Autonomic nervous system Flashcards
1
Q
What afferents can the PNS be split into
A
Motor afferents, sensory afferents
2
Q
What are the 2 sections of the PNS
A
Autonomic, somatic
3
Q
What are the 3 sections of the autonomic nervous system
A
Sympathetic, enteric, parasympathetic
4
Q
What does the somatic system control
A
Voluntary control of skeletal muscles
5
Q
Examples of bodily functions the ANS is involved in
A
Sweating, drooling, tearing up, hairs standing on end
6
Q
When does discovery of the ANS date back to
A
Mid 1600s, Thomas Willis relied on obsevation of carcasses
7
Q
What structure do the ganglia of the sympathetic nervous system form
A
Form segmental chain ganglia, organised segmentally according to lumbar and thoracic aspects in the organisation of the body
8
Q
Where in the CNS do NO sympathetic neurons emerge from
A
Brain, cervical or sacral spinal cord
9
Q
How does the sympathetic nervous system supply the gut
A
Three midline ganglia supply the gut
10
Q
What are the length of the pre- and postganglionic nerves of the sympathetic nervous system
A
Preganglionic neurons are short
Postganglionic nerves tend to be very long
11
Q
What are preganglionic neurons
A
Preganglionic neurons have cell bodies in the spinal cord that send out axons to the ganglion
12
Q
What are postganglionic neurons
A
Run from the ganglion to the effector organ
13
Q
What are the length of the pre- and postganglionic nerves of the parasympathetic nervous system
A
Preganglionic neurons are long
Post-ganglionic nerves are short
14
Q
Why do preganglionic nerves tend to be shorter in the sympathetic nervous system than in the parasympathetic nervous system
A
Sympathetic ganglia are often closer to the spinal cord (making them shorter) while parasympathetic preganglionic fibers tend to project to and synapse with the postganglionic fiber close to the target organ.
15
Q
What neurotransmitters do both sympathetic and parasympathetic neurons receive as input
A
Receives cholinergic input from the preganglionic neuron (ACh) that binds to nicotinic receptors
16
Q
Why is there a segmental chain ganglia organisation
A
The neural crest migrates through the rostral half of each somite, forming the segmental sympathetic chain ganglia
17
Q
Where is the output of the parasympathetic nervous system
A
Output in cranial nerves and sacral spinal cord
18
Q
What is the organisation of the ganglia in the parasympathetic nervous system
A
No segmental ganglia, ganglia close to targets
19
Q
What neurotransmitters does the postganglionic neuron of the sympathetic nervous system release onto target cells
A
Mostly releases noradrenaline onto alpha/beta adrenergic receptors
Sometimes releases ACh
20
Q
What neurotransmitters does the postganglionic neuron of the parasympathetic nervous system release onto target cells
A
Releases mainly ACh onto muscarinic ACh receptors
21
Q
What do autonomic nerves end in instead of synaptic junctions
A
Varicosities, form as a series of enlargements that release neurotransmitter
22
Q
What can autonomic nerves release in addition to the main neurotransmitters
A
Neuromodulators- modulate the action of primary transmitters
23
Q
Examples of neuromodulators released by sympathetic nerves
A
Enkephalin, ATP
24
Q
Examples of neuromodulators released by parasympathetic nerves
A
Somatostatin, nitrous oxide (NO)
25
How is the innervation of sweat glands unusual
Sweat glands receive cholinergic sympathetic innervation(sympathetic neurons don't usually release cholinergic transmitters)
26
Why do the sweat glands recieve cholinergic sympathetic innervation instead of noradrenaline
Target derived factors in development cause NA cells to switch to ACh cells in a late phenotypical switch (post-natal)
27
Examples of the target derived factors that cause NA cells to switch to ACh cells
Leukaemia inhibitory factor, ciliaric neurotrophic factor
28
How was the switch of the innervation of sweat glands discovered- procedure
By transplanting foot pad tissue (has a cholinergic neurotransmitter identity) onto a patch of skin dominated by noradrenergic innervation (Schotzinger and Landis, 1988)
29
How was the switch of the innervation of sweat glands discovered- results
