Chapter 13 The Spinal Cord, Spinal Nerves, and Spinal Reflexes Study Guide

List the four spinal cord regions from superior to inferior? 

• Cervical 

•  Thoracic 

•  Lumbar 

•  Sacral 

What fluid is in the central canal of the spinal cord and the subarachnoid space? 

Cerebrospinal fluid (CSF). 

What parts of the body are being served by the cervical and lumbar enlargements? 

• Cervical enlargement: Serves the arms and upper limbs. 

• Lumbar enlargement: Serves the legs and lower limbs. 

What do dorsal root ganglia contain? 

contain the cell bodies of sensory (afferent) neurons. 

What is the function of the dorsal roots

Carry sensory information toward the spinal cord. 

What is the function of rami communicantes? 

connect spinal nerves to the sympathetic trunk and carry sympathetic nerve signals. 

White ramus communicans contains what types of axons?

contains myelinated axons that innervate glands and smooth muscle 

Gray ramus communicans contains what types of axons? 

contains unmyelinated fibers that innervate glands and smooth muscle 

Spinal nerves are mixed nerves. What does this mean? 

they contain both sensory (afferent) and motor (efferent) fibers. 

In which location would a doctor perform a spinal tap? 

In the lumbar region, usually between the L3–L4 or L4–L5 vertebrae. 

What is meningitis? 

viral or bacterial infection of meninges 

What structures are mainly found in gray matter?

Contains neuron cell bodies, neuroglia, and unmyelinated axons; integrates information and initiates commands. 

What structures are mainly found in white matter? 

Contains myelinated and unmyelinated axons; carries information from place to place. 

What are organized areas of spinal cord grey matter called?  

They are called horns (gray horns). 

What is the function of sensory nuclei in the spinal cord?

Receive and process sensory information. 

What is the function of motor nuclei in the spinal cord? 

Send motor commands to muscles and glands. 

What are organized areas of spinal cord white matter called?

They are called columns (white columns). 

What type of information is carried by ascending tracts?

sensory information up toward the brain 

Descending tracts

motor commands down to the spinal cord

Where are the epineurium, perineurium, and endoneurium located on a typical peripheral nerve? 

1. Epineurium – outermost; network of collagen fibers 

2. Perineurium – middle layer; separates nerve into fascicles (bundles of axons) 

3. Endoneurium – innermost; surrounds individual axons

What is a dermatome?  

specific bilateral region of skin monitored by a single pair of spinal nerves

What is a nerve plexus

complex, interwoven network of nerve fibers 

List the four nerve plexuses. 

1. Cervical plexus 

2. Brachial plexus 

3. Lumbar plexus 

4. Sacral plexus 

Which cervical plexus nerve innervates the diaphragm? What would happen if this nerve was damaged?

The phrenic nerve (C3–C5) innervates the diaphragm. If damaged, it can cause difficulty breathing or paralysis of the diaphragm. 

Carpal tunnel syndrome is caused by compression of one or more nerves that innervate the wrist. Which plexus do these nerves belong to?  

The brachial plexus. 

The sciatic nerve belongs to which plexus? 

The sacral plexus. 

What type of CNS neurons are organized into functional groups called neuronal pools?

Interneurons (association neurons). 

Name five neural circuits concise?

Divergence, Convergence, Serial processing, Parallel processing, Reverberation

Divergence

One neuron spreads information to many neurons. Common in sensory pathways. 

Convergence

Several neurons send signals to one neuron. Helps combine information.

Serial processing

Information travels along one pathway, from neuron to neuron in order. 

Parallel processing

Multiple neurons process the same information at the same time.

Reverberation

Signals loop back and repeatedly stimulate neurons. Helps maintain breathing and muscle coordination. 

Define neural reflex. 

rapid, automatic response to specific stimuli 

List five steps of a simple neural reflex arc. 

1. Stimulus activates a receptor 

2. Activation of a sensory neuron

3. Information processing in the CNS

4. Activation of a motor neuron

5. Response by a peripheral effector

 

Differentiate between innate and acquired reflexes. 

