Autonomic nervous system Flashcards
1
Q
What is the ANS?
A
- a diffuse system that innervates
2
Q
What does the ANS innervate?
A
- visceral structures
- glandular myoepithelium
- fat
- vasculature and cardiac tissue
3
Q
The ANS has what components?
A
- afferent
- central
- efferent
4
Q
What do afferent and efferent neurons often both use?
A
- the same pathways
5
Q
What can afferent visceral axons also use to travel?
A
- somatic spinal nerves to reach the CNS
6
Q
What is normally talked about when taking about the ANS?
A
- general visceral efferent innervations
7
Q
Is the autonomic NS voluntary or involuntary?
A
- involuntary
8
Q
What does the ANS aim to do?
A
- aims to preserve a constant internal environment
9
Q
How can the ANS be divided?
A
- functionally
- anatomically
10
Q
What are the two division’s of the ANS?
A
- parasympathetic system
- sympathetic system
11
Q
What is the parasympathetic system?
A
- rest and digest functions - conserve energy
- arising from the brain and sacral spinal cord
12
Q
What is the sympathetic system?
A
- fight or flight - requires energy
- arising from the thoraco-lumbar spinal cord
13
Q
Each organ will receive innervation from both what?
A
- both sympathetic and parasympathetic nerve axons
14
Q
What does sympathetic dominance cause?
A
- increasing heart rate
- decreased gut motility
- dilating pupils
15
Q
What does parasympathetic dominance cause?
A
- reduced heart rate
- increased gut motility
- constricted pupils
16
Q
Balance between two systems determines overall effect - what does dual innervation allow?
A
- precise control over internal systems
17
Q
Some organs only receive sympathetic innervation - what are these?
A
- Liver
- vessels in muscle
- cutaneous and visceral vessels
- piloerector muscles
- sweat glands
- adipose cells
- adrenal medulla
18
Q
The autonomic nerve pathway consists of a 2- neurone chain?
A
- synapse in a ganglion
- post-ganglionic neuron (usually) unmyelinated
19
Q
Post-ganglionic (post-synaptic) nerves release different neurotransmitters - what are these?
A
- norepinephrine
- acetylcholine
20
Q
What can each neurotransmitter have?
A
- a different receptor type
21
Q
Different effects caused by a combination of different neurotransmitters and receptors - what can these be?
A
- can excite or inhibit target cells
22
Q
First efferent neurones synapse outside as a ganglia (pre-ganglionic) then what happens?
A
- then goes to post ganglionic neuron which is unmyelinated = slower conduction
23
Q
What is the advantage of 2-neurone setup?
A
- shifting neurons into the periphery conserves space in the CNS (limited space due to bones)
- non-myelination axons are slower, but more metabolically efficient (conserves energy)
24
Q
What happens when neurons are moved into the periphery? and what is a disadvantage of this?
A
- cell bodies are grouped into periphery pre-vertebral and paravertebral ganglia
- a disadvantage is reduced brain control, but visceral organs have a limited repertoire of actions
25
As there is non-myelination in a 2-neuron setup axons are slower why is this not an issue?
- reduced conduction speed not really an issues with smooth muscle contraction and gland secretion
26
Where are the main control centres for the ANS located?
- in the hypothalamus
- also connected to brainstem centres that regulate cardiovascular and respiratory function
27
What does the rostral hypothalamus influence?
- parasympathetic system
28
What does the caudal hypothalamus influence?
- sympathetic system
29
Other parts can influence but not command the control centres what are examples of this?
- E.g. cerebrum and limbic system (e.g. fear causing piloerection)
- E.g. olfactory stimulation causing drooling
30
What are the components of the reflex arcs?
- sensory receptor
- sensory neurone (GVA) - general visceral afferent neurone
- integrating centre
- pre-post ganglionic motor neurons (GVA)
- visceral effectors
31
unconscious sensations include the regulation of what?
- blood pressure
- digestion
- urination
- defecation
32
Where does the sympathetic NS originate from?
- originates from lateral/intermediate horn of thoracolumbar spinal cord
33
Where does the sympathetic NS leave?
- leaves via ventral roots around T1 to L3/4
34
The sympathetic NS synapse in ...
- Paired chain of ganglia alongside vertebral column (the sympathetic trunk aka sympathetic ganglion chain) OR
- Median prevertebral ganglia in the dorsal thoracic and abdominal cavities
35
Due to the way sympathetic NS synapses what does this mean for axons?
- has short preganglionic and long post-ganglionic axons
36
What is released from post-ganglionic neurones in the sympathetic NS?
