Nerves Flashcards
(174 cards)
1
Q
What are neurons
A
The basic functional unit of the nervous system
2
Q
What are the specialised morphological features of a neuron
A
Dendrites
Soma
Axon
Synaptic terminal
3
Q
What are the dendrites for generally
A
This is the input portion of the neuron where information is received
4
Q
What is the soma Of a neuron
A
The cell body containing the nucleus
5
Q
What is the axon
A
The output portion of the neuron which sends information to another neuron or target
6
Q
What do individual axons bundle together to form
A
Nerves in the PNS and tracts in the CNS
7
Q
What are nerves ensheathed in
A
Epineurium
8
Q
What are arbours
A
The branching of the dendrites
9
Q
What does the rate of conduction of a neuron depend on
A
The diameter of the axon
the degree of myelination
distance between non-myelinated nodes
10
Q
What creates the myelin sheath
A
Schwann cells (PNS) and oligodendrocytes (CNS)
11
Q
In the PNS small diameter on myelinated axons are ensheathed by membranes of what
A
Non myelinating Schwann cells
12
Q
What are neuron cell bodies in ganglia surrounded by
A
Satellite glia
13
Q
Besides oligodendrocytes, What isthe other major glia cell type
A
Astrocytes
14
Q
What do you astrocytes contribute to
A
The blood brain barrier and remove neurotransmitters from synapses
15
Q
What line is the central canal of the spinal-cord and the brain ventricles
What do they do
A
Ependymal cells
Secrete cerebrospinal fluid and assist in its circulation
16
Q
What do microglia do
What are they
A
Immune function
Resident phagocytes of the brain and spinal cord which are derived from mono sites i.e. from large white blood cells that are part of the innate immune system
17
Q
What do you call a ganglion in the CNS
A
A nucleus
18
Q
What does a “nerve fibre” refer to
A
An axon and it’s myelin sheath but can also refer to dendrites
19
Q
What does the central nervous system developed from
A
The neural tube which forms from the ectoderm
20
Q
What do peripheral nervous system neurons mostly develop from
A
Neural crest cells
21
Q
What are neurogenic placodes?
What do they give rise to
A
Bilateral patches of thickened ectoderm
Olfactory epithelium (including all olfactory receptor neurons)
Eye lenses
Inner ear (for hearing and balance)
Some somatosensory neurons
All vestibulocochlear
All taste and viscerosensory afferent neurons
22
Q
Where are the cell bodies of viscerosensory afferent neurons located
A
Cranial sensory ganglia associated with some cranial nerves
23
Q
How do neurons develop from neurogenic placodes
A
Neurons delaminate from a placode, migrate internally and coalesce with neural crest derived glia to form a ganglion
24
Q
What are the features of the brain but you have to know for first year
A
12 pairs of cranial nerves interface between the brain and periphery and viscera, carrying sensory, motor and autonomic information
(Eg from retina to Brain or from brain to muscles)
25
What are the 3 meninges
| From out to in
Dura, arachnoid and pia mater
26
What are the ventral roots
Bundles of efferent motor axons leaving the ventral regions of the spinal-cord
27
When does the spinal cord stop growing? What about the vertebral column?
