Prac manual 3.2 and 3.3

What is the conus medullaris?

The tapered inferior end of the spinal cord.

What is the filum terminale?

A thin strand of pia mater anchoring the spinal cord to the coccyx.

What is the cauda equina?

A bundle of spinal nerve roots descending below L1.

Why is the spinal cord shorter than the vertebral column?

The vertebral column grows faster during development, leaving the cord ending at L1-L2.

What causes the cervical and lumbar enlargements?

Increased numbers of neurons supplying the upper and lower limbs.

What is the epidural space and its clinical significance?

A fat‑filled space between dura and vertebral canal; site for epidural anaesthesia.

What is the lumbar cistern and its clinical significance?

CSF‑filled space below L2; safe site for lumbar puncture.

What do somatosensory neurons carry information from?

Skin, skeletal muscles, joints, and special senses.

What do somatomotor neurons innervate?

Skeletal muscle.

What are general sensory receptors?

Mechanoreceptors, thermoreceptors, nociceptors, chemoreceptors.

What is the epineurium?

Outer connective tissue layer surrounding the entire nerve.

What is the perineurium?

Connective tissue surrounding a fascicle of axons.

What is the endoneurium?

Connective tissue surrounding individual axons.

What two features determine nerve conduction velocity?

Axon diameter and myelination.

Where do cranial nerves attach to the CNS?

Brain and brainstem.

What are the general functions of cranial nerves?

Sensory, motor, and parasympathetic functions.

Where do spinal nerves attach to the CNS?

The spinal cord via dorsal and ventral roots.

What are the general functions of spinal nerves?

Mixed sensory and motor innervation to body wall and limbs.

Are dorsal roots sensory or motor?

Sensory.

Are ventral roots sensory or motor?

Motor.

What does the dorsal root ganglion contain?

Cell bodies of sensory neurons.

Is a spinal nerve sensory, motor, or mixed?

Mixed.

Are dorsal and ventral rami sensory, motor, or mixed?

Mixed.

How do spinal nerves exit the vertebral canal?

Through intervertebral foramina.

How many cervical spinal nerves are there?

8.

How many thoracic spinal nerves are there?

12.

How many lumbar spinal nerves are there?

5.

How many sacral spinal nerves are there?

5.

Why are there 8 cervical spinal nerves but only 7 cervical vertebrae?

C1-C7 exit above their vertebrae; C8 exits below C7.

Why are dorsal rami smaller than ventral rami?

They supply a smaller area (deep back muscles and skin).

What information is carried in dorsal roots?

Sensory information.

What information is carried in ventral roots?

Motor information.

What information is carried in dorsal rami?

Mixed sensory and motor to back muscles and skin.

What information is carried in ventral rami?

Mixed sensory and motor to limbs and anterior trunk.

What is the lateral horn associated with?

Sympathetic autonomic neurons (T1-L2).

Are lateral horns present at all spinal levels?

No — only T1-L2 (sympathetic) and S2-S4 (parasympathetic).

Can the olfactory nerve be seen on a brain specimen?

No — only the olfactory bulb and tract are visible.

Where is the olfactory nerve located?

In the nasal mucosa, passing through the cribriform plate.

What is the optic chiasm?

The crossing of optic nerve fibers.

What are the olives of the medulla?

Lateral bulges containing olivary nuclei involved in motor learning.

What are the pyramids of the medulla?

Longitudinal motor tracts (corticospinal tracts).

What travels through foramen spinosum?

Middle meningeal artery.

Which ventral rami form the cervical plexus?

C1-C4.

Which nerve arises from C3, C4, C5?

The phrenic nerve.

What does the phrenic nerve innervate?

The diaphragm.

Which ventral rami form the brachial plexus?

C5-T1.

Which ventral rami form the lumbar plexus?

L1-L4.

Which ventral rami form the sacral plexus?

L4-S4.

Are the roots of the brachial plexus continuations of the ventral roots?

False — they are continuations of the ventral rami, not the roots.

What structure lies between the anterior and posterior divisions of the brachial plexus?

The axillary artery.

Which muscle lies between the roots of the brachial plexus?

The anterior and middle scalene muscles.

What muscle compartment is innervated by the musculocutaneous nerve?

The anterior compartment of the arm.

Which nerve innervates most intrinsic muscles of the hand?

The ulnar nerve.

What muscle compartments are innervated by the radial nerve?

Posterior compartments of the arm and forearm.

What is the clinical implication of the radial nerve's location on the humerus?

It lies in the radial groove — mid‑shaft humeral fractures can injure it, causing wrist drop.

What nerve travels through the carpal tunnel?

The median nerve.

How does the ulnar nerve enter the wrist and hand?

Superficial to the flexor retinaculum, through Guyon's canal.

Which ventral rami contribute to the femoral nerve?

L2-L4.

What muscle does the femoral nerve run beside in the abdomen?

Psoas major.

Where is the femoral nerve located in the femoral triangle?

Lateral to the femoral artery.

What are the boundaries of the femoral triangle?

Superior: Inguinal ligament; Lateral: Sartorius; Medial: Adductor longus; Floor: Iliopsoas + pectineus; Roof: Fascia lata.

Which muscle compartment does the femoral nerve supply?

The anterior thigh compartment.

What is the general sensory area supplied by the obturator nerve?

Medial thigh.

Which muscle compartment does the obturator nerve innervate?

The medial thigh (adductor) compartment.

Which ventral rami contribute to the sacral plexus?

L4-S4.

What are the four main branches of the sacral plexus?

Sciatic, tibial, common fibular, pudendal.

What two nerves travel together in the sciatic nerve sheath?

Tibial nerve and common fibular nerve.

What muscle does the sciatic nerve typically emerge beneath?

Piriformis.

Which nerve supplies the dorsum of the foot?

Superficial fibular nerve.

Which nerve supplies the web space between toes 1 and 2?

Deep fibular nerve.

Which nerve supplies the plantar surface of the foot?

Tibial nerve (via medial and lateral plantar nerves).

What are the major nerves of the lumbar plexus?

Femoral and obturator nerves.

What are the major nerves of the sacral plexus?

Sciatic, tibial, common fibular, deep fibular, superficial fibular.

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