Nervous System

• Sensory neurons: Carry messages to the brain and spinal cord (CNS) from the body.
• Motor neurons: Carry messages from the brain and spinal cord (CNS) to the body.
• Interneurons: Found in the CNS, carry both sensory and motor messages and connect the sensory and motor neurons.
• Reflex: An involuntary/ automatic action in response to a stimulus.
• Reaction: A fast but voluntary response to a stimulus.
• Reaction time: A measure of how quickly an organism can respond to a particular stimulus.
• Reflex arc:

  1 - A receptor detects a stimulus

  2 - Sensory neurons send electrical impulses to the spinal cord

  3 - Information is processed in the spinal cord

  4 - Interneurons pass on the message to motor neurons

  5 - Motor neurons carry the impulse to the effector

  6 - Effector performs the response
• Reaction arc:

  1 - A receptor detects a stimulus

  2 - Sensory neurons send electrical impulses to the brain

  3 - Information is processed in the brain

  4 - Interneurons pass on the message to motor neurons

  5 - Motor neurons carry the impulse to the effector

  6 - Effector performs the response
• The role of sensory neurons in a reflex:

  • Send electrical impulses to the spinal cord
• The role of motor neurons in a reflex:

  • Carry the impulse to the effector
• The role of interneurons in a reflex:

  • Pass on the message (information processed in the spinal cord) to motor neurons
• Functions of the nervous system:

  • Collects information about the internal and external environment
  • Process information about the internal and external environment
  • Responds to the external environment (ensuring homeostasis)
  • Learning and memory
• Responding to stimuli:

  • Stimulus: A change that occurs in the internal or external environment
  • Receptor: An organ or cell that detects a stimulus and transmits a signal to the CNS via the sensory pathway
  • Response: An action produced by the CNS. It is a result from detection of a stimulus
• Nerve transmission steps:

  1 - Dendrites receive information from a stimulus.

  2 - Myelin sheath allows for fast impulses as the impulse can jump from one node of ranvier to the next very quickly.

  3 - Impulse moves along the axon to the axon terminal.

  4 - Chemicals called neurotransmitters are released from the axon terminal.

  5 - The neurotransmitter crosses the synapse (space between the neurons).

  6 - They activate an impulse on the next neuron by attaching to dendrites.