Term 2- Pt. 1 (spine and nerves) Flashcards
(145 cards)
1
Q
Which rami form the plexuses?
A
Ventral Rami
2
Q
Ventral and dorsal nerve roots combine to create
A
The spinal nerve (which is a mixed nerve)
3
Q
What type of neurons are sensory neurons (structure)?
A
Pseudounipolar- periphery goes to sensory receptors and central goes to dorsal horn
4
Q
Dorsal root cell bodies are located where?
A
dorsal root ganglion which is outside the spinal cord
5
Q
Dorsal rami function?
A
deep muscles of spine
cutaneous input of trunk
proprioception of z joints
6
Q
Ventral rami function?
A
cutaneous of extremeties
proprioception of trunk and extrememties
ANS to spinal columns
7
Q
What is a dermatome?
A
area of skin supplied by single dorsal nerve root
8
Q
What is a myotome?
A
muscle fibres innervated by a single ventral nerve root (only 3 true myotomes)
9
Q
Do dermatomes vary?
A
Yes they vary between people
10
Q
Which spinal nerves form the brachial plexus?
A
c5, C6, C7, C8, T1
11
Q
Explain brachial plexus
A
C5+ C6–> Superior
C7–> Middle
C8+T1–> Inferior
All split into Anterior + Posterior (ex anterior and posterior superior)
Anterior superior + Anterior middle–> Lateral
Posterior superior+Posterior middle+Posterior inferior–> Posterior
Inferior Anterior—> Medial
Medial splits into ulnar and medial aspect of median
Posterior splits into axilliary and radial
Lateral splits into lateral median and musculocutaneous
12
Q
What is CNS
A
Central nervous system –> Brain and Spinal cord
13
Q
PNS
A
Peripheral nervous system- everything else
nerve fibers spinal nerves etc.
14
Q
Functionally how is the nervous system divided?
A
ANS- autonomic- cardiac etc
Sympathetic- skeletal muscle joints
15
Q
What nerves make up the cervical plexus?
A
C1-C5
16
Q
What nerves make up the brachial plexus?
A
C6-T1
17
Q
What nerves make up the lumbar plexus?
A
L1-4
18
Q
What nerves make up the sacral plexus?
A
L4 on
19
Q
What does white matter carry in spinal cord? Why is it white?
A
Central sensory and central motor nerves- in periphery. Because of lipids myelin surrounding axons
20
Q
What does gray matter in spinal cord house?
A
Cell bodies of motor neurons
cell bodies of interneurons
glial cells
21
Q
Motor neuron cell bodies are in the
A
ventral horn
22
Q
How do motor neuron axons leave the ventral horn?
A
Grouped as the ventral nerve root
23
Q
Where are sensory neuron cell bodies?
A
Dorsal root ganglion- outside spinal cord- in PNS
Become the dorsal nerve root and bring signals to the dorsal horn
24
Q
Draw a sensory neuron
A
See midterm notes
25
Spinal nerves are _____
MIXED NERVES
| ventral and dsorsal nerve roots join to create spinal nerves just distal to dorsal root ganglion
26
Spinal nerves split into
Ventral and dorsal Rami
27
Are ventral or dorsal rami larger?
Ventral and they usually have names
28
The spinal nerves exit through
Intervertebral foramen
29
Do dermatomes overlap?
Yes
30
Anterior or ventral rami merge to form
Plexuses
31
What is the difference between upper and lower motor neurons?
Upper motor neurons give input to spinal cord
| Lower motor neurons innervated by ventral hornspinal cord
32
are alpha and gamma neurons upper or lower?
Lower motor neurons
33
What are the four characteristics of muscle?
Resting length: length of unstimulated muscle
Contractibility: ability to shoreten in response to nerve input
extensibility: ability to stretch or lengthen when force is applied to its end
Elasticity: the ability of a muscle to return to its resting length after stretching
34
Explain the layers of muscle
Endomysium - deepest- covers myofibril
Perimysium - covers fasicle (middle)
Epimysium- encases muscle (outermost layer)
35
thick and thin filaments are located in the
myofibril
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H bands and I bands
H bands are thick filaments only
| I bands are thin filaments only
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Thick filaments are
myosin- where ATP binds
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Thin filaments are
Actin + tropomyosin and troponin complex
39
What is troponin?
Provides region for calcium binding
40
What is titin?
