Science & Technology in Action

2nd Edition

The Human Nervous System

Health Research Board

The lesson describes how the nervous system is formed, how signals are transmitted from cell to cell, the role of neurotransmitters and the effects and treatment of disorders of the nervous system such as Parkinson’s disease.
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Contains the full lesson along with a supporting toolkit, including teachers’ notes.

Lesson excerpt

Our bodies have over ten million million (1013) living cells which must work in co-operation for us to live and grow. To co-operate they must communicate. The brain, spinal cord, nerves, sense organs and receptors are the vital parts of the human nervous system that facilitate communication between our cells. In this lesson we will look at the formation and function of the nervous system. 

How is our nervous system formed?
The central nervous system (CNS) begins to form halfway into the embryonic period, 28 days after conception. The development of the central nervous system is the first major event in the formation of organs in the developing embryo.

The nervous system develops from the ectoderm , the outer of the three germ layers. The skeletal system develops from themesoderm , the middle of the germ layers, with the cranium and vertebrae forming a protective cover around the brain and spinal cord.

How are messages transferred?
The brain is the main command centre sending and receiving signals to and from all parts of the body, storing information and giving us the amazing ability of self-awareness, i.e. consciousness.

The spinal cord is a complex dual carriageway. Information passes rapidly between the brain and almost all the organs of the body. 

Signals are conducted along specialised cells called neurons. There are three types of neuron; sensory neurons , motor neurons and interneurons. The neurons do not connect directly with one another; there is a small gap between them, called the synaptic cleft . 

True or False?

  1. The brain and spinal cord form the central nervous system.
  2. The spinal cord connects the brain to all the sense organs.
  3. Neurons are specialised cells to transfer information signals.
  4. Motor neurons carry signals to the central nervous system.
  5. Interneurons carry signals from the central nervous system.
  6. Signals are transferred to target cells by diffusion of chemicals.
  7. Some motor and sensory neurons may be about a metre in length.
  8. The axon is the time-saving feature for rapid information transfer.
  9. A refl ex arc is a long signal pathway involved in slow responses.
  10. There are 33 vertebrae and 33 pairs of spinal nerves.
  11. All organs below the head connect to the brain by the spinal cord.