Neuroanatomy 1 (6) Flashcards
(177 cards)
1
Q
What does the CNS include?
A
- brain
- spinal cord
2
Q
What does the PNS include?
A
- nerves
- ganglia
3
Q
What is grey matter composed of?
A
cell bodies, dendrites, axon terminals of neurons
4
Q
What occurs in grey matter?
A
Synapsing between neurons and information processing.
5
Q
What is the function of the anterior horns of the spinal cord?
A
They transmit motor signals.
6
Q
What is the function of the lateral horns of the spinal cord?
A
They transmit autonomic (unconscious) signals.
7
Q
What is the function of the posterior horns of the spinal cord?
A
They transmit sensory signals.
8
Q
Where can grey matter be found in the CNS?
A
- Cerebral cortex
- Cortical nuclei/diencephalon (ex: thalamus)
- Grey horns of spinal cord
9
Q
What is white matter composed of?
A
Bundles of axons forming communication pathways.
10
Q
What is the function of white matter?
A
To transmit signals from one location to another within the CNS.
11
Q
What does the anterolateral column carry?
A
Both ascending sensory and descending motor signals.
12
Q
What does the posterior column carry?
A
Ascending sensory signals only.
13
Q
Where can white matter be found in the CNS and PNS?
A
- Cerebral tracts (Corpus callosum)
- White columns of spinal cord
- Spinal pathways
- Peripheral nerves
14
Q
how many pairs of spinal nerves do we have?
A
31
15
Q
how many pairs of cranial nerves do we have?
A
12
16
Q
Signals travelling spinal nerves can enter/exit the spinal cord via connections known as ?
A
nerve “roots”
17
Q
What is the function of the dorsal root?
A
It provides a pathway for afferent (incoming) sensory information to flow from the spinal nerve into the spinal cord.
18
Q
Where might sensory information from the dorsal root go?
A
It may synapse in the dorsal grey horn or ascend in the posterior white column.
19
Q
What type of information does the dorsal root carry?
A
Sensory information.
20
Q
What is the function of the ventral root?
A
It provides a pathway for efferent (outgoing) motor signals to leave the spinal cord and enter the spinal nerve.
21
Q
Where might motor information from the ventral root go?
A
It may synapse in the ventral grey horn or descend in the white columns.
22
Q
What type of information does the ventral root carry?
A
Motor information.
23
Q
Nerves are ? that provide a route for signals to travel between PNS and CNS
A
WHITE matter pathways
24
Q
Spinal nerves are ? and will carry signals to and from targets/receptors on ?
A
IPSILATERAL
the same side of the body
25
Posterior/Dorsal root carries ? into CNS so it can ascend in the cord to reach the cortex
sensory/afferent information
26
Ventral/Anterior root carries ? out of CNS that has descended from the cortex to the cord
motor/efferent information
27
Ventral & Dorsal roots come together to form a ? in the intervertebral foramen
spinal nerve
28
What type of signals can each spinal nerve carry?
Both incoming (afferent) and outgoing (efferent) signals into and out of the CNS.
29
How are nervous signals classified?
By direction of flow, type of signal, and target/effector.
30
What does "somatic" refer to?
"Of the body" – things you are consciously aware of.
31
What types of functions fall under the somatic system?
Sensory input from skin and motor control of skeletal muscles.
32
What does "autonomic" refer to?
Things that are unconscious/involuntary, like internal organ activity.
33
What types of functions fall under the autonomic system?
Feedback from internal organs, and involuntary control of smooth and cardiac muscles, and glands.
34
What does GSE stand for and what does it do?
General Somatic Efferent – carries conscious/voluntary motor signals (e.g., skeletal muscle movement).
35
What does GSA stand for and what does it do?
General Somatic Afferent – carries general sensory signals (e.g., touch, pain from skin).
36
What does GVE stand for and what does it do?
General Visceral Efferent – carries involuntary motor signals to organs (e.g., heartbeat, digestion).
37
What does GVA stand for and what does it do?
General Visceral Afferent – carries sensory signals from organs (e.g., stretch of blood vessels).
