Anatomy of the Autonomic Nervous System Flashcards
What is the role of the autonomic nervous system?
Motor innervation of smooth muscle, cardiac muscle (which make up viscera) and glands.
Revice signals via visceral afferent fibres and respond to stimuli via visceral efferent fibres.
What are the division of the nervous system?
Divides into the CNS (brain and spinal cord) and the PNS (cranial nerves and spinal nerves)
The PNS further splits into somatic (motor to skeletal muscle) and autonomic functions.
The autonomic then divides into the sympathetic and parasympathetic division.
What does the autonomic system respond to?
What does it control?
Responds to signals from the internal environment to control involuntary processes.
What is the function of the sympathetic nervous system?
Stress - fight of flight
Increase HR and BP
Decrease blood for to extremities and GIT through vasoconstriction
Increase blood flow to heart and muscles through vasodilation
Dilates the pupils
What is the role of the parasympathetic nervous system?
Rest and digest function
Decrease HR and force of contraction –> decrease BP
Increase blood flow to the extremities and GIT
Constrict the pupils.
How is homoestasis between the parsympathetic and sympathetic nervous system regulated?
By the hypothalamus
Controls the balance between sympathetic and parasympathetic tone.
Where do sympathetic neurons arise from?
Spinal nerve T1-L2
Thoracolumbar outflow
Where do parasympathetic nerves arise from?
Brain stem and spinal segments S2-4
Cranioscaral outflow
What is common in all pathways of autonomic nerves?
Consits of a pre-ganglionic and post-ganglionic fibre, that synapse in a ganglia
Describe how the adrenal gland medulla is innervated by the autonomic nervous system?
By preganglionic sympathetic neurons only
No post-ganglionic neuron
No parasympathetic innervation
Therefore innervation of the adrenal gland by ANS causes a widespread sympathetic response via hormone release
Describe the pathway of a sympathetic efferent.
Pre-ganglionic fibre originates from the lateral horn of grey matter in the T1-L2 spinal segments.
Travels through the ventral root and mixed spinal nerve
Into myelinated white ramus communicants
Synpase with post-ganglionic in the sympathetic ganglion, may travel up or down a few levels
Post-g exist via the grey rammus communicans (unmyelinated) and travels to target tissue via the ventral or dorsal ramus
What neurotransmitters are realised by the sympathetic nervous system?
Between pre and post ganglioninc - ACh
By post-g at target tissue NA
What are splanchnic nerves?
Autonomic fibres that target viscera
Can be sympathetic or parasympathetic
What provides most sympathetic innervation to viscera?
Splanchnic nerves
What provides most parasympathetic innervation to viscera?
Vagus nerve
What are the expceptions to the rule that splanchnic nerves supply most sympathetic innervation to the viscera?
The pulmonary plexus
The cardiac plexus
What is the pattern of travel of the pulmonary plexus?
Pre-g symphattic fibres innervating the lungs synapse in the sympathetic chain at level T1-T4
What is the pattern of travel of the cardiac plexus?
Pre-g sympathetic fibres innervating the heart synapse in the sympathetic chain at levels T1-4, as well as some contribution from cervical ganglia
What is the pattern of travel of sympathetic splanchnic nerves?
Have thoracolumbar outflow (lateral horn, ventral root, spinal nerve, white communicants, sympathetic ganglion, grey communicants)
Travel through but do not synapse within the sympathetic chain
Prevertebral ganglion lie on surface of blood vessel supplying specific organs
The post-ganglionic fibres are carried along the vessel to the target tissue
Describe the sympathetic and parasympathetic innervation of the GIT
Describe the pathway of a parasympathetic efferent from the sacral spinal cord?
The efferent neuron will run from the ventral horn of grey matter of the sacral spinal cord S2-S4.
Through the ventral root
Into the spinal nerve
Alonf the dorsal/ventral ramus
To synpases within a ganglion before reaching the target tissue.
Where are parasympathetic autonomic ganglia found?
On or near the lining of the target tissue or organ
What neurotransmitter is associated with the parasympathetic nervous system?
Aceylcholine is released in th ganglion (between pre and post)
Acetylcholine is released by post-ganglionic parasympathetic fibres.
What are the different parasympathetic nerves arising from the brainstem?
Oculomotor nerve (CN3)
Facial nerve (CN7)
Glassopharangeal nerve (CN9)
Vagus nerve (CN10)
Only fancy guests like venison
What are the different ganglia for parasympathetic nerves found in the head and neck?
The ciliary ganglion
The otic ganglion
the Pterygopalating ganglion
The submandibular ganglion.
Where does the oculomotor nerve originate from?
