Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Y2S2M1 > Overview of ascending and descending tracts in the spinal cord > Flashcards

Overview of ascending and descending tracts in the spinal cord Flashcards

1
Q

Where do first order neurones carrying proprioceptive + tactile signals enter the spinal cord?

A

Enters the spinal cord via dorsal root

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What occurs once these first order neurones have entered the spinal cord?

A

They immediately join the dorsal columns without terminating and then travel in the dorsal columns. It remains ipsilateral until the level of the medulla.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where does the first order neurone terminate?

A

At the level of the medulla.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Where does the second order neurone travel to and what does it join?

A

A second order neurone in the medulla picks up the signal and then crosses over to the contralateral side, known as medullary decussation. It joins other fibres that carry pain and temperature information.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where does the second order neurone terminate?

A

The second order neurone then terminates at the thalamus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Where does the third order neurone travel to?

A

From the thalamus, the third order neurone carries the signal to the contralateral sensori-motor cortex in the post-central gyrus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which side of the spinal cord carries proprioceptive information from the right-hand side?

A

Proprioceptive information from the right side is carried by the right spinal cord.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What side of the spinal cord carries pain and temperature information from the right-hand side?

A

Pain & temperature from the right side is carried by the left spinal cord.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is syringomyelia?

A

A condition where scarred tissue forms within the central canal of the spinal cord, especially at the cervical spine level, leading to fibrosis that can cut fibres carrying pain sensation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is brown-sequard syndrome?

A

Results from injury to one half of the spinal cord, causing sensory dissociation where pain and temperature sensation is lost from the contralateral side and proprioceptive sensation is lost from the ipsilateral side.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the purpose of descending tracts?

A

The brain uses signals from ascending tracts to trigger movement via descending tracts.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What represents the highest centre for processing sensory information and motor commands?

A

The cerebral cortex.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Where is sensory information first represented in the cerebral cortex?

A

Sensory information from the body is first represented at the primary sensory cortex.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How is the primary motor cortex + primary sensory cortex separated?

A

The Primary Motor Cortex is separated from the Primary Sensory Cortex by the central sulcus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How are skeletal/somatic muscle movements normally initiated and from where?

A

Movements of skeletal/somatic muscles are initiated voluntarily, originating in the cerebral motor cortex.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Where are the neurones that control the somatic muscles of the body?

A

Somatic muscles are controlled by dedicated neurones of the motor strip of the frontal cortex.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the motor homunculus?

A

The motor map of cortical neurones can be reconstructed into a disjointed caricature of a distorted muscle-man.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does the brain command muscles to do?

A

The brain commands muscles to either rest or contract.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What do levels of muscle contraction vary depending on?

A

Levels of contraction vary depending on muscle tone and displacement of joints.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Do motor commands from the brain decussate?

A

Yes, the right motor cortex controls muscles on the left side of the body and vice versa.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are descending tracts formed by and where are the neurones cell bodies found?

A

Descending tracts are formed from axons of neurones with cell bodies in motor nuclei of the brain.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What do you call the neurones that carry the outputs of the brain?

A

The brain’s outputs are conveyed through a group of neurones collectively known as efferents.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What does the brain give motor commands to in the body?

A

The brain gives motor commands to glands, smooth muscle, and skeletal muscle.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the efferent system to skeletal muscle from the brain known as?