In infancy but the vertebral column keeps growing
Therefore the adult spinal cord ends around L1
28
Where are lumbar puncture and spinal anaesthesia performed
L4
29
Which nervous system due to 31 pairs of spinal nerves belong to
Somatic
30
How many coccygeal spinal nerves are there
1
31
How do you spinal nerves exit the vertebral column
Through the intervertebral foramina
32
Name 4 peripheral nerve plexuses
Cervical
Brachial
Lumbar
Sacral
33
What do thoracic rami nerves form
Intercostal nerves (NOT plexuses)
34
What is a dermatome
An area of skin that provides sensory input to one pair of spinal nerves or to cranial nerve five
35
What is a preganglionic neuron and where is it found
Which nervous system has these
A cell body in the central nervous system which conveys information to a postganglionic neuron
ANS
36
True or false: postganglionic neurons are neural crest derived
True
37
Give seven broad categories of clinical disorders regarding the nervous system
Developmental problems (spina bifida)
cell proliferation
Traumatic nerve injury
Cerebrovascular dysfunction (stroke)
Sensory dysfunction e.g. various anopias
Motor dysfunction e.g. palsy
The general degenerative diseases e.g. Alzheimer’s
38
Why is understanding of synaptic transmission important clinically
Target for pharmaceuticals
39
4 functions of glia
Structural support
Insulation
Immune function
Removal of chemicals
40
Etymology of dendrite
Dendro = tree
41
Do gap junctions allow 2 way transmission
Yes
42
What does central nervous system grey matter consist of
Neuron cell bodies, dendrites, axon terminals, bundles of unmyelinated axons, glia
43
What covers nerves
A collagenous matrix called epineurium
44
What are fascicles of axons covered by
Perineurium
45
What is perineurium
Concentric layers of large flat perineurial cells
these are the barrier to diffusion and infection
46
What are groups of axon Schwann cells embedded in
A gel like matrix: endoneurium.
47
What is the visceral nervous system
The ANS
48
Where are the cell bodies of general visceral afferent neurons
In the inferior ganglia of cranial nerves IX and X
49
What are cranial nerves
a) IX
b) X
a) petrosal
| b) nodose
50
What do general visceral sensory neurons do
Transmit “interoceptive” information To various nuclei in the nucleus of the solitary tract (NTS)in the medulla
51
Give an example of interoceptive information
E.g. Baroreceptors about changes in blood pressure
52
Are signals from general visceral sensory neurons perceived consciously
No but intense stimulation may cause pain or nausea
53
What regulates the activity of a print/motor neurons in the ANS
Descending projection
| Promoter neurons
54
Preganglionic sympathetic exons tend to be…
Short
55
What do you preganglionic sympathetic neurons release
Therefore they are
ACh
Cholinergic
56
Sympathetic postganglionic neurons release what?
What are they therefore ?
Noradrenaline
Adrenergic
57
Almost all sympathetic post ganglionic neurons release noradrenaline. What is the exception
Postganglionic neurons to sweat glands which release : ACh
58
Where are parasympathetic ganglia located
What does this mean for the length of the preganglionic and postganglionic axons
They are intramural so are located near or within the wall of the target effector
Pre: long
Post: short
59
How many postganglionic neurons can a preganglionic sympathetic neuron synapse with
What does this explain
20+ (supplying different effectors)
Why sympathetic effects tend to be widespread in the body
60
How many postganglionic neurons does a preganglionic parasympathetic neurons synapse with
4-5 (which all supply the same visceral effector)
61
True or false
parasympathetic effects tend to be widespread
False they are usually localised
62
Describe the thoracolumbar outflow of the SNS
myelinated preganglionic axons which originate from neuronal bodies in the intermediolateral nucleus of T1 to L2 spinal segments
63
How do sympathetic preganglionic axons concerned with blood vessels, sweat glands and hair follicles travel
Via the ventral roots and white rami to synapse onto neural crest derived postganglionic neurons in sympathetic chain ganglia at all levels
64
Where do the sympathetic chains meet
Coccyx
65
How do postganglionic axons exit the sympathetic chain
Via grey rami to rejoin and travel with spinal nerves to the target effectors
66
Why are there two pairs of spinal nerves rami at the thoracic spinal levels
That are white and grey rami to/from the sympathetic chain and dorsal and ventral running to the back/trunk and limbs
67
From which ganglion do postganglionic postganglionic axons travel to eye muscles, lacrimal and salivary glands
What about to the heart and lungs?
