Autonomic NS Flashcards
What does the autonomic NS comprise of?
Sympathetic and parasympathetic NS.
Smooth muscle, cardiac muscle, glands.
What is the principal function of the Autonomic NS?
Homeostasis
What is the main difference between the somatic and autonomic NS?
Somatic NS is a one motor neuron system - one neuron runs from the spinal cord to the skeletal muscle.
Autonomic NS is a two neuron system - preganglionic fibre runs from the spinal cord to a ganglion. From here a postganglionic fibre runs to smooth and cardiac muscle and glands.
Describe the anatomy of the parasympathetic NS.
Long Preganglionic fibres from brain stem or sacral spinal cord (cranio-sacral system).
Includes cranial nerves 3(oculomotor), 7(facial), 9(glossopharyngeal), 10(vagus).
Pelvic nerves
Ganglia are located near effector organs.
Describe the anatomy of the sympathetic NS.
Preganglionic fibres from thoracic and lumbar spinal cord.
Thoraco-lumbar system.
Ganglia arranged in three anatomical patterns; sympathetic chain, adrenal medulla, collateral ganglia.
Describe the anatomy of a sympathetic chain in relation to the SNS.
Short axons
Exit spinal cord via ventral roots.
Travel to organ as spinal nerve.
Describe the anatomy of the adrenal medulla in terms of the SNS?
Long preganglionic fibres
Chromaffin cells are modified post-ganglionic cells
Describe the collateral ganglia in terms of the SNS?
Pre-ganglionic axons pass through sympathetic chain without synapsing.
Ganglion located close to effector organ.
What are the three paths that an axon can take in relation to the SNS?
- Enter sympathetic chain via White ramus and terminate there.
- Enter the sympathetic chain via the White ramus and ascend or descend a few segments before terminating.
- Enter via the White ramus and exit via a splanchnic nerve and terminate in a prevertebral ganglia.
What are the three receptor types of the ANS?
Adrenergic
Nicotinic
Muscarinic
What are adrenergic receptors?
Respond to adrenaline and noradrenaline. Have alpha and beta receptors. Signal transduction is via activation of IP3 for alpha1, inhibition of cAMP for alpha2 and activation of cAMP for the three beta receptors.
Effector organs include vascular smooth muscle, adipose tissue, CNS, platelets, adrenergic nerve terminals, uterus, respiratory tract, cardiac muscle, kidney.
IP3 receptors are faster than cAMP.
What are cholinergic receptors?
Muscarinic-responds to acetylcholine, PNS, postganglionic fibres to effector organ.
Nicotinic - SNS and PNS, preganglionic fibres transmitting to ganglion of ANS.
Discuss muscarinic receptors.
All G-protein linked second messenger pathways.
Specific to organs, can be inhibitory or excitatory.
Specific agonists and antagonists.
Acetylcholine natural agonist (ligand).
5 types; M1-CNS, M2-heart, M3-smooth muscle, M4-CNS, M5-CNS
Discuss nicotinic receptors.
Can be N1/Nm - neuromuscular junction, or N2/Nn - autonomic ganglia, CNS and adrenal medulla.
What are the two major neurotransmitters of the ANS?
SNS-noradrenaline/adrenaline. Effector organ receptor is adrenergic.
PNS-acetylcholine. Effector organ receptor is muscarinic cholinergic.
Receptor on the ganglion for both PNS and SNS is nicotinic cholinergic and neurotransmitter is acetylcholine.