Autonomic Nervous System Flashcards
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?
Sympathetic
Parasympathetic
[Enteric]
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
Relaxes sphincters
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?
Ganglion impar
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?
Mydriasis
Increased heart rate, respiratory rate, blood pressure
Divert blood from gastrointestinal tract and sex organs to brain and skeletal muscles
Bronchodilation
Increased sweating
Sphincters close
What are the parasympathetic reflexes?
Gastric and intestinal Swallowing and defaecation Urination Pupillary (contraction) Cough Baroreceptor Sexual arousal
