11.3.1 Nerves, Reflexes and Synapses

• What mechanism is used to cross the synaptic gap?

  Chemical mechanism
• What happens when an electrical nerve impulse reaches the synaptic knob?

  Neurotransmitters are released
• How do neurotransmitters reach the second neuron?

  They diffuse across the synapse

  
• What do neurotransmitters bind to on the second neuron?

  Receptor molecules
• What is the specificity of receptor molecules on the second neuron?

  They bind only to specific neurotransmitters
• What is the result of neurotransmitter binding to receptors?

  Stimulates the second neuron to transmit an impulse
• What is a voluntary response?

  A conscious decision to act
• Where does the decision for a voluntary action begin?

  In the brain
• What travels down the motor neurone during a voluntary action?

  Electrical impulses
• What is a reflex action?

  An automatic response to a stimulus
• What is the purpose of a reflex action?

  To minimize further damage to the body
• Give an example of a reflex action.

  Knee jerk reflex
• What is the general sequence of a reflex action pathway?

  Stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response

  
• What is the nerve pathway followed by a reflex action called?

  Reflex arc

  
• What happens when receptors detect a stimulus?

  Electrical impulses travel along sensory neurones
• What does the CNS do with the information received?

  Coordinates the information and sends impulses
• What are effectors?

  Parts of the body that produce a response
• Give an example of an effector response.

  A muscle contracting to move an arm
• What are the three different types of neurones?

  Sensory, relay, motor

  
• What do sensory neurones carry?

  Electrical impulses from receptor to CNS
• Where is the cell body located in sensory neurones?

  In the middle of the nerve
• What is unique about relay neurones?

  They are only found in the CNS
• What do motor neurones carry?

  Electrical impulses from CNS to effector
• What does the human nervous system consist of?

  CNS and peripheral nervous system

  
• What enables humans to react to their surroundings?

  The nervous system
• What is a stimulus?

  A change in the environment
• What do receptors do?

  Detect stimuli and stimulate electrical impulses
• What are sense organs?

  Groups of receptors that respond to stimuli

  
• What happens when a pin is detected by a receptor?

  Electrical impulses are sent to the spinal cord
• What is the role of the relay neurone in a reflex action?

  Connects sensory neurone to motor neurone

  
• What does the motor neurone do in a reflex action?

  Carries impulse to the effector

  
• What is the function of the effector in a reflex action?

  Brings about a response
• What is a synapse?

  A small gap between two neurons
• What happens when a receptor cell is stimulated?

  Generates an electrical impulse
• What is the role of the sensory neurone?

  Carries impulse to the central nervous system
• What does the motor neurone do after the CNS processes the impulse?

  Carries the impulse to the effector
• What adaptations do nerve cells have for carrying impulses?

  Long axon and myelin sheath
• What are dendrites in nerve cells?

  Tiny branches leading to the cell body
• What is the function of myelin on the axon?

  Insulates the axon and speeds up impulses
• What is the process of neurotransmission at a synapse?

  1. Electrical impulse travels along presynaptic neurone.
  2. Neurotransmitters are released.
  3. Neurotransmitters diffuse across synapse.
  4. Bind to receptors on the second neuron.
  5. Stimulates the second neuron to transmit an impulse.