Peripheral Nervous System

Based on Lecture Vid

Cranial Nerve I: Olfactory

• responsible for the sense of smell, transmitting sensory information from the nasal cavity to the brain.

• part of external environment as this is where air enters

• sensory

Nerves

• covered by Pia mater and dura

• Nerve is escaping and goes out to destination site and is covered by connective tissue

Cranial Nerve II: Optic

• optic chiasma is where information crosses to the other side

• optic tract goes back into the brain

• sensory

  • retina brings in info about light

• Medial half crosses over, lateral does not cross

Cranial Nerve III: Oculomotor

• motor but partial sensory

• primary function: moving the eye and has 6 muscles

  • 4 of them come from this muscle

    • Superior rectus

    • Medial rectus

    • Inferior oblique

    • Inferior rectus

• goes to levator palpabrae muscle and branches into the iris as well

Cranial Nerve IV: Trochlear

• motor

• purpose: supply superior oblique muscle of the eye

• goes through fissure behind eye

Cranial Nerve V: Trigeminal

• thick and has multiple ganglia

• Semilunar ganglion divides info into 3 major branches that go into parts of your face

  • referred to as V1, V2, and V3

• sensory, only motor is the muscles of mastication

• referred pain source in trigeminal pain

  • ice cream freeze on forehead

What are the 3 divisions in the Semilunar ganglia in Nerve V?

• Ophthalmic (eye)

• Maxillary (upper jaw)

• Mandibular (lower jaw)

Cranial Nerve VI: Abducens

• goes to only one muscle of the eye

  • lateral rectus

Cranial Nerve VII: Facial

• goes to face

• mostly motor

  • responsible for all facial expressions

• has sensory functions and goes to…

  • lacrimal glands

  • submandibular glands

  • sublingual (salivation) - are parasympathetic

Cranial Nerve VIII: Vestibulocochlear

• auditory

• sensation for hearing and sense of balance in respect to gravity and movement

Cranial Nerve IX: Glossopharyngeal

• goes to tongue and pharynx

• innervates to Parotid gland

• plays role in taste and sensory info that comes from carotid areas that control BP and CO2 concentration and swallowing

Cranial Nerve X: Vagus

• longest nerve

• goes from back parts of pons, down neck, through chest and abdomen

• single nerve as it passes through the neck

  • divides into many branches at thoracic area

• major parasympathetic innnervation to all organs and picks up sensations form that organ as well

Cranial Nerve XI: Accessory

• motor to neck muscles

  • Sternocleidomastoid

  • Trapezius

• not just coming form brain but also cervical spinal nerves

  • C1-C5

    • sends info branch along cord and to origin points of nerve

• joins vagus nerve and helps control neck

Cranial Nerve XII: Hypoglossal

• goes to tongue

  • extrinsic: what you see in oral cavity

  • intrinsic: rolling of tongue and making it thinner etc.

Spinal Nerves and Plexuses

• come out of spine and form Plexuses

  • nerves that are superhighway of nerves that go into an area

    • lumbar

    • sacral

  • 31 pairs

Spinal Nerve Anatomy

• Nerves leaving area come out as rootlets and go into roots

• Dorsal and ventral root form spinal nerve and it branches into dorsal and ventral ramus

• dorsal goes into back supplying skin and muscles of back

• ventral comes to side of body

• Sympathetic chain ganglion

• Rami Communicates

Sympathetic chain ganglion

• only in thoracic and lumbar areas and coordinate fibers coming off spine itself

Rami communicates

• take info to and from ganglion

• sit parallel to cord

Cervical Plexus

• includes roots from C1-C5

• phrenic nerve

  • goes to diaphragm and allows you to breathe

  • originates from C1, C4, and C5

Brachial Plexus and Pectoral Nerves

• form major nerves going down arm

• shoulder and neck has a nerve highway

• 3 major cords that hold branching patterns fo axons and form final nerve terminals

Brachial Plexus

• 4 of them

  • Musculocutaneous

  • Radial

  • Median

  • Ulnar

• these 4 branches supply 75-95% of arm itself

• has roots from cervical are but some branch patterns from 1st thoracic

• only plexus that contains nerves from 2 different locations on the cord

Lumbar Plexus

• L1-L5

  • forms bulk of leg

• Obturator - does most of stuff from hip

• Femoral - goes down interior part of leg and supplies most of anterior part of leg itself

Sacral Plexus

• L4, L5, and all nerves of Sacral and Coxsaggital

• Pudenal - takes up things from the hip and anterior on the back side

• Sciatic - major nerve running down back of leg

Dermatomes

• area of skin innervated by the spinal cord itself

• innervated by the cutaneous branches of a single sensory nerve

• all spinal nerves EXCEPT C1 participate in dermatomes

Reflex arc

1. Stimulus

2. Receptor

3. Sensory Neuron

4. Integration Center

5. Association Neuron (interneuron)

6. Motor Neuron

7. Effector

8. Response

Stretch reflex

• Muscle spindle

  • modified muscle fiber that contracts with the rest of muscle but reports info through sensory neuron and how long it is and how quickly its changing its length

• info comes into the cord and is relayed to areas and cause contraction

• flexor muscle must be relaxed, If not does not fire

Overview of Stretch Reflex

1. Stretching muscle activates muscle spindle

2. Excited y motor neurons of the spindle cause the stretched muscle to contract

3. afferent impulses from the spindle result in inhibition of the antagonist

   • Patellar reflex

     • tapping patellar tendon stretches quads and starts reflex action

     • quads contract and the antagonistic hamstrings relax

Golgi Tendon Reflex

• is like a safety valve

• opposite of stretch reflex

• contracting the muscle activates Golgi Tendon Organs

• Afferent Golgi tendon neurons are stimulated, neurons inhibit contracting muscle, and antagonistic muscle is activated

• as a result, contracting muscle relaxes and the antagonist contracts

Flexor Reflex

• initiated by a painful stimulus (actual or perceived) that causes automatic withdrawal of the threatened body part

Crossed extender reflex

• consists of two parts

  • stimulated side is withdrawn

  • contralateral side is extended

Neurotransmission Scenario

• both sympathetic and parasympathetic secrete acetylcholine in preganglionic

• parasympathetic releases ACETYCHOLINE in postganglionic

• sympathetic releases NOREPINEPHRINE in postganglionic

• these systems innervate various organs and must have dual innervation with opposite affects of those organs

Location of Parasympathetic and Sympathetic

• Sympathetic is part of chain ganglion

• Parasympathetic is more towards target tissue of the CNS

Parasympathetic releases what during postganglionic?

Acetylcholine

Sympathetic releases what during postganglionic?

Norepinephrine (think fight or flight)

Parasympathetic (Craniosacral)

• divisions come from brain and sacral spine

• all ganglion are away from CNS

Sympathetic (Thoracolumbar)

• divisions come from thoracic lumbar areas and go through set of ganglion (sympathetic trunk)

• anatomically close to origin of spinal cord itself

Sympathetic Ganglia

• rami communicate with chain ganglion

• has to make a connection and send fibers to a spinal nerve

Visceral reflex arc

• include parasympathetic or sympathetic innervations

• sympathetic stops at chain ganglion

Levels of Control in ANS

• can influence but not a lot

  • ie. can’t really decide to not be hungry