1 organisation and classification of nerves Flashcards
(91 cards)
1
Q
CNS = central components
A
brain + spinal cord
2
Q
PNS = peripheral components
A
peripheral nerves = sensory + motor neurones
3
Q
brain segments
A
forebrain, midbrain and hindbrain
4
Q
spinal chord segments total
A
31
5
Q
divisions of PNS = pas
A
Peripheral = autonomic + somatic
6
Q
divisions of autonomic = SP + EC
A
- sympathetic
- parasympathetic
- enteric (gut) and cardiac plexuses
7
Q
ENS = branch of ANS = both sympathetic and parasympathetic
A
enteric (or intrinsic) nervous system
8
Q
PNS: both autonomic and somatic have
A
sensory and motor components
9
Q
ANS…
A
- involuntary
- HR, respiration, digestion, pupil contraction
10
Q
somatic nervous system…
A
- voluntary = conscious control
- sensory info relays to muscle commands
11
Q
overlap between CNS and PNS…
A
part of ANS lies in CNS
12
Q
The nervous system 2 main divisions
A
CNS + PNS
13
Q
symp =
A
fight or flight response
14
Q
paraSymp =
A
rest and digest
15
Q
neurone =
A
a nerve cell
16
Q
dendrites
A
receive information = signal inputs
17
Q
axon terminals
A
transmit information
18
Q
both axons and dendrites are…
A
NEURITES = projections from the neurone cell body
19
Q
neurons main component of brains…
A
grey matter
20
Q
all motor neurons transmit
A
acetylcholine
21
Q
synapses are at
A
axon terminals
22
Q
structural classes of neurones
A
- unipolar
- pseudo-unipolar
- bipolar
- multipolar
23
Q
unipolar structure =
A
one structure extends off cell body
= has 1 axon
= has no dendrites
24
Q
unipolar neuron function
A
found in sensory ganglia
no dendrites = no input, sends signal from cell body
25
unipolar vs pseudounipolar
unipolar = one unbranched axon
pseudounipolar = axon branches, goes in opposite directions, branch to different targets
26
bipolar structure =
cell body runs in the axon
one axon + one dendrite
cell body in between the 2 projections
27
bipolar neuron function
- found in sensory structures
- rare
- retinal neurones
28
multipolar neuron structure =
one long axon, multiple dendrites
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multipolar neuron function
= motor and relay neurones
get signal from lots of dendrites, transmit long distance to effector
30
Weigert's stain = goes dark
stains myelin
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white matter = stains darker
mostly axons = myelin stains dark with Weigert's = tracts
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grey matter = stains pale
mostly cell bodies = nuclei
33
In CNS cell bodies =
nucleus/nuclei -> found in grey matter of CNS
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In PNS cell bodies =
ganglion/ganglia
35
In CNS bundle of axon =
tracts -> found in white matter of CNS
36
In PNS bundle of axon =
nerves
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4 main groups of nuclei (neuron cell bodies) in grey matter of CNS
- SS = somatosensory
- VS = viscerosensory
- VM = visceromotor
- SM = somatomotor
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somatosensory area of grey matter CNS
superficial dorsal horn
| = interneurones responding to inputs from sensory neurons from body's external tissues (somato-)
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viscerosensory nuclei
deep dorsal horn
| = interneurones responding to inputs from sensory neurons from internal organs (viscero-)
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visceromotor nuclei
intermediate/ lateral horn
| = motor neuron cell bodies supplying body's internal organs
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somatomotor nuclei
ventral horn
| = motor neuron cell body supplying body's external tissues
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somato-
external tissues = somatic nervous system
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viscero-
internal organs = ANS
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dorsal root ganglion
posterior/back
info into CNS
sensory neurons
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ventral root ganglion
anterior/front
info away from CNS
motor neurons
46
ganglia definition (PNS)
nodular masses of neurone cell bodies (ganglion cell) & supporting neuroglia (satellite cell)
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2 types of ganglia in PNS
- sensory ganglia = cell bodies of sensory neurons (dorsal root ganglia)
- autonomic ganglia = cell bodies of motor neurons only in the ANS (involuntary)
48
efferent
motor
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afferent
sensory
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structure of peripheral nerves = 3 layers of connective tissue
1. Endoneurium = covers individual axons
2. Perineurium = covers individual fascicles
3. Epineurium = covers the whole nerve
51
bundle of axons is called
a fascicle
52
spinal nerves are mixed
contain both sensory (afferent) and motor (efferent) fibres
53
neuroglia = glia/glial cells which are
supporting cells for neurons
54
Glial cell dysfunction implicated in
neurological disorders e.g. autism, schizophrenia, neurodegeneration
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types of glial cells in CNS -> eamo
- ependymal cells
- astrocytes
- microglia
- oligodendrocytes
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types of glial cells in PNS -> ss
- satellite cells
| - schwann cells
57
astrocytes = most common
| CNS
- Structural
- Glucose metabolism - glucose -> lactate then can be taken up by neurons
- Growth - produce growth factors
- BBB regulation
- Potassium clearance -> pump K+ into capillaries
- Ultimate layer of protection around brain and CNS
- Regulate neurotransmitters
58
ependymal cells
| CNS
- Lining walls of ventricles (cavities in brain filled with CSF)
- Lining of CNS
- Produce CSF
- Have cilia on luminal side
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microglia = less common
| CNS
- Immune defence
| - Become phagocytic
60
oligodendrocytes = myelinate axons
| CNS
1 does about 50
| most common in white matter
61
PNS glia = schwann cells
similar to oligodendrocytes =
- phagocytic activity
- myelinate axons in PNS
membranes wrap around axon - myelin lipid insulation
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PNS glia = satellite cells
surround sensory, sympathetic, and parasympathetic ganglia
regulate external environment
similar to astrocytes
very sensitive to injury + inflammation
63
myelination occurs in both...
