GCSE›AQA GCSE Biology›Mind mapsThe Nervous SystemAQA GCSE Biology: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsStructureCNS is the brain and spinal cord onlyPNS is all nerves outside the CNSSensory nerves carry impulses to the CNSMotor nerves carry impulses to effectorsThree neuronesSensory: receptor → CNSRelay: in the CNS, links sensory to motorMotor: CNS → effector (muscle or gland)Sensory has long dendrite, motor has long axonReflex arcReceptor → sensory → relay → motor → effectorRelay neurone bypasses the brainAutomatic, unconscious and fastVoluntary responses are conscious and slowerNervous systemfast electrical controlSynapsesHigher Tier: impulse cannot jump the synaptic cleftVesicles release neurotransmitter into the gapIt diffuses and binds to receptorsSets off a new impulse; transmission is one-wayThe brainControls voluntary responsesInterprets sensory informationHard to study: complex, ethical limits on invasive workMRI is non-invasive but shows correlation onlyDamage studies: Broca's area controls speechExam tipsCNS is brain and spinal cord onlyReflexes are faster: relay synapses straight to motor neuroneGive advantages and limitations of MRI