The innervation for the transplanted tissue remained cholinergic (switch did not occur) because it receives transcription factor signals from the sweat glands themselves (Schotzinger and Landis, 1988)
30
What can be done if you sweat a great deal (hyperhidrosis)
The sympathetic chain innervating the sweat glands can be cut or regionally infected with Botulinum toxin to prevent sympathetic stimulation
31
How are piloerector muscles innervated and what is the result of input
Receive noradrenergic inputs that cause the hair shaft to move into an erected position
32
What is peripheral vasoconstriction
Sympathetic nerves innervating the smooth muscle cause them to contract which reduces blood flow to the fingers and heat loss (shown by, Pirzgalska et al 2015)
33
Paravertebral chain of sympathetic ganglia- what supplies head
Superior cervical ganglion at the top of the sympathetic chain
34
Paravertebral chain of sympathetic ganglia- what supplies heart and lungs
Middle cervical and stellate ganglia
35
Paravertebral chain of sympathetic ganglia- what supplies abdominal and pelvic organs
Pre-vertrebal ganglia
36
What are the 3 ways the sympathetic ganglia are innervated
Terminate in ganglia, pass along chain before terminating, some synapse with midline ganglia
37
How do some preganglionic nerves synapse with midline ganglia before innervating the ganglia
Synapse with midline/pre-vertebral ganglia via the splanchnic nerves eg celiac ganglia and mesenteric ganglia, which in turn project to the gut and internal organs
38
How do the preganglionic neurons enter and the postganglionic nerves leave the sympathetic ganglia
Preganglioic neurons enter via the white ramus
| Postganglionic nerves leave via the grey ramus
39
Where do the preganglionic and postganglionic sympathetic neurons synapse
In the sympathetic ganglion
40
What innervates the gut
The main pre-vertebral ganglia innervate the gut
41
What are the pre-vertebral ganglia that innervate the gut suppled by
The greater, lesser and least splanchnic nerves
42
What are the 3 main pre-vertebral ganglia that innervate the gut
The celiac ganglion, the superior mesenteric ganglion, the inferior mesenteric ganglion
43
What supplies the foregut
The celiac ganglion
44
What supplies the midgut
The superior mesenteric ganglion
45
What supplies the pelvic organs
The inferior mesenteric ganglion
46
What does the rostral-most porttion of the parasympathetic nervous system consist of
Cranial nerves 3, 7, 9 and 10
47
What is cranial nerve 3 from the parasympathetic nervous system
Oculomotor, the iris
48
What is cranial nerve 7 from the parasympathetic nervous system
Facial, tear and salivary glands
49
What is cranial nerve 9 from the parasympathetic nervous system
Glossopharyngeal, salivary gland
50
What is cranial nerve 10 from the parasympathetic nervous system
Heart, lungs and viscera
51
Pupil reflex- parasympathetic input
Parasympathetic input stimulates post-ganglion fibres from the ciliary ganglion that innervate the iris constrictor muscles, constricting the pupil and decreasing light passage to the retina
52
Pupil reflex- sympathetic input
Sympathetic input stimulates post-ganglion fibres from the superior cervical ganglion, causing pupil dilation and increasing light passage to the retina
53
What drugs can cause parasympathetic stimulation of the eye
Opiates, making pinpoint pupils
54
What drugs can cause sympathetic stimulation of the eye
Sympathomimetic drugs eg Amphetamines dilate pupils (cycloplegic effect)
55
What are the symptoms of Horner's syndrome
Pupils constricted, eyelid droops, dry flushed facial skin
56
What can cause Horner's syndrome
Can be caused by lesion of sympathetic superiori cervical ganglion, damaging the axons between the ganglion and the target organ eg due to tumour, carotid artery lesions
57
Which facial nerve controls lacrimation and salivation
Facial nerve VII
58
What is lacrimation
Tearing up
59
How does facial nerve VII control lacrimation
Parasympathetic innervation of the pterygopalatine ganglion regulates secretions of the lacrimal gland and nasal mucosa
60
How does facial VII control salivation
Parasympathetic innervation of the submandibular ganglion regulates secretions of submandibular and sublingual salivary glands
