Spinal cord and spinal nerves

CNS

Central nervous system

dorsal horn

-posterior Crescent shaped projection of gray matter within the spinal cord where sensory neurons enter the spinal cord

sensory neuron

-posterior root afferent -Neurons that carry incoming information from the sensory receptors to the brain and spinal cord.

afferent

-sensory -in neurons, another name for sensory -conveying toward a center

ventral horn

-skeletal motor neuron cell bodies - anterior somatic motor info exits through the ventral horn

sensory receptor

-specialized cell that transmits signals to sensory neurons

PNS connections

-ventral carries motor axons from CNS (efferent) -dorsal root carries sensory axon into the CNS (afferent) -dorsal root ganglion contains sensory cell bodies

coccygeal

1

the crossing of a nerve fiber or tract from the right side of the CNS to the left, or vice versa is called____.

decussation

mixed nerves

nerves composed of both sensory and motor fibers

below L2 the vertebral canal is occupied by

the cauda equina

lateral column

white mater middle column

ascending tracts

(sensory) -carry sensory info toward brain -sensory signals up the spinal cord

dura mater

- (tough mother) - outermost layer - dense, irregular CT - stops at S2 thick, outermost layer of the meninges surrounding and protecting the brain and spinal cord

dorsal root ganglion

- contains sensory cell bodies -A group of sensory neuron cell bodies found just posterior to the spinal cord on either side. A pair of root ganglia exists for each spinal nerve that expands from the spinal cord. The ganglia are part of the peripheral nervous system (PNS).

ventral column

-(anterior) Ventral white mater Column on the front of the vertebrae

dorsal column

-(posterior) white mater column on back of the vertebrae

arachnoid

-(spidery) -middle later, avascular - thin layer against deep surface of dura that gives rise to web-like extensions of collagen and elastic fibers to pia mater Weblike middle layer of the three meninges

how many pairs of spinal nerves?

-31 -all but T2-T12 form plexuses -intercostal nerves

spinal cord segment/4 regions

-8 Cervical, 12 Thoracic, 5 Lumbar, 5 Sacral, 1 Coccygeal. -Spinal cord is organized into functional units called

foramen magnum

-A large opening at the base of the skull through which the brain connects to the spinal cord.

effector

-An organ (a gland or muscle) that becomes active in response to nerve impulses.

central canal

-CSF fills canal

cerebrospinal fluid

-Fluid in the space between the meninges that acts as a shock absorber that protects the central nervous system.

motor neuron

-anterior root efferent -a neuron that sends an impulse to a muscle or gland, causing the muscle or gland to react

white matter

-arranged in 3 columns which contain multiple tracts (fasciculi- not exactly the same as a fascicle in a spinal nerve) 1.ventral (anterior) column 2.lateral column 3.dorsal (posterior) column Whitish nervous tissue of the CNS consisting of neurons and their myelin sheaths.

*epidural space

-between dura mater and vertebral canal -filled w/fat and CT

ventral root

-carries motor axons from CNS efferent -the basal branch of each spinal nerve; carries motor neurons

dorsal root

-carries sensory axon into the CNS (afferent) -the sensory branch of each spinal nerve

cauda equina

-collection of spinal nerves below the end of the spinal cord -"horse's tail", a fan of nerve fibers below the spinal cord

gray commissure

-connecting point

spinal reflexes

-fast, automatic -involuntary -predictable -response to stimuli

*subarachnoid space

-filled w/CSF -lumbar cistern is subarachoid space inferior to medullary cone (site of spinal tap) a space in the meninges beneath the arachnoid membrane and above the pia mater that contains the cerebrospinal fluid

integrating center

-gray matter -The place where decisions are made.

dermatomes

-highly inaccurate -area of skin providing sensory input to a given nerve -clinically useful, but overlap -Axons that carry info from cutaneous receptors gather together in nervies that enter the spinal cord.

gray matter

-highly organized collections of nuclei -has 3 parts 1. ventral anterior horn 2. lateral horn 3. dorsal horn - gray commissure -central canal

pia mater

-innermost, thinnest layer -(delicate mother) -adheres tightly to surface of cord, holding blood vessels in place -collagen + few elastic fibers -terminal filum is extension anchoring cord inferiorly (~S5) Inner layer of meninges; intimately attached to brain following contours; carries small blood vessels to nourish underlying nervous tissue;

efferent

-motor -conveying away from the center -Also known as motor neurons

descending tracts

-motor neurons relaying impulses DOWN the spinal cord

thoracic

12

lumbar

5

sacral

5

cervical

8

vertebra

Backbone

meninges

The organs of the central nervous system (brain and spinal cord) are covered by 3 connective tissue layers -dura mater -arachnoid -pia mater

between the dura mater and vertebral bone, one is most likely to find

adipose tissue

the outermost connective tissue wrapping of a nerve is called the

epineurium

outside the CNS, the somas of neurons are clustered in swellings called

ganglia

which of these is not a region of the spinal cord?

pelvic

PNS

peripheral nervous system

in the spinal cord, the somas of the lower motor neurons are found in

the anterior horns