Superior cervical ganglion
Middle/inferior cervical and T1–5 ganglia
68
What is the stellate ganglion
A fusion of the inferior cervical ganglion and the T1 ganglion
69
How many pairs of sympathetic ganglion are there
~25
70
Where do you preganglionic sympathetic axons concerned with the adrenal medulla synapse
Onto neural crest derived adrenal chromaffin cells
71
What can neural crest derived adrenal chromaffin cells be considered to be
Modified sympathetic postganglionic neurons that have lost many neuronal characteristics and are specialised to release the cycles of adrenaline and noradrenaline as hormones into the bloodstream
72
What happens to preganglionic axons concerned with the abdomen and pelvis
They pass through the sympathetic chain ganglia without synapsing and from the splanchnic nerves which synapse with sympathetic abdominal ganglia/prevertebral ganglia: a coeliac ganglion and mesenteric ganglia
73
Postganglionic axons from the coeliac ganglion and mesenteric ganglia go where?
To supply the stomach, spleen, liver, kidney, intestines, rectum, bladder, genitals and enteric plexus
74
Describe the anatomical basis of parasympathetic outflow
There is a craniosacral outflow:
Preganglionic axons from neuron cell bodies in the brain and in S2–4
(This is controversial)
75
How do the cranial components of the parasympathetic nervous system travel
They hitchhike along cranial nerves III, VII, IX, and X To sign apps on neural crest derived postganglionic neurons in parasympathetic ganglia located near the wall of the target effector
76
In the head many postganglionic parasympathetic fibres hitch hike along branches of which cranial nerve?
Trigeminal (V)
77
Which cranial nerve is the oculomotor nerve
III
78
What is common about cranial nerves
| III, VII, IX and X
They are all mixed cranial nerves
i.e. contain different functional components including parasympathetic fibres
79
Where is the Edinger Westphal nucleus
How do you preganglionic axons from here travel
On the rostral aspect of the oculomotor nucleus in the midbrain
They hitchhike along cranial nerve III synapse in the ciliary ganglion in the posterior orbit
80
What happens to nerves from the ciliary ganglion
The postganglionic axons project as short ciliary nerves and also travel with the nasociliary nerve (a branch of Va) to sphincter pupillae and ciliaris muscle
81
How do you preganglionic axons from the superior salivary nucleus (pons) travel
What happens to postganglionic fibres
With the greater Petrosal nerve (a branch of VII) to synapse in the pterygopalatine ganglion
They travel long branches of the Va/Vb to lacrimal, nasal and Palatine glands
82
How might preganglionic parasympathetic axons travel From the superior salivary nucleus if not via the greater petrosal nerve?
Post ganglionic?
Via the chorda tympani (branch of VII) and then The lingual nerve (branch of Vc) to synapse at the submandibular ganglion
Project to the submandibular and sublingual salivary glands after re-entering the lingual nerve.
83
Which nerve is the facial cranial nerve and which nerve is cranial nerve nine
Facial: VII
IX: glossopharyngeal
84
How do you preganglionic exons from the inferior salivary nucleus travel
Along the lesser Petros a nerve (branch of IX) to synapse at the otic ganglion
85
Where are the following things located:
a) otic ganglion
b) inferior salivary nucleus
c) submandibular ganglion
a) just inferior to foramen ovale
b) upper medulla
c) near ducts of submandibular salivary glands
86
Does cranial nerve IX only contain parasympathetic fibres
No, it also contains general visceral sensory fibres which transmit information from the oropharynx and carotid bodies to the NTS
87
Where do the general visceral sensory fibres originate from
Placode derived neurons in the petrosal ganglion
88
What is the name of the inferior ganglion of cranial nerve IX
Petrosal ganglion
89
Which cranial nerve is vagal
X
90
Describe the preganglionic axons of the Vagus
Preganglionic exons from the dorsal motor nucleus of the vagus in the medulla travel as part of the vagal nerve (X) to synapse in intramural ganglia in the viscera of the thorax and abdomen
91
Where do the pre-ganglionic parasympathetic axons from sacral spinal cord segments S2–4 synapse
In intramural ganglia in part of the colon, the rectum, bladder and genitals
92
How many neurons involved in the ganglionated plexuses of the enteric nervous system
From Where are they derived
400-600 million
Neural crest
93
What do neurons of a) myenteric plexus and B) submucosal plexus control?