61
How does cranial nerve 9 control salivary secretion
Parasympathetic of the otic ganglion leads to increased secretion of saliva from the parotid glands
62
How do CNS control centres drive cardiovascular effects
CNS control centres project from the brain down the spinal cord to the ventral horn, where preganglionic sympathetic neurons innervate the stellate ganglia which innervate the heart
63
What is the result of increased sympathetic input into the heart
Increased heart rate, force of contraction and conduction
64
What is the main effect of sympathetic activation on the lung
Bronchodilation- sympathetic innervation of bronchi leads to bronchodilation which causes increased respiratory capacity
65
What leads to neurotransmitter release by the sympathetic nervous system during fight or flight
Greater splanchnic nerve carries descending inputs from the brain down the spinal cord- stimulation of the adrenal medulla causes a huge systematic release of noradrenaline and adrenaline
66
What is known to phenocopy the flight/fight state and how
Adrenal medulla tumours cause the adrenal medulla to massively increase, causing a huge increase of catecholamines in circulate that phenocopy the fight/flight state
67
Why does a phenocopy happen as a result of adrenal medulla tumours
Chomaffin cells in the adrenal medulla have a common embryonic origin with SNS neurons, meaning they release the same neurotransmitters
68
Sympathetic stimulation- pupils
Dilate
69
Sympathetic stimulation- heart
Heart rate increases
70
Sympathetic stimulation- blood vessels
Peripheral vasoconstriction
| Muscle vasodilation
71
Sympathetic stimulation- bronchi/lung
Bronchodilation
72
Sympathetic stimulation- liver
Glycogenolysis, gluconeogenesis
73
Sympathetic stimulation- salivary glands
Viscous salivary secretions
74
Sympathetic stimulation- GI tract
Contraction of sphincters, decreased motility
75
What is the vagus nerve
The 10th cranial nerve, major PNS nerve that supplies thorax and abdomen (vagus means wandering)
76
What does the vagus nerve control
Gut reflexes and motility, blood pressure, heart rate
77
What neurons attached to the vagus nerve control blood pressure and heart rate
Sensory neurons in the petrosal ganglia and nodose ganglia attached to the vagus nerve
78
Study showing the role of Piezeo2 channels in the neurons controlling the baroreflex
Neurons subject to optogenetic stimulation had a sharp decrease in blood pressure and heart rate, showing the importance of Piezo2 in monitoring BP and HR
79
What channel was discovered in the neurons that control blood pressure and heart rate in the vagus nerve
Piezeo2, a mechanosensory channel- senses stretch in the aortic arch and carotid sinus
80
What is the baroreflex
How sensory nerves that run along the vagus nerve control blood pressure
81
What is the micturition reflex- P1, sensing
Sensory nerves sense bladder stretch and send signals to the CNS (somatic nervous system), causing the urge to urinate
82
What is the micturition reflex- P2, contraction
Parasympathetic stimulation (by Beta3) of the smooth muscle of the bladder walls causes contraction
83
What is the mictuition reflex- P3, expulsion
The sphinctre muscles are voluntarily relaxed via the pudendal and the sphinctre opens
84
What happens to the micturition reflex during sympathetic stimulation
The micturition reflex is suppressed
85
What is micturition
The ejection of urine from the urinary bladder to outside the body
86
What 2 nerve types are involved in male genital 'reflexes'
Afferent via spinal and autonomic nerves
87
What is the effect of parasympathetic nervous system stimulation on male genital 'reflexes'
PSNS stimulation onto helicine arteries causes them to dilate, causing erection
88
What is the effect of sympathetic nervous system stimulation on male genital 'reflexes'
Sympathetic stimulation leads to emission of seminal fluid and closure of bladder sphincter, leading to ejaculation
89
What controls ejaculation
Pudendal (spinal) control over penile muscles causes ejaculation
90
Defecation reflex- why are the anal sphincters normally closed
Closed by sympathetic tonic (continuous low level) stimulation