• Innate reflexes – basic neural reflexes formed 

before birth 

• Acquired reflexes – rapid, automatic learned 

motor patterns 

Differentiate between monosynaptic vs polysynaptic reflex. 

Monosynaptic reflex – involve a single synapse 

Polysynaptic reflex – involve at least one 

interneuron  

What type of reflex is a patellar reflex? Is it monosynaptic or polysynaptic? 

A stretch reflex and it is monosynaptic. 

Are withdrawal reflexes monosynaptic or polysynaptic? 

polysynaptic 

Are crossed extensor reflexes monosynaptic or polysynaptic?  

polysynaptic 

What kind of body movements occurs in an ipsilateral reflex?

Movement occurs on the same side of the body as the stimulus.

What kind of body movements occurs in an contralateral reflex?  

Movement occurs on the opposite side of the body from the stimulus. 

Compare and contrast the plantar reflex (negative Babinski reflex) and the Babinski sign (positive Babinski reflex). 

• Plantar reflex (negative): Toes curl downward. 

• Babinski sign (positive): Big toe moves upward and other toes fan outward.

The reflex centers in the spinal cord are responsible for relaying what type of neural messages?

motor output over spinal nerves

Tom is a football player who gets hit hard from behind along his spine. About a week later, he is diagnosed with bacterial meningitis, an infection of the CSF carried through the bloodstream. Given that the infection was associated with blood, which hypothesis is most likely to have occurred?

The pia matter tore away from the spinal cord, damaging the associated blood vessels, which leaked into the subarachnoid space.

Arrange the spinal meninges from superficial to deep layer.

dura mater, arachnoid mater, pia mater

These structures support the spinal cord by preventing lateral movement.

denticulate ligaments

The spinal cord is anchored to the sacrum and coccyx via a strand of fibrous tissue called the

filum terminale.

Spinal nerves are

both sensory and motor.

If the posterior root of a spinal nerve is severed,

sensory input would be blocked.

A posterior and anterior root of each spinal segment unite to form a

spinal nerve.

An epidural block will

provide mainly sensory anesthesia.

Blood vessels that supply the spinal cord run along the surface of the

pia mater.

The dura mater tapers inferiorly to form the

coccygeal ligament.

The condition in which a person loses all feeling and movement of the arms and legs due to spinal cord injury is termed

quadriplegia.

During a(n) ________, a needle is inserted into the subarachnoid space in the inferior lumbar region.

lumbar puncture

The six projections from the gray matter seen in cross-sections of the spinal cord are called __________.

horns

The __________ gray horns contain somatic and visceral sensory nuclei.

posterior

Bundles of axons in the central nervous system are known as

tracts.

Myelinated axons cross from one side of the spinal cord to the other through the

anterior white commissure.

Nerve tracts or fasciculi make up the

white columns.

Axons crossing from one side of the spinal cord to the other within the gray matter are found in the

gray commissures.

The connective tissue layer that covers Schwann cells is the __________.

endoneurium

The axillary, radial, and ulnar nerves branch from which plexus?

brachial

Sensory information from visceral organs is carried by the

sympathetic nerve.

Nerve plexuses are formed by interconnecting branches of the

anterior rami.

Regional loss of sensory or motor function from nerve trauma or compression is termed

peripheral neuropathy.

Large bundles of axons from several spinal nerves in the brachial plexus are termed

trunks.

Preganglionic and postganglionic fibers of the autonomic nervous system that innervate internal organs are collectively called

sympathetic nerves.

In the condition ________, a virus infects spinal ganglia, causing a painful rash whose distribution corresponds to that of the affected sensory nerves as seen in their dermatomes.

shingles

A viral disease that destroys the cells of the anterior gray horn will

lead to skeletal muscle weakness or paralysis.

Neural circuits occur in all of these patterns EXCEPT __________.

multipolar

While building a doghouse, Tom misses the nail and hits his thumb with the hammer instead. The pain sensation is immediate and intense. Which of the following is the pattern of neuronal pool interaction most likely to process that sensation?

serial processing

A reflex that leads to secretion of saliva is a(n) __________ reflex.

visceral