1
Q
what is the purpose of peripheral nerves?
A
to relay information into and out of the CNS
2
Q
What are the two types of nerve cells?
A
- sensory neurons
- motor neurons
3
Q
Describe a sensory neuron
A
- nerve endings in the skin and projects into the CNS via the dorsal roots
- relays sensory information from the periphery to the CNS
- Afferents (arrive)
4
Q
Describe a motor neuron
A
- have cell bodies within the spinal cord and axons project out into the periphery via the ventral root
- innervates muscles
- Efferents (exits)
5
Q
How is a spinal nerve formed?
A
by the joining of the dorsal and ventral root filaments (rootlets) as they extend out of the spinal cord medially and combine to form roots, which combine to form the spinal nerve
6
Q
What are rami?
A
Divisions of tthe spinal cord
7
Q
What are the different rami
A
- dorsal rami
- ventral rami
8
Q
What is the dorsal rami’s function?
A
Innervates skin of the back and muscles adjacent to vertebral column
9
Q
What si the ventral rami’s function?
A
branch into mixed nerves that supply skin/muscle of the lateral/ventral trunk with sensory/motor axons
10
Q
What are plexuses?
A
regions where the spinal nerves fuse together and merge before forming distinct nerve bundles
11
Q
What are the different plexuses?
A
- cervical plexus
- brachial plexus
- lumbrosacral plexus
12
Q
What is the level of the cervical plexus
A
C1-4
13
Q
What is the level of the brachial plexus
A
C5-T1
14
Q
What is the level of the lumbrosacral plexus?
A
L1-S4
15
Q
What is a myotome?
A
Each muscle is supplied by a particular level/segment of the spinal cord and by its corresponding
spinal nerve
16
Q
What is a dermatome
A
An area of skin innervated by a particular level/segment of the spinal cord and its
corresponding spinal nerve
17
Q
What is the pathway for voluntary movement?
A
- activation of the upper motor neuron, which relays electrical impulses to activate lower motor neurons
- lower motor neurons generate an action potential which is conveyed to the muscle group
18
Q
Describe a reflex pathway
A
Involves two neurons
- sensory neurons projecting into the CNS
- motor neurons for contraction
- contained entirely within a spinal segment and does not require CNS input
19
Q
What is a sign of a lower motor nerve lesion
A
reflexes are no longer intact because efferent motor neuron is affected
20
Q
What is a sign of an upper motor neuron lesion?
A
reflexes persist because the neurons involved in spinal reflexes are both still intact
21
Q
Which area of the spinal cord contains the pathway for pain?
A
superficial dorsal horn
22
Q
Which area of the spinal cord contains the pathway for gentle touch?
A
deep dorsal horn
23
Q
Where does motor output originate in the spinal cord?
A
the ventral horn
24
Q
What are fasiculi?
A
bundles of nerve fibers
25
What is the epineurium?
a outermost tough fibrous connective tissue layer that surrounds the fasciculi and holds them together
26
What are the features of a myelinated nerve?
- large axon diameter
- fast conduction velocities
- touch, vibration, motor
27
What are the features of an unmyelinated nerve?
- small axon diameter
- slow conduction velocities
- pain, cold, hot
28
What are the 4 main classes of axons?
- A-alpha
- A-beta
- A-delta
- C
29
What are the features of A-alpha fibers?
- large axon diameter and thick myelin sheath
- conduct impulses very quickly
- emanate from motor neurons (send information to muscle groups)
- proprioceptors
30
What are the features of A-beta fibers?
Relatively large diameter, relatively thick sheath
- slower conduction than A-alpha
- Associated with innocuous tactile sensation
31
What are the main features of A-delta fibers?
- small axon diameter and thin myelin sheath
- relatively slow conduction
- conduct modalities of pain (sharp stabbing) and temperature
32
What are the main features of C fibers?
unmyelinated with a very small axon diameter
- slow conduction
- perception of temperature, pain and itch
33
What are the different sensory endings?
- mechanoreceptors
- thermoreceptors
- noicireceptors
- special sensory receptors
34
Describe the mechanoreceptor?
mechanical deflection touch
35
describe the thermoreceptors
temperature (hot/cold)
36
Describe the nociceptor
noxious (pain)
37
describe the special sensory receptor endingd
vision/taste/olfaction
38
What are the two pathways in the central nervous system?
- Ascending tracts
| - descending tracts
39
Describe the ascending tracts
entirely sensory
Divided into:
- Dorsal column medial lemiscus pathway (discriminative touch)
- Spinothalamic pathway (pain perception)
40
Describe the descending tracts
modulates activity for different muscle groups (cause motor contraction)
- coricospinal and corticobulbar tracts (voluntary motor control)
- reticulospinal, tectospinal and vestibulospinal tracts (maintains muscle tone and upright posture)
41
What are ascendinf sensory pathways?
neural pathways b which sensory information from the peripheral nerves is transmitted to the cerebral cortex
42
How are ascending sensory pathways categorised?