a) gut motility
| b) secretion
94
Is the ENS only sensory neurons
What does this mean
No: it includes sensory neurons, interneurons and motor Neurons
The ENS of the small intestine and colon has complete reflex pathways controlling contraction, local bloodflow and transmucosal fluid movement
95
How is sensory information from the GI tract transmitted to the CNS
Where are each derived
Via somatic sensory axons (derived from neurons in the dorsal root ganglia) and general visceral sensory axons (from neurons in the nodose ganglion) in the vagus
96
Are enteroendocrine cells neural crest derived
No
97
Which cells produce over 90% of the bodies serotonin
What do these cells interact with
Enterochromaffin cells
They are polymodal sensors and have recently shown to synapse with nodose neurons, connecting the lumen directly to the brainstem
Can trigger emesis and nausea
98
What do you prevertebral sympathetic ganglion receive input from
Both from preganglionic sympathetic neurons in the CNS and from intestinofugal neurons in the ENS
99
What is CCHS
Describe
Congenital central hypoventilation syndrome
Autonomic reflex circuits depend on the transcription factor PHOX2b, does mutations in PHOX2b underlie this autonomic regulation disorder
100
Describe Raynaud’s syndrome
Paradoxical vasoconstriction of arteries in extremities caused by hyperactivity of sympathetic innovation to peripheral blood vessels
Results in discolouration and numbness in fingers
101
What is Horner’s syndrome
Impaired cervical sympathetic function
102
What is hyperhidrosis
Excessive sweating
103
Describe Hirschsprung’s disease
“Aganglionic megacolon”
A failure of neural crest cells to colonise the distal colon, resulting in the absence of ENS ganglia in this region, hence no peristalsis, severe constipation and colonic distension
104
How can glaucoma be treated
Cholinesterase inhibitors
Or
Muscarinic receptor agonists
105
What is used to reduce GI hypermotility
Muscarinic receptor antagonists
106
What can adrenoceptor agonist be used for
Cardiac arrest and asthma
107
What can adrenoceptor β antagonist be used for
CV conditions
Glaucoma
Anxiety
108
True or false: all autonomic ganglia are neural crest derived
True
109
What is interoceptive information
Information not consciously perceived most of the time
110
What is divergence
A neuron synapsing with many other neurons
111
What is the new view on the sacral autonomic outflow
It is sympathetic
112
Why is the biology of neurons particularly unusual
You are born with almost all of the neurons you ever have: they are not replaced
113
Nerve cells are very long left. What does this mean for function
Minor degradation over time can affect function
114
What part of a neuron contains the nucleus
Soma
115
Name some diseases which cause the death of neurons with peripheral axons
What is the course of treatment in these cases
Degenerative diseases: ALS/motoneuron disease, Frieditch’s ataxia
Infectious diseases: spinal poliomyelitis, tabes dorsalis caused by syphilis
Loss of neurons is permanent so the treatment is to provide support for life with alternative means
116
Are Schwann cells and oligodendrocytes the same
While they both produce myelin that envelops axons they are a distinctly different type of cell with different properties
117
How fast are motoneuron axons
What other axons are similar
Motor neurons are large and fast conducting
Touch and proprioceptive sensory receptor axons
118
Which axons are of intermediate velocity
Fast pain nociceptors
Thermal receptors
Preganglionic autonomic axons
119
Which axons have no myelin and are slow conducting
Nociceptors for slow pain
Warm thermal receptors
Postganglionic autonomic axons
120
Give two examples of peripheral neuropathies
Charcot-Marie-Tooth disease
Guillan Barre Syndrome
121
Describe Guillan Barre Syndrome
An acute autoimmune disease of the peripheral nerve myelin sheath
Usually a post infection complication
Similar to MS but not as persistent usually
122
Describe Charcot-Marie-Tooth disease
The most common hereditary peripheral neuropathy
123
What does peripheral nerve demyelination result in
Decreased conduction velocity and consequent sensory deficits, muscle weakness, muscle wasting, loss of reflexes and impaired gait.
124
What can generalised nerve damage follow
Poor vascular perfusion of nerve terminals e.g. in ischaemia or frostbite
125
What is the most common form of peripheral neuropathy seen in the UK?
