Chapter 14. Nervous System: Spinal Cord and Spinal Nerves

Match the reflex with its action. biceps reflex triceps reflex cremasteric reflex patellar reflex plantar reflex

-flexes elbow -extends elbow -elevates testis -extends knee -flexes toes

The left and right cervical plexuses are formed primarily by the anterior rami of spinal nerves ______.

C1-C4

The left and right cervical plexuses are located deep on each side of the neck, immediately lateral to cervical vertebrae ______.

C1-C4

Cervical nerves ______ unite to form the superior trunk of the anterior rami.

C5 and C6

Each brachial plexus is formed by the anterior rami of spinal nerves ______.

C5-T1

Which spinal nerves give rise to the inferior trunk of the brachial plexus?

C8 and T1

Which are characteristic of somatosensory pathways?

Each pathway transmits information to different regions of the brain.

The anterior rami of spinal nerves ______ are called intercostal nerves because they travel in the intercostal space sandwiched between ______.

T1-T11; two adjacent ribs

The nerves emerging from a sacral plexus innervate the ______ region, pelvis, perineum, posterior thigh, and almost all of the ______.

gluteal; leg and foot

Receptors that transmit sensory information by way of the posterior funiculus-medial lemniscus pathway, regarding limb position, precise pressure, vibration, and discriminative touch, originate ______.

in the limbs, trunk, neck, and posterior head

The reticulospinal tract is an example of a(n) ______ motor pathway.

indirect

Impulses transmitted through the direct, pyramidal, or corticospinal pathway, pass directly from upper to lower motor neurons (no ______ involved) and are responsible for ______ control of skeletal muscles.

interneurons; conscious

Each anterior root and its corresponding posterior root unite within the ______ to become a spinal nerve.

intervertebral foramen

A first-order neuron ______.

is the first neuron to transmit sensory information from the periphery of the body to the brain

In the spinal cord, the gray matter may be subdivided into the following components: anterior, posterior, and ___ horns, and the gray commissure

lateral

The white matter region on each lateral side of the spinal cord is the ______.

lateral funiculus

The cell bodies of ______ motor neurons are found within brainstem cranial nerve nuclei or in the anterior horn of the spinal cord.

lower

The anterior rami of spinal nerves L1-L4 form the ______ plexus.

lumbar

All upper motor neurons of the corticospinal tracts pass through the ______.

medulla oblongata

A stretch reflex is a ______ reflex that monitors and regulates skeletal muscle length.

monosynaptic

A spinal nerve contains ______ axons.

motor and sensory

Reflexes are rapid, automatic, involuntary reactions of ______ to a stimulus.

muscles or glands

The spinal nerves connect the central nervous system to ______ and receptors.

muscles, glands

The central nervous system forms primarily from the embryonic ______.

neural tube

Each brachial plexus innervates the ______ and the entire ______ of one side.

pectoral girdle; upper limb

The initial component of a reflex arc is a(n) ______.

receptor

Awareness of the stimulus occurs after the ___ action has been completed, in time to correct or avoid a potentially dangerous situation.

reflex

Awareness of the stimulus occurs after the ____ action has been completed, in time to correct or avoid a potentially dangerous situation.

reflex

The spinal cord and spinal nerves are responsible for ______, which are our quickest reactions to a stimulus.

reflexes

Which pathway originates from the reticular formation in the mesencephalon?

reticulospinal

Which tract functions to control unskilled automatic movements related to posture and maintaining balance?

reticulospinal tract

Which of the following is an indirect motor pathway?

rubrospinal tract

The longest nerve in the body is the ______ nerve.

sciatic

A first-order neuron synapses with a ______ neuron.

second-order

A second-order neuron is also known as a ___ neuron.

secondary

The posterior rami of spinal nerves tend to follow a ______ pattern as they innervate the deep muscles and skin of the neck and back.

segmental

Ascending pathways are ______ pathways.

sensory

The spinal cord in an adult is ______ than the vertebral canal that houses it.

shorter

A reflex arc is the neural wiring of a ______ reflex.

single

In sensory pathways, tertiary neurons conduct information to a specific location of the primary ______ cortex.

somatosensory

Stretch in a muscle is monitored by a stretch receptor called a muscle ______.

spindle

An impulse from a lower motor neuron ______ a skeletal muscle.

stimulates or excites

A third-order neuron is also known as a ___ neuron.

tertiary

In sensory pathways, secondary neurons synapse with the cell bodies of ___ neurons.

tertiary

A secondary neuron extends from a primary neuron to the ______.

tertiary neuron or cerebellum

In sensory pathways, secondary neurons synapse on cell bodies of tertiary neurons within the ______.

thalamus

The sciatic nerve is actually composed of two divisions wrapped in a common sheath. What are the two divisions?

tibial and common fibular

In sensory pathways, where do tertiary neurons conduct information?

to the cerebral cortex

There are five roots of anterior rami that unite to form the superior, middle, and inferior ______ in the posterior triangle of the neck.

trunks

The cell bodies of ______ motor neurons are found in the cerebral cortex.

upper

Identify the anatomical component of motor pathways.

upper and lower motor neurons

Motor pathways use a(n) ______ motor neuron and a(n) ______ motor neuron.

upper; lower

The left and right sacral plexuses are formed from the ______ rami of spinal nerves ______ and are located immediately inferior to the lumbar plexuses

anterior; L4-S4

The lumbar plexus is subdivided into a(n) ______ division and a(n) ______ division.

