Home / Summaries / Neuroanatomy / corticospinal-spinal-motor

Neuroanatomy - The Spinal Cord & Motor Control of the Body

Q: What is the function of the spinal cord?

It provides a pathway for sensory and motor impulses between the brain and the rest of the body.

Q: Where is the spinal cord located and what are its boundaries?

It lies in the vertebral canal , extending from the medulla oblongata to L2 vertebra .

Q: What do each segments of the spinal cord give rise to?

Each segments give rise to a single pair of spinal nerves , serving as the point of origin

Q: Where do spinal nerves emerge from?

They emerge laterally from the intervertebral foramen

Q: Where does the cervical enlargement extend to and from?

Cervical enlargement extends from C3 to T2

Q: Where does the lumbar enlargement extend to and from?

Lumbar enlargement extends from T11 to the end of the spinal cord

Q: What is the function of the cervical and lumbar enlargement?

1. Cervical enlargement gives rise to the peripheral nerves that innervate the upper limbs 2. Lumbar enlargements give rise to the peripheral nerves that innervate the lower limbs

Q: What is the conus medullaris?

It is the lower termination point of the spinal cord proper

88 important questions on Neuroanatomy - The Spinal Cord & Motor Control of the Body

What is the function of the spinal cord?

It provides a pathway for sensory and motor impulses between the brain and the rest of the body.

Where is the spinal cord located and what are its boundaries?

It lies in the vertebral canal, extending from the medulla oblongata to L2 vertebra.

What is the vertebral canal?

Bony tunnel formed by stacked vertebral foramina of stacked vertebrae

How many segments is the spinal cord divided into?

31 segments

What are the divisions of the spinal cord segments?

8 cervical segments
12 thoracic segments
5 lumbar segments
5 sacral segments
1 coccygeal segments

What do each segments of the spinal cord give rise to?

Each segments give rise to a single pair of spinal nerves, serving as the point of origin

Where do spinal nerves emerge from?

They emerge laterally from the intervertebral foramen

Where does the cervical enlargement extend to and from?

Cervical enlargement extends from C3 to T2

Where does the lumbar enlargement extend to and from?

Lumbar enlargement extends from T11 to the end of the spinal cord

What is the function of the cervical and lumbar enlargement?

1. Cervical enlargement gives rise to the peripheral nerves that innervate the upper limbs
2. Lumbar enlargements give rise to the peripheral nerves that innervate the lower limbs

What is the conus medullaris?

It is the lower termination point of the spinal cord proper

Where does the conus medullaris extend to and from?

It extends from L1 to L2

What is the purpose of the cauda equina?

Cauda equina allows the continuation of some spinal nerves that need to travel further from the conus medullaris due to the spinal cord being shorter than the vertebrae.

What is the filum terminale and its functions?

Filum terminale is an extension of the pia mater that anchors the spinal cord to the coccyx

How does the spinal nerve exit the vertebral canal?

The spinal nerve exits the vertebral canal at the intervertebral foramen that is either above or below the vertebra of the same number except cervical nerve 8

Name the three layers of the spinal meninges (connective tissue cover) from outermost to innermost.

Dura mater, arachnoid mater, pia mater.

What do spinal meninges do?

1. Protection of spinal cord
2. Contains and circulates cerebrospinal fluid

What are each spinal meninges made of?

1. Dura mater - sleeve of dense fibrous tissue
2. Arachnoid mater - thin, delicate membrane
3. Pia mater - rich network of blood vessels

Where do each spinal meninges extend to?

Dura and arachnoid mater extend to S2 vertebra.
Pia mater extends beyond spinal cord as filum terminale

What is subarachnoid space and its functions?

Subarachnoid space is space between arachnoid and pia mater that contains cerebrospinal fluid.

What is the function of subarachnoid space?

The cerebrospinal fluid in the subarachnoid space is essential for shock absorption and transport of nutrients, gases, and waste products.

What is epidural space?

Space that separates dura mater and surrounding bone

What does the epidural space contain?

Loose connective tissue, adipose tissue, and blood vessels

What is the purpose of lumbar puncture?

To acquire a sample of cerebrospinal fluid from the subarachnoid space

How is lumbar puncture carried out?

A spinal needle is inserted and removed between L3 and L4 because this area only contains the lower spinal nerves, minimising damage to spinal nerves

What is the purpose of epidural anaesthesia?

