Edexcel International A Level Biology

Revision Notes

8.13 Nervous & Hormonal Coordination

Test Yourself

Nervous & Hormonal Coordination

  • Both plants and animals must respond to changes in their external and internal environments in order to survive
    • They need to
      • Find favourable external conditions e.g. avoiding locations that are too hot or cold
      • Find food
      • Avoid harm e.g. from predators or high blood glucose
  • While plants use chemical signals to co-ordinate responses to stimuli, animals bring about coordination by both nervous and hormonal control
  • Changes in the environment, or stimuli (singular stimulus) are detected by specialised receptor cells 
    • Receptor cells are located in the sense organs e.g. the nose and eyes
    • Receptor cells can also be found inside the body e.g. pressure receptors in the blood vessels
  • Receptor cells send signals via either the nervous system or the hormonal system to the body's co-ordination centres in the brain or spinal cord
  • Signals are then sent on to the parts of the body which respond, known as the effectors
    • Effectors can be either muscles or glands e.g.
      • An arm muscle would respond to a hot surface by contracting to move the hand away
      • The pancreas responds to high blood sugar by secreting insulin

Sensory receptors of the body

Receptors are cells that detect stimuli in the internal and external environment

The nervous system

  • The human nervous system consists of
    • Central nervous system (CNS) – the brain and spinal cord
    • Peripheral nervous system (PNS) – all of the nerves in the body
  • The nervous system allows detection of stimuli in our surroundings and the coordination of the body's responses to the stimuli
  • Information is sent through the nervous system in the form of electrical impulses that pass along nerve cells known as neurones 
    • A bundle of neurones is known as a nerve
    • There are different types of neurones including sensory neurones, relay neurones, and motor neurones
  • The nerves connect the receptors in the sense organs with the CNS, and connect the CNS with effectors
    • The CNS acts as a central coordinating centre for the impulses that come in from, and are sent out to, any part of the body
  • Nerve impulses pass through the nervous system along the following pathway

stimulus rightwards arrow receptor rightwards arrow sensory neurone rightwards arrow CNS rightwards arrowmotor neurone rightwards arroweffector

  • An example of this nerve pathway in action might be

hot surface rightwards arrow pain receptor in skin of hand rightwards arrow sensory neurone rightwards arrowCNS rightwards arrow motor neurone rightwards arrow arm muscle

    • The muscle in the arm responds by contracting to move the hand away from the hot surface

The human nervous system

The nervous system allows the detection of stimuli and the co-ordination of appropriate responses

The hormonal system

  • Hormones are chemical substances produced by endocrine glands and carried by the blood
    • Endocrine glands are ductless and secrete hormones directly into the blood 
    • Hormones are sometimes known as chemical messengers 
  • Hormones transmit information from one part of an organism to another and bring about change by altering the activity of one or more specific target organs
    • Hormones can leave the blood and bind to specific receptors on the cell surface membranes of target organs
  • Hormones are slower in action than nerve impulses and are therefore used to control functions that do not need instant responses
  • Endocrine glands that produces hormones in animals are known collectively as the endocrine system
    • Endocrine glands can be stimulated to secrete hormones by the action of another hormone or by the arrival of a nerve impulse
  • The pathway of hormone action is as follows

stimulus rightwards arrow receptor rightwards arrow hormone rightwards arrow spaceeffector

  • An example of this pathway in action might be

high blood sugar rightwards arrow cells in the pancreas rightwards arrow insulin rightwards arrow liver cells 

    • The liver cells respond to insulin by converting glucose into glycogen

The major endocrine glands in the body

Hormones are secreted into the blood by the endocrine glands 

Comparison of Nervous and Hormonal control Table

Comparison of Nervous & Hormonal Control table

You've read 0 of your 0 free revision notes

Get unlimited access

to absolutely everything:

  • Downloadable PDFs
  • Unlimited Revision Notes
  • Topic Questions
  • Past Papers
  • Model Answers
  • Videos (Maths and Science)

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Naomi H

Author: Naomi H

Naomi graduated from the University of Oxford with a degree in Biological Sciences. She has 8 years of classroom experience teaching Key Stage 3 up to A-Level biology, and is currently a tutor and A-Level examiner. Naomi especially enjoys creating resources that enable students to build a solid understanding of subject content, while also connecting their knowledge with biology’s exciting, real-world applications.