Flashcards in Autonomic Nervous System Deck (52)
Name 5 differences between the somatic and autonomic nervous systems.
1) Somatic is voluntary and conscious, autonomic is involuntary and unconscious
2) Somatic outflow is to skeletal muscle, autonomic outflow is to smooth muscle, cardiac muscle, glands
3) Somatic involves a single lower neurone from the anterior horn to the neuromuscular junction, autonomic involves a preG and postG neurone
4) The neurotransmitter released by the somatic lower motor neurone is always acetylcholine, the major neurotransmitters released by the autonomic neurones are acetylcholine and noradrenaline
5) For somatic the effect is always excitatory (muscle contraction), for autonomic the effect can be excitatory or inhibitory
What are the three divisions of the autonomic nervous system?
What is the outflow of the sympathetic nervous system?
Thoracolumbar - lateral horn of spinal segments T1 to L2
What is the outflow of the parasympathetic nervous system?
Craniosacral - cranial nerves 3, 7, 9, 10, and spinal segments S2 to S4
What are the relative lengths of the pre and post ganglionic neurone in the sympathetic and parasympathetic nervous systems?
Parasympathetic = long pre-ganglionic neurone, terminal ganglion on in in effector organ, short post-ganglionic neurone
Sympathetic = short preganglionic, paravertebral ganglion in sympathetic trunk, long postganglionic neurone (except in the case of the splanchnic nerves where there is a prevertebral ganglion close to the effector organ)
What are the neurotransmitter released and the post synaptic receptors in all the autonomic ganglia?
Neurotransmitter = acetylcholine
Receptor = nicotinic
What are the neurotransmitter released and the post synaptic receptors at the synapse between a parasympathetic postganglionic neurone and an effector cell?
Neurotransmitter = acetylcholine
Receptor = muscarinic
What are the neurotransmitter released and the post synaptic receptors at the synapse between a sympathetic postganglionic neurone and an effector cell?
Neurotransmitter = noradrenaline
Receptor = adrenergic
(can also me nitroxidergic for vasodilation)
What are the neurotransmitter released and the post synaptic receptors at the synapse between a sympathetic postganglionic neurone and a sweat gland effector cell?
Neurotransmitter = acetylcholine
Receptors = mucarinic
Is the effect of activation of nicotinic or muscarinic receptors longer lasting?
Muscarinic is longer lasting
What are the pelvic splanchnic nerves formed from and what do they supply?
Formed from the parasympathetic nerves from spinal segments S2 to S4, they supply the hind gut, the kidney, the urinary bladder, the sex organs.
What are the effects of the parasympathetic nervous system?
Rest and digest.
Miosis - eyes adapted for near vision only
Decreased heart rate, respiratory rate, blood pressure
Increased motility and secretion of gastrointestinal tract
The sympathetic trunk extends from the base of the skull to the inferior end of the vertebral column, what is the name of the point at which the two trunks meet in front of the coccyx?
What is the difference between the white ramus communicans and the grey ramus communicans?
White ramus communicans allows the preganglionic neurone (myelinated) to move from the anterior ramus of the spinal nerve to the sympathetic ganglion.
Grey ramus communicans allows the postganglionic neurone (unmyelinated) to move back from the ganglion to the anterior ramus of the spinal nerve.
Which part of the mediastinum does the sympathetic trunk run through?
The posterior medistinum
Where do the sympathetic splanchnic nerves in the thorax arise?
Greater = spinal segments T5 to T9
Lesser = spinal segments T10 to T11
Least = spinal segment T12
Where is the ganglion of the sympathetic splanchnic nerves?
The preganglionic neurone runs right through the sympathetic trunk without synapsing, as there is a prevertebral (collateral) ganglion closer to the effector cell.
What is Horner's syndrome?
A lesion in the hypothalamospinal pathway which runs from the hypothalamus to the lateral horn of T1 to the contralateral sympathetic nerves to the blood vessels of the face. Horner's syndrome causes miosis, ptosis, anhydrosis.
What are the effects of the sympathetic nervous system?
Increased heart rate, respiratory rate, blood pressure
Divert blood from gastrointestinal tract and sex organs to brain and skeletal muscles
What are the parasympathetic reflexes?
Gastric and intestinal
Swallowing and defaecation
What are the sympathetic reflexes?
What effects of the sympathetic nervous system do beta blockers stop, and which do they not stop?
Beta blockers stop the increased heart rate and contractility, but they don't decrease sweating.
What is derived from tyrosine?
L-dopa -> dopamine -> noradrenaline ->adrenaline
What does adrenaline cause in the liver?
Gluconeogenesis and glycogenolysis.
What are the effects of muscarinic agonists (e.g aminata muscarina from toadstools, pilocarpine)?
What are the effects of nicotinic agonists, and where are the nicotinic receptors?
There are nicotinic receptors on the motor end plates of skeletal muscle, and in all the autonomic ganglia.
Nicotinic agonists cause:
What is pseudocholinesterase?
Plasma acetylcholinesterase (not tissue cholinesterase), deficiency causes prolonged and profound effects to drugs like suxamethonium.
What is hemicholium?
Blocks uptake of choline.
What is botulinum toxin?
Blocks exocytosis of acetylcholine from synaptic vesicles.
What are some irreversible acetylcholinesterase inhibitors?
Sarin (chemical weapon)
Cause muscle fasciculation and death.
What are three reversible acetylcholinesterase inhibitors?
What is curare?
Reversible nicotinic receptor antagonist, causes flaccid paralysis so you die of respiratory failure.
What are the antidotes to curare?
What is suxamethonium?
Depolarising block that is slowly broken down by acetylcholinesterase and causes tonic paralysis.
What is atropine/belladonna?
Reversible muscarinic antagonist, causes pupils to dilate.
What is hyoscine?
A muscarinic receptor antagonist used as an antiemetic.
What is tropicamide, and why is it better for use in opthalmology than atropine?
Muscarinic anagonist, shorter lasting than atropine so can be used to dilate pupil to get a good look in the patient's eyes.
Tropicamide can cause glaucoma, but pilocarpine can be used to prevent glaucoma.
What are the effects of noradrenergic neurones?
What is controlled by aloha adrenoceptors?
So they increase inositol trisphosphate intracellularly, and prevent orthostatic hypotension, and maintain blood pressure.
[alpha 2 are more in the periphery, alpha 1 are more central]
What is methyltyrosine?
Inhibits noradrenaline and adrenaline synthesis.
How does cocaine affect noradrenergic neurones?
Blocks uptake 1 so causes persistence of noradrenaline in the synaptic cleft.
Causes prolongued vasoconstriction.
What is despiramine an example of?
A tricyclic antidepressant - block uptake 1
What is isoprenaline?
Beta 1 and Beta 2 agonist
What is salbutamol?
Beta 2 agonist used to treat asthma
What is phenoxybenzamine?
Blocks alpha 1 receptors to reduce blood pressure
What is prazosin?
Treats hypertension, antagonist of alpha 1 receptors
What is propranolol?
B1 and B2 antagonist
What is atenolol?
B1 antagonist, used in heart failure
What is pheochromocytoma?
Noradrenaline and adrenaline secreting tumour in the adrenal medulla.
What is dobutamine?
A B1 receptor agonist
What is the difference between salbutamol and salmeterol?
They are both B2 receptor agonists but salmeterol is longer lasting