Numbing of lower spinal nerves that innervate the lower half of the body (ex: relieving pain for child birth)

What structures protect the spinal cord?

Bony vertebral canal

Spinal meninges

Epidural fat

Cerebrospinal fluid (CSF)

Denticulate ligaments

Describe the location of denticulate ligament

Denticulate ligament is situated between the posterior/dorsal and anterior/ventral root of spinal nerve

What are denticulate ligaments?

Denticulate ligaments are extensions of pia mater surrounding the spinal cord that fuse with the dura mater and arachnoid mater

How does denticulate ligament protect the spinal cord?

They prevent the spinal cord from being displaced

What is the composition and function of anterior/ventral gray horns?

Contains cell bodies of motor neurons
Supplies skeletal muscles by sending out axons of motor neurons into the spinal cord via ventral roots

What is the composition and function of posterior/dorsal gray horns?

Contains sensory neuron axons
Receives incoming sensory signals and sends them to the spinal cord via dorsal roots ganglia

What is the composition and function of lateral gray horns?

Contains cell bodies of autonomic motor nuclei
Regulates activity of smooth muscle, cardiac muscle, and glands

What are white columns?

Three columns of white matter that contain nerves tracts

What are nerve tracts?

They are bundles of axons that are distinctly grouped by common origin or destination and delivery of similar information

What are the two tracts that pass through the white columns?

1. Sensory/ascending tracts
2. Motor/descending tracts

What are the two structures that form the spinal nerves?

Joining of anterior root of spinal nerve and posterior root of spinal nerve = individual spinal nerves

Which spinal nerves exit the vertebral canal via intervertebral foramen that is above the vertebra of the same number?

Spinal nerves from C1 to C7

Which spinal nerves exit the vertebral canal via intervertebral foramen that is below the vertebra of the same number?

Spinal nerves T1 to Co1

Where does the 8th cervical spinal nerve exit the vertebral canal?

It exits the vertebral canal at intervertebral foramen between C7 and T1 vertebra.

What does the posterior ramus innervate?

Skin and muscles of the back

What does the anterior ramus give rise to?

It gives rise to peripheral nerves that innervate the upper limbs, lower limbs, and anterior and lateral trunks.

Why is the anterior ramus thicker than the posterior ramus?

Because the anterior ramus gives rise to more peripheral nerves than the posterior ramus.

What is the rami only found between spinal nerve and sympathetic trunk ganglion (T1 to L2)?

Rami communicantes

What are nerve plexuses?

Nerve plexuses are networks of interweaving anterior branches/rami of spinal nerves that eventually split into peripheral nerves, innervating specific muscles or areas of the skin

List the four nerve plexuses with the origin of rami per plexus

1. Cervical plexus (C1-C4)
2. Branchial plexus (C5-T1)
3. Lumbar plexus (L1-L4)
4. Sacral plexus (L4-S4)

What does the cervical plexus innervate?

Head and neck
Lungs (via phrenic nerve)

What does the brachial plexus innervate?

Muscles of upper limb

What does the lumbar and sacral plexus innervate?

Muscles of lower limb

What is the importance of the complex network of nerves?

The complex interconnected nature of nerves allows damage to one nerve to be compensated by another.

What are the components of peripheral nerves?

Axons
Connective tissues
Blood vessels

What is the arrangement of groups of axons in peripheral nerves called?

Fascicles

Are peripheral nerves sensory, motor, or mixed?

Mixed (both sensory and motor)

Are the axons of peripheral nerves myelinated?

They can be myelinated or not

What are the three types of connective tissue present in peripheral nerves?

Epineurium
Perineurium
Endoeurium

Where are each of the connective tissues found within the peripheral nerves?

Epineurium - around the entire peripheral nerve
Perineurium - around a fascicle
Endoeurium - around each axon

What is the purpose of connective tissues around peripheral nerves?

To protect the nerve from tensile forces that are generated from bodily movements

Where are the cell bodies of upper motor neurons in the corticospinal tract located?

In layer V of the primary motor cortex

What cortical areas provide input to the corticospinal tract?

50% from the primary motor cortex, and the rest from premotor, supplementary motor, somatosensory areas, and parietal lobe

Through which structure do corticospinal fibers pass after leaving the cortex?

The fibers converge and pass through the posterior limb of the internal capsule

What percentage of corticospinal fibers decussate, and where does this occur?

