(a) Structures and functions of the central nervous system (CNS)

• Central Nervous System (CNS) consists of the brain and spinal cord.
• The Peripheral Nervous System (PNS) consists of the somatic nervous system (SNS) and the autonomic nervous system (ANS).
• The somatic nervous system (SNS) contains sensory and motor neurons.
• Sensory neurons take impulses from sense organs to the CNS.
• Motor neurons take impulses from the CNS to muscles and glands.
• The autonomic nervous system (ANS) consists of the sympathetic and parasympathetic systems.
• The sympathetic and parasympathetic systems have antagonistic actions on heart rate, breathing rate, peristalsis and intestinal secretions.
• The sympathetic system speeds up heart rate and breathing rate while slowing down peristalsis and production of intestinal secretions.
• The parasympathetic system changes these in the opposite way.    

(b) Structure and function of converging, diverging and reverberating neural pathways

• In a converging neural pathway, impulses from several neurons travel to one
• This increases the sensitivity to excitatory or inhibitory signals.
• In a diverging neural pathway, impulses from one neuron travel to several neurons so affecting more than one destination at the same time.
• In a reverberating pathway, neurons later in the pathway link with earlier neurons, sending the impulse back through the pathway.
• This allows repeated stimulation of the pathway.