neurones

• A neuron

  Nerve cells that process & transmit messages electrically & chemically
• Neurone structure

  Cell body

  Nucleus

  Dendrites

  Axon

  Myelin Sheath

  Terminal buttons

  
• Cell body


  Contains the nucleus
• Dendrites

  Extended from the neuron cell body & receive messages from the other neurons & carry the nerve impulses towards the cell body
• Axon


  Transmits electrical impulses away from the cell body towards the terminal buttons

  Range from length form a fraction of a cm to 1m

  Covered in a fatty segment called the myelin sheath
• Myelin sheath


  Protects the axon & accelerates the transmission of electrical signals along the axon as the electrical impulses have to jump over the gaps along the axon
• Terminal buttons


  located at the end of the neuron and are responsible for housing neurotransmitters in vesicles &sending the signal on to other neurons

  At the end of the terminal button is a gap known as a synapse
• Sensory neurones

  Have long dendrites & short axons
• Sensory neuron function


  Carry messages from the peripheral NS to the central NS

  Processed in the somatosensory cortex in the parietal lobe

  Carry messages from the receptors in the body such as organs, muscles, skin or joints send messages to the brain & spinal cord
• Relay neurones


  Only found in visual system, brain & spinal cord

  Short dendrites & either long or short axons
• Relay neuron function


  Transfer messages between sensory & motor neurones: a bridge between the two
• Motor neurones


  Connect central NS to effectors

  Short dendrites & long axons
• Motor neuron function


  Carry messages away from the brain stem & spinal cord to organs & muscles in the body
• Neuron in resting state


  The inside of a neuron is chemically negatively charged compared to the outside
• Action potential along a neuron

  When the neuron is stimulated the charge inside becomes positive for a split second causing an action potential to occur

  Creating an electrical impulse to travel along the axon of the neuron

  The resting state is then re-established back to negative inside & positive outside
• Reflex arc


  A stimulus is detected by receptor cells in the peripheral NS

  The peripheral NS passes on the information to the brain stem via sensory neurones

  In the brain stem the sensory neuron connects with the relay neuron which transfers the message to the motor neuron

  The motor neuron then carries this message back to an effector