Why is this a major clinical problem?
Damage caused by micro vascular lesions in diabetes type 2
It prevents sufferers from being aware of minor trauma, a major way that diabetic leg ulcers can be generated.
126
How are the various layers of connective tissue offering mechanical support and protection to myelinated axons divided
Endoneurium covers the individual myelinated axons
Perineurium covers bundles of axons (usually destined for a specific nerve)
A tough epineurium covers the whole nerve
127
When is mechanical trauma to nerves particularly common
Eg
Where nerves are close to bones and under the skin
e.g. ulnar nerve at elbow or common fibular nerve at the head of fibula
Around joints that may dislocate (eg axillary nerve at shoulder )
128
Do all areas of skin have the same sensitivity
No different areas of skin have inherently different sensitivity
129
Why is testing motor function difficult for nerve damage
How can this be remedied? What is a problem with this?
Different individuals have different muscle strength so absolute measures are not straightforward
Local damage can be tested by comparing the two sides however one must remember that systemic neuropathy will produce systemic effects
130
What is trigeminal neuralgia
A condition where nociceptive axons from the face become hypersensitive to direct mechanical activation at the site of pressure (from pulsations of a nearby artery)
131
True or false:
during embryonic development the axon of nerve cells have difficulty finding that targets accurately
Eg?
False: the axons of nerve cells find a way to their targets very accurately
Eg: Upper limb motoneuron axons found their way through spinal nerves through a peripheral brachial plexus to the peripheral nerves and out to innovate the muscle
132
What most neural crest cells do when forming dorsal root ganglia
Grow one branch out to the periphery and another into the spinal-cord
133
Name a major mechanism allowing the specificity of nerve development
Chemotaxis - The guidance of axons to the target by molecular cues
134
Other than chemotaxis what is a second mechanism to encourage growth of nerves
Neurotrophic factors
135
True or false
In adult nervous systems the neurons are made stable contact with the target and there is no long-distance growth and no to a communication between neurons and targets
False
While there is no long-distance growth there is still continual two-way communication between the neurons and that targets by a chemical signalling mechanisms that we know little about
136
In the mature PNS neurons the axon provides a means of communication between what?
Between the soma and the distal nerve
137
What is axotomy?
What does this result in?
Cutting or crushing the axons, disturbing its internal structure
The distal part of the axon becomes metabolically and electrically isolated. Wallerian degeneration follows.
138
Give the three steps of Wallerian degeneration
1) Initially the distal part of the axon breaks down and the myelin sheath degenerates
2) Schwann cells, having lost their lives in Milan, become phagocytic and clear the myelin and axon debris
3) The Schwann cells divide and the newly generated cells release diffusible neurotrophins and express cell adhesion molecules that promote and guide axonal regeneration
139
What happens to the soma of the damged neuron while Wallerian degeneration occurs?
Chromatolysis - the soma changes and its phenotype becomes supportive of axon growth
140
What are growth cones
Generated by axons during embryonic development they are large dynamic structures which send out long cytoplasmic processes that sense the molecular environment both by contact and through diffusible signals
141
Give a simile to describe growth cones
Like an ‘amoeba on a leash’
142
Do the neurotrophic factor is released by Schwann cells act specifically
No they encourage growth generally
Both secreted and surface molecules guy in the direction of growth towards its target
143
Do injured PNS axons have capacity to regrow
Yes: they form new growth cones that grow along the connective tissue and Swan cells along the course of the degenerated nerve
144
Are Schwann cells important in the regeneration of PNS axons
Yes they provide an environment favourable for growth, providing both chemotactic and neurotrophic support
145
Briefly discuss CNS nerve repair
Oligodendrocyte do not support or promote axon growth so long distance nerve repair does not happen
146
How might regenerates axons differ from the original
While Schwann cells re-myelinate axons as they grow it is not done to the same extent as the original axons, so conduction is slower
Regenerate actions may reach the appropriate structures but some form incorrect connections
If axons form synapses with each other a neuroma is formed
147
Give for factors that affect the extent of regrowth of nerves.