38
How does communication between the brain and body occur?
Through chains of neurons (like a relay race), called axon relays.
39
What does it mean to "decussate"?
It means a signal crosses over from one side of the CNS to the other (left ↔ right).
40
Where are sensory receptors located?
At the end of peripheral nerves in the skin layers.
41
What is the function of sensory receptors in the skin?
To gather information about the environment and send it to the CNS for processing.
42
Through which structure does afferent/sensory information enter the CNS?
The dorsal root of the spinal nerve.
43
Through which columns can sensory information ascend the spinal cord?
Posterior, lateral, and anterior white columns.
44
Where do the majority of sensory signals synapse in the brain?
In the thalamus.
45
Where do motor (efferent) signals originate in the brain?
In the pre-central gyrus of the frontal lobe (primary motor cortex).
46
Through which columns do motor signals descend in the spinal cord?
Anterior and lateral columns.
47
Through which structure do motor signals exit the CNS?
The ventral root of the spinal nerve.
48
What is the term for the structure targeted by motor signals?
An effector.
49
How many neurons are involved in most sensory tracts?
Three neurons (except for the spinocerebellar tracts, which use two neurons).
50
Where is the first-order neuron located?
In the dorsal root ganglion of the spinal nerve.
51
What does the first-order neuron do?
It conducts impulses from sensory receptors to the spinal cord or medulla oblongata.
52
Where is the second-order neuron located?
In the dorsal horn of the spinal cord or the medulla oblongata.
53
What does the second-order neuron do?
It relays impulses to the thalamus.
54
Where is the third-order neuron located?
In the thalamus.
55
What does the third-order neuron do?
It conveys impulses to the postcentral gyrus (the general sensory area of the parietal lobe).
56
Which sensory tract is the exception to the three-neuron pathway?
spinocerebellar tract
57
what are the major ascending, sensory tracts?
1. Spinothalamic: pain and temperature
2. Spinocerebellar: proprioception
3. Posterior/dorsal column: discriminative touch
4. Spinotreticular tract
5. Spinotectal tract
6. Spinomesecephalic tract
7. Spino-olivary tract
58
What type of sensation does the posterior/dorsal column pathway transmit?
General somatic afferent (GSA) signals for fine/discriminative touch, conscious proprioception, and vibration.
59
Where does the first-order neuron in the dorsal column pathway originate? (posterior/dorsal column pathway)
In a peripheral receptor (e.g., skin, joint).
60
How does the first-order neuron reach the CNS? (posterior/dorsal column pathway)
It travels via the spinal nerve, enters the dorsal root, and ascends without synapsing in the spinal cord.
61
In which part of the spinal cord does the first-order axon ascend? (posterior/dorsal column pathway)
In the dorsal (posterior) columns.
62
What are the two divisions of the dorsal columns and what do they carry?
(posterior/dorsal column pathway)
Fasciculus Gracilis (FG) – lower limbs (medial)
Fasciculus Cuneatus (FC) – upper limbs (lateral)
63
Where does FG synapse?
(posterior/dorsal column pathway)
In the nucleus gracilis (NG) of the medulla oblongata.
64
Where does FC synapse?
(posterior/dorsal column pathway)
In the nucleus cuneatus (NC) of the medulla oblongata.
65
Where is the second-order neuron located?
(posterior/dorsal column pathway)
In the nucleus gracilis or cuneatus of the medulla.
66
What happens to the second-order neuron in the medulla?
(posterior/dorsal column pathway)
It decussates (crosses over) and ascends via the medial lemniscus pathway.
67
Where does the second-order neuron synapse?
(posterior/dorsal column pathway)
In the thalamus (specifically, the ventral posterolateral nucleus).
68
Where is the third-order neuron located?
(posterior/dorsal column pathway)
In the thalamus.
69
Where does the third-order neuron's axon project?
(posterior/dorsal column pathway)
To the postcentral gyrus of the parietal lobe
70
What happens in the postcentral gyrus?
