Plexuses are found in the cervical

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					                                   Peripheral Nervous System
I.    Structure of a Nerve
A.    Nerve – cordlike organ of the PNS consisting of peripheral axons enclosed by connective tissue
      1.      Connective tissue coverings include:
      –       __________________ – loose connective tissue that surrounds axons
      –       __________________ – coarse connective tissue that bundles fibers into fascicles
      –       ________________ – tough fibrous sheath around a nerve
      2.      Classification of Nerves
              a. Sensory and motor divisions
                       1) Sensory (afferent) – carry impulse _____________ the CNS
                       2) Motor (efferent) – carry impulses ______________ from CNS
              b. Mixed – sensory and motor fibers carry impulses to and from CNS; most common type
                 of nerve
B.    Peripheral Nerves
      1.      Mixed nerves – carry _______________ and ________________ (visceral) impulses
      2.      The four types of mixed nerves are:
      –       Somatic ____________ and somatic ______________
      –       Visceral ____________ and visceral ______________
      3.      Peripheral nerves originate from the _____________ or _____________ chord
II.   Cranial Nerves
A.    Introduction
      1.      _________ pairs of cranial nerves arise from the brain
      2.      They have sensory, motor, or both sensory and motor functions
      3.      Each nerve is identified by a number (I through XII) and a name
      4.      Four cranial nerves carry __________ fibers that serve muscles and glands
B.    Types (On Old Olympus’ Towering Top A Finn And German Viewed Some Hops)
      1.      Cranial Nerve I: Olfactory
              a. Arises from the olfactory epithelium
              b. Passes through the __________ plate of the __________ bone
              c. Fibers run through the olfactory __________ and terminate in the primary olfactory
              d. Functions solely by carrying afferent impulses for the sense of smell (sensory only)
      2.      Cranial Nerve II: Optic
              a. Arises from the _______________ of the eye
              b. Optic nerves pass through the optic canals and converge at the optic ___________
              c. They continue to the ___________ where they synapse in the lateral geniculate nuclei
              d. From there, the optic radiation fibers run to the __________ __________
              e. Functions solely by carrying afferent impulses for vision
      3.      Cranial Nerve III: Oculomotor
              a. Fibers extend from the ventral midbrain, pass through the _________ __________
                 _______________, and go to the extrinsic eye muscles
              b. Functions in raising the eyelid, directing the eyeball, constricting the iris, and
                 controlling lens shape
              c. Parasympathetic cell bodies are in the ____________ ganglia
4.    Cranial Nerve IV: Trochlear
      a. Fibers emerge from the dorsal midbrain and enter the orbits via the superior orbital
         fissures; innervate the ____________________ oblique muscle
      b. Primarily a motor nerve that directs the eyeball
5.    Cranial Nerve V: Trigeminal
      a. Composed of three divisions: ophthalmic (V1), maxillary (V2), and mandibular (V3)
      b. Fibers run from the face to the pons via the superior orbital fissure (V1), the foramen
      ______________ (V2), and the foramen ovale (V3)
      c. Conveys sensory impulses from various areas of the _________ (V1) and (V2), and
         supplies motor fibers (V3) for __________________
6.    Cranial Nerve VI: Abdcuens
      a. Fibers leave the inferior pons and enter the orbit via the superior orbital fissure
      b. Primarily a motor nerve innervating the _________________ rectus muscle
7.    Cranial Nerve VII: Facial
      a. Fibers leave the pons, travel through the internal acoustic meatus, and emerge through
         the stylomastoid foramen to the lateral aspect of the face
      b. Mixed nerve with five major branches
      c. Motor functions include facial ______________, and the transmittal of autonomic
         impulses to _____________ and _______________ glands
      d. Sensory function is ____________ from the _____________ two-thirds of the tongue
8.    Cranial Nerve VIII: Vestibulocochlear (auditory)
      a. Fibers arise from the ___________ and _____________ apparatus of the inner ear,
        pass through the _____________ acoustic meatus, and enter the brainstem at the pons-
        medulla border
      b. Two divisions – cochlear (___________) and vestibular (_____________)
      c. Functions are solely sensory – equilibrium and hearing
9.    Cranial Nerve IX: Glossopharyngeal
      a. Fibers emerge from the medulla, leave the skull via the ___________ foramen, and run
         to the throat
      b. Nerve IX is a mixed nerve with motor and sensory functions
      c. Motor – innervates part of the ________ and ____________, and provides motor fibers
         to the parotid salivary gland
      d. Sensory – fibers conduct ___________ and general sensory impulses from the tongue
         and pharynx
10.   Cranial Nerve X: Vagus
      a. The only cranial nerve that extends beyond the _________ and _________
      b. Fibers emerge from the medulla via the ______________ foramen
      c. The vagus is a ___________ nerve
      d. Most motor fibers are _____________ fibers to the heart, lungs, and visceral organs
      e. Its sensory function is in __________
11.   Cranial Nerve XI: Spinal Accessory

