Introduction to Peripheral Nervous System

Questions and Answers

What is the primary function of the cervical enlargement in the spinal cord?

To protect the spinal nerves from injury

To support spinal cord growth

To connect the brain to the lower body

To innervate the upper limbs (correct)

Where are the cell bodies of the fibers in the dorsal roots located?

Within the spinal cord

In the spinal ganglion (correct)

In the dorsal horn

In the ventral horn

What condition occurs when a hernia develops at the lumbosacral level?

It spares the nerve roots of the same level (correct)

It affects only sensory fibers

It causes damage to the spinal cord directly

It compresses the nerve roots of the same level

Which type of hernia touches specifically the spinal nerve or one nerve root?

Lateral hernia Signup and view all the answers

What primarily characterizes cauda equina syndrome?

Saddle anesthesia in the sacral region Signup and view all the answers

What structure continues from the conus medullaris to attach to the coccyx?

Filum terminale Signup and view all the answers

What happens to spinal cord fibers after a lesion in the central nervous system?

They cannot regenerate Signup and view all the answers

Which of the following could be a cause of cauda equina syndrome?

Epidural metastasis Signup and view all the answers

What characterizes the neurons of the dorsal ganglion?

They are pseudounipolar Signup and view all the answers

What is the function of the meningeal branch of spinal nerves?

Innervates the structures of the CNS Signup and view all the answers

Which of the following correctly describes the relationship between the autonomic nervous system (ANS) and somatic nervous system (SNS)?

ANS involves two neurons whereas SNS involves one Signup and view all the answers

What type of question do dorsal roots typically not have at their location?

Dorsal roots Signup and view all the answers

The epidural space in the vertebral canal contains which of the following?

Connective tissue and blood vessels Signup and view all the answers

What results from the damage at the S2-S4 levels in cauda equina syndrome?

Atonic bladder and loss of rectal tone Signup and view all the answers

What is the main consequence of a central hernia in the lowest part of the spinal cord?

Cauda equina syndrome Signup and view all the answers

Which statement about preganglionic and postganglionic neurons is accurate?

Preganglionic neurons form synapses in the autonomic ganglion Signup and view all the answers

What distinguishes the white communicating branch from the grey communicating branch?

White branch contains myelinated preganglionic axons, grey contains unmyelinated postganglionic axons Signup and view all the answers

What part of the body is affected by saddle anesthesia?

Pelvic area including rectal and bladder function Signup and view all the answers

Which branch of the spinal nerve is responsible for the innervation of the back of the body?

Dorsal branch Signup and view all the answers

Which of these options describes a potential outcome of cauda equina syndrome besides sensory-motor loss?

Loss of sexual function Signup and view all the answers

What is the primary distinction between Schwann cells and oligodendrocytes regarding their function in nervous system myelination?

Schwann cells form the myelin sheath around axons in the PNS, whereas oligodendrocytes do so in the CNS. Signup and view all the answers

Which plexuses are commonly described together as the lumbosacral plexus?

Lumbar and sacral plexuses Signup and view all the answers

What is a key characteristic of dermatomes with respect to nerve innervation?

Dermatomes can overlap significantly, leading to redundancy in sensory innervation. Signup and view all the answers

How might diabetic neuropathy selectively affect sensory and motor functions?

It can lead to either loss of sensory or motor function, depending on the individual. Signup and view all the answers

Which neurological condition directly involves autoantibodies affecting acetylcholine receptors?

Myasthenia gravis Signup and view all the answers

What typically characterizes radiculopathy as a clinical condition?

A sensory or motor dysfunction due to spinal root pathology with associated symptoms. Signup and view all the answers

Which of the following statements about nerve lesions is accurate?

Peripheral axons have the potential for regeneration after damage. Signup and view all the answers

What distinguishes myopathy from other muscle-related diseases?

It can have various causes like toxins and infections, affecting muscle tissue. Signup and view all the answers

What is indicated by lesions in the femoral nerve?

Inability to walk due to quadricep dysfunction. Signup and view all the answers

Which characteristic of the thoracic level of the spinal nerves is notable?

They remain isolated without forming plexuses. Signup and view all the answers

What is the primary origin of cranial nerves?

