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