Topic 5 - Homeostasis

• What is homeostasis?

  Maintaining a stable internal environment despite changing conditions
• Why does the body need to maintain optimal conditions?

  For optimal enzyme action and cell function
• What are internal factors?

  blood Ph

  blood glucose concentration
• What are external factors?

  The amount of fluids you drink

  Room temperature
• What systems does homeostasis use?

  automatic control systems
• How are signals passed along the control system?

  receptor ➔ coordination centre ➔ effector
• What is the role of a receptor?


  Detects changes in the internal or external environment
• What is the role of a coordination centre?

  Interprets changes and organizes a response
• Where are the coordination centres located in the body?

  Brain and spinal cord
• What are the types of effectors?

  muscles and glands
• What does muscles do?

  contract
• What do glands do?

  release hormones
• Which system is fast reacting?

  nervous system
• Why is the nervous system fast reacting?

  it relies on electrical impulses that can travel very quickly.
• What systems acts more generally across the body?

  Endocrine system
• Why is the endocrine system generally across the body?

  it involves releasing hormones into the blood stream which means they spread throughout the entire body.
• What feedback does homeostasis use?

  negative feedback
• Why does homeostasis use negative feedback?

  the levels of something get too high they're brought back down, and whenever the levels of something get too low, they're brought back up.
• What passes along nerve cells?


  electrical impulses
• What is the gap between two neurones called?

  synapse
• What is released across a synapse?

  chemicals
• What is part of the central nervous system?

  brain and spinal cord
• What is the role of a sensory neurone?

  To transfer a signal from a receptor to the CNS
• What is the role of a motor neurone?


  To transfer a signal from the CNS to an effector
• What is the role of a relay neurone?


  To transfer a signal from a sensory neurone to a motor neurone
• What is a reflex?

  an automatic response to a stimulus
• What is the pathway of a reflex arc

  Stimulus → receptor → sensory neurone → relay neurone → motor neurone → synapses → effector → response
• Why are reflexes important?

  They protect us from harm
• How does the endocrine system work?

  Glands are organs that release small chemicals called hormones.

  These chemicals are normally released into the bloodstream, allowing them to travel around the body.

  They can then bind to specific cells that have the correct receptors.

  This will bring about some change within the cells.
• Where is the pituitary gland located?

  base of the brain
• What does the pituitary gland do?

  Secretes hormones to regulate other glands.
• Where is the TSH hormone released from?

  pituitary gland
• Which gland releases thyroxine

  thyroid gland
• Where is the thyroid gland?

  neck
• What is the role of thyroxine?


  controls metabolic rate
• What is the role of adrenaline?

  Stimulates fight or flight response (higher heart rate etc)
• Which organ is adrenaline released from?

  adrenal glands
• What does adrenaline do?

  Increases heart rate

  Increases blood pressure

  Increases blood flow to muscles

  Increases blood sugar (glucose) levels by stimulating the liver to break glycogen down into glucose
• Where is insulin released from?

  pancreas
• Which organ is testosterone released from?

  testes