Definitions Flashcards
Fasciculus Gracilis
Sensory, fine touch, proprioception, vibration from ipsilateral side of the cord. Medial to the Cuneatus and carries sensory from below T-8
Fasciculous Cuneatus
Sensory, fine touch, vibration, proprioception from ipsilateral side of the body. Lateral to the gracilis and carries information above T-8
Spinocerebellar tract
Carries proprioception from the limbs to the cerebellum
Lateral corticospinal tract
Carries motor information to the ipsilateral anterior horn alpha motor neurons
Anterior corticospinal tract
Carries motor innervation to the ipsilateral and contralateral anterior horn.
Anterior comissure
Where pain and temperature tracts desiccate in the spinal cord.
Spinothalamic tract
Pain and vibration from the contralateral side of the body.
Where is the lumbar cistern ?
The space in the spinal column after the cord has terminated (L1-L2 in adults) and the S-2 root.
Where is the epidural space.
Between the vertebral periosteum and the dural sac.
What is the difference between spinal anesthesia and epidural anesthesia ?
Spinal anesthesia is given in the subdural space. You must penetrate the dura and it requires much less anesthetic.
How many spinal nerves are there ?
31 duhh 8-cervical 12- thoracic 5-lumbar 5-sacral and 1 coccageal
What nerves flex the elbow ?
C5- C6
What nerves flex the wrist
C6 C7
What nerves extend the elbow ?
C7 C6
What are lower motor neurons ? What modulates function of LMN?
Alpha motor neurons who’s cell bodies are in the anterior horn. They are modulated by renshaw cells
What cell bodies are in the lateral horn ?
The preganglionic motor neurons of the visceral efferent system ( Parasympathetic and Sympathetic )
How many layers of grey matter are there ?
10 they are called Rexed lamina.
Rexed lamina 1-6
Posterior horn
Rexed lamina 7-9
Anterior horn
rexed lamina 10
Central canal
Describe the somatotrophic organization of the anterior horn
The flexor muscles are posterior and the extensor muscles are more anterior. Distal motor groups are found more lateral in the horn
Where do neurons in the anterior corticospinal tract cross over ?
They cross over at the level in which they innervate the LMN. The anterior tract is mainly concerned with maintaining posture.
Where does the lateral corticospinal tract cross over ?
The lateral corticospinal tract crosses at the level of the brainstem and is the main supply of innervation to the alpha motor neurons in the anterior horn
What does the spinocerebellar tract perform ?
The spinocerbellar tract provides proprioreceptive information to the ipsilateral cerebellum
Spinothalamic tract ?
Located in the anterior lateral column and provides pain and temperature to the contralateral side of the body.
What artery perfuses the posterior 1/3 of the spinal column ?
Posterior vertebral arteries
What perfuses the anterior 2/3 of the spinal cord ?
Anterior vertebral arteries
What are the two arterial systems that perfuse the spinal column ?
The vertebral - Basalar system and the segmental arteries
What is the most prominent segmental artery perfusing the spinal cord ?
Artery of Adamkiewitz which branches off of the aorta at T-12. This artery is important because abdominal surgery or trauma can block this artery and infarct the cord.
Describe the components of a myotactic stretch reflex ?
The muscle fascicle is stretched and 1a fibers from the muscle synapse directly with the a-motor neuron of that muscle. Inhibitory interneurons prevent the antagonist muscle from contracting.
What determines desired muscle length of a muscle spindle ?
A gamma motor neuron.
What type of reflex is a withdrawal reflex and what fiber types mediate it ?
It is a flexor reflex mediated by A-delta and C fibers.
Pain and Temperature
Spinothalamic - Anteriolateral cord
Where do tracts in the dorsal columns cross ?
Caudal Medulla
The anterior spinal artery is formed from branches of the … ?
Vertebral Arteries
What spinal modality transfers mechanical stimuli ?
The posterior column - Medial Lemniscus system
What spinal modality transports noxious stimuli ?
The anteriolateral System ( Spinothalamic )
What type of fibers carry pain and temperature ?
A-Delta and C fibers. They go to the posterior horn, substantial gelatinosa of the spinothalamic tract
What type of fibers carry discriminative touch ?
A-Beta Fibers which run in the posterior column - medial leminiscal pathway
Muscle enteroreceptors carry which type of fibers ?
1a and 2
Tendons carry which type of enternoreceptors ?
Golgi tendon organs and 1b
Joints carry which type of enternoreceptors ?
