Nervous Communication

• The nervous system is made up of a complex network of cells called neurons.
• What are the three main types of neurons?

  1. Sensory neurons
  2. Relay neurons
  3. Motor neurons
• Sensory neurons transmit electrical impulses from receptors to the central nervous system.
• Motor neurons transmit electrical impulses from the central nervous system to effectors
• Relay neurons transmit electrical impulses between sensory neurons and motor neurons.
• The nervous system:

  A stimulus is detected by receptor cells and an electrical impulse is sent along a sensory neuron. When the electrical impulse reaches the end of the neuron chemicals called neurotransmitters take the information across to the next neuron, which then sends an electrical impulse. The central nervous system processes this information and sends impulses along motor neurons to an effector.
• What is the role of the nervous system?

  The Nervous System collects, processes and responds to information that it receives from the environment.
• What is the peripheral nervous system?

  The Peripheral Nervous System is made up of millions of neurons that connect the central nervous system to the rest of the body.
• What is the spinal cord?

  The Spinal Cord is an extension of the brain. It is responsible for reflex actions.
• What is the somatic nervous system?

  The Somatic Nervous System controls conscious activities like running and playing games.
• What is the autonomic nervous system?

  The Autonomic Nervous System (ANS) controls unconscious activities like digestion.
• What is the Sympathetic Nervous System?

  The Sympathetic Nervous System (SNS) increases bodily activities, getting the body ready for action. It is the fight or flight system. E.g. increased heart rate, sweating etc.
• What is the Parasympathetic Nervous System?

  The Parasympathetic Nervous System (PaNS) decreases bodily activities, calming down the body. It is the rest and digest system. E.g. decreases heart rate, sweating etc.
• What is a reflex?

  A reflex is an automatic and involuntary action, there is no conscious thought involved and it cannot be stopped.
• Reflexes are short lived reactions.
• Reflexes are controlled by simple neurone pathways, these pathways are usually localised to the part of the body where the reflex occurs.
• The reflex arc:

  This response starts with a receptor which detects the stimulus to respond to, this receptor makes a signal which is passed onto a sensory neurone which carries the signal into the spinal cord where it reaches a relay neuron. A relay neuron is an intermediate neurone that carries the signal to a motor neuron, this motor neuron brings the signal to the effector - such as a muscle.
• What does a reflex arc have to have, in terms of the structure, to make it overridable?

  There must be a relay neurone involved in the reflex arc for it to be overridable.
• Why is reflexes being localised important?

  Due to reflexes being localised to the part of the body where they occur this means that we can respond to stimuli quickly since signals don’t have to go to the brain and back.
• Why don't reflexes involve many synapses?

  Reflexes don't involve many synapses because they are slow to transmit across neurones, this lack of synapses allows reflexes to be efficient in protecting the body from harm by maintaining the speed of the electrical impulse.
• Although reflexes occur at the point of response, some signals are still sent to the brain. This allows the brain to override the response if its comprehensive decision making process deems this necessary.

  The simplicity of a reflex also means that it doesn’t have to be learnt, and is effective from birth.