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How is the peripheral nervous system defined?

- All neural structures outside of the CNS
- The link between the central neurons system and the outside world

What system is the link between the central nervous system and the outside world?

peripheral nervous system

KNOW figure 13.1

What is a fascicle? (in terms of nerve structure)

bundle of axons within a nerve

T / F Nerves contain connective tissue.

True. Nerves contain layers of connective tissue.

What are the three layers of connective tissue found in nerves? How do they differ?

a) Endoneurium - surrounds each neuron
b) Perineurium - surrounds each fascicle
c) Epineurium - surrounds whole nerve

What is the endoneurium? Perineurium? Epineurium?

Layer of connective tissues in nerves.
a) Endoneurium - surrounds each neuron
b) Perineurium - surrounds each fascicle
c) Epineurium - surrounds whole nerve

What layer of connective tissue in nerves, surrounds each fascicle?


T / F Axons of neurons make up the bulk of mass in a nerve.

False. Myelin and connective tissue

What is an efferent only nerve? Afferent only?

- Efferent only - motor only
- Afferent only - sensory only

What types of signals do mixed nerves carry?

Both motor and sensory.

What nerve type makes up the majority of nerves found in the body? (afferent only / efferent only / mixed / the type that annoying people get on)

Mixed nerves make up vast majority

What type of nerves arise from the brain?

Cranial nerves

Where do spinal nerves arise from?

Spinal cord

How many pairs of cranial nerves are found in the body?

12 pairs of cranial nerves originate from the brain

Where does each cranial nerve originate from? (forebrain, brain stem, cerebrum, cerebellum)

- First 2 originate from the forebrain
- Last 10 originate from the brain stem

Almost all of the cranial nerves innervate the_____ and _____.

head ; neck

Unlike in the questions below, I will likely not have the numbers with the
name, on the exam.

Which cranial nerve carries smell information to the brain?

Olfactory (i)

T / F The olfactory nerve (I) is efferent only.

False. Afferent only nerve.

What type of neurons are part of the optic nerve (II)?

Afferent only

What is the function of the optic nerve (II)?

Carries visual information from the eye to the brain.

T/F the olfactory nerve(I) is efferent only?

False - Afferent only

What type of neurons are part of the optic nerve(II)?

Afferent only

What is the function of the optic nerve(II)?

Carry visual information from the eyes to the brain

What is the function of the oculomotor nerve(III)?

Serves muscles that move the eyes

what is the third (III) nerve and only contains efferent only neurons?

oculomotor nerve (III)

what is the function of the trochlear nerve(IV)?

serves muscles that move the eyes

the trochlear nerve(IV) has only ______ neurons?


`What is the largest cranial nerve?

Trigeminal (V)

What nerve is the major sensory nerve of the face?

Trigeminal (V)

T/ F The trigeminal nerve (V) only has afferent neurons?

False- mixed

What are the three divisions of the trigeminal (V) nerve? Where are they?

Opthalmic- upper part of face
maxillary- Cheek
Mandibular - Jaw

What number is the abducens nerve?


What is the function of the abducens nerve (VI)?

Serves muscles that move the eyes

What is the chief motor nerve of the face?

Facial nerve (VII)

What is an example of an afferent function of the facial nerve (VII)?

Carries taste information to the anterior 2/3 of the tongue

What are the five branches of the facial nerve (VII)?

Temporal Branch
Zygomatic Branch
Buccal Branch
Mandibular branch
Cervical Branch

What is bell's Palsy?

when the cervical nerve is infected by a virus and becomes inflamed. Causes temporary loss of motor function

what is the function of the vestibulocochlear nerve (VIII)?

carries information for the equilibrium and hearing from the inner ear to the brain

T/F the Vestibulocochlear nerve (VIII) contains both afferent and efferent neurons?

False- afferent only

What cranial nerve carries taste and touch from the posterior portion of the tongue and the pharyynx to the bran?

Glossopharyngeal (IX)

What is the only cranial nerve that leaves the head and neck region?


What cranial nerve innervates visceral organs?

Vagus (X)

What nerve briefly travels alongside the vagus nerve but innervates the muscles of the neck, larynx, and pharynx?

Accessory (XI)

What type of neurons are in the accessory nerve (XI)?

Efferent only

What is the function of the Hypoglossal nerve (XII)?

Serves muscles that move the tongue

T/F the hypoglossal nerve has only efferent neurons?


How many pairs of spinal nerves are found in the body?

31 pairs

T/F spinal nerves can be divided up by being efferent only or afferent only?

False- all spinal nerves are mixed

How many pairs of spinal nerves are n the cervical region? Thoracic region? Lumbar region? Sacral region? Coccygeal region?