A

The somatic efferent motor system.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What are the neurones of the somatic motor system called and what do they innervate?
They are commonly known as motoneurones and they innervate skeletal muscles.
26
What two categories can we divide motoneurones into?
Motoneurones with cell bodies in the brain and motoneurones with cell bodies in the spinal cord.
27
Where are all motoneurones cell bodies found?
Motor neurone cell bodies are always located in the CNS.
28
What are upper motoneurones and where are they located?
Motoneurones with cell bodies in the brain are known as upper motoneurones, located in hierarchically higher centres of the CNS.
29
What are cortical upper motoneurones also called and what do they form?
Cortical upper motoneurones are also called Pyramidal Upper Motoneurones and they comprise the Pyramidal System of the Brain.
30
What happens if we get lesions to the pyramidal motor system?
Lesions of the pyramidal motor system impair movements.
31
What are cortical upper motoneurons also called?
Cortical upper motoneurons are also called Pyramidal Upper Motoneurones.
32
What do cortical upper motoneurons form?
They comprise what is known as the Pyramidal System of the Brain (Motor).
33
What happens if we get lesions to the pyramidal motor system?
Lesions of the pyramidal motor system impair movements in a characteristic way that distinguishes this particular system. They give rise to pyramidal motor signs.
34
What are non-cortical upper motoneurons also called?
These are also called Extra-Pyramidal Upper Motoneurones.
35
What do non-cortical upper motoneurons form?
They comprise what is known as the Extra-pyramidal Motor System of the brain.
36
What happens if we get lesions of the extra-pyramidal motor system?
Lesions of the extra-pyramidal motor system impair movements in a characteristic way that is different from that arising from injuries/defects of the pyramidal system. They give rise to extra-pyramidal motor signs.
37
Which upper motoneurons lesions are more common?
Extra-pyramidal/non-cortical lesions.
38
Where do upper motoneurons have their cell bodies?
Upper motoneurons have their cell bodies in either the cerebral cortex (Pyramidal) or basal ganglia or brainstem (Extra-pyramidal).
39
What do the axons of upper motoneurons travel through to reach lower motoneurons?
Their axons travel through the spinal cord to reach lower motoneurons of the spinal cord.
40
What are the axons of upper motoneurons traveling in the spinal cord collectively known as?
Descending Fibre Tracts.
41
What can each descending tract be viewed as?
Each descending tract can be viewed as an example of a fasciculus.
42
Where are descending tracts found?
Descending tracts are found in either Anterior (Ventral) or the Lateral funiculus of the spinal cord.
43
What are ascending and descending tracts mixed within?
Ascending & Descending Tracts are mixed within the Anterior (Ventral) & Lateral Funiculi.
44
Name the descending tracts.
Pyramidal: corticospinal tracts (lateral & anterior), corticobulbar tracts. Extra-pyramidal: vestibulospinal tracts, reticulospinal tracts (lateral & anterior), rubrospinal tracts, tectospinal tracts.
45
Where does the corticospinal tract start and end?
It starts off in the primary motor cortex (cerebral cortex) and ends in the spinal cord.
46
What are the two variants of the corticospinal tract?
There are 2 variants: the lateral corticospinal tract (bigger) and the anterior corticospinal tract. The lateral corticospinal tract fibres decussate at the level of the medulla, while the anterior corticospinal tract remains on the same side until the level of their destination.
47
Where do the corticospinal tract fibres terminate?
These fibres terminate at the level where they connect to the lower motor neurone.
48
Name some other descending tracts of the brain.
Other descending tracts include the Rubro-spinal tract (starts at the brain stem, specifically at the nucleus red) and the lateral Reticulo-spinal tract (neurons start from the Reticulo formation of the brain stem and terminate in the spinal cord).
49
What can the somatic nervous system be split into?
The somatic nervous system can be split into afferents and efferents.
50
What are somatic efferents carried by?
Efferents are carried by descending tracts.
51
What are the efferents of descending tracts divisible into?
These are divisible into pyramidal (originate in cerebral cortex) and extra-pyramidal systems (don’t originate in cerebral cortex).
52
How do descending tracts produce their actions?
By commanding lower motoneurons of the spinal cord.
53
Which muscles does the pyramidal tract activity command?
The pyramidal tract activity commands muscles beyond the wrist, e.g., finger movement.
54
What does the extrapyramidal motoneuron produce?
Extrapyramidal motoneurons produce general activities of muscles of the body through commanding lower motoneurons.
55
What do lower motoneurons do?
Lower motoneurons activate skeletal muscle.
56
What are somatic afferents carried by?
They are carried by the ascending tracts (A-LSST fibres, DC, and D & V SCT).
57
Which pathways give rise to conscious sensation?
The A-LSTT & DC both send signals to the cerebral cortex, giving rise to conscious sensation.
58
Which pathways give rise to non-conscious sensation?
The D & V SCT fibres only reach the cerebellum and therefore give rise to non-conscious sensation.
59
Which side of the spinal cord carries pain and temperature information from the right-hand side?
Pain & Temperature from the right side is carried by the left spinal cord.
60
How is most of the body’s sensory information conveyed to the brain?
Through the spinal cord
61
How are sensory signals in the head and neck conveyed?
Sensory signals are conveyed to the brain via the brainstem largely through CNV (Trigeminal Nerve).
62
What is the difference between cranial nerves (CN) and spinal nerves (SN) sensory mechanisms?
Sensory mechanisms for spinal and cranial nerves are very similar; they differ only on anatomical substrates.
63
What are the 2 major sensory organ systems of the body?
Skin and muscles of the body.
64
What is the largest organ of the body?
Skin.
65
Describe the sensory innervation of the skin.
The skin is populated by many sensory receptors, allowing the body to be aware of its environment. The skin's sensory territories are organized into dermatomal slices.
66