The extent of damage, in particular the destruction of the connective tissue layers of the nerve
Distance
Time
Substrate
148
How does distance affect regrowing axons
Axons grow at a maximum rate of 1 mm a day
this delays long distance growth
149
Why is time important factor which affects the extent of regrowth of axons
While target tissues and Schwann cells provide trophic factors to encourage axon growth, they themselves also depend on trophic factors released by nerves.
Muscles that are not innovated atrophy and stop releasing trophic factors over time
Regrowing axons that do not reconnect relatively early therefore progressively lose the signals that encourage, support and guide the growth
150
Why does the substrate matter when considering the extent of the regrowth of axons
Cut or damaged axons cannot cross a gap
151
How can you try to fix a nerve that must cross a gap
Re-apposing the ends of cut or damage nerves is the best option but is not also always possible
Nerve graphs are possible but should ideally be from the same patient
152
What is the best kind of nerve graft
Why is this not always possible
Autografts - From the same patient
Few of us have spare nerves
153
Which nerve is often used in an autograft?
Why is it not ideal
Sural nerve
It is relatively small in diameter
154
Give three methods that might improve nerve degeneration treatment in the future
Using engineer tissue that can help promote growth for bridging gaps across cut nerves
Methods for extending the distance over which regenerating axons can grow (by extending the range and duration of the growth promotion and preventing target atrophy)
More accurately targeting axons to the correct peripheral structures
155
Describe the following diseases:
A) ALS
B) Friedeitch’s ataxia
Sensory neuron and large CNS neuron degeneration leading to loss of motor function
156
Describe neural degeneration in syphilis
Sensory neurons/dorsal root ganglia degenerate in the tertiary stage of syphilis, leading to tabes dorsalis– loss of the somatosensation
157
Tabes dorsalis is associated with which disease?
Syphilis
158
How many layers of myelin can there be
>100 double layers
159
Give Four ways axons are vulnerable to mechanical damage
One. Compression
Two. Traumatic compression/tearing associated with fracture or dislocation
Three. Traumatic stress with stretch e.g. avulsion of spinal roots
Four. Cutting or tearing in wounds
160
What can sciatica be caused by
L5 prolapsed Disc causing pain in back and leg
161
Describe Bell’s Palsy
The facial nerve as it exits the skull is a pure motor nerve that innervates the muscles of the facial expression
It leaves a skull through a narrow bony tunnel and can be compressed within this tunnel leading to paralysis of the face
162
Which nerve is likely to be damaged hit by a car
The common fibular nerve as it runs on the lateral surface of the fibula at car bumper level
163
Which nerve is likely to be damaged while sitting during a car accident
The sciatic nerve as it lies behind the hip joint and is at risk in posterior dislocation following impact on the knee while sitting
164
Jim is in nerves are usually in what cell
Schwann cells
165
Name a famous person who suffered avulsion of the spinal roots in the upper brachial plexus
What is this palsy called
Kaiser Wilhelm II
Erb’s palsy (waiter’s tip)
166
Which to Cambridge students studied nerve regeneration
Rivers and Head
167
What form is on the growing tip of the axon
Actin
168
What transmit materials between the cell body and the growth cone
Microtubule proteins
169
Is it the nerve that emerges through the space above or below the prolapsed disc that is damaged
Below
Eg a T4/5 disc prolapse will compress L5 nerve root
170
During a lumbar puncture where does the needle traverse
The epidural space
171
What is the nerve root of the femoral nerve
L2-4 POSTERIOR divisions
172
Attachements of the inguinal ligament?
Anterior Superior iliac spine to pubic tubercle
173
A fracture of the surgical neck of the humorous will damage which structures
Axillary nerve and circumflex arteries
174
Give the movement around the following joints
a) S2 and 3
b) C4 and 5
c) between L5 and S1
d) C1 and occiput
e) C1 and 2
a) no movement
b) flexion, extension, and lateral flexion
c) flexion, extension, and lateral flexion
d) flexion and extension only
e) rotation only