       12.     Cranial Nerve XII: Hypoglossal
               a. Fibers arise from the medulla and exit the skull via the hypoglossal canal
               b. Innervates both extrinsic and intrinsic muscles of the tongue, which contribute to
                  swallowing and speech
III.   Spinal Nerves
A.     Introduction
       1.      Thirty-one pairs of mixed nerves arise from the spinal cord and supply all parts of the
               body except the head
       2.      They are named according to their point of issue
       –       __ cervical (C1-C8)
       –       ___ thoracic (T1-T12)
       –       __ Lumbar (L1-L5)
       –       __ Sacral (S1-S5)
       –       __ Coccygeal (C0)
B.     Spinal Nerves: Roots
       1.      Each spinal nerve connects to the spinal cord via two medial roots
       2.      Each root forms a series of __________ that attach to the spinal cord
       3.      Ventral roots arise from the ventral horn and contain __________ (efferent) fibers
       4.      Dorsal roots arise from sensory neurons in the dorsal root ganglion and contain
               _______________ (afferent) fibers
C.     Nerve Plexuses
       1.      All ventral rami except _________ form interlacing nerve networks called plexuses
       2.      Plexuses are found in the cervical, brachial, lumbar, and sacral regions
       3.      Each resulting branch of a plexus contains fibers from several spinal nerves
       4.      Fibers travel to the periphery via several different routes
       5.      Each muscle receives a nerve supply from more than one spinal nerve
       6.      Damage to one spinal segment ________ completely ___________ a muscle
       7.      Cervical Plexus
               a. The cervical plexus is formed by ventral rami of _________
               b. Most branches are cutaneous nerves of the neck, ear, back of head, and shoulders
               c. The most important nerve of this plexus is the _____________ nerve
               d. The phrenic nerve is the major motor and sensory nerve of the _______________
       8.      Brachial Plexus
               a. Formed by C5-C8 and T1 (C4 and T2 may also contribute to this plexus)
               b. It gives rise to the nerves that innervate the ______________ limb
               c. Nerves of the brachial plexus
                        1) Median – branches to most of the flexor muscles of arm
                        2) _____________ – supplies the flexor carpi ulnaris and part of the flexor
                           digitorum profundus
                        3) ________________ – innervates essentially all extensor muscles
       9.      Lumbar Plexus
               a. Arises from L1-L4 and innervates the thigh, abdominal wall, and psoas muscle
               b. The major nerves are the _____________ and the ______________

      10.    Sacral Plexus
             a. Arises from L4-S4 and serves the buttock, lower limb, pelvic structures, and the
             b. The major nerve is the _________, the longest and thickest nerve of the body
                (The sciatic is actually composed of two nerves: the tibial and the common fibular nerves)
D.    Dermatomes
      1.      A dermatome is the area of skin innervated by the ___________ branches of a
      2.      All spinal nerves except ______ participate in dermatomes
E.    Innervation of Joints
          – Hilton’s law: any nerve serving a muscle that produces _______________ at a joint also
              innervates the joint itself and the skin over the joint
F.    Motor Endings
      1.      PNS elements that activate effectors by releasing neurotransmitters at:
                   • Neuromuscular junctions
                   • Varicosities at smooth muscle and glands
      2.      Innervation of Skeletal Muscle
              a. Takes place at a neuromusclular junction
              b. _________________ is the neurotransmitter that diffuses across the synaptic cleft
              c. ACh binds to receptors resulting in:
                   • Movement of Na+ and K+ across the membrane
                   • Depolarization of the interior of the muscle cell
                   • An end-plate potential that triggers an action potential
      3.      Innervation of Visceral Muscle and Glands
              a. Autonomic motor endings and visceral effectors are _____________ than somatic
              b. Acetylcholine and norepinephrine are used as neurotransmitters
              c. Visceral responses are _______________ than somatic responses

