nervous system and endocrine system

• nervous system -


  specialised network of cells and our primary internal communication

  consists of the central nervous system and peripheral nervous system

  based on electrical and chemical systems
• nervous systems 2 functions -

  • collect, process and respond to information in the environment
  • co-ordinatie the working of different organs and cells in the body
• central nervous system (CNS) -

  • brain is centre of all conscious awareness
  • outer layer is the cerebral cortex - 3mm thick - covers brain like an orange peel
  • highly developed in humans and distinguishes our higher mental functions from other animals
  • divided into 2 hemispheres
  • acts very rapidly
  • spinal cord is extension of the brain - passes messages to and from the brain and connects nerves to the PNS - responsible for reflex actions
• peripheral nervous system (PNS) -

  • sends info to CNS from the outside world and transmits messages from the CNS to muscles and glands in the body
  • subdivided into: autonomic nervous system (ANS) and somatic nervous system (SNS)
• endocrine system -

  • instructs glands to release hormones directly into bloodstream
  • effects any cell in the body that has a receptor for that particular hormone - most effect more than one organ - leading to many diverse and powerful responses
  • communicates via chemicals
  • acts more slowly than the nervous system
• endocrine system example hormones -

  • thyroid gland produces thyroxine - increases heart rate - also affects cells throughout body increasing metabolic rates - in turn affects growth rate
  • key endocrine gland is pituitary gland - located in brain - 'master gland' because it controls the release of hormones from all the other endocrine glands in body
• gland - 


  organ in the body that synthesises substances such as hormones
• hormone - 


  biochemical substance that circulates in the blood but only affects target organs

  produced in large quantities but disappear quickly

  effects very powerful
• somatic nervous system (SNS) -

  • transmits info from receptor cells in the sense organs to the CNS
  • also receives info from the CNS that directs muscles to act
  • governs muscle movement and receives information from sensory receptors
• autonomic nervous system (ANS) -

  • transmits info to and from internal bodily organs
  • system operates involuntarily
  • governs vital functions in the body such as breathing, heart rate, digestion, sexual arousal and stress response
  • 2 main divisions: sympathetic and parasympathetic
• fight or flight response -

  
  

  endocrine system and ANS work in parallel - during stressful events

  1. stressors perceived
  2. hypothalamus activates pituitary gland
  3. triggers activity in sympathetic branch of the autonomic nervous system
  4. ANS changes from normal resting state (parasympathetic state) to psychologically aroused sympathetic state
• sympathetic state -

  • increases heart rate
  • increases breathing rate
  • dilates pupils
  • inhibits digestion
  • inhibits saliva production
  • contracts rectum
• parasympathetic state (normal resting state) -

  • decreases heart rate
  • decreases breathing rate
  • constricts pupils
  • stimulates digestion
  • stimulates saliva production
  • relaxes rectum
• adrenaline -

  • stress hormone
  • released from adrenal medulla into bloodstream
  • triggers physiological changes in the body (eg increased heart rate) which creates the physiological arousal necessary for the fight or flight response
• parasympathetic action -

  • once threat has passed - parasympathetic nervous system returns body to its resting state
  • works in opposition to sympathetic nervous system - actions are antagonistic to sympathetic system
  • parasympathetic system acts as a a 'brake' and reduced the activities of the body that were increased by the actions of the sympathetic branch