sympathetic NS

• structure of sympathetic NS

  -Cell bodies of preganglionic neurine in thoracic and lumbar region

  -Nerves emerge from spinal cord and form synapses with:

  1. -Paravertebral sympathetic chains:

  Form synapse close to where they emerge

  . Prevertebral ganglia/plexuses:

  Pass through chain – to these that are in abdomen

  Adrenal medulla

  Gland on top of kidneys

  From synapse with chromaffin cells
• sympathetic neuroeffector pathways

  ACh and noradrenalin

  
• exceptions to normal SNS pathway

  1-ACh at pre and post

  
• sympathetic neurotransmitter release

  noradrenalin synthesised by tyrosine

  packaged into vesicles

  released into synaptic cleft

  acts pf specific receptors - ADRENORECEPTORS (alpha or beta)

  
• alpha and beta adrenoreceptors

  metabotropic receptors

  single protein that spans across cell membrane

  extra - cellular and intra-cellular loops

  Attaches to G protein → 2nd messenger system → enzyme activation/ion transport → response
• sympathetic control of pupil diameter

  SNS activated

  ACh released

  triggers release of noradrenalin on postsynaptic membrane

  act as alpha receptors

  activated

  radial muscles contract

  moves fast

  pupil dilates = mydriasis
• sympathetic cotransmission

  Noradrenalin (NA) + Neuropeptide Y (NPY) + ATP

  act together to cause vasoconstriction