(posterior/dorsal column pathway)
The conscious perception of touch, proprioception, and vibration occurs.
71
Which sensory tract conducts conscious proprioception and discriminative touch (except head)?
The dorsal column-medial lemniscus pathway.
72
What is the exception for proprioception coverage in this pathway?
It excludes the temporomandibular joint (TMJ) and most of the head.
73
What type of sensation does the spinocerebellar tract transmit?
General somatic afferent (GSA) signals for unconscious proprioception (body position in space)
74
Where does the 1st-order neuron originate? (spinocerebellar tract )
In peripheral receptors
75
Through which structure does the 1st-order axon enter the CNS?
(spinocerebellar tract )
Via the dorsal root of the spinal nerve.
76
Where does the 1st-order neuron synapse?
(spinocerebellar tract )
In the dorsal grey horn of the spinal cord, in a region called Clarke’s column (nucleus dorsalis)
77
Where is the 2nd-order neuron located?
(spinocerebellar tract )
In the dorsal grey horn (Clarke’s column) of the spinal cord.
78
What happens to the axon of the 2nd-order neuron?
(spinocerebellar tract )
It ascends in the lateral column, crosses sides once in the spinal cord and crosses again before entering the cerebellum.
79
How does the spinocerebellar tract enter the cerebellum?
(spinocerebellar tract )
Through the inferior cerebellar peduncle.
80
What is the functional outcome of this spinocerebellar tract?
It allows the cerebellum to coordinate limb movements and maintain posture.
81
Where does the final synapse occur in this pathway? (this spinocerebellar tract)
In the ipsilateral cerebellar hemisphere.
82
Which body parts send proprioceptive info through the posterior spinocerebellar tract?
The trunk and lower limbs.
83
What if sensory information enters below L3?
It ascends in the fasciculus gracilis until reaching Clarke’s column at L3 to synapse.
84
Does the spinocerebellar tract transmit to the contralateral or ipsilateral cerebellum?
Ipsilateral — injury to this tract results in same-side (ipsilateral) deficits.
85
Which tract carries unconscious proprioception from the upper limbs?
The cuneocerebellar tract.
86
What type of sensations does the Anterolateral System (ALS) primarily carry?
Non-discriminative (crude) touch, pain, and temperature.
87
Where do most ALS fibres project to for conscious perception of pain and temperature?
The thalamus, via the spinothalamic tract.
88
Which tracts are included in the Anterolateral System (ALS)?
- Spinothalamic tracts (anterior & lateral)
- Spinoreticular tract
- Spinotectal tract
- Spinomesencephalic (spinoperiaqueductal) tract
- Spino-olivary tract
89
What type of sensation does the spinothalamic tract transmit?
General somatic afferent (GSA) for pain, temperature, and non-discriminative (crude) touch.
90
Which part of the spinothalamic tract carries pain and temperature information?
The lateral spinothalamic tract.
91
Which part of the spinothalamic tract carries crude touch information?
The anterior spinothalamic tract.
92
In the lateral spinothalamic tract, where does the 1st-order neuron originate and terminate?
It originates in a peripheral receptor, travels via a spinal nerve, enters the dorsal root, and synapses in the dorsal grey horn.
93
In the lateral spinothalamic tract, where does the 2nd-order neuron originate and travel?
It originates in the dorsal grey horn, decussates (crosses over) at the level of entry, and ascends in the lateral white column to the thalamus.
94
What neurotransmitter is primarily used at the 1st synapse in the lateral spinothalamic tract?
Substance P.
95
In the lateral spinothalamic tract, where does the 3rd-order neuron originate and terminate?
It originates in the thalamus and terminates in the primary somatosensory cortex (post-central gyrus) of the parietal lobe.
96
What is the function of the anterior spinothalamic tract?
It transmits non-discriminative (crude) touch sensations.
97
Do the anterior and lateral spinothalamic tracts follow similar neuron pathways?
Yes, both involve three neurons:
1. Peripheral receptor → dorsal horn
2. Dorsal horn → decussates → ascends to thalamus
3. Thalamus → somatosensory cortex
98
What is the Gate Pain Theory?
