LECTURE 15 - THE PERIPHERAL NERVOUS SYSTEM

what are the 2 subdivisions of the peripheral nervous system? what direction does the information travel? what type of information does each subdivision carry?

-afferent division

• carries sensory information towards the central nervous system

-efferent division

• carries motor information from the central nervous system to peripheral tissue (like muscles, glands, etc.)

what are the 2 subdivisions of the efferent division?  how do they differ?  what structures does each innervate?

-somatic nervous system

• serves skeletal muscle

• under our conscious control

-autonomic nervous system

• serves cardiac muscle, smooth muscle, and various glands

• involuntary

what type of information does the dorsal root carry? the ventral root? what is the dorsal root ganglion? Be able to identify these 3 structures on a diagram.

-dorsal root

• sensory nerve entry point

-dorsal root ganglion

• collection of sensory neuron cell bodies

-ventral root

• motor nerve exit point

what are mixed nerves? what two structures form mixed nerves?

mixed nerves: contain both somatic sensory & somatic motor fibers.

• formed by the union of the dorsal and ventral roots.

what is the general spinal nerve structure?

-individual axons/nerve fibers are surrounded by endoneurium

• endoneurium = loose areolar connective tissue

-bundles of axons/nerve fibers form fascicles

• perineurium = layer of dense irregular connective tissue that surrounds an individual fascicle

-fascicles are “bundled” together forming a nerve trunk

• epineurium = layer of dense irregular connective tissue that surrounds the entire nerve trunk

• continuous with dura mater

• provides strength & support

Be able to identify the following terms/structures on a diagram and know their histology when necessary: 

• nerve fibers

• endoneurium

• fascicles

• perineurium

• nerve trunk

• epineurium

histology:

• endoneurium = loose areolar connective tissue

• perineurium = layer of dense irregular connective tissue that surrounds an individual fascicle

• epineurium = layer of dense irregular connective tissue that surrounds the entire nerve trunk

what is a nerve plexus? what are the 4 nerve plexuses discussed in class? what structures does each innervate?

nerve plexus: merging network of spinal nerve trunks leading to and from specific body regions.

includes:

• cervical plexus

• brachial plexus

• lumbar plexus

• sacral plexus

what structures does each innervate?

• cervical plexus

• brachial plexus

• lumbar plexus

• sacral plexus

-cervical plexus

• innervates the neck, jaw, upper back, & diaphragm

-brachial plexus

• innervates the shoulder, arm, & hand

-lumbar plexus

• innervates the lower back, lower abdominal wall, thigh, and genitalia

-sacral plexus

• innervates the hip region, posterior thigh, calf, & foot

what are reflexes?

reflexes: rapid, automatic, involuntary, reactions of muscles/glands to a stimulus

what are the components of a reflex arc?

components of a reflex arc:

• begins at a sensory receptor within the peripheral nervous system —→

• signal travels towards the spinal cord (central nervous system) —→

• integration —→

• signal carried to effector —→

• motor response produced —→

be able to diagram a basic reflex arc

?

know the functions of the cranial nerves given in class.  is each nerve motor, sensory, or mixed?

I. olfactory (special sensory)

II. optic (special sensory)

III. oculomotor

IV. trochlear (motor)

V. trigeminal (mixed)

I. olfactory (special sensory)

• SENSORY

• function: smell

II. optic (special sensory)

• SENSORY

• function: vision

III. oculomotor

• MOTOR

• function: eye movements, eyelid and iris movement

IV. trochlear (motor)

• MOTOR

• function: eye movement

V. trigeminal (mixed)

• MIXED

• ophthalmic (SENSORY): orbital structures, nasal cavity, skin of forehead, superior eyelid, eyebrows, part of nose

• maxillary (SENSORY): inferior eyelid, upper lip, gums, teeth, cheek, nose, palate, part of pharynx

• mandibular (MIXED):

  • SENSORY: lower gums, teeth, lips, palate, tongue. 

  • MOTOR: muscles of mastication

know the functions of the cranial nerves given in class.  is each nerve motor, sensory, or mixed?

VI. abducens

VII. facial

VIII. vestibulocochlear (special sensory)

IX. glossopharyngeal (mixed)

X. Vagus (mixed)

XI. accessory (motor)

XII. hypoglossal (motor)

VI. abducens

• MOTOR

• function: eye movements

VII. facial

• MIXED

• functions: SENSORY from taste receptors on the anterior 2/3 of the tongue.  MOTOR: muscles involved in facial expressions, lacrimal and salivary glands

VIII. vestibulocochlear (special sensory)

• SENSORY

• functions:

  • vestibular branch: balance and equilibrium

  • cochlear branch: hearing

IX. glossopharyngeal (mixed)

• MIXED

• functions:

  • SENSORY: taste of posterior 1/3 of tongue and pressure within the throat

  • MOTOR: swallowing and salivation

XI. accessory (motor)

• MOTOR

• runs to/from the muscles of the upper back

XII. hypoglossal (motor)

• MOTOR

• function: tongue movements

what is the vagus nerve? is it sensory or motor? what important structure does it innervate?

X. Vagus (mixed)

X. Vagus (mixed)

• MIXED

• runs to/from the chest and abdomen

• functions:

  • SENSORY: visceral pain

  • MOTOR: controls heart, lungs, and G.I. tract