Brainstem Signup and view all the answers

Which structure contains the majority of the spinal nerve roots that are positioned lower than the spinal cord?

Cauda equina Signup and view all the answers

How many cervical neuromeres are there, and why is this number unique?

8; it includes one additional nerve due to a unique exit pattern. Signup and view all the answers

What does the autonomic nervous system primarily control?

Involuntary bodily functions Signup and view all the answers

At what point does the spinal cord typically end in adults?

At L1 vertebra Signup and view all the answers

What is a consequence of the upward shift of the spinal cord during development?

Spinal nerves exit at a higher vertebral level than the cord Signup and view all the answers

Which condition is associated with the compression of the cauda equina?

Cauda equina syndrome Signup and view all the answers

Which description accurately reflects the anatomical organization of spinal nerves?

Each spinal nerve exits below its corresponding vertebrae, except cervical nerves. Signup and view all the answers

How many thoracic neuromeres are present in the spinal cord?

12 Signup and view all the answers

What is found within the vertebral column that corresponds to individual spinal nerves?

Neuromeres Signup and view all the answers

Study Notes

Peripheral Nervous System (PNS)

Composed of spinal and cranial nerves; spinal nerves arise from the spinal cord, cranial nerves from the brainstem.
The autonomic nervous system (ANS) bridges the peripheral and central nervous systems (CNS), managing glands and blood vessels at the peripheral level, while centers for control are in the CNS.

Spinal Nerves and Neuromeres

Spinal nerves organized into neuromeres:
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
Spinal cord ends at L1, with a notable upward position due to continued growth of the vertebral column during development.

Cauda Equina

Spinal nerves exit lower than the spinal cord's termination due to this upward shift, creating the cauda equina, which is crucial as compression can lead to cauda equina syndrome.

Spinal Cord Features

Contains two enlargements:
- Cervical enlargement (C5 to T1): innervates upper limbs.
- Lumbosacral enlargement (L1 to S3): innervates lower limbs.
Mixed spinal nerves formed from merging dorsal (sensory) and ventral (motor) roots.

Complicated Fiber Distribution

Spinal nerves form complex distributions at the periphery, often creating networks called plexuses for innervation.
Dorsal roots arrive from pseudounipolar neurons located in the dorsal ganglion.

Herniation Effects

Herniation can arise from disk issues, pressing on spinal nerve roots, potentially causing pain or loss of motor control.
Central hernia can lead to cauda equina syndrome; lateral hernia typically affects the nerve root at the same level.

Peripheral Nerve Structure

Enveloped by epineurium; may have myelin sheaths produced by Schwann cells, allowing regeneration post-injury.

Dermatomes and Myotomes

Dermatomes represent skin areas innervated by specific spinal nerves; myotomes refer to muscle groups innervated by spinal segments.
Limb and trunk innervation patterns vary significantly due to developmental origins.

Neuropathies and Conditions

Peripheral neuropathies affect sensitive and motor axons, with potential causes including diabetes.
Neuromuscular junction diseases, such as myasthenia gravis, result in motor symptoms without sensory loss.
Myopathies, including Duchenne muscular dystrophy, have various causes and affect muscle performance.

Back Pain and Radiculopathy

Back pain can stem from multiple causes, and radiculopathy typically presents as sensory/motor dysfunction due to spinal root pathologies, often linked to disk herniation.
Cauda equina syndrome involves sensory loss and autonomic dysfunction due to issues affecting nerve roots below L1-L2.

Spinal Nerve Branches

Each spinal nerve connects to the medulla through medial roots, dividing into:
- Dorsal branch (innervates back)
- Ventral branch (larger, innervates anterior body)
- Meningeal branch (innervates CNS structures)
- Communicating branches (link ventral branch to sympathetic chain).

Autonomic vs. Somatic Nervous Systems

ANS involves a two-neuron pathway; preganglionic neurons are myelinated, connecting to autonomic ganglia, while postganglionic neurons are unmyelinated.
Communicating branches: white (myelinated preganglionic axons) and grey (unmyelinated postganglionic axons) connect the system to target organs.

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Description

This quiz covers the essential aspects of the peripheral nervous system (PNS), including its components like spinal and cranial nerves, and the role of the autonomic nervous system. Learn how these systems interact with the central nervous system and their functions in controlling various bodily processes.