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Chapter 13 - Spinal Cord, Spinal Nerves, and Somatic Reflexes
Terms in this set (117)
What is the information highway between brain and body?
What extends through vertebral canal from foramen magnum to L1?
What on the spinal cord receives sensory information and issues motor signals to muscles and glands?
What is the spinal cord a part of?
Central nervous sytem
What are the spinal nerves a part of?
Peripheral nervous system
Name three functions of the spinal cord
Conduction, locomotion, reflexes
What function of the spinal cord is passing information up and down the spinal cord by way of bundles of fibers?
What function of the spinal cord is repetitive, coordinated actions of several muscle groups?
What function of the spinal cord has central pattern generators that are pools of neurons providing control of flexors and extensors (walking)?
What function of the spinal cord is involuntary, stereotyped responses to stimuli (remove hot hand from stove)?
What function of the spinal cord involves the brain, spinal cord, and peripheral nerves?
What is a cylinder of nerve tissue within the vertebral canal that is as thick as a finger?
Because the vertebral column grows faster, where does the spinal cord extend to?
How many pairs of spinal nerves arise from the cervical, thoracic, lumbar, and sacral regions of the cord?
What is the tapered end of the spinal cord called?
What is located at L2-S5 and resembles a horse's tail?
What are three layers enclosing the spinal cord called?
What are the three layers of the meninges from superficial to deep?
Dura mater, arachnoid mater, and pia mater
What is the outermost layer of the meninges that is a tough collagenous membrane surrounded by epidural space filled with fat and blood vessels?
What layer of the meninges is a layer of simple squamous epithelium lining dura mater and loose mesh of fibers filled with CSF and creates subarachnoid space?
What layer of the meninges is a delicate membrane adherent to the spinal cord and has ligaments that anchor the cord?
How can you tell the difference between the ventral root and the dorsal root?
The dorsal root has a ganglion
What is a failure of vertebral arch to close covering spinal cord?
How common is spina bifida?
A congenital defect in 1 baby out of 1000
How can mothers reduce the risk of their baby getting neurological issues?
By taking folic acid supplement during pregnancy
If a baby has spina bifida, when should they get surgery to fix it?
Within the first 72 hours
Is the dorsal root of the spinal nerve sensory or motor and where is it going?
It is sensory (afferent) and it's going to the CNS
Is the ventral root sensory or motor and where is it going?
It is motor (efferent) and it's going to the PNS
The central area of the spina cord is what?
Gray matter shaped like a butterfly
What is gray matter?
Neuron cell bodies with little myelin
What is white matter?
How do spinal cord tracts run?
Bilaterally with ascending sensory tracks and descending motor tracks
How is the white matter organized in the spinal cord?
Into three columns
What are the white columns?
Bundles of myelinated axons that carry signals up and down
Where are the three white columns?
Dorsal (posterior) columns, lateral columns, and anterior columns
What is each column filled with?
Named tracts (named fibers with a similar origin, destination, and fucntion)
What does decussation mean when pertaining to nerve tracts?
The fibers cross sides
What does contralateral mean?
Origin and destination are on opposite sides
What does ipsilateral mean?
Origin and destination are on the same side
What do sensory neurons travel across from their origin in the receptors to their destination in the sensory areas of the brain?
Which of the three neurons detects a stimulus and transmits the signal to the spinal cord or brain stem?
First order neuron
Which of the three neurons continues as far as the thalamus (the gateway) at the upper part of the brainstem?
Second order neuron
Which of the three neurons carries the signal the rest of the way to the sensory region of the cerebral cortex?
Third order neuron
Dorsal column ascending pathway senses what sensations?
Deep touch, visceral pain, vibration, and proprioception
What two ascending tracts carry signals from the arm and leg respectively?
Fasciculus gracilis (gracile fasciculus) and Fasciculus cuneatus (cuneate fasciculus)
Where do the Fasciculus gracilis (gracile fasciculus) and Fasciculus cuneatus (cuneate fasciculus) decussate?
In the second order neuron in the medulla
Where is the third order neurons for the Fasciculus gracilis (gracile fasciculus) and Fasciculus cuneatus (cuneate fasciculus)?
In the thalamus (carries signal to cerebral cortex)
What does the spinothalamic pathway sense?
Pain, pressure, temperature, light, touch, tickle, and itch
Where does the spinothalamic pathway decussate?
In the second order neuron in the spinal cord
What does the spinocerebellar pathway sense?
Proprioceptive signals in limbs and trunk
What does proprioceptive mean?
Helps us know where out body is even with our eyes closed
Where do second order nerve ascend?
In the lateral column
How many types of neurons does a descending tract have?
Which descending tract neuron begins with a soma in the cerebral cortex or brainstem and has an axon that terminates on a lower motor neuron?