CNS (oligodendrocytes) and PNS (schwann cells)
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process of myelination
wrap axon in spiral of concentric layers of fatty myelinated membrane
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myelination ability for schwann cells vs oligodendrocytes
schwann cell (PNS) = only one part of one axon
oligodendrocytes (CNS) = around several full axons
66
unmyelinated axon
= not naked! still associate with schwann cell
- have supporting schwann cell
- axon lies in channel called mesaxon
- one schwann cell can support several axons
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classifying demyelinating disease = damage to myelin sheath
1. Demyelinating myelinoclastic
| 2. Demyelinating leukodystrophic
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Demyelinating myelinoclastic =
secondary cause, damage due to toxins
69
Demyelinating leukodystrophic =
primary cause, damage due to abnormal myelin, degenerates
genetic causes, some idiopathic
70
MS = common demyelinating disease in CNS
aetiology = autoimmune
- Environmental/genetic factors lead to loss of tolerance to self-proteins
- Inflammation and injury to the myelin sheath and nerve fibres
- Multiple areas of scarring (sclerosis i.e. lesions/plaques)
- Physical, mental, psychiatric problems
71
parasympathetic preganglionic fibre length
long, myelinated
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sympathetic postganglionic fibre
long, many branches
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sympathetic preganglionic fibre
short, myelinated
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parasympathetic postganglionic fibre
short, few branches
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neurotransmitter preganglionic
```
symp = ACh
parasymp = ACh
```
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neurotransmitter postganglionic
```
symp = noradrenaline (=speed up response)
parasymp = ACh
```
77
what is nerve classification based on
- fibre diameter
| - conduction velocity
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two nerve classification systems are
= applied to both somatic + autonomic
letters A, B, C = motor fibres + some non-muscle sensory fibres
roman numerals I, II, III, IV = sensory fibres from muscle
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nerve classification I, II, III, IV
I = fastest
for sensory motor afferents
from dorsal root = sensory neurons
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nerve classification A, B, C
A = fastest
for motor efferents
from ventral root = motorneurons
81
exception for nerve classification
non-myelinated sensory fibres are frequently referred to as C-fibres, not type IV
82
nerve conduction velocity (NVC)
-> greater the axon diameter and extent of myelination, the faster the conduction velocity
* A = ~120 m/sec; B = ~18 m/sec; C = 0.5-2.0 m/sec
| * I = 75-120 m/sec; II = 35-75 m/sec; III = 5-35 m/sec; IV = 0.5-2.0 m/sec
83
NCV myelinated vs non-myelinated
Myelinated fibres thick (>4µm) - higher NCV than non-myelinated fibres thin (<2µm)
84
classifications of axons from skin
* A-alpha – group 1 – proprioceptors of skeletal muscle
* A-beta – group 2 – mechanoreceptors of skin
* A-delta – group 3 – pain or temperature
* C – group 4 – temperature, itch and pain
```
B = preganglionic sympathetic
C = postganglionic sympathetic
```
85
sensory receptors classified by location
* Exteroceptors – external surface
* Interoceptors – internal organs
* Proprioceptors – internal, but concerned with position of muscles, tendons, joints
86
sensory receptors classified by stimulus detected
* Mechanoreceptors – touch, pressure, vibration, stretch
* Thermoreceptors – hot, cold, temperature change
* Photoreceptors - light
* Chemoreceptors – chemicals
* Nociceptors – pain (usually chemicals)
87
nociceptors detect...
pain
88
sensory receptor ending = muscle spindle
skeletal muscles – stretch – non-adapting
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sensory receptor ending = free endings, unencapsulated
connective tissue, joints and skin – pain/touch/pressure and light – slow or fast adapting
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sensory receptor ending = Meissner's/ Krause's bulbs
oral mucosa, lips, genitalia, fingertips – touch, vibration, light pressure – rapid adapting
91
sensory receptor ending = Ruffini organs
deep dermis, ligaments, joint, cartilage – stretch, deep pressure – very slow adapting