IV.   Reflexes
A.    Introduction
      1.      A reflex is a __________________________ ________________________
      2.      Reflexes may:
                  • Be inborn (_____________) or learned (___________________)
                  • Involve only peripheral nerves and the spinal cord
                  • Involve higher brain centers as well
B.    Reflex Arc
      There are five components of a reflex arc
      1.      Receptor – site of _______________
      2.      Sensory neuron – transmits the afferent impulse to the ______________
      3.      Integration center – either ____________ or ________________ region within the CNS
      4.      Motor neuron – conducts efferent impulses from the integration center to an __________
      5.      Effector – muscle fiber or gland that ______________ to the efferent impulse

C.    Stretch and Deep Tendon Reflexes
      For skeletal muscles to perform normally:
      –       __________ ________ ________ (proprioceptors) must constantly inform the brain as to
          the state of the muscle
      –       Stretch reflexes initiated by muscle ___________ must maintain healthy muscle tone
D.    Muscle Spindles
      1.      Are composed of 3-10 ___________ muscle fibers that _________ myofilaments in their
              central regions, are noncontractile, and serve as receptive surfaces
      2.      Muscle spindles are wrapped with two types of afferent endings: primary sensory endings
              of type _____ ________and secondary sensory endings of type _____ __________
      3.      These regions are innervated by _____________ () efferent fibers (these are small
              diameter slow neurons)
                    Note: contractile muscle fibers are extrafusal fibers and are innervated by
                        ___________ () efferent fibers (large diameter fast neurons)
      4.      Operation of the Muscle Spindles
              a. Stretching the muscles ________ the muscle spindle
                   • There is an increased rate of action potential in _______________
              b. Contracting the muscle ________________ tension on the muscle spindle
                   • There is a decreased rate of action potential on __________
E.    Stretch Reflex
      1.      Stretching the muscle activates the muscle spindle
      2.      Excited  motor neurons of the spindle cause the stretched muscle to ____________
      3.      Afferent impulses from the spindle result in inhibition of the ________________
      4.      Example: patellar reflex
                   • Tapping the patellar tendon stretches the quadriceps and starts the reflex action
                   • The quadriceps __________ and the antagonistic hamstrings _____________
 F.   Golgi Tendon Reflex
      1.      The ___________________ of the stretch reflex
      2.      Contracting the muscle activates the Golgi tendon organs
      3.      Afferent Golgi tendon neurons are stimulated, neurons ______________ the contracting
              muscle, and the antagonistic muscle is __________________
      4.      As a result, the contracting muscle relaxes and the antagonist contracts
 G.   Flexor and Crossed Extensor Reflexes
      1.      The flexor reflex is initiated by a painful stimulus (actual or perceived) that causes
              automatic withdrawal of the threatened body part
      2.      The crossed extensor reflex has two parts
                   • The stimulated side is ______________
                   • The contralateral side is ______________
 H.   Superficial Reflexes
      1.      Initiated by gentle cutaneous stimulation
      2.      Example:
          – Plantar reflex is initiated by stimulating the lateral aspect of the sole of the _________
          – The response is downward ____________ of the toes
          – Indirectly tests for proper ______________ tract functioning

        –   Babinski’s sign: ________________ plantar reflex indicating corticospinal damage
            where the great toe dorsiflexes and the smaller toes fan laterally

V. Autonomic Nervous System (ANS)
A. Introduction
   1.      The ANS consists of motor neurons that:
   –       Innervate ___________________________ ________________________________
   –       Make adjustments to ensure optimal support for body activities
   –       Operate via _____________________ control
   –       Have __________________ as most of their effectors
   2.      ANS versus Somatic Nervous System (SNS)
           The ANS differs from the SNS in the following three areas
                • ___________________
                • _______________________
                • ___________________________
   3.      Effectors
           a. The effectors of the somatic NS are _____________________ muscles
           b. The effectors of the ANS are cardiac muscle, smooth muscle, and glands
           c. Efferent (motor) Pathways
                1) Heavily myelinated axons of the somatic motor neurons extend from the CNS to
                   the effector
                2) Axons of the ANS are a __________-neuron chain
                • The preganglionic (first) neuron has a lightly myelinated axon
                • The ganglionic (postganglionic) (second) neuron extends to an effector organ
   4.      Neurotransmitter Effects
           a. All somatic motor neurons release ______________________, which has an excitatory
           b. In the ANS:
                     1) All ________________________ fibers release _______
                     2) Postganglionic fibers release ______________ or __________ and the effect
                        is either stimulatory or inhibitory
           c. ANS effect on the target organ is dependent upon the neurotransmitter released and the
              receptor type of the effector