A theory proposing that a "gate" in the dorsal horn of the spinal cord can modulate pain signals, either allowing or blocking them from reaching the brain.
99
How does the Gate Pain Theory explain modulation of pain?
The "gate" can be influenced by larger, non-pain sensory fibers (e.g., touch) or descending brain signals, which may inhibit pain transmission.
100
What part of the spinal cord is key to the Gate Pain Theory?
dorsal horn
101
What is the main function of the spinoreticular tract?
Influences levels of consciousness via input to the reticular formation.
102
In the spinoreticular tract, where does the 1st-order neuron originate and terminate?
It originates in a peripheral receptor, travels via a spinal nerve, enters the dorsal root, and synapses in the dorsal grey horn.
103
In the spinoreticular tract, where does the 2nd-order neuron travel and terminate?
It remains ipsilateral, ascends in the anterolateral white columns, and synapses in the reticular formation of the medulla, pons, and midbrain.
104
Do fibers of the spinoreticular tract cross the midline?
Most remain uncrossed (ipsilateral).
105
Where does the spinomesencephalic tract terminate?
In the periaqueductal gray matter (PAG) of the midbrain.
106
What is the spinomesencephalic tract's role in pain modulation?
It connects to the limbic system (affective/emotional response to pain) and activates the descending analgesia system via the PAG.
107
What is the main function of the spinotectal tract?
Coordinates reflexive turning of the head and eyes toward a cutaneous stimulus.
108
In the spinotectal tract, where does the 1st-order neuron originate and terminate?
It originates in a peripheral receptor, travels via a spinal nerve, enters the dorsal root, and synapses in the dorsal grey horn.
109
In the spinotectal tract, where does the 2nd-order neuron travel and terminate?
It crosses the midline, ascends in the anterolateral white column, and synapses in the superior colliculus of the midbrain.
110
Where does the spinotectal tract lie in relation to other tracts?
It lies near the lateral spinothalamic tract in the anterolateral column.
111
What is the function of the spino-olivary tract?
Conveys cutaneous and proprioceptive input to the cerebellum to help control body and limb movements.
112
In the spino-olivary tract, where does the 1st-order neuron originate and terminate?
It originates in a peripheral receptor, enters the dorsal root, and synapses in the dorsal grey horn.
113
In the spino-olivary tract, where does the 2nd-order neuron travel and terminate?
It crosses the midline, ascends in the anterolateral column, and synapses in the inferior olivary nucleus of the medulla.
114
In the spino-olivary tract, what happens to the 3rd-order neuron's axon?
It crosses the midline again and enters the cerebellum via the inferior cerebellar peduncle.
115
how many decussations occur in the spino-olivary pathway?
Two decussations: once after the 2nd-order neuron and once after the 3rd-order neuron.
116
Where is the 1st-order neuron located in general sensory cranial nerve pathways?
In the sensory ganglion of the cranial nerve.
117
Where does the 2nd-order neuron typically synapse in sensory cranial nerve pathways?
In the ipsilateral sensory nucleus of the cranial nerve in the brainstem.
118
Where is the 3rd-order neuron in cranial nerve sensory pathways, and where does it project?
Located in the contralateral thalamus and projects to the contralateral sensory cortex.
119
What is the exception to the 3-neuron sensory pathway for CN I (olfactory nerve)?
1st neuron: Olfactory epithelium
2nd neuron: Olfactory bulb → Projects directly to olfactory cortex (no thalamus relay)
120
What is the exception to the 3-neuron sensory pathway for CN II (optic nerve)?
1st neuron: Retina
2nd neuron: Thalamus (lateral geniculate body) → Projects to visual cortex
121
What are the two main classifications of motor tracts in the spinal cord?
Pyramidal tracts and extrapyramidal tracts.
122
Where do motor instructions originate in pyramidal vs. extrapyramidal tracts?
Pyramidal: Motor cortex of the frontal lobe
Extrapyramidal: Brainstem and cerebellar cortex
123
What type of movements are pyramidal tracts responsible for?
