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List the layers that comprise the spinal meninges
dura mater, arachnoid mater, pia mater
What is the purpose of the meningeal spaces?
- a)epidural space: lies between dura mater and vertebrae; it is good for epidural shots; numbs lower part of body
- b)subarachnoid space: lies between the arachnoid membrane and pia mater; cerebrospinal fluid flows here; good for taking CSF samples near the lumbar
How many segments does the spinal cord contain?
- 31 segments
- 8 pairs cervical, c1-c8
- 12 pairs thoracic, t1-t2
- 5 pairs lumbar, l1-l5
- 5 pairs sacral, s1-s5
- l pair coccygeal, c1
How far into the vertebral column does the spinal cord extend?
spinal cord runs from foramen magnum to L2
What is the purpose of the filum terminale?
anchors cord to coccygeal vertebrae
How many pairs of spinal nerves are there?
31 pairs of spinal nerves
Why do the cervical and lumbar enlargements exist?
- -more axons in and out of these areas
- -cervical enlargement innervates upper limbs
- -lumbar enlargement innervates lower limbs
How are the gray and white matter arranged in the spinal cord?
- -white matter on the outside, arranged into columns
- -gray matter on the inside, arranged into horns
What is the purpose of the sensory and motor nuclei within the gray matter?
- -axons carrying information to and from the cranial nerves form a synapse first at these nuclei
- -somatic sensory nuclei: takes info from tactile receptors
- -visceral sensory nuclei: takes info from organ systems
- -visceral motor nuclei: sends commands to organ systems
- -somatic motor nuclei: sends commands to skeletal muscles
Be able to label the Sectional Organization of Spinal Cord
What types of neurons travel through the dorsal root?
carries sensory neurons
What types of neurons travel through the ventral root?
carries motor neurons
The dorsal root and the ventral root will merge to form?
they merge to form spinal nerves, give us one nerve on each side
What structure is within the dorsal root ganglion?
contains cell body of unipolar sensory neurons
Why is there a dorsal root ganglion but not a ventral root ganglion?
ventral root contains motor neurons and they are multipolar, so their cell bodies lie in the gray matter
What info is carried in the ascending tracts?
sensory info to the brain
What info is carried in the descending tracts?
carries motor commands
How is funiculus different from a fasciculus?
- -fasiculus=nerve tracts
What structures are innervated by the axons that travel through the dorsal ramus?
the skin and skeletal muscles of the back
What structures are innervated by the axons that travel through the ventral ramus?
motor commands to ventrolateral body wall & limbs
Will the white ramus contain myelinated or unmyelinated axons?
white ramus contains myelinated preganglionic axons
Will the gray ramus contain myelinated or unmyelinated axons?
gray ramus contains unmyelinated postganglionic axons
What structures are innervated by the motor axons that travel through the white ramus?
innervates visceral organs
What structures are innervated by the motor axons that travel through the gray ramus?
innervates smooth muscle in the body wall & limbs
What structures are innervated by the preganglionic fibers within the sympathetic nerve?
innervates thoracic activity
What structures are innervated by the postganglionic fibers within the sympathetic nerve?
innervates thoracic activity
Where does the information in the dorsal ramus originate from?
sensory info from skin and muscles of back
What type of sensory information travels through the sympathetic nerve?
sensory info from visceral organs
Where does sensory info in the ventral ramus originate from?
sensory info from ventrolateral surface, structures in body wall and limbs
What structures are surrounded by the perineurium, epineurium and endoneurium?
- a)perineurium: surrounds fassicles
- b)epineurium: surrounds entire spinal nerve
- c)endoneurium: surrounds axons
Where is the myelin sheath in relationship to those structures?
it lies deep to endoneurium
Which nerves make up the nerve plexuses?
What does each plexus innervate?
- a)cervical: innervates neck and top part of shoulders
- b)brachial: innervates shoulders and upper limbs
- c)lumbar/sacral: innervates hips, legs & small portion of abdominal wall
Functions of the specified nerves:
- -phrenic nerve controls diaphragm, breathing
- -ulnar nerve "funny bone" causes tingling sensation when you hit your elbow
- -median nerve causes the carpal tunnel syndrome
- -sciatic nerve compresses due to back pain
What is the arrangement of the neuronal pools?
- 1. Divergence: one piece of sensory info processed by several neurons at same time
- 2. Convergence: several neurons synapse on a single neuron
- 3. Serial Processing: info is processed further at each step
- 4. Parallel Processing: one piece of sensory info is further processed by several neurons at once
- 5. Reverberation: positive feedback loop will increase initial response/stimulus
What are the various classifications of the reflexes?
- 1. innate reflexes: present at birth
- 2. acquired reflexes: develop later
- 3. spinal reflexes: processed in spinal cord
- 4. cranial reflexes: processed in brain
- -monosynaptic: 1 synapse; sensory synapse directly with motor
- -polysynaptic: 1 or more interneurons
- -visceral reflex: controls organ systems
- -somatic reflex: controls skeletal muscles
What is the structure of the basic reflex arc?
- (1) Receptor: The receptor activates a nerve impulse in a sensory neuron in response to a change in the body's internal or external environment. Monitors environment.
- (2) Sensory neuron: This neuron conducts the impulse from the receptor, through dorsal root, to its axonal end in the central nervous system.
- (3) Interneuron: This is a receiving area (usually in the central nervous system) in which the incoming sensory impulse connects with an outgoing motor impulse. The impulse may be repressed, transmitted, or rerouted in the center area.
- (4) Motor neuron: The job of the motor neuron is to transmit the impulse/carry motor command to the proper body organ, through ventral root.
- (5) Effector: The effector is the organ of the body that responds to the impulse from a motor neuron. An effector may be either a muscle or a gland.
What are the 3 reflexes discussed in work?
- a)stretch reflex:
- -muscle spindle is receptor in muscle, detects stretch
- -initial stimulus muscles stretch
- -response-muscle contracts to decrease stretch
- b)tendon reflex:
- -stimulatory interneuron: stimulates, increases activity
- -inhibitory interneuron: inhibits, decreases activity
- -example is as your bicep contracts, tricep relaxes, working together to relieve tension in tendon
- c)crossed extensor reflex:
- -example is that stepping on thumb tack activates the injured leg to lift and activates other foot to shift weight off injured leg
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