Nervous system and endocrine system

• The nervous system 


  Specialised network of cells in human body and is our primary internal communication system

  Based on electrical and chemical signals

  2 main functions:

  • Collect process and respond to information in environment
  • Cor ordinate working of different organs and cells in body

  It is divided into two subsystems:

  • central nervous system
  • peripheral nervous system
• Central nervous system


  Made up of brain and spinal cord

  Brain:

  • Centre of all conscious awareness
  • outer layer (cerebral cortex) only 3mm thick and covers brain like orange peel
  • Only found in mammals

  Spinal cord:

  • Extension of brain
  • Passes messages to and from the brain and connects nerves to PNS
  • Responsible for reflex actions such as pulling your hand away from a hot plate
• Peripheral nervous system


  Transmits messages via millions of neutrons to and from central nervous system - PNS further divided into

  • Autonomous nervous system - governs vital functions in the body such as breathing, heart rate digestion, sexual arousal and stress responses
  • Somatic nervous system - governs muscle movements and receives information from sensory receptors
• The endocrine system - glands and hormones


  Works alongside nervous system to control vital functions in the body - acts more slowly than the nervous system but has very widespread and powerful effects

  Various glands eg thyroid gland produce hormones -secreted into bloodstream - affect any cell in body that has receptor for that particular hormone

  eg thyroid produces thyroxine - increases heart rate and metabolic rates

  Pituitary gland - controls release of hormones from all other endocrine glands in body
• Endocrine and ANS working together - fight or flight 


  • Stressor perceived -hypothalamus activates pituitary gland - triggers activity in sympathetic branch of autonomic nervous system - ANS changes from normal resting state (parasympathetic state) to phsysiologically aroused sympathetic state
  • Adrenaline released from the adrenal medulla into bloodstream - triggers physiological changes in body which creates physiological arousal necessary for fight/flight response
• • Happens in instant as soon as threat is detected, automatic
  • Once threat has passed the parasympathetic branch of ANS works in opposition to sympathetic system- rest and digest