80% decussate (cross over) at the medulla oblongata, forming the lateral corticospinal tract (LCST).

What happens to the remaining 20% of corticospinal fibers that don’t decussate in the medulla?

They travel ipsilaterally until they decussate at the spinal cord near the exit level, forming anterior and ventral corticospinal tract

What is the percentage distribution of exit from corticospinal tract?

55% at cervical levels

20% at thoracic levels

25% at lumbo-sacral levels

How do upper motor neurons connect to lower motor neurons (LMNs) in corticospinal tract?

Upper motor neurons make direct or indirect synaptic connections with LMNs on the contralateral side.

What is the functional role of the corticospinal tract?

It mediates voluntary control of rapid, finely coordinated, and skilled movements

What is the decussation of pyramids?

The crossing-over of about 80% of corticospinal tract fibres in the lower part of the medulla oblongata

What is the function of anterior corticospinal tract?

Controls movement of proximal parts of free limbs and trunk of body

What is the difference between the lateral and anterior corticospinal tracts in terms of function?

Lateral CST: Controls limb muscles, especially distal parts

Anterior CST: Controls proximal parts of free limbs and trunk muscles

What is the lateral funiculus, and which tract runs through it?

The lateral funiculus is a region of white matter in the spinal cord where the lateral corticospinal tract descends.

What is the anterior white commissure’s role in the corticospinal pathway?

It is a site in the spinal cord where fibers from the anterior corticospinal tract cross over (decussate) to synapse with LMNs on the opposite side.

What distinguishes the extra-pyramidal system from the pyramidal (corticospinal) system?

The extra-pyramidal system includes fibers involved in motor control that do not pass through the pyramids of the medulla oblongata

Where do all tracts of extra-pyramidal system originate?

All originate in brainstem

What are the main functions of the extra-pyramidal system?

- Selective activation and suppression of movements

- Initiation of movements

- Setting the rate and force of movement

- Ensuring smooth, coordinated motion

What are the four tracts of the extra-pyramidal system?

1. Rubrospinal tract
2. Tectospinal tract
3. Reticulospinal tract
4. Vestibulospinal tract

What is the origin of rubrospinal tract?

Red nucleus of the midbrain receiving input from motor cortex and cerebellum

Describe the pathway of nerves in the rubrospinal tract.

Red nucleus of midbrain --> decussation of axons in the ventral tegmental decussation --> continues ventrally descending with lateral CST --> reaches lower motor neuron at ventral horn

What is the function of rubrospinal tract?

Controls tone of limb flexor muscles by facilitating flexor and inhibiting extensor muscles

What is the origin of tectospinal tract?

Tectum of the superior colliculus of midbrain receiving visual input

Describe the pathway of nerves in the tectospinal tract

Tectum of suerpior colliculus --> decussation of axons in dorsal tegmental decussation --> continues running near the ventral median fissure of spinal cord --> mostly terminate at cervical level

What is the function of tectospinal tract?

Mediates reflex movement to visual stimulus

What are the origins of reticulospinal tract?

1. Reticular formation of pons
2. Medulla oblongata

Describe the pathway of nerves in the reticulospinal tract

Reticular formation of pons or medulla oblongata --> continues running in ventral funiculus

What is the function of reticulospinal tract?

Somatic control - reflex activity, muscle activity via control of alpha and gamma motor neurons
Autonomic control - vital functions like breathing and circulatory system

What is the origin of vestibulospinal tract?

Vestibular nuclei of pons and medulla that receive input from cerebellum and vestibular nerve

What is the function of vestibulospinal tract?

Control of muscle tone for maintenance of posture and balance

What are the symptoms of lower motor neuron disorder?

1. Flaccid paralysis
2. Decreased muscle tone
3. Decreased muscle stretch reflexes
4. Profound muscle atrophy
5. Fasciculations (involuntary muscle spasms) present

What are the symptoms of upper motor neuron disorder?

1. Spastic paralysis
2. Increased muscle tone
3. Increased muscle stretch reflexes
4. Minimal muscle atrophy
5. Fasciculations absent

What causes extra-pyramidal symptoms?

Damage to, or pharmacological interference with, the extra-pyramidal pathways or basal ganglia

The question on the page originate from the summary of the following study material:

Neuroanatomy

View summary

A unique study and practice tool
Never study anything twice again
Get the grades you hope for
100% sure, 100% understanding

Remember faster, study better. Scientifically proven.

flashcards
& notes