spinal cord Flashcards
The spinal cord extends from the foreman magnum to what vertebra ?
foreman magnum to L1
What are the three functions of the spinal cord ?
Conduction , passes info up and down the spinal
Locomotion, repetitive actions of muscle groups
Reflexes, involuntary responses to stimuli
What are central pattern generators?
Pools of neurons providing control of flexors and extensors EX. like walking
How many pairs of spinal nerves arise from C, L, T and sacral regions of the cord ?
31
Where do the nerves that control the upper limbs arise and what is this enlargement called ?
C4-T1 are cervical and control upper limbs , the enlargement is the cervical enlargement and is the whole cervical region.
Where do the nerves that control the lower limbs and pelvic?
T9-T12 are pelvic and lower limbs , the enlargement is called the lumbar enlargement and is before the lumbar region.
define medullary cone
Taper of the distal cord
define cauda equina
“horse tail” bundles of nerves originating form the lumbar enlargement and the medullary cone .
What vertebra make up the cauda equina?
L2-L5
Define terminal filum
fibrous continuation of the cord beyond the medullary cone. consists of pia matter and neuroglia elements.
Where is epidural anesthesia utilized during childbirth?
In the epidural space that is filled with fat and blood vessels
What anchors the cord to the coccyx ?
filum terminale and denticulate ligaments
Define denticulate ligaments
extension of the pia that extends through the arachnoid to the dura.
What does the denticulate ligament do?
suspends the spinal cord in the dural sheath.
What is spinabifida ?
Failure of vertebral arch to close covering spinalcord affects one in a thousand babies.
What are the two froms of spina bifida?
spinabifida occulta and spinabifida
manifesta
.
Dorsal root of spinal nerve is totally what kind of fibers
Sensory nerves
Ventral roots of the spinal nerve is totally what kind of fibers?
Motor nerves
What is white matter in the spinal column ? What two names is assigned to the white matter ?
The white matter is called White columns or funiculi , they are bundles of myelinated axons that carry signals up & down the cord
What are the symptoms of spina bifida ?
Bowel and bladder control , ADD, and learning disabilities
Define Coccygeal ligament
fused terminal filum and dura that anchors the cord and meninges to Co1
Explain spina bifida occulta
Hidden , the most mildest form , most children with occulta wont have health problems and the cord is unaffected
Explain spina bifida Myelomeningocele
Most severe form, occurs when the meninges and spinal cord push through a hole in the back . Typically will have some sort of paralysis and hydrocephalies” accumulation of fluid in and around the brain”.
How is spina bifida diagnosed
Test between 16-18 week of pregnancy. They measure the amount of Alpha-fetoprotein that the fetus produces. They check through ultrasound, or aminocentesis
Define decussation
Fibers cross sides
How many pathways do the motor neurons have ?
two pathways
How many pathways do the sensory neurons have ?
Three pathways, they must go through the thalamus to get to the central gyrus
What are the three ascending pathways of sensory neurons?
1st order, detect signal and sends to cord.
2nd spinal cord to thalamus “main sensory relay center”
3rd Thalamus to sensory “Precenteral gyrus”
What are the three types of sensory input from the body?
Discriminative touch, pain and temp, and proprioception
Explain Discriminative touch
touch, pressure, and vibration perception. Allows us to see 3-D EX. seeing a cube, not a square
Explain Pain and temperature touch
what it sounds like and including itch, and tickle
Explain proprioception touch
muscle stretch, joint position, and tendon tension .
Where does discriminative touch system cross ?
medulla (spinal cord)
Where does the pain system cross?
low spinal cord
Where does the proprioception cross?
It doesn’t , It works with the cerebellum , which is ipsilateral
Where does the Fasiculus gracilis and cuneatus carry signals ?
legs and arms
The decussation of second order neurons occurs where ?
cuneate nucleus , in medulla
What are upper motor neurons?
begins at soma in cerebral cortex and terminates at the lower neuron
What are lower motor neuron?
Large neurons in the ventral horns that send their axons out via spinal roots and directly control the muscles.
What percent of the lateral corticospinal decussate in the medulla ?
90%
What percent of the ventral corticospinal decussate at the spinal segment?
10%
Descending tracts are divided into what two types of tracts?
Pyramidal tracts and extrapyramidal
In the category of pyramidal tracts what are corticospinal tracts ?
They carry signals for precise , coordinated, limb movements . They form ridges called pyramids.
In the category of pyramidal tracts what are corticobulbar tracts?
axons that intervate the muscles of the face
What are extrapyramidal tracts ?
All other motor components , influences the activity of the pyramidal system , exerts its effects on voluntary movement.
What are the three extrapyramidal tracks?
Tectospinal, Reticulospinal, & vestibulospinal Tracts
Explain the Tectospinal Tract.
Found in the cervical cord only, controls movement of head
Explain the Reticulospinal Tract.
Controls movement of limbs for posture & balance
Explain the Vestibulospinal Tract.
What Balance & posture (Inner ear signals)
What cuases poliomyelitis ?
Fecal contaminated water, causes paralysis & respiratory arrest
What is ALS (Amyotrophic lateral sclerosis)?
Degeneration of motor neurons & sclerosis of spinal cord due to astrocyte failure. Causes paralysis & muscle atrophy
What surrounds each nerve fiber?
Endonerium
What encases nerve bundles?
Perineurium
What encases the nerve as a whole?
HEpineurium
True or False. Blood vessels penetrate only to the perineurium ?
True
How many pairs of spinal nerves are there?
31
What do Dorsal ramus supply?
Dorsal body, muscle, & skin
What do Ventral ramus supply?
Ventral Skin, Muscles, & limbs
What do meningeal branches supply?
Meninges, Vertebrae, and ligaments
What are shingles? What are the symptoms?
Reactivation of the herpes Zoster Virus
Skin erupts along path or nerve (Dermatome)
True or False. Varicella-Zoster virus (chicken pox) remains for life in dorsal root ganglia?
True
What are Dermatomes?
Areas on the skin supplied by sensory fibers of spinal nerves.
True or False. Dermatomes overlap each other by 50%?
True, require numbing to more than one nerve in order to numb the whole area
What are the four important properties for reflexes?
Reflexes require stimulation, reflexes are quick, reflexes are involuntary, & reflexes are stereotyped (occur the same way every time).
What are the 5 steps of a somatic reflex ?
- stimulation of somatic receptors
- afferent fibers carry signal to dorsal horn of spinal cord
- interneurons integrate the info
- efferent fibers carry info to skeletal muscles
- skeletal muscles respond
What kind of proprioceptor is the muscle spindle?
Stretch receptor that responds to prolonged or onset stretch, wrapped with afferent fibers
What do the primary, secondary, & gamma motor fibers respond to?
Primary- muscle stretch
Secondary- prolonged stretch
Gama motor neuron- Twists the muscle spindle to shorten slack
What helps muscles from working against each other?
Reciprocal inhibition
Define Golgi tendon organ.
Stretch receptors located within the tendons, they don’t respond to length but to how hard it is pulling. By producing inhibitory (Glycine) potentials. Decreases muscle contraction and prevents muscle injury
Define spinal shock
Loss of sensation & motor paralyses but gradual recovery of reflexes