1b fibers
Nocioreceptors communicate with which pathway ?
The spinothalamic pathway in the anteriolateral column
Where do neurons enter, travel, and cross over in the posterior column, medial lemiscial pathway ?
The A-Beta neurons that make up the posterior column enter the dorsal root and transcend the ipsilateral dorsal column until the nucleus gracillus and nucleus cuteness. they then cross over and synapse in the VPL
Where does the posterior column become the medial lemiscus pathway ?
After synapsing in the nucleus gracillus and nucleus cutineform the fibers cross over and travel in the medial lemiscus through the rostral medulla. They then travel through the pons and midbrain and synapse in the VPL of the thalamus.
Describe the changes in the somatotropic organization of the posterior column as it passes through the medial lemiscial layer
When the secondary neurons from the nucleus gracillus and nucleus cunueatus enter the leminiscus the upper limbs are more posterior and the lower limbs are anterior. As the tracts progress rostrally they rotate counter clockwise. mid way the upper limbs are more medial and vice versa. As the fibers continue rostrally the final orientation is the upper limb fibers are more anterior and the lower limbs are more posterior.
What kind of fibers compose the anteriolateral systems ?
They are slow conduction fibers of the A-Delta or C fibers
What fibers carry temperature and pain ?
A- delta fibers are heat activated and cold activated. They also carry pin prick pain fibers.
What fibers are responsible for dull poorly localized pain ?
C fibers which are unmylenated and respond to mediators released after tissue has been damaged.
What are the role of C fibers ?
They are responsible for dull poorly localized pain from muscles and also respond to histamine for itching as well as mechanical and thermal stimuli
What is Lissauers tract ?
The tract that pain and temperature fibers pass through after they enter the dorsal horn before they cross over to the lateral corticospinal tract.
Describe the somatotropic organization of the anterolateral tract as it ascends the spinal cord
The anterolateral tract ascends the cord with the lower extremity positioned more laterally and the upper limb positioned more medially.
Where does the spinothalamic tract terminate ?
In the VPL of the thalamus
What happens to fibers of the spinothalamic tract after they exit the VPL ?
They pass through the posterior limb of the internal capsule and corona radiate to the primary somatosensory cortex
What will lesions of the spinothalamic tract present as clinically ?
Loss of pain and temperature on the contralateral side of the body 1-2 levels above or below the site of the lesion
What is the purpose of the spinocerebellar tract ?
To carry proprioreceptive information to the ipsilateral cerebellum from the lower extremity
What is the cuenocerebellar tract
Proprioreceptive information to the ipsilateral cerebellum from the upper extremity.
Where do cuteness receptors, proprioreceptors and golgi tendon organs synapse after entering the dorsal grey matter of the spinal cord ?
In clark’s nucleus which extends from C8-L3
What type of fibers come from Golgi receptors ?
1b
What type of fibers relay from muscle spindles to clark’s nucleus
1a and 2
What happens when fibers leave the clarke nucleus ?
They travel in the posterior spinocerebellar tract to the brainstem where they enter the cerebellum through the inferior peduncle and synapse in the ipsilateral lobe.
What does the cuenocerebellar tract carry ?
Information similar to that in Clarke nucleus but from the upper extremity ( Above C8 )
Somatosensory receptors above C8 travel where ?
With the faculous cuneous to the accessory cuneate nucleus
What is the purpose of the anterior spinocerebelar tract?
To take input from the sensory and motor systems to modulate postural stability in real time for the upper limb
What is the purpose of the rostral spinocerebellar tract ?
It has the same role as the anterior spinocerebellar tract and modulates postural stability for the lower extremity.
What do lesions in the spinocerebellar tracts cause ?
Ataxia or loss of muscle coordination due to loss of proprioreceptive modulation in the cerebellum.
What type of receptors do the anteriolateral tracts have in the periphery ?
Free nerve endings.
What will a syringomyelia in the anterior cervical spine compressing the white matter cause ?
This will inter rump the spinothalamic tracts as they cross over in the anterior comissure and the patient will present with bilateral loss of pain and temperature sensation in the hands.
How are spinal border cells unique ?
The reside in the anterior horn and receive input from lower limb muscles as well as descending input to the lower motor neurons
Proprioreceptive input and externoreceptor input from the lower limb ?
Posterior spinocerebellar tract.
Integrates information from the upper limb with descending input
Rostral spinocerebellar