What is a dermatome?
Dermatomes are slices of skin whose sensation is conducted by a single spinal nerve.
67
Describe the sensory system of the head.
In the head region, we do not have spinal nerves; instead, we have sensory nerve territories of the trigeminal nerve.
68
What are the divisions of the trigeminal nerve?
Ophthalmic, mandibular, and maxillary divisions.
69
What is the sensory supply of muscles and what are they known as?
Muscles are richly supplied with millions of tiny muscle sense organs known as proprioceptive organs.
70
What is proprioception?
Proprioception is a special sense that provides awareness of body position in 3-D space.
71
What are the proprioception receptors in muscles?
1. Muscle Spindles: Muscle length sensors that respond to stretching. 2. Golgi Tendon Organs: Sense force development in muscles. 3. Joint Receptors: Provide information about the angle at the joint.
72
What else is the muscle also supplied by?
The muscle is supplied by general sensory afferents, which are free nerve endings responsible for general sensations such as pain and temperature.
73
Name key neural levels for sensory innervation.
Diaphragm (C3-5), Biceps (C5-6), Wrist (C8-T1), Nipple (T4), Umbilicus (T10), Hip Flexion (L1-2), Knee jerk (L3-4), Knee Flexion (S1), Great Toe (L5), Foot Plantar Flexion (S1-2), Bladder (L1-2 or S2-S4), Anal Sphincteric Tone (S2 to S4).
74
What is the importance of sensation?
Sensation allows the body to be aware of signals arising on the body surface, which are transmitted to the brain for interpretation.
75
What is decussation?
Decussation is when the left side of the body’s sensations are represented in the right brain and vice versa.
76
What is the sensory homunculus?
The sensory homunculus is a representation of the body’s surfaces and muscles in the brain, with varying amounts of brain tissue dedicated to different body parts.
77
What are ascending tracts?
Ascending tracts are fibre tracts by which sensory information is conveyed to the brain via the spinal cord.
78
What broad categories can ascending tracts be divided into?
1. Dorsal columns: Carry proprioceptive and tactile sensation. 2. Antero-lateral spinothalamic tract: Carries pain, temperature, pressure, and crude touch. 3. Dorsal & ventral spinocerebellar tracts: Carry proprioceptive and tactile sensation.
79
What sensory stimulus does the A-L STT carry?
Pain, temperature, and crude touch, which are relayed to the brainstem and then to the thalamus for conscious sensation.
80
What pathways carry proprioceptive signals and tactile sensation?
1. Some go directly to the cerebellum via the D & V Spinocerebellar tract (non-conscious sensation). 2. Some travel through the dorsal columns to the cerebral cortex for conscious sensation.
81
What is the order of the brainstem to cortex?
SC → medulla oblongata → pons → midbrain → thalamus → cortex.
82
How are sensory signals detected by the body conveyed to the brain?
Via a relay system of 3 neurones in a chain, starting from the skin’s surface to a neurone in the brain.
83
Where do primary sensory neurones carry signals and how do they enter the spinal cord?
Primary sensory neurones carrying different types of sensory signals enter the spinal cord through the dorsal roots.
84
Where are primary sensory neurones' cell bodies found?
In the dorsal root ganglion, which is part of the peripheral nervous system.
85
What happens when the primary sensory neurone reaches the spinal cord?
It divides into axonal processes that terminate in the dorsal horn of its respective spinal segment and travel to adjacent segments.
86
What do the axonal segments that travel to spinal segments above and below travel in?
The Posterolateral Tract of Lissauer.
87
What happens to the axon intended for its respective spinal segment?
It enters the dorsal horn and terminates on a cell body of a secondary sensory neurone.
88
What does the lamina that the first order neurone terminates on depend on?
It depends on the modality it represents, with pain fibres terminating in Laminae I & II and other modalities in Laminae III & IV.
89
Where does the second order neurone's axon go?
It travels towards the midline, the central canal, crosses the midline, and emerges on the opposite side.
90
Where does the second order neurone then travel to and join?
It travels into the white matter of the opposite side and joins the spinothalamic tract.
91
What is the white matter of the spinal cord split into?
Dorsal funiculus, lateral funiculus, and ventral funiculus.
92
Where do the second order neurones ascend, terminate, and onto what?
They ascend through the medulla, pons, midbrain, and end in the thalamus, particularly in the ventral posterolateral (VPL) nucleus.
93
What marks the decussation of second order neurones?
Anterior White Commissures, where axons of second-order sensory neurones cross the midline.
94
Where does spinal decussation occur?
Spinal sensory decussation occurs for all 31 neural levels.
95
Where does spinal decussation occur?
Spinal Sensory Decussation occurs for all 31 neural levels of the spinal cord.
96
Where do the 3rd order sensory neurones ascend and terminate?
Axons of 3rd Order Sensory Neurones of the VPL (thalamus) ascend further to terminate in the post-central gyrus of the Cerebral cortex.
97
What do the axons of the 3rd order neurones travel via?
Axons of 3rd Order Sensory Neurones of the VPL travel via the internal capsule.
98
Describe the organisation of the spinothalamic (ST) tract.
The spinothalamic tract is somatotopically organised throughout its full extent, preserving the spatial mapping of the body’s surface. Fibres from the lowest part of the body ascend dorsolaterally, while fibres from the cervical cord ascend in the ventro-medial part.
99
What's sensory dissociation?
The way in which pain and temperature sensation is carried to the brain via the spinal cord uses a different pathway from that used by proprioceptive signals.
100
In the ST tract, where is sensory information from the RHS of the body perceived?
Sensory information from the right side of the body is represented & perceived by the Left Brain.
101
Where does pain + temperature information travel to and from?
Pain and Temperature information crosses the midline at the same neural level as its respective dermatome and is carried on the contralateral spinal cord, Medulla, Thalamus and Cortex.

Y2S2M1 (22 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions