the CNS consists of
the spinal cord and brain.
integrates and processes info on its own in addition to relaying info to and from the brain
the adult spinal cord has
posterior median sulcus(shallow)
anterior median fissure(wide)
-it includes localized enlargements (cervical and lumbar) which are expanded regions where there in increased gray matter to provide innervation of the limbs.
the adult spinal cord extends from the
foramen magnum to L1
the spinal cord tapers to a conical tip
the conus medullaris. THe filum (strand of fibrous tissue) originates at this tip and extends through the vertebral canal to the second sacral vertebra, which becomes the coccygeal ligament.
the spinal cord has
31 segments, each with a pair of dorsal root ganglia(containing sensory neuron cell bodies)
a pair of dorsal roots and ventral roots
sensory and motor fibers unite as a single
spinal nerve distal to each dorsal root ganglion.
spinal nerves emerge from
intervertebral foamina and are mixed nerves since they contain both sensory and motor fibers.
is the largest nerve in the body.
the caudal equina is the
inferior extension of the ventral and dorsal roots and the filum terminale in the vertebral canal.
the spinal meninges are a series of
specialized membranes that provide physical stability and shock absorption for neural tissues fo the spinal cord.
the crainal meninges
membranes taht surrounds the brain
3 meningeal layers
the arachnoid mater
the pia mater
the spinal dura mater is the
tough, fibrous outermost layer that covers the spinal cord;caudally it forms the coccygeal ligament with the filum terminale.
the epidural space separates the
dura mater from the inner walls of the vertebral canal
subdural space is the
internal to inner surface of the dura mater.
separates the dura mater from the middle meningeal layer
subarchnoid space is the
internal to arahnoid mater. it contains cerebrospinal fluid, which acts as a shock absorber and used for spinal tap
the pia mater
is the innermost meningeal layer. it is bound firmly to the underlying neural tissue.
paired dendiculate ligaments are supporting fibers extending
laterally from the spinal cord surface binding the spinal pia mater and arachnoid mater to prevent either side to side or inferior movement of the spinal cord
the central gray mater surrounds the
the central canal and contains cell bodies of neurons and glial cells.
the grey matter projfections toward the outer surfaces of the spinal cord
the peripheral white matter contains
myelinated and unmyelinated axons in tracts and columns
neuron cell bodies in the spinal cord gray matter are orgainzed into groups
the posterior gray horns contain
somatic and visceral sensory nuclei.
anterior gray horns are involved with
somatic motor control.
the lateral gray horns contain
visceral motor neurons
the gray commisures are posterior and anterior of the
the white mater can be divded into six colums
each of which contains tracts
ascending tracts relay information from the spinal cord to the brain
descending tracts carry info from the brain to spinal cord
there are 31 pairs of spinal nerves
outermost layer of the spinal nerve is called the epneurium
is a dense network of collagen fibers
middle layer is called
perineurium-partitions the nerve into a series of bundles (fasicles) and conveys blood vessels into each individual fiber
inner most layer is called
endoneurium-composed of delicate connective tissue fibers that surround individual axons.
the first branch of spinal nerve in the thoracic and upper lumbar region, which contains myelinated axons going to an autonomic ganglion.
each spinal nerve has both a
dorsal ramus and ventral ramus
provides sensory/motor innervation to the skin and muscle of the back)
(supplies ventrolateral body surface, body wall and limbs
each pair of spinal nerves monitors a region of the body surface
is a complex interwoven network of nerves
cervice plesux consists of the
ventral rami of c1-c4 and some fibers from c5. muscles of the neck are innervated
brachial plexus orginate from cords or trunks
superior,middle,inferior trunks give rise to the lateral cord, medial cord, and posterior cord
lumbar plexus and sacral plexus orginate from the posterior adb wall and ventral rami of nerves suppllying the pelvic girdle and lower limb.
the lumbar plexus contains fibers from spinal segment t12-l4 and the sacral plexus contains fibers from spinal segments l4-s4
a neural reflex is a rapid, automatic, involuntary motor response to stimuli.
reflexes help preserve homeostasis by rapidly adjusting the functions of organs or organ systems.
a reflex are is the
neural "wiring" of a single reflex
a receptor is a specialized cell that monitors condition
in the body or external environment. each receptor has a characteristic range of sensitivity.
5 steps invlolved in the neural relfex
1)arrival of stimulus and activation of a receptor
2)relay of info to the CNS
4) activation of a motor neuron
5) response by a peripheral effectors
reflexes are classified by
1)development (innate, acquired
2) info is processed (spinal , cranial
3) motor response
4) complexity of the neural circuit
innate reflexes are geneticlly deteremined
acquired reflexes are learned following repeated exposure to a stimulus
cranial reflexes are prcoessed in the
spinal reflex the important interconnections and processing occur
inside the spinal cord.
somatic reflexes control skeletal muscle contractions, and
visceral (auto)reflexes control the activities of a smooth and cardiac muscles and glands
a monosynaptic reflex is the
polysnaptic reflexes have at least one interneuron places between the sensory afferent and the motor efferent
they have longer delay between stimulus and response
spinal reflexes range from simple to more complex polysynaptic reflexes
the stretch reflex is a monosynaptic reflex that auto regulates skeletal muscle length and muscle tone.
it includes :patellar, biceps, triceps, and ankle jerk reflex.
a patellar reflex is the familiar
knee jerk, where in a rap on the patellar ligament stretches the muscle spindles in the quadriceps muscles
a postural reflex is a
stretch reflex that maintains normal upright posture.