91
Defecation reflex- what triggers the defecation reflex
Detection of a full sigmoid rectum by visceral sensory afferents
92
Defecation reflex- what causes defecation
Peripheral nervous system stimulates of bowel smooth muscle, tonic sympathetic control of sphinctres is inhibited, voluntary opening of sphincters
93
What 2 networks comprise the enteric nervous system
Submucosal plexus, myenteric plexus (Rao and Gershon, 2016)
94
What comprises the enteric nervous system
Intrinsic nerve networks (plexi) in the intestinal wall
95
How does peristalsis occur via the enteric nervous system
Food in gut casues serotonin release -> stimulates submucosal plexus -> stimulates myenteric plexus (shown by Hibberd et al, 2018)
96
Study showing role of enteric nervous system in controlling peristalsis
Optogenetic stimulation of calretinin expressing myenteric neurons promotes peristalsis
97
How does the enteric system develop
Enteric crest arises only from cervical levels and colonises the entire gut
98
What disorders can be caused if invading crest cells don't make it to the end of colonising the gut
Hirschprung's disease and congenital megacolon
99
What causes a megacolon
If invading crest cells don't enter the gut wall or fail to survive it leads to a defective nerve plexus, causing a megacolon
100
What controls the autonomic nervous system
The hypothalamus
101
Rest and digest responses produced by the parasympathetic division
Slowed heart rate, decreased blood presure, increased digestive functions, reduced sweating
102
How are the actions of the ANS unlike those of the somatic motor system
ANS actions are typically multiple, widepsread and relatively slow
103
Where are the soma of preganglionic neurons
Spinal cord (localise in lateral horn) and brain stem
104
What does it mean to say the ANS is a disynaptic pathway
It involves 2 synapses, one between the pre and post ganglionic neuron, and one between the post ganglionic neuron and the target organ
105
Where are the soma of postganglionic neurons located
The autonomic ganglia
106
Can the sympathetic and parasympathetic divisions act simultaneously?
Yes, operate in parallel by complementary distinct pathways and neurotransmitter systems
107
Where do the preganglionic neurons of the sympathetic division lie
Sympathetic preganglionic neurons- interomediolateral grey matter of spinal cord
108
Where do the preganglionic neurons of the parasympathetic division lie
Parasympathetic preganglionic neurons- variety of brain stem nuclei and lower spinal cord
109
What 3 types of tissue does the ANS innervate
Glands, smooth muscle, cardiac muscle
110
How do the physiological influence of the sympathetic and parasympathetic divisions interact
Generally oppose one another and are reciprocal, as neural circuits in the CNS inhibit activity in one division while the other is active
111
What behaviours are related to the PNS
Digestion, growth, immune reponses and energy storage
112
Which time span are the SNS vs PNS aimed at
SNS mobilises the body for short-term emergency at the expese of processes aimed at long-term health, while the PNS works for the long-term good
113
What is the effect of the parasympathetic vs sympathetic sysyem on smooth muscles of the gastrointestinal tract
Smooth muscle of gastrointestinal tract is dually innervated- intestinal motility (thus digestion) is stimulated by parasympathetic axons and inhibited by sympathetic axons
114
Which glands are innervated by only one division of SNS vs PSNS
Sweat glands innervated by sympathetic axons alone, lacrimal glands innervated only by parasympathetic input
115
What is the enteric division
A unique neural system embedded in the lining of the esophagus, stomach, intestines, pancreas and gallbladder
116
What are both the enteric networks supplies by
Sensory nerves, interneurons, autonomic motor neurons
117
What does the enteric division control
Many physiological processes involved in the trasport and digestion of food, from oral to anal openings
118
What do enteric sensory neurons monitor
Tension and stretch of the gastrointestinal walls, chemical status of stomach and intestinal contents, blood hormone levels
119