anterior; posterior

The receptors in somatosensory pathways ______.

are located in the joints, skeletal muscles, and skin

Action potentials ______ the brain through sensory pathways.

ascend to

Pathways that transmit sensory impulses are also called ______ pathways because the information travels from sensory receptors superiorly through the spinal cord to the brain.

ascending

The anterior corticospinal tracts innervate ______.

axial skeletal muscle

Portions of the superior, middle and inferior trunks divide inferior to the ______ into an anterior division and a posterior division, which primarily contain axons that innervate the anterior and posterior parts of the ______.

clavicle; upper limb

In general, we are ______ of information transmitted along somatosensory pathways to the brain, and ______ of the information transmitted along viscerosensory pathways.

conscious; unconscious or unaware

During development, the individual vertebrae ______ spinal cord growth is complete.

continue to grow after

Which statements correctly describe the corticospinal tracts?

control appendicular and axial skeletal muscles

Each brachial plexus is composed of anterior rami, trunks, divisions, and ___ when examined from a medial to lateral perspective.

cords

A descending motor tract of the direct pathway is the ______ tract.

corticospinal

Axons of lower motor neurons of the corticobulbar tract form parts of the ______ nerves.

cranial

Impulses traveling along the corticobulbar tracts control voluntary movement of ______.

cranial and facial muscles

Primary motor neurons of the ______ motor pathway originating in the primary motor cortex, whereas primary motor neurons of the ______ motor pathway originate in the brainstem.

direct; indirect

Spinal reflexes ______ require the involvement of the brain.

do not

An impulse from an upper motor neuron ______ a lower motor neuron.

excites or inhibits

The posterior division nerves of the sacral plexus tend to innervate muscles that ______ part of the ______ limb.

extend; lower

The axon of a primary neuron of a somatosensory pathway ______.

extends to the spinal cord or brainstem

The nerves arising from the anterior division of the sacral plexus tend to innervate muscles that ______ parts of the lower limb.

flex

In general, nerves from the anterior division of the brachial plexus tend to innervate muscles that ______ the parts of the upper limb. Nerves from the posterior division of the brachial plexus tend to innervate muscles that ______ the parts of the upper limb.

flex; extend

Match the reflex with the correct description. spinal reflex visceral reflex polysynaptic reflex ipsilateral reflex

-The integration center in this type of reflex is the spinal cord. -A gland may be the effector in this type of reflex. -This reflex includes one or more interneurons. -The receptor and effector in this reflex are located on the same side of the body.

Match the anatomical components of primary or first-order neurons of somatosensory pathways with their locations. axons cell bodies dendrites

-project to secondary or second-order neurons in the CNS -posterior root ganglia of spinal nerves, sensory ganglia of cranial nerves -part of a stimulus-specific receptor

There are ______ pairs of spinal nerves.

31

A typical adult spinal cord ranges between ______ centimeters (cm) in length.

42 and 45

The spinal cord extends inferiorly from the brain through the foramen magnum, then through the vertebral canal, and ends at the level of the ______ vertebra.

L1

A reflex arc always begins at a receptor in the ______, communicates with the ______, and ends at a peripheral effector, such as a muscle or gland cell.

PNS; CNS

An ______ reflex is one that is developed after birth.

acquired

During development, the cranial and spinal nerves form primarily from ______.

alar and basal plates

The cell bodies of lower motor neurons are in the ______.

anterior horns of the spinal cord

A nerve plexus is a network of interweaving ______ of spinal nerves.

anterior rami

The anterior rami (sometimes called roots) of the brachial plexus are simply the continuations of the ______ rami of spinal nerves ______.

anterior; C5-T1

Spinal nerve T12 is called a subcostal nerve because it arises ______ the ribs.

below

In which reflex does the elbow flex?

biceps reflex

The components of the ______ plexus extend laterally from the neck, pass superior to the first rib, and then continue into the axilla.

brachial

The nerve plexus that supplies the arm is the ______ plexus.

brachial

The gray matter in the spinal cord is ______ located, and its shape resembles a letter H or a ______.

centrally; butterfly

The spinocerebellar pathway conducts information to the ______.

cerebellum

A third-order neuron extends from the secondary neuron to the ______.

cerebrum

Identify the characteristic of the anterior corticospinal tracts.

decussate in spinal cord

The spinal cord is partitioned into a ______ gray matter region and a ______ white matter region.

deep; superficial

The gray matter of the spinal cord is dominated by the ______ and ______ of neurons.

dendrites; cell bodies

Motor pathways are ______ pathways.

descending

After leaving the intervertebral foramen, a typical spinal nerve almost immediately splits into branches, termed ______.

rami

The two main branches of a spinal nerve are the ventral and ___ rami.

posterior

White matter that lies between the posterior gray horns is a ______.

posterior funiculus

In the spinocerebellar pathway, sensory information travels to the cerebellum along ______ neurons.

primary and secondary

The neurons in sensory pathways are termed ______.

primary, secondary, and sometimes tertiary neurons

The types of sensory information transmitted along the posterior funiculus-medial lemniscus pathway include ______.

proprioceptive, limb position

Pathways that transmit information from internal organs to the brain are called ___, whereas pathways that transmit information from proprioceptors and the body wall are called.

viscerosensory somatosensory

Primary motor neurons of the direct motor pathway issue impulses for ______ control of skeletal muscles; primary motor neurons of the indirect motor pathway issue impulses for ______ control of skeletal muscles.

voluntary; involuntary