Anchors Z disc to M line- contributes to passive stiffness
41
What is Nebulin?
not sure but thought to act to regulate actin
42
What is the sliding filmanet theory?
Repetetive cycles of crossbridge between actin and myosin
Occurs in the presence of increased Ca 2+ and requires ATP
causes myosin conformation to change as one head binds to ATP and the other binds to Actin
Actin slides over myosin causing shortening and bringing the Z discs closer together, H and I bands become smaller and A band covers more region
43
What is a rigor state?
Myosin bound to ADP and actin - rigor mortis = lack of ATP (replaced by ADP)
44
What is happening in a muscles relaxed state?
Myosin is bound to ATP
45
What is happening in a muscles bound state?
Myosin is bound to Actin
46
What is a power stroke of a muscle?
Binding to actin causes ATPase activity ATP is hydrolyzed and ADP remains bound to myosin head
47
What controls muscle contraction?
Ca 2+ which is released by neuro stimuli
48
How does muscle contract?
Tropomyosin is shielding myosin from actin binding. Ca 2+ bind to toponin which pulls tropomyosin away from Myosin
49
What organelle monitors and controlls Ca 2+ output? How does this occur?
Sarcoplasmic Reticulum
| It contains high levels of calsequestrin which mops up Ca 2+ that is floating free to stop muscle contraction
50
How do the muscle contractions within the sarcomere transfer out of the muscle cell to the membrane?
```
Dystrophin Glycoprotein complex
links via actin cytoskeleton
aka costameres
anchors to connective tissue
without this there would be no functional movements
DCG is linked to collagen
```
51
What happens without dystrophin?
Muscular Dystrophy
| do not form appropriate DCG's and so do not have exercise tolerance and muscle degenerate
52
What are the three types of muscle contraction?
Concentric: muscle shrotening- forced produced by muscle is greater than external force
Isometric: no length change- force produced is equal to external resistance- no length change
Eccentric: force produced by muscle fails to match external resistance = muscle lengthening
53
Eccentric example
Passive elbow extension
54
Isometric example
Holding are up / stabilizing the arm
55
Does actin and myosin stay the same for each type of contraction?
Yes all muscle contractions are the same at cell level
| contraction is determined by balance of force produced
56
Muscle force depends on____
muscle length
57
Full force is when
actin and myosin cross optimally- maximal cross bridges
| as they get further apart less acitn binds and muscle force becomes weaker
58
How do passive elements contribute?
they provide resistance to lengthening
59
High force movements occur at _____ velocity
low velocity
high velocity at low force
optimal power is somewhere betwen
60
what are the different types of neurons?
Pseudounipolar--> Sensory
| Multipolar neuron-- Motor
61
Neurons are classified by
The number of axons leaving the soma
unipolar-one
bipolar-2
multipolar- 3 or more
62
What is the presynaptic terminal?
Holds neurotransmitters that will be released into synpatic cleft w electrical stimuli
63
How is information in the nervous system coded?
Frequency of action potentials moving own neuron
| amount of neurons firing on a cell
64
Cytoplasm of neurons has a relative_____ charge
negative
65
extracellular fluid has a relative ______ charge
Positive
66
What is a neurons resting membrance potential?
-70mV
67
What are the primary ions in a neuron?
Cl, K, Na
68
What is a resting membrane potential?
The difference in ion concentration across a neurons cell membrane
69
Stage of an action potential?
Reaches threshold--> Depolarization->Repolarization. Hyperpolarization (overshoot). resting
70
How does an action potential occur?
Electrical stimulus releases Na + from axon hillock
Negative charge in neuron changes to positive charge as Na+ enters- depolarization
Na+ closes and K+ opens causing hyperpolarization as K+ rushes out of neuron
Na+ K+ pump restores K+ to cytoplasm and Na+ to extracellular
3Na+ are exchaged for 2 K+ creating the negative charge inside the neuron
71
What secretes myelin?
Schwaan cells in the PNS
72
What are nodes of ranvier?
partial coating of myelin where ions can be exchanged - signal "jumps" from node to node
THE GAP
73
What is ssaltatory conduction?
The idea that the electrical signal jumps from node to node in axon
74
What cells in the CNS create myelin sheath?
oligodendrocites
75
Do neurons ever touch eachother?
NO
76
What is the gap between neurons called?
a synapse
77
Neurostransmitters are released from the presynaptic cell and bind ____
to receptors on post synaptic cell
78
What is an inhibitory post synaptic potential?
