Chapter 12 lecture

Cauda equina -

roots of nerves extend from end-to-end of spinal cord

Conus medullaris 

• Cone-like regions of the spinal cord inferior to the lumbosacral enlargement 

Cervical and lumbosacral enlargements - give rise ____________

to spinal nerves of limbs

spinal enlargements

cervical and lumbosacral

ventral roots merge

laterally to form a spinal nerve

spinal nerves contain

sensory and motor axons-dorsal

spinal cord extends from __________

foramen magnum to L2

subarachnoid space fluid

-cerebrospinal fluid

Subarachnoid space location

between arachnoid mater and pia mater

subdural fluid

serous fluid

Subdural location

between arachnoid mater and dura mater

Epidural space

between the periosteum of vertebral canal and dura mater

Arachnoid mater

- wispy, meningeal layer that is bound tightly to surface of the spinal root

Dura mater attaches to

rim of foramen magnum and ends at level of second sacral vertebra

dura matter function

forms thecal sac that surrounds spinal cord

Meninges -

connective tissue membranes surround the brain and spinal cord

Dorsal roots

- contain sensory axons

Dorsal root ganglion -

collections of cell bodies of the sensory neurons

Ventral roots

- contain motor axons

Grey matter contains (horns)

dorsal, lateral, and ventral horns

dorsal horn

contain sensory neurons that synapse with interneurons

ventral horn

-- contains neuron cell bodies of somatic motor system

lateral horn

contains neuron cell bodies of autonomic motor system

Describe the spinal cord and the branching of a spinal nerve including the location and function of the following structures (gray matter, white matter, horns, columns, rootlets, dorsal roots, ventral roots, spinal nerves)

r

-surrounds grey matter, everything else

• myelinated axons forming tracts / Nerve=track; bundles of myelinated axons sending signals 

-contains dorsal, ventral, and lateral column

-connect each half of the spinal cord

Central canal

-located in the center of the gray commissure

columns in white matter

• ventral, dorsal, and lateral 

nerve =

track; bundles of myelinated axons sending signals

myelinated axons form

tracts

white matter location

surrounds grey matter

Explain why spinal nerves are considered mixed nerves including the functions of the axons that pass through the dorsal and ventral roots

They contain both sensory (afferent) and motor (efferent) axons allowing them to transmit signals to and from the central nervous system (CNS)

Describe the components of a reflex arc

Sensory receptors - respond to stimuli and produce action potentials in sensory neurons

Sensory neurons - propagate action potentials to CNS

Interneurons in CNS - synapse with sensory neurons and with motor neurons

Motor neurons - carry action potentials from CNS to effector organs

Effector organs - respond to action potentials

Contrast the function of autonomic and somatic reflexes

Autonomic - mediated through autonomic nervous system, responsible for maintaining variables within their normal ranges, ex. blood pressure

Somatic - mediated through somatic motor system, includes responses such as removing the body from painful stimuli and keeping body from falling

Compare and contrast the functions of a stretch reflex, a Golgi tendon reflex, and a withdrawal reflex

Stretch reflex - muscles contract in response to stretching force applied to them, innervated by specific motor neurons

Golgi tendon reflex - prevents contracting muscles from applying excessive tension to tendons, golgi tendon organ, prevent damage to tendons that could be caused by excessive tension

Withdrawal reflex - remove body limb or part from painful stimulus

Describe the connective tissue components of a nerve (endo, peri, epineurium)

Endoneurium - surrounds individual axons and their schwann cell sheath

Perineurium - surrounds group of axons (fasciles)

Epineurium - surrounds entire nerve

Describe a dermatome and its clinical importance

Dermatomes - specific cutaneous distributions, areas of skin supplied with sensory information by a pair of spinal nerves

Importance - help with pain detection and location because pain can be related to specific spinal nerve

Explain the branching of the spinal nerves into rami

Dorsal ramus - innervate deep muscles of trunk responsible for movements of vertebral column

Ventral ramus - innervate depend upon which part of spinal cord is considered, remaining spinal nerve ventral rami - form five plexuses

Plexus - organization produced by intermingling of nerves

Explain the branching of the spinal nerves into plexuses

Cervical plexus

-innervates superficial neck structures, skin of neck, posterior portion of head

-ansa cervicalis: loop between C1 and C3

-phrenic nerve: part of both cervical and brachial plexuses, innervates the diaphragm

Brachial plexus

-five ventral rami form three trunks

-separate into six division: form cords that give rise to branches and nerves

Lumbar and Sacral plexus

-usually considered together because of their close relationship

-four major nerves exit and enter lower limb

List the major nerves that exit the brachial and lumbosacral nerve plexus

Brachial - axillary, radial, musculocutaneous, ulnar, median, other smaller nerves

Lumbosacral - obturator, femoral, tibial, common fibular