Chapter 13: Spinal Cord, Nerves, & Somatic Reflexes Flashcards
conduction
nerve fibers that conduct info up and down the spinal cord (CNS)
neural integration
input from multiple sources, integrated & executed output
locomotion
repetitive, coordinated contractions of several muscle groups
reflexes
STAY AT THE SPINAL CORD LEVEL
involuntary stereotyped responses
spinal cord
cylinder of nervous tissue that arises from the brainstem at the foramen magnum of the skull
spinal cord passes through_____ and gives rise to ___ pairs of spinal nerves.
vertebral canal; 31
Where do the 31 spinal nerves pass?
1st pair: between the skull & C1
rest through intervertebral foramina
What 2 parts of the spinal cord are thicker than elsewhere?
- cervical enlargement (upper limbs)
- lumber enlargement (lower limbs)
medullary cone
cord tapers to a point inferior to lumbar enlargement
cauda equina
bundle of nerve roots that occupy the vertebral canal from L2 to S5
meninges
three fibrous connective tissue membranes that enclose the brain & spinal cord
What are the 3 meninges (superficial to deep)?
-dura mater, arachnoid mater, & pia mater
What is special about the pia mater?
it is continuous with the brain & spinal cord
What space surrounds the meninges?
epidural space
spina bifida? How is it prevented?
- congenital defect in which one or more vertebrae fail to form a complete vertebral arch for enclosure of the spinal cord
- prevented via folic acid(B vitamin)
The ____ is shaped like a butterfly and is surround by the ___ in 3 columns.
gray matter; white matter
gray matter (2)
- little myelin
- site of info processing, synaptic integration
white matter (2)
- abundantly myelinated
- carry signals from one part of the CNS to another
columns of funiculi
3 pairs of these white matter bundles (posterior, later, ventral columns)
ascending tracts
carry sensory info up the spinal cord (afferent)
BODY->SPINAL CORD->BRAIN
descending tracts
carry motor info down the spinal cord (efferent)
decussation
the fibers pass up or down the brainstem & spinal cord they CROSS OVER from left to right (CROSS OVER EVENT)
contralateral
when the origin & destination of a tract are on opposite sides of the body
ipsilateral
when the origin & destination of a tract are on the same side of the body
What are the 3 sensory neurons of the ascending tract?
first order, second order, third order neurons
first order neuron (ASCENDING)
detect the stimulus & transmit signal to spinal cord/brain
presynaptic
second order neuron (ASCENDING)
continues to the thalamus at the upper end of brainstem
-interneurons
third order neuron (ASCENDING)
carries the signal the rest of the way to the cerebral cortex
-interneurons
ascending tracts (5)
- gracile fasciculus
- cuneate fasciculus
- spinothalamic tract
- spinoreticular tract
- spinocerebellar tract
gracile fasciculus
Location?
Decussate?
Function?
posterior
medulla oblongata
sensations of the limbs and trunk (lower level)
proprioception
nonvisual sense of the position and movements of the body
cuneate fasciculus
Location?
Decussate?
Function?
posterior
medulla oblongata
same as gracile fasciculus from T6 and up
medial lemniscus
formed from the second order neurons of gracile & cuneate systems that decussate in the medulla
Carry signals for pain, pressure, temp, light touch, tickle. and itch
spinothalamic tract
Carry signals for vibration, visceral pain, deep & discriminative touch, and proprioception
gracile & cuneate fasciculus
spinothalamic tract
Location?
Decussate?
Function?
anterior and lateral
in the spinal cord
pain, pressure, temp, touch, etc
spinoreticular tract
Location?
Decussate?
Function?
anterior and lateral
in the spinal cord
sensation of pain from tissue injury
spinocerebellar tract
Location?
Decussate?
Function?
lateral
no decussation
feedback from muscles (proprioception)
How many neurons involved in descending tracts?
2 (upper and lower motor neurons)
Upper motor neurons (DESCENDING TRACT)
originate in the cerebral cortex and terminate on a lower motor neuron
Lower motor neuron (DESCENDING TRACT)
originate in brainstem or spinal cord (leads the rest of the way)
corticospinal tract
Location?
Decussate?
Function?
cerebral cortex
medulla oblongata
precise fine coordinated movements
tectospinal tract
Location?
Decussate?
Function?
midbrain
midbrain
reflex turning of head to sound and sights
lateral & medial reticulospinal tract
Location?
Decussate?
Function?
reticular formation of brainstem
no decussation
awareness of pain
lateral & medial vestibulospinal tract
Location?
Decussate?
Function?
brainstem
no decussation
control balance & posture
Polio & ALS
both cause destruction of motor neurons & production of skeletal muscles from lack of innervation (mixing of afferent & efferent)
Each spinal nerve has 2 points of attachment, where are they?
posterior dorsal root & anterior ventral root
posterior dorsal root
INPUT to spinal cord
anterior ventral root
OUTPUT out of the spinal cord
What are the 3 divisions of nerves in the distal branches?
anterior ramus
posterior ramus
meningeal branch
Nerve plexus are found where
in the anterior rami branch
what are the 5 nerve plexuses?
cervical brachial lumbar sacral coccygeal
Shingles remains for life in the ____ _____
posterior root ganglion
radial nerve injury
crutch paralysis
sciatic nerve injury
sharp pain from “ass to toes”
dermatome
specific area of the skin that receives sensory input from spinal nerves
reflexes
quick involuntary stereotyped responses of muscle
properties of reflexes (4)
requires stimulation
quick
involuntary
stereotyped
conditioned reflexes
learned reponses
pathway of reflex arc (5 steps)
- somatic receptors
- afferent nerve fibers
- integrating center
- efferent nerve fibers
- effectors
muscle spindle
stretch receptors embedded in skeletal muscles
stretch reflex
when a muscle is stretched, it “fights back” and contracts maintain tone
tendon reflex
knee jerk
contraction of muscle when tendon is tapped
flexor reflex
quick contraction of flexor muscles resulting in withdrawal of a limb from an injurious stimuli
paraplegia
paralysis of both lower limbs
quadriplegia
paralysis of all four limbs
hemiplegia
paralysis on one side of the body
paresis
partial paralysis or weakness of the limbs