Function of Spinal Cord

- used for impulse conduction

- reflexes

How long is the typical adult spinal cord?

16 -18 inch long

Conus medullaris

official "end" of the spinal cord

Cauda equina

a group of nerve roots inferior to the conus medullaris that resembles a horse's tail

Cervical (C4- T1)

intervates the upper limbs

Lumbar(T9 -T12)

innervates the lower limbs

Dura Mater

runs from f. magnum to S2; not part of periosteum of bone; epidural space

Pia Mater

forms strands that anchors conus medullaris to coccyx aka filum terminale

Cross Section

anterior median fissure and posterior median sulcus

What does the external white matter consist of?

bundles of myelinated axons; anterior, posterior, lateral funiculi; tracts cross in medulla

What does the inner gray matter consist of?

cellbodies, association neurons; H-shaped or butterfly (horns); gray commissure

2 Divisions of the Peripheral Nervous System (PNS)

Afferent Division and Efferent Division

Afferent division contains...

somatic sensory, visceral sensory, special senses

Efferent division contains...

somatic motor (voluntary); visceral motor/ autonomic (involuntary)

Structure of PNS

nerves, ganglia, and receptors outside CNS

Nerves in the PNS

bundles of axons, vessels, adipose; connective tissue coverings; cranial and spinal nevers, sensory and motor neurons

Ganglia

cluster of cell bodies

List the Cranial Nerves

1) Olfactory

2) Optic

3) Oculomtor

4) Trochlear

5) Trigeminal

6) Abducens

7) Facial

8) Vestibulocochlear

9)Glossopharyngeal

10) Vagus

11) Accessory

12) Hypoglossal

I. Olfactory Nerve

Sensory = detection of odors; anosia (loss of smell)

II Optic Nerve

Sensory = visual signals; optic chiasm; anopsia

optic chiasm

point at which optic nerves converge

III Oculomotor Nerve

Motor = innervates upper eyelide msucle; supplies superior, inferior, medial rectus and inferior oblique eye musces; lens muschle; iris muscle

ptosis

upper eyelid dropp

strabismus

eyes cont focus together

IV Trochlear nerve

Motor = controls the supeiror oblique eye muscle; downwards, lateral movment impaired

V  Trigeminal Nerve

Sensory = sensations from face, nose, mouth

Motor = chewing muscles

3 divisions of the Trigeminal nerve

ophthalmic, maxillary and mandibular

VI Abducens Nerve

Motor = innervates the lateral rectus eye muscle

trigmeinal neuralgia

inflammation; can cause intense pulsating pain that lasts from minutes to hours

Diplopia

double vision/ cross eyed

VII  Facial Nerve

Sensory = Taste budds on anterior 2/3 tongue

Motor = innervates facial muscle, salivary glands, lacrimal (tear) glands

Bell's Palsy

characterized by paralyzed facial muscles, eyelid droop, sagging corner of mouth

VIII  Vestibulcochlear

Sensory = auditory balance sensations; vesitublar lesion (dizziness); cochelar lesion (deafness); no foramen enter through the internal auditory canal

IX  Glossopharyngeal

Sensory = posterior tate buds, somatic snesory from throat/ear

Motor = innervates swallowing muscle, parotid gland

X  Vagus Nerve

Sensory = sensations from viscera

Motor = smooth muscles of viscera; cardiac muscle; muscles of larynx and most pharynx muscles

XI  Accesory Muscles

Motor = innervates the trapezius, sterncleidomastoids; wouldnt be able to elevate shoulder or turn head to opposite side

XI  Hypoglossal Nerves

Motor = innervates intrinsic and extrinsic tongue muscles

Number of spinal nerve pairs

31

Structure of spinal nerve

arise form each cord segment; mixed nerves (sensory and motor) and two roots

Two roots of the spinal nerves

Ventral/ Anterior roots = motor neurons

Dorsal/Posterior Roots = sensory neurons

Rami

when the nerve splits once the spinal nerve leaves the intervertebral foramen

Plexuses

formed by nerves which are net work of anterior rami of spinal nerves

Cervical Plexus

C1-C4; nerves run to head and neck

Brachial

C5-T1; nerves run to shoulder and arms

Lumbrosacral

L1-S4; nerves run to legs, genitals

dermatome

sensations carried by spinal nerves

referred visceral pain

a phenomenon in wich pain or discomfort from one organ is mistakenly referred to a dermatome

Reflex arcs

provide rapid reacts to possibly threatening situations; only 2-3 neurons are involved; begins at PNS receptor and communicate w/ the CNS ; ends at a perpheral effector -muscle or gland

Reflexes include

visceral and somatic reflexes

Ipsalateral reflex

both the receptor and effector organs are on the same side

contralateral

sensory impulses from a receptor cross over going though the spinal cord to activate effector organs in the opposite limb

monosynaptic

simplest of all reflexes; sensory axons synapse directly on the motor neurons, whos axons projects to the effect; very small delay occurs in this reflex resulting in a very prompt reflex response

polysynaptic

exhibit a number of synapses involving interneuron's within the relfex; more componenst result in a prolonged delay between stimulus and response