B.   Divisions of the ANS
     1.      The sympathetic mobilizes the body during ___________________ situations
     2.      The parasympathetic performs maintenance activities and __________________ body
     3.      The two divisions ____________________ each other’s activity
     4.      Role of the Parasympathetic Division
             a. Concerned with keeping body energy use ___________
             b. Involves “rest and digest” activities
             c. Its activity is illustrated in a person who relaxes after a ______________
                  • Blood pressure, heart rate, and respiratory rates are ________
                  • Gastrointestinal tract activity is ______
                  • The skin is warm and the pupils are _____________________
     5.      Role of the Sympathetic Division
             a. The sympathetic division is the “fight-or-flight” system
             b. Involves E activities – ___________________ _______________________________
             c. Promotes adjustments during exercise – blood flow to internal organs is
                _______________, flow to muscles is ________________
             d. Its activity is illustrated by a person who is threatened
                  • Heart rate ________________, and breathing is _______________ and deep
                  • The skin is cold and sweaty, and the pupils _________________

        6.        Autonomic nervous system: targets
                     Sympathetic                       Parasympathetic

Eye                  ______________ pupil              ______________ pupil

Salivary glands      ______________ mouth              ________ of dilute saliva

Heart rate           __________________                __________________

Lungs (bronchi)      __________________                __________________

GI activity          __________________                __________________

Liver                ________________ blood sugar      None

Adrenal medulla      Stim.secretion                    none

Penis                __________________                __________________

        7.      Sympathetic Outflow
                a. Arises from spinal cord segments T1 through L2
                b. Sympathetic neurons produce the _____________ horns of the spinal cord
                c. Sympathetic Trunks and Pathways
                              The paravertebral _________________ form part of the sympathetic
                                    trunk or chain
C.      Visceral Reflexes
        1.      Visceral reflexes have the same elements as somatic reflexes
        2.      They are always ______________________ pathways
        3.      Afferent fibers are found in spinal and autonomic nerves
D.      Referred Pain
        1.      Pain stimuli arising from the viscera are perceived as somatic in origin
        2.      This may be due to the fact that visceral pain afferents travel along the same pathways as
                somatic pain fibers
E.      Neurotransmitters and Receptors
        1.      Introduction
                a. Acetylcholine (ACh) and norepinephrine (NE) are the two major neurotransmitters of
                   the ANS
                b. Epinephrine is produced by the adrenal medulla, and is considered to be part of the
                   ANS as well
        2.      Cholinergic Receptors
                a. A cholinergic receptor binds to acetylcholine (ACh)
                b. The two types of receptors that bind ACh are ________________________ and
                c. These are named after drugs that bind to them and mimic ACh effects

              d. Nicotinic Receptors are found on
                       1) Motor end plates (somatic targets)
                       2) All ganglionic neurons of both sympathetic and parasympathetic divisions
                       3) The hormone-producing cells of the adrenal __________________
              e. The effect of ACh binding to nicotinic receptors is always ____________________
     3.       Mechanisms of action of neurotransmitters
              a. Cholinergic receptors
                       1) Nicotinic receptors: open ____ channels; get ________________________.
                       2) Muscarinic receptors: get one of two effects:
                                a) Open _______ channels: get _______________________; therefore
                                   smooth muscle will _____________.
                                b) Open _____ channels; get __________________________; cause
                                   smooth muscle to _______________ or at
                                   SA node: _____________________.
                             Remember: Atropine ______________ muscarinic receptors. Therefore,
                                what effect does atropine have on the heart? ______________________
              b. Adrenergic receptors
                       1) α-1 receptors: found on smooth muscle cells.
                       Usually open _______ channels, which causes smooth muscle to
                       2) α-2 receptors: found on presynaptic membrane.
                          Usually open K+ channels, which causes hyperpolarization
                       3) β-1 receptors: Location: _____________
                          When epinephrine from the adrenal medulla binds to β-1 receptors,
                          ________________________, which ____________________ and
                          _____________ of contraction.
                       4) β-2 receptors: Location: ________________ muscle
                          Action: causes ______________________
     4.       Effects of Drugs
              a. Atropine – _____________ parasympathetic effects
              b. Over-the-counter drugs for colds, allergies, and nasal congestion – stimulate
                 _____________ receptors; this results in ___________________________
              c. Beta-blockers – attach mainly to _____ receptors and reduce heart rate and prevent
F.   Interactions of the Autonomic Divisions
     1.       Most visceral organs are innervated by both sympathetic and parasympathetic fibers
     2.       This results in dynamic antagonisms that precisely control visceral activity
              a. Sympathetic fibers ___________ heart and respiratory rates, and _____________
                 digestion and elimination
              b. Parasympathetic fibers ______________ heart and respiratory rates, and allow for
                 digestion and the discarding of wastes
     3.       The sympathetic division controls blood ________________ and keeps the blood vessels
              in a continual state of ______________ constriction