- norepinephrine
- And also specialised postganglionic neurones in the adrenal medulla, into bloodstream
37
The sympathetic trunk - where do the presynaptic sympathetic neuron's leave?
- leaves the vertebral foramen with the spinal nerve
38
Where do rami communicans branch from?
- spinal nerve
39
What do rami communicans (RC) do?
- coney sympathetic axons between the spinal nerve and sympathetic trunk
40
Norepinephrine is what system?
- sympathetic
41
Acetylcholine is what system?
- parasympathetic
42
White RC carry what?
- carry presynaptic (myelinated) sympathetic neurons to the ganglia
43
What do grey RC carry?
- carries postsynaptic (unmyelinated) sympathetic neurons back to the spinal nerve (to the target)
44
For all regions of the body, the initial pathway for sympathetic preganglionic axons is identical: what is this?
ventral root -> spinal nerve -> (white) ramus communicans -> sym. trunk
45
Following the sympathetic trunk, the pathway for sympathetic neurones depends on what?
- the body region
46
How is innervation to the body wall conducted?
* sym. trunk > grey rami communicans > spinal nerve
47
How is innervation of the head conducted?
sym. trunk > ansa subclavia > cranial sympathetic trunk
48
How is innervation to abdomen and pelvis conducted?
- sym. trunk > major, minor and lumbar splanchnic nerve > various ganglia
49
Innervation of the head:
At the cranial end of the trunk, the cervicothoracic ganglion is quite visible - what is this and how is it formed?
- the largest autonomic ganglion in the body
- formed from fusion of cervical and thoracic ganglia
50
What does the ansa subclavia connect?
- the cervicothoracic ganglion to the middle cervical ganglion and the cervical sympathetic trunk
51
Why is ansa called a handle?
- because nerves form a loop enclosing subclavian artery
52
Innervation of the abdomen:
Splanchnic nerves run through what?
What do they not do here?
What nerves are splanchnic nerves?
- the sympathetic trunk
- don't synapse here
- these are the pre-synaptic nerves
53
Where do splanchnic nerves synapse?
and give examples
- synapse at named (prevertebral) abdominal ganglia, e.g.
* Coeliac ganglion
* Cranial mesenteric ganglion
* Caudal mesenteric ganglion
54
Nerves can pass through a ganglion without what?
- synapsing
55
Where does the parasympathetic NS originate from?
- originates from the brain stem and sacral segments of the spinal cord
56
What nerves innervate the head?
where do they originate from?
- Cranial nerves III, VII, IX and X
- originating from PS nuclei III, VII, IX, X in the brainstem)
57
What nerves innervate thoracic and abdominal viscera?
- Vagus nerve (CNX)
58
What innervates the pelvic viscera and where does it come from?
- Sacral PS nerves
- originating in spinal cord intermediate grey matter
59
Where do parasympathetic nerves synapse?
- Synapse in ganglia located close to or within target organ
60
Due to where parasympathetic nerves synapse what does this means for their neurones?
- generally long presynaptic and short postsynaptic neurones
61
What does the post-synaptic neurone in the PSns release?
- acetylcholine
62
Where does the vagus nerve start and reach as far as?
- starts in brainstem and reaches as far as colon
63
Where do cranial and recurrent laryngeal nn. branch from?
- from vagus at base of skull and cranial thorax
64
There is rich vagal innervation to where?
- heart and lungs
65
Caudal to the root of the lung, vagus n. on each side splits into what?
- dorsal and ventral branches
66
Left and right dorsal and ventral branches of vagus nerve each fuse, and do what?
- pass through the diaphragm at the oesophageal hiatus
67
What supplies the abdominal viscera?
- many smaller branches of the vagus nerve
68
Vagal nerve trunks run in nerve plexuses on what vessels?
- on coeliac and cranial mesenteric vessels
69
How is the pelvic viscera innervated?
- PS supply to the pelvic viscera are supplied by pelvic nerve, arising from sacral spinal nerves
70
Where are the two subdivisions co-located?
- Between the cranial cervical ganglion and the middle cervical ganglion
71
In the two subdivision the vagus nerve (CNX; PS) and the cranial sympathetic trunk (S) run together as what?
- the vagosympathetic trunk
72
What is the two subdivision located inside of?
- Located inside carotid sheath
73
For the pelvic viscera the pelvic nerve expands into what and recieves what?
- expands into the pelvic plexus, which also receives fibres from the hypogastric nerve (S).
74
Where does the pelvic nerve branch from?
- Branches from the pelvic plexus supply the pelvic viscera