Voluntary control of skeletal muscles of the limbs and trunk.
124
What type of movements are extrapyramidal tracts responsible for?
Subconscious, reflexive, or postural movements.
125
Which motor tracts are considered pyramidal?
Lateral and ventral corticospinal tracts.
126
Which tracts are considered extrapyramidal?
Rubrospinal, tectospinal, vestibulospinal, and reticulospinal tracts.
127
Where do upper motor neurons (UMNs) originate and terminate?
Begin in the cortex and terminate in the brainstem or spinal cord.
128
Where are lower motor neurons (LMNs) located?
For cranial nerves: Motor nuclei in the brainstem
For spinal nerves: Ventral horn of the spinal cord
129
What is the function of lower motor neurons (LMNs)?
They innervate skeletal muscles and produce movement.
130
What is the destination of the corticospinal tract?
It terminates in the spinal cord on LMNs in the ventral horn.
131
What is the function of the corticospinal tract?
Controls voluntary movement of the limbs and trunk.
132
What is the destination of the corticobulbar (corticonuclear) tract?
It terminates in the brainstem on cranial nerve motor nuclei.
133
Which cranial nerves are associated with the corticobulbar tract in the midbrain?
CN III (oculomotor) and IV (trochlear).
134
Which cranial nerves are associated with the corticobulbar tract in the pons?
CN V (trigeminal) through VIII (vestibulocochlear).
135
Which cranial nerves are associated with the corticobulbar tract in the medulla?
CN IX (glossopharyngeal) through XII (hypoglossal).
136
Where do axons of LMNs exit the spinal cord?
Through the ventral (anterior) root of the spinal nerve.
137
What structure do LMN axons form after exiting the spinal cord?
The motor root of the spinal nerve.
138
What is the primary function of the corticospinal tract?
Voluntary (conscious) motor control of skeletal muscles of the body (GSE).
139
The corticospinal tract is part of which motor system?
The pyramidal motor system.
140
In the corticospinal tract, where does the upper motor neuron (UMN) originate?
In the primary motor cortex of the frontal lobe (pre-central gyrus).
141
Through which major structures does the corticospinal tract descend after leaving the cortex?
Internal capsule → crus cerebri (midbrain) → basilar pons → pyramids of the medulla.
142
Where does the corticospinal tract decussate (cross the midline)?
At the decussation of the pyramids in the medulla oblongata.
143
After decussation, in which column does the lateral corticospinal tract descend?
In the lateral column of the spinal cord.
144
In the corticospinal tract, where does the UMN synapse with the LMN?
In the anterior (ventral) grey horn of the spinal cord.
145
In the corticospinal tract, where does the lower motor neuron (LMN) originate?
In the anterior grey horn of the spinal cord.
146
How does the LMN reach its skeletal muscle target?
It exits via the ventral root and travels through a peripheral spinal nerve.
147
What is the difference between the lateral and anterior corticospinal tracts?
Lateral CST: Fibers cross in the medulla and control distal limb muscles.
Anterior CST: Fibers remain uncrossed until the spinal cord, then cross and control axial muscles.
148
What are the signs of an upper motor neuron lesion (UMNL) in the corticospinal tract?
Spasticity (increased tone)
Exaggerated reflexes (e.g. Babinski sign)
Weakness or paralysis with voluntary effort
149
What are the signs of a lower motor neuron lesion (LMNL)?
Flaccid paralysis
Muscle atrophy
Loss of reflexes
150
Which other areas provide input to the corticospinal tract?
The sensory cortex, cerebellum, and other association areas.
151
What is the role of the corticospinal tract in coordination and precision?
It allows for coordinated, precise, and voluntary movements, especially of limbs.
152
What is the main functional difference between the pyramidal and extrapyramidal systems?
Pyramidal: Controls voluntary movement
Extrapyramidal: Regulates involuntary/postural movements
153
Name four extrapyramidal tracts.
Rubrospinal, tectospinal, vestibulospinal, and reticulospinal tracts.
154
What are five roles of the extrapyramidal system?