      This sympathetic tone (vasomotor tone):
     –       Constricts blood vessels and causes blood pressure to ________ as needed
     –       Prompts vessels to dilate if blood pressure is to be _______________
      Alpha-blocker drugs interfere with vasomotor fibers and are used to treat hypertension
     4.      Parasympathetic tone:
     –       _____________ the heart
     –       Dictates normal activity levels of the digestive and urinary systems
     5.      The sympathetic division can override these effects during times of ___________
     6.      Drugs that block parasympathetic responses increase heart rate and block fecal and
             urinary retention
     7.      Cooperative Effects
                            ANS cooperation is best seen in control of the external genitalia
             a. Parasympathetic fibers cause ___________________ and are responsible for
                __________________ of the penis and clitoris
             b. Sympathetic fibers cause ___________________ of semen in males and
                _____________________ in females
     8.      Unique Roles of the Sympathetic Division
             a. Regulates many functions not subject to parasympathetic influence
             b. These include the activity of the adrenal medulla, sweat glands, arrector pili muscles,
                 kidneys, and most blood vessels
     9.      Localized Versus Diffuse Effects
             a. The parasympathetic division exerts _________________________, highly localized
             b. The sympathetic division exerts _________________________, diffuse effects
             c. Effects of Sympathetic Activation
                   Sympathetic activation is long-lasting because NE:
                          • Is inactivated more ______________ than ACh
                          • Is an indirectly acting neurotransmitter, using a
G.   Levels of ANS Control
     1.      The _____________________ is the main integration center of ANS activity
     2.      Subconscious cerebral input via limbic lobe connections influences hypothalamic
     3.      Other controls come from the cerebral cortex, the reticular formation, and the spinal cord
     4.      Hypothalamic Control
      Centers of the hypothalamus control:
     –       Heart activity and blood pressure
     –       Body temperature, water balance, and endocrine activity
     –       Emotional stages (rage, pleasure) and biological drives (hunger, thirst, sex)
     –       Reactions to fear and the “fight-or-flight” system


1.    Draw the structure of a nerve. Label epineurium, perineurium, endoneurium, fascicle

2.    Define sensory, motor, mixed nerves

3.    Describe how nerve fibers are regenerated. What limitations can interfere with the process?

4.    List the 12 cranial nerves. Know name, number, and major functions.

5.    Know the names, number of nerves in each group, and location of the 31 spinal nerves.

6.    What type of neuron is found in the dorsal root? Ventral root?

7.    What is a plexus? Name some examples. Why do we have plexuses?

8.    What is a dermatome?

9.    What is Hilton’s law?

10.   Compare and contrast the innervations of skeletal muscle with the innervations of visceral
      (smooth) muscle.

11.   What is a reflex?

12.   Describe the five major components of a reflex arc.

13.   What is a Golgi tendon organ?

14.   Describe the structure and operation of a muscle spindle.

15.   Describe the stretch reflex, the Golgi tendon reflex, the flexor and crossed extensor reflexes, and
      the plantar reflex. What condition is indicated by Babinski’s sign?

16.   How does the ANS differ from the SNS?

17.   Be able to draw and label preganglionic and posganglionic nerves, and indicate the type of
      neurotransmitter each releases. How many neurons are found between the CNS and the effector
      in each system? Where are nicotinic and muscarinic receptors found?

18.   Know the general actions produced by the sympathetic and parasympathetic systems.

19.   How do nicotinic receptors work? Muscarinic receptors?

20.   Describe the mechanisms of action of the following adrenergic receptor subtypes: α-1, α-2, β-1,

21.   Describe sympathetic tone and parasympathetic tone.

22.   Why does sympathetic action last longer than parasympathetic action?

23.   What part of the CNS is the main integration center of the ANS?


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