Unit III: The Nervous System (Spine, Nerves and Reflexes) Flashcards
Where does the spinal cord begin and end?
Begins at the base of the brain and goes down to T12.
Cervical and Lumbosacral enlargements
Cervical supplies to the shoulder and upper limbs.
Lumbosacral innervates structures of the pelvis and lower limbs.
Conus Medullaris
Lower end of the spinal cord tappers off around the lumbar vertebrae. Between L1 and L2.
Causa Equina (L2 to S5)
A bundle of nerves at the end of the spinal cord that resembles a horse’s tail.
Meninges of the Spinal Cord
Protection of the spinal cord (similar to the brain). Specialized membranes surrounding the spinal cord, provide the necessary physical stability and shock absorption.
Epidural Space
Adipose tissue between vertebra and dura mater
Subarachnoid Space
Filled with cerebrospinal fluid between the arachnoid membrane and the outer surface of the pia mater.
Spinal Tap/Lumbar Puncture
The withdrawal of CSF with the insertion of a needle into the subarachnoid space in the inferior lumbar region.
Gray Matter in the Spinal Cord
Mostly cell bodies, the butterfly shape in the middle of the spinal cord.
Posterior (dorsal horns)
Interneurons are found here
Anterior (ventral) horns
Cell bodies of motor neurons
Lateral horns
Sympathetic neurons
What runs through the central canal?
CSF
Posterior (dorsal) root
brings sensory information into the spinal cord.
Anterior (ventral) root
Axons of motor neurons that extend into the peripheral to control somatic and visceral effectors
What are the function of the spinal nerves?
Allow communication with the peripheral organs.
posterior and anterior roots fuse into a spinal nerve
Tract
A bundle of axons in the CNS that is somewhat uniform in diameter, myelination, and propagation speed.
Ascending Tracts
Carry sensory information toward the brain.
Descending Tracts
Convey motor commands to the spinal cord.
How many columns can white matter be divided in?
- posterior, anterior and lateral.
Posterior Column
Between the posteior horns and median sulcus.
Ascending Tracts
Anterior Tract
Between the anterior horn and anterior median fissure.
Ascending and descending*
Lateral Column
Between the anterior and posterior columns on each side.
**Ascending and descending. **
How many pair of spinal nerves are there?
31.
Do sensory nerve fibers enter the ventral side of the dorsal side of the spinal cord?
Sensory nerve fibers enter the dorsal side of the spinal cord (afferent)
Do motor nerves leave from the ventral or dorsal side of the spinal cord?
Motor nerves leave from the ventral side (efferent)
Posterior (dorsal) rami
Serve the skin and muscles of the posterior trunk.
Anterior (Ventral) Rami
T2-T12 forms intercostal nerves- serve muscles between the ribs, skin, and muscles of the anterior and lateral trunk.
Cervical Plexus C1-C5
Serves the diaphragm and muscles of the shoulder and neck.
Phrenic Nerve
Phrenic Nerve
The major nerve of the cervical plexus, supplies the diaphragm, a key breathing muscle.
If damaged this can result in death due to respiratory paralysis.
Brachial Plexus (C5-C8 and T1)
Nerves that innervate the upper limb and pectoral girdle.
Axillary, radial, median, ulnar.
What results from radial nerve damage?
Wrist drop or inability to extend hand at the wrist.
What results from median nerve damage?
Inability to pick up small objects.
What results from ulnar nerve damage?
Claw hand or inability to spread fingers apart.
Lumbar Plexus
L1-L4
Major nerves, femoral, and obturator
Sacral Plexus
L4-S4
Sciatic nerve
Tibial and common fibular (peroneal)
What results from tibial and common fibular damage?
Inability to extend the hip and flex the knee.
Sciatica
What is a dermatome?
Area of the skin is innervated by the cutaneous branches of a single spinal nerve.
All spinal nerves expect C1
What is the clinical importance of dermatomes?
Damage or infection.
Shingles!
What are reflexes?
They are rapid, predictable motor responses to a stimulus.
How are reflexes classified?
Innate vs. Acquired
Response
Complexity of circuit
Processing site.
Innate vs. Acquired
innate- genetically determined
Acquired- with time, these reflexes are learned.
monosynaptic vs. polysynaptic
mono- one synapse
poly- more than two synapses
What is a reflex arc?
Direct route from a sensory neuron to an interneuron to an effector
What are the five components of a reflex?
Receptor, sensory neuron, integration center, motor neuron, effector
What type of reflex in the plantar reflex?
Monosynaptic
Babindki’s Sign
Abnormal plantar reflex where the great toe dorsiflexes (flexes upward) and the smaller toes fan laterally.
Paralysis
Loss of motor function
Flaccid Paralysis
Severe damage to the ventral root.
Motor nerve impulses do not reach muscles.
NO VOLUNTARY MOVEMENT POSSIBLE.
Muscles begin to atrophy
Spastic Paralysis
Occurs when the spinal cord is cut crosswise (transected) or crushed.
Affected muscles stay healthy because they are still stimulated by reflex arcs and movement occurs.
Movements are involuntary.
Paraplegia
Transaction between T1 and L1.
only legs are affected
Quadriplegia
Transaction just below C5
All limbs are affected
Death
Transaction above C3
Respiratory paralysis
Phrenic Nerve!!!!