When inhibitory neurotransmitters bind to post synaptic cell-- hyperpolarization (more negative) of post synpatic cell
79
Depolarization
when cell potential becomes more positive as a result of sodium increase
80
hyperpolarization
when cell become more negative than resting potential due to loss of K+
81
How can neurotransmitter effect cell? (int :directly?)
Directly - through ion channels
| indirectly- through intracellular activity
82
What are the three muscle fibre types?
Slow oxidative (S,SO)- resistant to fatigue muscles for posture, nto strong but have endurance
Fast glycolytic (FF, FG)- fatigue quickly forceful and quick but quick to tire (for running)
Fast oxidative (FOG,FR (fatigue resistant)) -intermediate
83
What is the Henneman size principle?
recruitment of motor units in a muscle proceed from small motor units to large motor units
84
As requirement for force goes up muscles recruit____
larger motor units
85
How do motor units contribute to muscle force?
Size and frequency
86
When force decreased motor units are let go in ____ order
reverse order- largest leave first
87
Force in muscle goes up because
more motor units are being receruited and larger ones!
88
Where does th espinal cord end?
Around L1/L2- it is shorter than the spinal canal
89
Below C7 (neck) spinal segments are _____ to the vertebrae
rostral/ infront of / ventral to
90
What in the spinal cord indicates the number of neurons?
X section in gray matter--> largest for spine segments supplying limbs
91
X section of white matter decreases _____
caudally-towards the tail
| meaning fewer ascending and descending fibres
92
Stretch reflex and gamma reflex loop are supressed by acticity in ________
descending pathways
| aka Jendrassik Maneuver
93
Segmental level of an SCI is determiend by _______
Myotomes, dermatomes and reflexes
94
sensory and motor abnormalities in SCI are appropriate to the functions of ___
tracts that have been transected
95
Muscle tone is perceived as
resistance to continuous passive stretch
96
How is muscle tone generally assessed?
By performing PROM
97
Tone is essential to
normal posture, balance and movement
98
Supraspinal, segmental and peripheral should all be _____
balanced to get "normal" muscle tone
99
What is peripheral influence on msucle tone?
Passive properties such as muscle stretch
100
Segemental control of muscle tone?
Monosynpatic reflex
101
Normal relaxed muscle in someone with typical tone should be
highly extensible and low stiffness
102
Titin can be thought of as
a bungee cord that resets sarcomere length
103
Resistance in passive stretch comes from
weak cross bridges
104
Muscle spindles are located in______
infrafusal fibres
105
gamma motor neurons are located ___
infrafusal fibres
106
Alpha motor neurons are located____
Extrafusal fibres
107
How does stretch reflex work?
patellar tendon tap. stretch spindles> Ia afferent activity increase>Ia direct connection to alpha motor neuron> increase neuron firing> inccrease contraction to knee extensors > knee extends
108
As muscle contracts spindle activity
decreases. It increases when muscles are stretched
109
Spindle contractile elements are innervated via
gamma motor neurons (efferent projection to muscle spindle)
110
What do gamma motor neurons do?
Maintain spindle sensitivity and inherent muscle activity
111
Draw a spinal circuit of both a monosynpatic reflex and polysynaptic reflex
use paper
112
How do proprioceptors contribute to movement?
provide info to interneurons in spinal cord which then sum excitatory and inhibitory input (pre motor convergence)
113
What is hypertonia?
Muscle tone too high
114
What is hypotonia?
Muscle tone too low
115
What is an example of supraspinal input being compromised and how may it affect a person?
Stroke, CP, SCI, ABI
| Causes hypertonia / spasticity
116
What is an example of the segmental system being compromised?
Ventral horn cells--> hypotonia (because motor neurons are here)
Central horn--> hypertonicity ( cant control the stretch reflex )
117
Peripheral nerve injuries always cause _____
hypotonia
118
What are the descending pathways we learned?