Upper motor neuron
Which descending tract neuron is in the brainstem or spinal cord and leads the rest of the way to the muscle or other target organ?
Lower motor neuron
What suffix do most descending tracts end in?
Which descending tract is in charge of precise, coordinated limb movements?
What lobe is responsible for motor function?
Once the "message" leaves the frontal lobe, where does it go next?
The upper motor neuron in the cerebral cortex
Once the "message" leaves the upper motor neuron, where does it go next?
Lower motor neuron in the spinal cord
Where does the corticospinal tract decussate?
What descending motor tract is in charge of reflex movements of the head?
What descending motor tract controls limb movements important to maintain posture?
What descending motor tract is in charge of postural muscle activity in response to inner ear signals?
What are two diseases causing destruction of motor neurons and skeletal muscle atrophy?
Poliomyelitis and ALS
What is caused by poliovirus spread by fecally contaminated water?
Weakness caused by poliomyelitis progresses to what?
Paralysis and respiratory arrest
What is sclerosis of the spinal cord due to astrocyte failure to reabsorb glutamate neurotransmitter?
Amyotrophic lateral sclerosis
what does amyotrophic lateral sclerosis do?
Paralysis and muscle atrophy
What is a bundle of nerve fibers?
What covers nerves?
What surrounds a fascicle?
What separates individual nerve fibers?
What penetrates only to the perineurium?
What are skin eruptions along the path of a nerve?
What is caused by the varicella-zoster virus (chicken pox) that remains for life in dorsal root ganglia and is very painful?
What occurs after age 50 if immune system is compromised or with stress?
What is the treatment for shingles?
No special treatment
What is formed from the ventral rami branch and anastamose?
How many are nerve plexuses are there?
Where is the first nerve plexus?
Cervical in the neck (C1-C5)
What does the first nerve plexus supply?
Neck and phrenic nerve to the diaphragm
Where is the second nerve plexus?
Brachial in the armpit (C5-T1)
What does the second nerve plexus supply?
Upper limb and some of the shoulder and neck
Where is the third nerve plexus?
Lumbar in the lower back (L1-L4)
What does the third nerve plexus supply?
Abdominal wall, anterior thigh, and genitalia
Where is the fourth nerve plexus?
Sacral in the pelvis (L4, L5, and S1-S4)
What does the fourth nerve plexus supply?
Remainder of butt and lower limb
Where is the fifth nerve plexus?
Coccygeal (S4, S5, and C0)
Which plexus gets injured in birth if shoulder is stuck or if a mother pulls a child's arm?
Where does each spinal nerve receive sensory input from?
A specific area of skin called a dermatome
What are quick involuntary stereotyped reactions of glands or muscles to sensory stimulation?
What are automatic responses to sensory input that occur without our intent or often even our awareness?
What are function caused by somatic reflex arc?
Stimulation of somatic receptors
Afferent fibers carry signal to dorsal horn of spinal cord
Interneurons integrate the information
Efferent fibers carry impulses to skeletal muscles
Skeletal muscles respond
What are sense organs that monitor the length of the skeletal muscles (proprioceptors)?
What respond to onset of stretch or prolonged stretch?
What reflex helps maintain equilibrium and posture such as when your head tips forward as you fall asleep and muscles contract to raise the head?
Stretch (myotatic) reflex
What reflex stabilizes joints by balancing tension in extensors and flexors smoothing muscle actions?
What is caused by a very sudden muscle stretch?
What kind of reflex is a knee-jerk (patellar) reflex?
What does testing somatic reflexes do?
Help diagnose many diseases
What prevents muscles from working against each other (it's a reflex phenomenon that prevents muscles from working against each other by inhibiting the antagonists)?
What reflex occurs during withdrawal of foot from pain?
Flexor (withdrawal) reflex
What controls the sequence and duration of muscle contraction in a reflex?
Neural circuitry in spinal cord
What is an example of a flexor reflex?
Polysynaptic reflex arc
What reflex maintains balance by extending other leg?
Crossed extensor reflex
What reflex extends up and down the spinal cord?
What reflex arcs are explained by pain at one foot causing muscle contraction in other leg?
Contralateral reflex arc
What are proprioceptors in a tendon near its junction with a muscle that is a 1mm long encapsulated nerve bundle?
Golgi tendon organ
What does excessive tension on tendon inhibit?
Motor neuron decreasing muscle contraction
What reflex also functions when muscle contracts unevenly?
Golgi tendon reflex
How many people a year are paralyzed due to spinal cord trauma?
10,000 - 12,000 people/year
How many spinal cord traumas occur in traffic accidents?
What does this damage pose risk of?
What are early spinal cord injury symptoms called?
Spinal shock (can be caused by football injury)
Tissue damage at time of spinal cord injury is followed by what?
Post-traumatic infarction (tissue death)
Who are more likely to get a spinal cord injury?
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