Chapter 13 – Spinal Cord and Spinal Nerves (Tortora & Derrickson, 16e)

A comprehensive set of flashcards in Q&A style covering anatomy, physiology, reflexes, plexuses, and disorders of the spinal cord and spinal nerves based on the lecture notes.

What are the two major functions of the spinal cord?

It processes reflexes and conducts sensory impulses to the brain and motor impulses to effectors.

Which three structures protect the spinal cord?

Bone (vertebrae), connective tissue (meninges), and cerebrospinal fluid (CSF).

Name the three layers of the meninges from outermost to innermost.

Dura mater, arachnoid mater, pia mater.

Where does the spinal cord begin and end in the adult?

It begins as a continuation of the medulla oblongata at the foramen magnum and ends around the level of the second lumbar vertebra (L2).

How many pairs of spinal nerves exist in humans?

31 pairs.

Which roots attach a spinal nerve to the spinal cord?

Anterior (ventral) and posterior (dorsal) roots.

What type of information travels in posterior (dorsal) roots?

Sensory (afferent) information.

What type of information travels in anterior (ventral) roots?

Motor (efferent) information.

Which space lies between dura mater and vertebral bone and what does it contain?

The epidural space; it contains fat and blood vessels.

What is found in the subarachnoid space?

Cerebrospinal fluid (CSF).

What are denticulate ligaments and their function?

Lateral extensions of pia mater that anchor the spinal cord to the dura, stabilizing it within the vertebral canal.

Define gray commissure.

A cross-bar of gray matter that connects the two halves of the spinal cord’s gray matter.

What is the function of white matter tracts in the spinal cord?

They conduct nerve impulses to and from the brain.

What is the function of gray matter in the spinal cord?

It receives and integrates incoming and outgoing information to perform spinal reflexes.

Which connective-tissue sheath surrounds an entire spinal nerve?

Epineurium.

Which sheath encloses each nerve fascicle?

Perineurium.

Which sheath surrounds individual axons?

Endoneurium.

After exiting the intervertebral foramen, into what branches does a typical spinal nerve divide?

Posterior (dorsal) ramus, anterior (ventral) ramus, meningeal branch, and rami communicantes.

What does the posterior (dorsal) ramus supply?

Skin and deep muscles of the posterior trunk.

What does the anterior (ventral) ramus supply?

Muscles and skin of the limbs, and the lateral and anterior trunk.

What does the meningeal branch re-enter to supply?

It re-enters the vertebral cavity to innervate vertebrae, ligaments, blood vessels of the cord, and meninges.

Define a plexus.

A network of anterior rami of spinal nerves (except T2–T12) that combine and split to form peripheral nerves.

Which spinal nerves form the cervical plexus and what major muscle does it innervate via the phrenic nerve?

Anterior rami of C1–C4 (with some C5); it innervates the diaphragm.

Which spinal nerves form the brachial plexus?

Anterior rami of C5–C8 and T1.

Which spinal nerves form the lumbar plexus?

Anterior rami of L1–L4.

Which spinal nerves form the sacral plexus?

Anterior rami of L4–L5 and S1–S4.

Which spinal nerves form the coccygeal plexus?

Anterior rami of S4–S5 and the coccygeal nerve.

What region of skin is supplied by a single spinal nerve?

A dermatome.

List the five components of a reflex arc in order.

Receptor, sensory (afferent) neuron, integration center, motor (efferent) neuron, effector.

Give two distinguishing features of a reflex arc.

It is fast and involuntary, bypassing higher brain centers.

Differentiate ipsilateral and contralateral reflexes.

Ipsilateral reflexes stay on the same side of the spinal cord; contralateral reflexes involve the opposite side.

Define monosynaptic reflex.

A reflex involving only one synapse between the afferent and efferent neuron.

Define polysynaptic reflex.

A reflex involving two or more synapses and at least one interneuron.

What receptor initiates the stretch reflex?

The muscle spindle.

Is the stretch reflex monosynaptic or polysynaptic and ipsilateral or contralateral?

Monosynaptic and ipsilateral.

What is the main function of the stretch reflex?

To maintain muscle tone and posture by resisting sudden stretch.

Which receptor triggers the tendon reflex?

Golgi tendon organ.

Is the tendon reflex monosynaptic or polysynaptic?

Polysynaptic.

What is the primary function of the tendon reflex?

To prevent excessive tension in a tendon, protecting it from damage.

Which stimulus typically triggers the flexor (withdrawal) reflex?

A painful or harmful stimulus detected by nociceptors.

Is the flexor reflex ipsilateral or contralateral?

Ipsilateral.

What reflex maintains balance when the flexor reflex is activated?

The crossed-extensor reflex.

Is the crossed-extensor reflex ipsilateral or contralateral?

Contralateral.

Define reciprocal innervation.

A neural circuit that simultaneously contracts one muscle and relaxes its antagonist.

Compare reflex arcs to normal nerve impulses regarding consciousness.

Reflex arcs are unconscious and automatic; normal impulses may involve conscious thought.

What term describes paralysis of one limb?

Monoplegia.

What term describes paralysis of the lower half of the body?

Paraplegia.

What term describes paralysis of one side of the body?

Hemiplegia.

What term describes paralysis of all four limbs?

Quadriplegia (tetraplegia).

Which viral disease can reactivate to cause shingles?

Varicella-zoster virus.

What nervous system disorder involves immune attack on myelin in the CNS?

Multiple sclerosis (MS).

Which infectious disease can destroy motor neurons and cause paralysis but is preventable by vaccine?

Poliomyelitis (polio).

Which cervical plexus nerve keeps the diaphragm alive?

The phrenic nerve (C3–C5).

Damage to the upper roots of the brachial plexus often produces what condition?

Erb-Duchenne palsy (waiter’s tip).

Which brachial plexus nerve injury results in wrist drop?

Radial nerve injury.

What is the largest nerve arising from the lumbar plexus and what joints does it act upon?

The femoral nerve; it supplies hip flexors and knee extensors.

Name the longest and thickest nerve in the body.

The sciatic nerve.

Into what two major branches does the sciatic nerve split at the knee?

Tibial nerve and common fibular (peroneal) nerve.

Which nerve of the sacral plexus supplies the gluteus maximus?

Inferior gluteal nerve.

What cutaneous nerve supplies the skin of the lateral thigh?

Lateral femoral cutaneous nerve (L2–L3).

Which nerve injury produces “winging” of the scapula due to paralysis of serratus anterior?

Long thoracic nerve injury.

Which spinal nerves (thoracic levels) give rise to intercostal nerves rather than plexuses?

Anterior rami of T2–T12.

Which column of white matter lies between the posterior median sulcus and the posterior gray horn?

Posterior (dorsal) white column.

What small central space within gray matter contains CSF?

The central canal of the spinal cord.