Adjust postural tone
Prepare for involuntary movements
Assist in automatic movements (e.g., walking, writing)
Inhibit involuntary movements (e.g., tremors)
Modify tone during emotional and attentive states
155
Where does the Rubrospinal Tract originate and where does it decussate?
It originates in the red nucleus of the midbrain and decussates immediately as it exits the red nucleus in the caudal midbrain.
156
What is the pathway and termination site of the Rubrospinal Tract?
After decussating, it descends in the ventrolateral white column of the spinal cord and synapses on lower motor neurons in the anterior grey horn.
157
What functions does the Rubrospinal Tract serve?
It helps mediate involuntary movement, maintain posture and muscle tone, and contributes to control of flexor muscles and fine hand movements.
158
Which inputs does the Rubrospinal Tract receive?
It receives input from the cerebellum, cerebral cortex, and corticospinal tracts.
159
Where does the Tectospinal Tract originate and terminate?
It originates from the tectum of the midbrain (superior colliculi), crosses the midline, and descends to terminate in the upper cervical segments of the spinal cord.
160
What is the function of the Tectospinal Tract?
It controls head and neck movements in response to visual and auditory stimuli.
161
What are the two types of Vestibulospinal Tracts and where do they originate?
Lateral VST: originates from the lateral vestibular nucleus (medulla)
Medial VST: originates from the medial vestibular nucleus
162
What is the pathway and function of the Lateral Vestibulospinal Tract?
It descends uncrossed in the anterior column of the spinal cord and regulates antigravity muscle tone for balance and equilibrium.
163
What sensory inputs does the Vestibulospinal Tract receive?
From the vestibular apparatus (inner ear via CN VIII) and the cerebellum.
164
Where do the Pontine and Medullary Reticulospinal Tracts originate and descend?
Pontine RST: from reticular formation in the pons, descends uncrossed in the anterior column.
Medullary RST: from reticular formation in the medulla, descends in the lateral column (both crossed & uncrossed fibers).
165
What are the functions of the Reticulospinal Tracts?
Influence voluntary movements and reflexes
Pontine RST: facilitates extensor tone (postural support)
Medullary RST: inhibits extensor tone (modulates reflexes)
Carry autonomic fibers from the hypothalamus to spinal cord autonomic centers
166
What inputs do the Reticulospinal Tracts receive?
Cerebral cortex, cerebellum, and hypothalamus.
167
What is the role of the Spinomesencephalic Tract in pain modulation?
It carries pain signals to the periaqueductal gray (PAG) of the midbrain, which then activates descending pain-inhibiting pathways.
168
How does the PAG modulate pain in the spinal cord?
It sends descending signals (via reticular formation) that inhibit the release of Substance P in the dorsal horn, blocking transmission of pain from first to second-order neurons.
169
What type of innervation do upper motor neurons (UMNs) from the cortex usually provide to cranial nerve nuclei?
Mostly bilateral innervation.
170
What is the name of the motor pathway from the cortex to cranial nerve nuclei?
Corticobulbar (also called corticonuclear) tract.
171
What is the typical projection of lower motor neurons (LMNs) from cranial nerve nuclei?
LMNs project to ipsilateral muscles.
172
Which cranial nerve is an exception to the usual ipsilateral projection of LMNs?
Cranial Nerve IV (Trochlear nerve).
173
How is the trochlear nerve (CN IV) an exception in motor pathways?
The trochlear nucleus innervates the contralateral superior oblique muscle.
174
Which part of the facial motor nucleus receives only contralateral UMN input?
The lower part, which controls muscles of the lower face.
175
How is the facial nerve (CN VII) an exception in UMN innervation?
The lower face receives only contralateral cortical innervation, while the upper face receives bilateral innervation.
176
Which part of the hypoglossal nucleus receives only contralateral cortical input?
The neurons innervating the genioglossus muscle (tongue protrusion).
177
How is the hypoglossal nerve (CN XII) an exception in UMN innervation?
The genioglossus muscle receives contralateral input from the cortex.