The parasympathetic fibres originate from the Edinger-Westphal Nucleus in the midbrain
All other fibres arise from the oculomotor nucleus
Where does the ocoulomotor nerve sysnpase?
Pre-ganglionic fibres synpase in the ciliary ganglion
What are the target tissues and associated functions of the PANS oculomotor nerve?
Ciliary muscles - lens accomodation
Sphincter papillae - constric the pupil
Where does the facial nerve originate from?
Parasympathetic fibres from the Salivatory-Lacrimal (superior salivatory) nucleus of the pons
The facial nucleus gives rise to all other fibres
Where does the facial nerve parasympathetic fibres synapse?
The pterygopalatine ganglion
the submandibular ganglion
What is the target tissue or the facial PANS fibres and the associated function?
From pterygopalatine fibres to the lacrimal glands to produce eye lubricating fluids
From the submandibular gangliong fibres go to the sublingual and submandibular glands to produce saliva
Where does the glassopharangeal nerve originate from?
Parasympathetic fibres arise from the Inferior Salivatory Nucleus of the medulla
Where does the glassopharangyeal nerve synapse?
The otic ganglion
What is the function of the PANS glassopharangeal fibres and their target tissue?
Targets to parotid gland to prodcue saliva.
Where does the parasympathetic vagus nerve originate from?
The dorsal motor nucleus of vagus
What is the function of the vagus nerve?
Synapses throughout the body
Targets - thoracic and abdominal visceral (up to the splenic flexure)
Therefore is responsible for the majority of the thoracic and abdominal parasympathetic innervation.
What is horners syndrome?
A lesions along the sympathetic nerves supplying the eyes
These travel along the internal carotid then the opthalamic arteries
The superior tarsal or Mullers muscle (smooth muscle so under autonomic control is unable to function)
How does Horners syndrome present?
Miosis - a permenantly small pupil
Ptosis - upper eyelid drooping
Anhidrosis - an inability to sweat
Enophthalmos - a sunken appearance to the eye
Central iris
What is oculomotor nerve palsy?
Damage to the nervous supply to the levator palpebrae superiors (skeletal muscle)
Supplied by CN3 Oculomotr nerve
What are the symptoms of oculomotor nerve palsy?
Ptosis
Pupillary dilation
Able to sweat
Inferolateral iris
What are the two types of visceral afferents?
Reflexive
Nociceptive
What are reflexive afferents?
Signals do not reach our consciousness as fibres project only to brainstem or hypothalamus
(e.g not awatre of distend bowel and peristalsis)
What are nociceptive afferenets?
Reach conscious control but are poorly localised
Pain information
For example menstraul cramp from upterus is generalised to abdomen
What is the pathway of a visceral afferent?
Can follow sympathetic or parasympathetic efferent fibres
Ganglia in the Dorsal Root Ganglion
What is the pelvic pain line?
Pain from viscera above or in contact with the inferior layer of the peritoneum travel with sympathetic splanchnic nerves T10-L1
Pain from sub-peritoneal organs is carried by pelvic splanchnic nerve (s2-4)
Where will pain from above the pelvic pain line be felt?
Dermatimes T10-L1
From umbilicus to inguinal area
Where wil pain originating below the pelvic pain line be felt?
Dermatomes supplied by S2-S4
Genitals and bottom
What is the peripheral nervous system composed of?
31 pairs of spinal nerves
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
12 Paris of cranial nerves
What is the difference between the white and grey ramus communicants?
The white communicans is myelinated
The grey communicants is unmyelinated.
What type of fibres are sympathetic and parasympathetic fibres?
Efferent fibres.
Label the relevant cranial nerves containing parasympathetic fibres.
2 - oculomotor
10 - facial
9 - glassopharangeal
8 - vagus
Label the four different parasympathetic ganglion in the head and neck.
Yellow is cilliary ganglion
Green is pterygoidganglion
Pink is Otic ganglion
Blue is Submandibular ganglion
Identify the Edinger-Westphal Nucleus of the midbrain.
Pink most superior in midbrain
Identify the oculomotor nucleus
Orange most superior in midbrain
Identify the salivatory lacrimal nucleus.
The superior pink spot (second overall) in the pons
Identify the facial nucleus.
Yellow second down in the pons??
Identify the inferior salivatory nucleus.
The first down pink in medulla
(the third overall)
Identify the nucleus ambiggus
The long yellow nucleus in the medulla
Identify the dorsal motor nucleus of vagus
Long pink nucleus in medulla
Where does innervation from the vagus nerve stop?
The midgut is the last structure to receive parasympathetic innervation from the midgut
Therefore terminates at the junction between the midgut and the hindgut (2/3 way along the transverse colon)