Can be divided into the type of information they transmit:
- conscious tracts: comprised of the dorsal column-medial lemiscal pathway and the anterolateral system
- unconscious tracts: comprised of the spinocerebellar tracts
43
What is the basic layout for ascending tracts?
3 inter-related neurons
- primary (in periphery)
- Secondary in CNS
- tertiary (in thalamus)
44
Describe th Dorsal column-medial lemniscal pathway (DCML)
Carries the sensory modalities of fine touch (tactile sensation), vibration and proprioception
45
What structures does the DCML comprise of?
- in the spinal cord, information travels via the dorsal (posterior) columns
- in the brainstem, it is transmitted through the medial lemniscus
46
What is the function of primary sensory neurons in the DCML?
carry sensory information regarding touh, proprioception or vibration from the peripheral nerves to the medulla oblongata
47
How do primary sensory nerve signals from the upper limb differ from signals from the lower limb in the DCML?
Signals from the upper limb (T6 and above):
o travel in the fasciculus cuneatus (the lateral part of the dorsal column).
o synapse in the nucleus cuneatus of the medulla oblongata.
Signals from the lower limb (below T6):
o travel in the fasciculus gracilis (the medial part of the dorsal column).
o synapse in the nucleus gracilis of the medulla oblongata
48
Where can secondary sensory neurons be found in the DCML?
Begin in the cuneate nuclus or gracilis
49
What is the function of secondary sensory neurons in the DCML?
receive the information from the preceding neurons and deliver it to the tertiary neurons in the thalamus
50
How do secondary sensory neurons reach the thalamus in the DCML?
decussate in the medulla oblongata
traval in the contralateral medial lemniscus to reach the thalamus
51
What is the function of tertiary sensory neurons in the DCML?
transmit the sensory signals from the thalamus to the ipsilateral primary sensory cortex of the brain
52
Where do tertiary sensory neurons travel in the DCML?
ascend from the ventral posterolateral nucleus of the thalamus, travel through the internal capsule and teminates at the sensory cortex
53
Describe the spinothalamic pathway
Anterolateral system has two tracts:
- anterior spinothalamic tract: sensory modalities of crude touch and pressure
- lateral spinothalamic tract: sensory modalities of pain and temperature
54
Describe the first order neurons of the spinothalamic pathway
- arise from the sensory receptors in the periphery
- enter the spinal cord, ascend 1-2 vertebral levels and synapse at the tip of the dorsal horn (substantia gelatinosa)
- primary afferent fibers stay in the spinal cord
55
Describe the second order neurons of the spinothalamic pathway
carry the sensory information from the substantia gelatinosa to the thalamus.
Synapse with first order neurones, then decussate within the spinal cord and form two distinct tracts:
o Crude touch and pressure fibres – enter the anterior spinothalamic tract.
o Pain and temperature fibres – enter the lateral spinothalamic tract.
Although functionally distinct, these tracts run alongside each other -> can be considered as a single pathway.
Travel superiorly within the spinal cord, synapsing in the thalamus.
56
Describe the third order neurons of the spinothalamic pathway
carry the sensory signals from the thalamus to the ipsilateral primary sensory cortex of the brain.
ascend from the ventral posterolateral nucleus of the thalamus, travel through the internal capsule
terminate at the sensory cortex.
57
What are the descending motor pathways?
pathways by which motor signals are sent from the brain to the lower motor neurones, which directly innervate muscles to produce movement
58
How are motor tracts differentiated?
Functionally divided into 2 groups:
- pyramidal tracts
- extrapyramidal tracts
59
What are pyramidal tracts?
A group of descending motor tracts
- originate in the cerebral cortex, carrying motor fibres to the spinal cord and brain
stem. Responsible for the voluntary control of the musculature of the body and face.
- Corticospinal tracts
- Corticobulbar tracts
60
What are extrapyramidal tracts?
A group of descending motor tracts that originate in the brainstem, carrying motor fibers to the spinal cord.
Responsible for the involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion
61
What is different about the descending pathways to the ascending pathways
There are no synapses within the descending pathways.
- At the termination of the descending tracts, the neurones synapse with a lower motor neurone.
- All the neurones within the descending motor system are classed as upper motor neurones.
- Their cell bodies are found in the cerebral cortex or the brain stem, with their axons remaining within the CNS
Phase 2 4. Neurology
flashcards
Decks in class (29)
# Cards
-
Intro to neuroanatomy97
-
Terminology32
-
Anatomy of the neck169
-
Anatomy of the spinal cord and vertebral column36
-
Anatomy of the face128
-
Development of the CNS88
-
Cranial nerves and brainstem97
-
Anatomy of the cranial cavity24
-
The brain24
-
Anatomy of the upper respiratory tract72
-
Anatomy of the oral cavity35
-
Pain physiology12
-
Nervous system signalling81
-
Motor control98
-
Motor control lab34
-
learning and memory52
-
Visual pathways8
-
spinal cord pathways61
-
Pain physiology70
-
Reflexes46
-
Visual pathway0
-
PBL 19
-
PBL 26
-
Spinal injury38
-
Head Injury23
-
PBL 456
-
PBL314
-
PBL 527
-
PBL 679