Cervical -8
Thoracic - 12
Lumbar - 5
Sacral - 5
Coccygeal - 1

T/F Spinal nerves are long so they can extend directly to effector organs?

False- very short (about an inch)

What is a ramus?

Major branch of nerves

Which ramus serves body tissues in the posterior region of the trunk?

Dorsal ramus

What type of neurons does a dorsal ramus carry?

Mixed - both motor and sensory

T/F The dorsal ramus is the short branch, when compared to the ventral ramus?


Of the two rami that we learned, which is the large branch?


Which direction does a ventral ramus travel?

Extends anteriorly

What body tissues are served by ventral rami?

Body tissues of the trunk and limbs

What is a nerve plexus?

A region where multiple ventral rami meet and intersect

T/F After passing through a nerve plexus, different spinal nerve rami travel separately and don't intermingle?

False- travel together

T/F Dorsal rami do not form nerve plexuses?


What pairs of ventral rami do not enter a plexus?

The ventral rami of T-1 through T-12 do not enter a plexus

Where is the cervical plexus located?

Located in the posterior portion of the neck, deep to the sternocleidomastiod muscle

The cervical plexus is formed by the intermingling of ventral rami ___ through ___?

C-1 through C-5

What nerve plexus is located at the meeting of the shoulder and neck?

Brachial rami

The brachial plexus is formed by intermingling the ventral rami of ____ through ____?

C-5 through C-8 and part of T-1

What nerve plexus is located within the anterior of the pelvis?

Lumbar plexus

The lumbar plexus is formed by the intermingling of ventral rami of ____ through ____?

L-1 through L-4

The sacral plexus is formed by the intermingling of ventral rami ___ through ___?

L-4 through S-4

Where is the sacral plexus located?

Posterior to the pelvis

What are sensory receptors?

Specialized neurons that respond to outside environment

What are the three ways that sensory receptors can be classified?


How are sensory receptors classified if they are grouped based on the cue that activates the cell?

Classification of receptors by stimulus

What are mechanoreceptors? What are some examples of what they detect?

Responsive to mechanical forces
Touch, vibration, pressure, stretch

What group of sensory receptors detect temperature changes?


Where are cold thermoreceptors located? Heat receptors?

Cold are superficial
Heat are deeper

What type of receptors respond to light?


What do chemoreceptors respond to?

Chemical changes or presence of chemicals

What are nociceptors?

Response to damaged stimuli and cause pain

What are exteroceptors? Where are the located?

Sensitive to external stimuli
located near the surface

What are interoceptors? Where are they located?

Sensitive to internal stimuli
Usually subconscious perception of internal stimuli

T/F Interoceptors are the conscious perception of internal stimulus?

False- Subconscious

What are proprioceptors? Where are they found?

Provide feedback on body movements and limb position
internal receptors found in skeletal muscles, joints, tendons, and ligaments

What types of information are sent to the brain from proprioceptors?

information related to body structure, position and stretch

What is the difference between complex and simple receptors?

Complex- sense organs
Simple- modified dendritic endings

Unencapsulated dendritic endings and encapsulated dendritic endings are two groups within what division of sensory receptor complexity?

Simple receptors

Unencapsulated dendritic endings are mostly free dendrites of group ____ neurons?

Group C

What group of simple receptors is widespread and abundant in epithelial and connective tissue?

Unencapsulated dendritic endings

What two stimuli do unencapsulated dendritic endings usually respond to?

Temperature and pain

What is an itch receptor?

A small subtype of free nerve endings

What is the difference between encapsulated and an unencapsulated dendritic endings?

Encapsulated - sensory neurons with a connective tissue capsule
Unencapsulated - free dendrites of Group C neurons

What are the three types of encapsulated dendritic endings that we learned?

Meissner's corpuscle
Pacinian corpuscle
Muscle spindles

Where are Meissner's corpuscles abundantly found?

hairless skin

What type of encapsulated dendritic endings detect light pressure?

Meissner's corpuscle

Where are pacinian corpuscles located?

located deep in the skin

What types of stimuli do pacinian corpuscles detect?

Deep pressure and vibrations

What type of encapsulated dendritic ending is located in skeletal muscles?

Muscle spindles

What type of encapsulated dendritic ending detects when a muscle is stretched?

Muscle spindle

What is a dermatone?

The area of skin innervated by the branches of a single spinal nerve

Why are dermatomes important for diagnosing damage?

They can pinpoint which nerves are damaged

What is Hilton's law?

Any nerves serving a muscle that produces movement at a joint also innervates the joint and skin over that joint

How can you locate which nerve in innervating a particular joint?

Hilton's law

Cranial Nerves - Location

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