What is the info supplied by enteric sensory neurons used for
Info used by motor and interneurons in the gut to govern muscle motility, the production of mucus and digestive secretions, and the diameter of local blood vessels
120
Where does the enteric division receive indirect input from
The brain- PNS and SNS axons provide supplementary control and can supercede the functions of the enteric division in some circumstances
121
Example of a circumstance where the brain may supercede the function of the enteric division via PNS and SNS axons
Enteric nervous system and digestive stress are inhibited by the strong activation of the SNS that occurs during acute stress
122
How does the hypothalamus control the ANS
Integrates the info about body status it receives, anticipates some of its needs, provides a coordinated set of neural and hormonal outputs
123
What connects the hypothalamus to the autonomic nervous system
Connections of the periventricular zone (in hypothalamus) to the brain stem and spinal cord nuclei that contain the preganglionic neurons of the SNS and PNS
124
What area of the brain other than the hypothalamus is important for autonomic control
The nucleus of the solitary tract, located in the medulla and connected to the hypothalamus
125
What does the solitary tract nucleus do
Integrates sensory information from the internal organs and coordinates output to the autonomic brain stem nuclei
126
What happens if the brain stem is disconnected from all structures above it including the hypothalamus
Autonomic functions still operate well
127
How does ACh activate postganglionic neurons
ACh bind to nAChRs, evoking a fast EPSP that usually triggers an action potential in the postganglionic cell
128
Evidence for ACh activating postganglionic neurons
Drugs that block nAChRs eg curare can block autonomic output
129
What can ACh released by pregabglionic neurons activate as well as nAChRs
mAChRs and GPCRs that can cause the opening/closing of ion channels that lead to very slow EPSPs and IPSP
130
How evident are the effects of ACh on mAChRs and GPCRs
Effects are usually not evident unless that preganglionic nerve is activated repeatedly
131
How can neuromodulators affect the action of neurotransmitters
Can interact with GPCRs and trigger EPSPs that can last for several minutes- can make postsynaptic neurons more responsive to the fast nicotinic effects when they come along
132
How is the pattern of firing in preganglionic neurons important in determining postganglionic activity
More than one action potential is required to stimulate the release of neuromodulators
133
Why do postganglionic cells use different neurotransmitters in the SNS and PSNS
Postganglionic cells are autonomic motor neurons that actually trigger glands to secrete, sphincters to contract or relax etc
134
Which postganglionic neurons release ACh vs NS
Parasympathetic postganglionic neurons- ACh
| Sympathetic postganglionic neurons- NA
135
What does parasympathetic ACh bind to on its targets
Binds entirely to mChRs
136
How widespread are the effects of parasympathetic ACh vs sympathetic NA released by postganglionic neurons
Parasympathetic ACh has very local effects
| Sympathetic NA often spreads very far, even into the blood where it can circulate widely
137
What are sympathomimetic drugs
Drugs that promote the actions of NA or inhibit the muscarinic actions of ACh, aka mimicing activation of the SNS
138
Example of sympathomimetic drug
Atropine is an antagonist of mAChRs that causes signs of SNS like pupil dilation, because blocking PNS actions shifts ANS activity towards the SNS
139
What are parasympathomimetic drugs
Drugs that promote the muscarinic effects of ACh or inhibit the actions of NA aka mimic activation of PNS
140
Example of a parasympathomimetic drug
Propanolol- antagonist of the beta receptor for NA, slows heart rate and lowers blood pressure, sometimes used for physiological efefcts of stage fright
141
Where is adrenaline realised from
Adrenal medulla
142
How is the adrenal medulla nothing more than a modified sympathetic ganglion
As it releases adrenaline (made from NA), a it efefcts target tissues almost identically to the SNS, causing a body-wide set of sympathetic effects
