Edexcel IGCSE Biology

Revision Notes

2.10.5 Co-ordination Systems in Humans

The Human Nervous System & Endocrine System

  • There are two different control systems in humans that work together to help us respond to stimuli. These are:
    • The nervous system
    • The hormonal system (also known as the endocrine system)
  • Changes in our external environment or in the internal environment of our bodies act as stimuli
  • The nervous and hormonal systems coordinate a suitable response to these stimuli
  • This allows us to make sense of our surroundings, to respond to the changes that occur in our surroundings and coordinate and regulate body functions

The nervous system

  • Information is sent through the nervous system as electrical impulses – these are electrical signals that pass along nerve cells known as neurones
  • These impulses travel along neurones at very high speeds (up to 100 metres per second)
  • This allows rapid responses to stimuli (e.g. the withdrawal reflex that causes you to move your hand away extremely quickly when it touches a flame)
  • The nervous system coordinates the activities of sensory receptors (eg. those in the eye), decision-making centres in the central nervous system (CNS), and effectors such as muscles and glands
  • The nervous system is used to control functions that need instant (or very rapid) responses

The human nervous system, IGCSE & GCSE Biology revision notes
The human nervous system

The endocrine system

  • Information is sent through the endocrine (hormonal) system as chemical substances known as hormones
  • Hormones are carried by the blood and can therefore circulate around the whole body
  • Hormones transmit information from one part of the organism to another and bring about a change (they provide a signal that triggers a response)
  • They alter the activity of one or more specific target organs
  • Hormones are used to control functions that do not need instant responses
  • Hormones are produced by endocrine glands
  • The endocrine glands that produce hormones in animals are known collectively as the endocrine system
    • A gland is a group of cells that produces and releases one or more substances (a process known as secretion)

Features of the Nervous System and the Endocrine System Table

Comparing the features of the nervous & endocrine system table, downloadable AS & A Level Biology revision notes

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