Corticospinal tract
Corticobulbar tract
Reticulospinal tracts
Vestibulospinal tract
119
Corticobulbar tract
Directly projects to cranial nerve nuclei (CN III, IV, VI indirectly)
some project to CN from reticular formation
Some fibers bilateral and some crossed
whole set of spinal nerves in brainstem
project to cranial nerves w motor element
Swallowing, speech, dysphagia
120
Lateral Corticospinal tract
AKA Pyramidal tract
Fibers originate in frontal and parietal lobes
Dessucates at medullary pyramids
Terminates on interneurons of ventral horn of spinal cord then synapses with motor neurons
efferent fibers originate in motor cortex
projects ALL the way down spinal cord
Efferent
dedicated to hands face, closer to central sulcus is legs and trunk
Cell bodies in cortex- upper motor neurons
terminates on interneurons
Polysynaptic
movement of ipsilateral limbs (still contralateral to motor cortex though)
121
Anterior/ Ventral Corticospinal tract
```
Does not decussate
small tract
fibers branch to axial muscles
projects to medial brain stem pathways
controils trunk muscles
```
122
Lateral Vestibulospinal tract
projects ipsilaterally to all segments of the spinal cord
facilitates extensor motor neurons antigravity muscles (posture and balance)
Inhibits flexor motor neurons
input mediated by interneurons and propriospinal neurons
Nucleus located in mid pons
123
Medial vestibulospinal tract
mostly ipsilateral but some bilateral projections
input to motor neurons controlling neck and back
facillitation of extensor motor neurons
inhibits felxor motor neurons
124
Medullary Reticulospinal tracts
Monosynaptic inhibitory to MN supplying neck and back
polysynaptic inhibitory connections w extensor MN of appendicular msucles
may also excite flexor MN via interneurons
125
Pontine reticulospinal tract
terminates on and facillitates MN of axial muscles and extensors of the limbs
may also inhibit flexor MN
126
Ascending pathways
```
Dorsal Column pathways
Spinothalmic tract (anterolateral system)
```
127
Dorsal column pathway
major pathway for touch and priprioception
crosses at the medulla
vibration, pressure, discriminative touch
originates in nucleus gracillis (lower limb) and nucleus cuneatus (upper limb) in dorsal horn of spinal cord
teriminates in primary somatosensory cortex
128
Reticulospinal tracts are part of
the brain stem
129
Spinothalamic tract (anterolateral system)
Neurons lie in dorsal and medial part of spinal gray matter - nucleus proprius
terminates on primary somatosoensory cortex
axons cross at midline and travel along contralateral side
CONVEYS PAIN AND TEMP
contains light touch and pressure
difficult to detect light touch and pressure if dorsal columns intact
130
Draw the dorsal spinal tract vs spinothalamic tract
use paper
131
Spinal thalamic tracts decussate at the
level of spinal segment
132
What is the relay site before the somatosensory cortex for both sensory pathways
thalamus
133
What are the three main myotomes?
Cervial - C3-C5 diapharagm,C5-C* arms and hands
Thoracic- T1- muscles of fingers T1-12-muscles of abdonem and chest
Lumbar- S2-S1- feet and legs and hips, S3-S5 bladder, bowel and sex organs
134
Complete vs imcomplete SCI
incomolete- some movement and sensation, potential for recover
Complete- not much potential for recovery no movement or sensation
135
Spinal reflexes can be a local sign of
CNS dysfunction
136
What is hyperreflexia?
brisk jerks with phasic reflexes
137
hypertonia
increased resistance to rapid passive stretch
138
Clonus
series of multiple muscle contractions elicited by rapidly applied maintained stretch
139
slow development
slow time course- develops after spoinal cord injury
140
What is spinal spasticity?
exaggerated tendon jerks- can become osscilatory with re-excitation
Flexor spasms
response to input from flexor reflex afferents
lack of moderation by vestibulospinal and reticulospinal tracts
141
What is the clasp knife phenomenon?
triggered due to lack of descending control
| muscle gives away- initial resistance but then just flaccid
142
What is spinal shock?
Initial period of hyporeflexia and flaccid paralysis
probably due to sudden withdrawal of descending drive
affects areas above and below lesion
denerveation (super sensitivity)
increased number of postsynaptic receptors
sprouting of afferent terminals
143
How long does it take to recover from spinal shock?
weeks to months
| usually recover with hypertonocity
144
Lower motor neurons
alpha and gamm motor leurons
found in CNS and PNS - travelling from anterior (ventral) horn
muscle weakness, deminished musce tone,fasiculations, neurogenic atrophy
Guilliame Baure, botulism, polio
145
Upper motor neurons
Only in CNS
clonus, exaggerated deep tendonreflexes, muscle weakness
Stroke, MS, TBI
