Homeostasis and Response

• homeostasis is the regulation of the internal conditions to maintain optimum conditions in response to changes in internal/external conditions
• homeostasis maintains optimal conditions for enzyme action and all cell functions
• in the human body, homeostasis controls:

  • blood glucose concentration
  • body temperature
  • water levels
• your internal environment is regulated by your automatic control system
• nervous and chemical responses are regulated by control systems
• control systems include:

  • receptors
  • coordination centres
  • effectors
• receptors are cells which detect stimuli
• stimuli are changes in the environment
• coordination centres are made up of:

  • the brain
  • spinal cord
  • pancreas
• coordination centres receives and processes information from receptors
• effectors include:

  • muscles
  • glands
• effectors produce responses and restores optimum levels
• parts of the nervous system:

  • CNS (Central Nervous System)
  • sensory neurons
  • motor neurons
  • effectors
• The CNS (Central Nervous System) is made up of the brain and spinal cord for vertebrates
• The CNS is connected to the body by sensory and motor neurones in mammals
• sensory neurones carry information as electrical impulses from receptors to CNS
• motor neurones carry electrical impulses from the CNS to effectors
• effectors are your muscles and glands which respond to nervous impulses
• the nervous system allows us to react to our surroundings and to coordinate our behaviour
• pathway of CNS:

  1. stimulus
  2. receptor
  3. coordinator
  4. effector
  5. response
• information from receptors pass alone neurones as electrical impulses to the CNS
• CNS coordinates the response of effectors such as muscles contracting and glands secreting hormones
• reflex arc is the nerve pathway which follows a reflex action from the receptor to effector
• synapses is the connection between two neurones
• synapses are the nerve signals transferred by chemicals
• reflexes are rapid, automatic responses to certain stimuli
• reflexes reduces the chance of injury
• reflexes allow adrenaline to automatically release in a shock
• reflexes dont involve the conscious part of the brain
• hormones are chemical molecules released directly into the blood
• hormones are carried in the blood to other parts of the body but they only affect some organs, called target organs
• target organs are the organs that are affected by hormones
• hormones control organs and cells that need constant adjustment
• hormones are produced and secreted by endocrine glands
• endocrine glands make up the endocrine system
• hormones have long lasting effects
• examples of glands in the endocrine system:

  • pituitary gland
  • thyroid
  • adrenal gland
  • pancreas
  • ovaries
  • testes
• the pituitary gland produces a lot of hormones that regulate body conditions

  it is also called the master gland as the hormones act on other glands to make them release hormones
• the thyroid gland produces thyroxine which regulates:

  • metabolism
  • heart rate
  • temperature
• the adrenal gland produces adrenaline which prepares the body for the fight or flight response