Neuroanatomy Packet - Section 4 Flashcards
How would a descending tract carry information from the brain to influence motor neurons indirectly?
Through interneurons
What makes up a mixed spinal nerve?
- Motor axons that innervate particular skeletal muscles (concerned with movements of the neck, trunk, back or limbs)
- Sensory axons that innervate corresponding regions of skin and muscle
Name this structure: a sensory region or skin innervated by an individual nerve root.
Dermatome
Name this structure: the muscle fibers that receive their motor innervation from a given spinal nerve.
Myotome
What is the clinical term for tingling?
Paresthesia
What is the clinical term for total loss of sensation?
Anesthesia
Name this structure: A network of the ventral rami of spinal nerves that come together and then redistribute themselves with a different arrangement of peripheral nerves.
A somatic nerve plexus
A skeletal muscle generally receives its information from:
a single peripheral nerve
Name the four main somatic nerve plexi:
- Cervical
- Brachial
- Lumbar
- Sacral (lumbosacral)
The cervical plexus consists of what spinal nerves?
C1-C4
What does the cervical plexus innervate?
Skin and muscles associated with the neck
The brachial plexus consists of what nerves?
C5-T1
The brachial plexus innervates what?
Skin and muscle acting on the upper limb
The lumbar plexus consists of what nerves?
L1-L4
What structures does the lumbar plexus innervate?
Skin and muscles of lower abdominal wall in the inguinal region
Anterior and medial compartments of the thigh
The sacral/lumbosacral plexus consists of what nerves?
L4 (4th and 5th rami) - S4
Where is the sciatic nerve found?
The sacral plexus
What is the largest nerve in the body?
The sciatic nerve
What does the sacral plexus innervate?
Skin and muscles of the gluteal region, posterior compartment of the thigh and all of the leg and foot
What is a spinal segment?
The region of the spinal cord from which a specific spinal nerve projects
How many spinal segments are there?
31
What spinal segments lack sensory roots?
The first (C1) and the last (S4)
At what vertebral level does the spinal cord end in an adult?
1st lumbar vertebra
What is the general function of the radial nerve?
Extension of all joints in the arm and hand
What is the general function of the median nerve?
Thumb side of hand and wrist
What is the general function of the ulnar nerve?
Finger side of hand and wrist
What are the two major branches of the sciatic nerve?
Tibial, common fibular
What are the most common locations for radiculopathies?
C6, C7, L5 and S1 (S1 much, much more common than cervical)
Where is the location of a peripheral mononeuropathy?
This is an injury to a peripheral nerve arising directly from the plexus. The neuropathy could be complete or incomplete.
Give an example of an incomplete lesion involved in a peripheral mononeuropathy. What are the resultant symptoms?
Entrapment of a nerve within a muscle
Compression of a nerve within a bony tunnel (carpal tunnel, cubital tunnel syndromes).
Symptoms are: loss of sensation or paresthesia and weakness of those muscles supplied by the particular nerve
What is a common cause of a plexopathy?
Motorcycle accident (any kind of shearing force trauma)
A lesion to a spinal nerve, a dorsal or a ventral root is a:
radiculopathy
Give an example of a radiculopathy.
Herniated intervertebral disc that compresses an individual nerve root
What are the symptoms of a radiculopathy?
Burning or tingling pain radiating down a limb in the dermatome
Diminished sensation over the dermatome supplied by the affected root
Reduced strength in muscles supplied by that spinal nerve (the myotome of the affected root)
Why is a dermatomal pattern of injury not strictly precise?
Because adjacent dermatomes overlap
In a radiculopathy, can you have complete paralysis of any given muscle or group of muscles?
No because some axons innervating the muscle will arise in different (adjacent) nerve roots
What is a fancy term for cell bodies of gray matter in the spinal cord?
perikarya
What can be found in the white matter of the spinal cord?
Ascending and descending axons connecting the brain and spinal cord
Propriospinal axons which interconnect different segments of the spinal cord
What can be found in the intermediate zone of the gray matter of the spinal cord?
Mixture of sensory and motor cell bodies
A lesion of the _____ will result in loss of pain-temperature sensation contralaterally, below the level of the lesion.
spinothalamic tract
The fasciculus gracilis and fasciculus cuneatus are collectively termed the:
posterior columns
What is stereognosis?
The ability to identify objects by touching and handling them with eyes closed.
A lesion of the posterior columns results in:
Decrease in stereognosis and some proprioception ipsilaterally, below the lesion
Why is light touch usually spared in unilateral spinal cord lesions?
Because light touch combines the pathways of the posterior columns and the anterolateral system, therefore there is always some input spared.
T or F: The spinocerebellar tract runs totally ipsilaterally with no decussation.
True. Cerebellar lesions will be ipsilateral always.
What is the function of the spinocerebellar tract?
Unconscious proprioception
The superior cerebellar peduncle connects the cerebellum to the:
midbrain
The middle cerebellar peduncle connects the cerebellum to the:
pons
The inferior cerebellar peduncle connects the cerebellum to the:
medulla
The patient has bilateral paralysis, fasiculations and muscle atrophy at the level C8-T1 along with bilateral pain-temperature loss at the level of T1-T2. What is the pathology?
Syringomelia, affects crossing of pain-temp fibers (anterior commissure) and perhaps ventral horns
Sensory loss over a given dermatome can result from:
Peripheral nerve or its entry point to the spinal cord.
What is Brown-Sequard syndrome?
Hemisection of the right cervical cord. Loss of pain and temp on the left side of the body below the neck, and paralysis and loss of proprioception-stereognosis below the neck on the right.
A patient with a tumor experiences loss of pain-temp in the left lower extremity followed by spastic paralysis on the riht. Where is the tumor?
In the R anterolateral aspect of the spinal cord, compressing first the right spinothalamic tract and then enlarging to involve the right corticospinal tract.
Name this CN: Chews and feels the front of the head
5, trigeminal
Name this CN: Moves the face, tastes, salivates, cries
7, facial
Name this CN: Tastes, salivates, monitors carotid body and sinus.
9, glossopharyngeal
Name thie CN: Tastes, swallows, lifts palate, talks, communicates with thoraco-abdominal viscera.
10, vagus
Name this CN: turns head, lifts shoulders.
11, accessory
Nucleus aMbiguous is Motor, in the Medulla, housing what CN nuclei?
9 and 10
