autonomic nervous system
• Somatic nervous system (SNS)


  • Nerves that we actively control
  • Receives information from sensory receptors and sends this information to the CNS which in turn relays this information to motor neurons to control muscle movement
• Autonomic nervous system (ANS)


  • Connects the CNS to the internal organs of which we do not have direct control
  • Works automatically, we do not have to think in order for the nerves to work
• Parts of the ANS


  • Sympathetic nervous system
  • Parasympathetic nervous system
• Parasympathetic nervous system (PNS)

  • Prepares the body for rest and digest
  • Slows the heartbeat down and reduces blood pressure
  • Directs tissue repair
• Sympathetic nervous system (SNS)

  • Prepares the body to spend energy, particularly in an emergency situation (fight or flight)
  • Increases heart rate and blood pressure, dilates blood vessels in the muscles and legs, constricts blood vessels in the mouth
  • Releases sugar from the liver into the blood for energy
• Parasympathetic vs Sympathetic responses

  Parasympathetic: constricts pupils, increases salivation, decreases respiration rate, decreases heart rate, dilates blood vessels, stimulates digestive processes, contracts bladder muscles, stimulates defecation

  Sympathetic: dilates pupils, decreases salivation, increases respiration rate, increases heart rate, constricts blood vessels, relaxes bladder muscles, inhibits defecation
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• Central nervous system (CNS)


  Made up of the brain and spinal cord
• CNS


  • Contains all the vital and reflex control centres
  • Responsible for processing and coordinating information
• Brain


  • Involved in many different physiological processes
  • Has three main functions: to take information from the world, interpret it, and act on it
• Brain


  • Some parts are more primitive and concerned with vital functioning
  • The cerebral cortex is involved in higher order thinking, such as problem solving
• Peripheral nervous system


  Receives and transmits information to and from the CNS to the peripheral receptors and effectors
• Peripheral nervous system


  • Responsible for automatic actions (which do not involve the brain), such as pulling your hand away from something hot
  • The brain does register the pain but this is after your hand has been removed
• Parts of the peripheral nervous system

  • Somatic nervous system
  • Autonomic nervous system
• Somatic nervous system


  • The nerves that we actively control
  • Receives information from sensory receptors and sends this to the CNS which then relays it to motor neurons to control muscle movement
• Autonomic nervous system


  • Connects the CNS to the internal organs of which we do not have direct control
  • Works automatically, the brain does this for us (e.g. telling the heart to beat or the digestive system to release enzymes)
• Subdivisions of the autonomic nervous system


  • Sympathetic nervous system
  • Parasympathetic nervous system
• Parasympathetic nervous system


  • Relaxes the body after the sympathetic nervous system has prepared it for action
  • Helps the body rest, digest, and direct tissue repair
• Sympathetic nervous system


  Prepares the body for action (e.g. increases heart rate, blood pressure, respiration rate)
• Parasympathetic nervous system


  Slows the body down after the emergency has passed (e.g. decreases heart rate, blood pressure, increases digestion)
• The sympathetic branch also stimulates the endocrine system to begin releasing hormones
• The PNS is active when we are relaxed