4 - Zill - Nervous System Flashcards
Legal Definition of Death
Irreversible cessation of function of nervous system
You just stepped on a nail, how does the signal get to your nervous system?
Afferent Axon conducts toward CNS on sensory neuron
Motor Neuron conducts on Efferent Axon away from CNS to lift leg
What can be used to test nervous system function and locate site of lesion?
Reflex tests
How many spinal nerves are there?
31
Cervical Spinal Nerves exit point?
C1-C7
C8 and all others
C1-C7:
Above corresponding vertebrae
C8-all:
Below corresponding vertebrae
Somatic Nervous System
Efferents v Afferents
Voluntary, conscious movement
Efferents: Control skeletal muscles, volunary activities, conscious actions
Afferents: Sense of body position, sensation of touch, pain, pressure
SAME:
Sensory
Afferents
Motor
Efferents
Autonomic Nervous System
Involuntary, unconscious part of nervous system
Visceral Efferents
Parasympathetic and sympathetic, control smooth and cardiac muscle, glands, and internal organs.
Largely unconscious–automatic
Where are the Autonomic, Sympathetic Chain of Ganglia located?
para (side) vertebral
Where do the dorsal and ventral roots combine?
Spinal nerve
Where are cell bodies of all sensory neurons located?
Doral Root Ganglion
Dermatome
Area of skin innervated by a single spinal nerve
What are dermatomes used for clinically?
Testing nerve damage, anesthesia
What are the dermatomes of the hand?
Thumb = C6
Pointer, Middle = C7
Ring, Littler = C8
What level of a herniated disc would produce numbness of the thumb?
Thumb = C6,
So herniation ABOVE: C5 and C6
What level of herniated disc would produce numbness in the little finger?
Little finger = C8
Rule: C1-C7 = Above, C8 = Below
Herniation between C7 - T1
Spinal Nerves, how many of each?
Cervical - 8
Thoracic - 12
Lumbar - 5
Sacral - 5
Coccygeal - 1
What is the rule for exiting of spinal nerves?
C1-C7 = Above
At C8 and below = Below
Dermatomes of the lower extremity:
Inguinal Ligament (anterior to hip)
Big Toe
Little Toe
Inguinal Ligament - L1
Big Toe - L4
Little Toe - S1
Dorsal Ramus
Ventral Ramus
Dorsal Ramus - Sensory and motor axons to region of back
Ventral Ramus - Sensory and motor acons to other parts of body
Plexus
Lumbosacral Plexus
Forms from ventral rami of spinal nerves
Lumbosacral - innervates lower extremity
Conus Medullaris
Location in Newborn?
Location in Adult?
Where spinal cord ends
Newborn: L3
Adult: L1
Cauda Equina
Dorsal and ventral roots that grow down from the conus medullaris
Dura Mater
Where does the dural sac end?
Tough outer layer around spinal cord, below L1 adult (L3 newborn), dural sac surround cauda equina.
Dural sac ends inferiorly at S2
Epidural Space
What does this space contain?
Separation of dural sac from inner side of vertebral canal
Also contains Internal Vertebral Venous Plexus
Only VEINS and FAT
Epidural Anesthesia
Can block conduction in spinal nerves by injection into epidural space; effect is by diffusion.
Arachnoid Layer
Subarachnoid Layer
Attached to inner side of dura, has fine strands that extend to the pia mater
Subarachnoid layer contains CSF
Pia Mater
Thin layer, contains blood vessels supplying cord.
Denticulate Ligaments
Use?
Projections of pia on each side of cord that extend to arachnoid to inner dura; 21 pairs stabilize spinal cord.
Used as landmarks in neurosurgery
Filum Terminale
Thin strand of Pia that extends below Conus Medullaris, pierces S2, attaches to Co1
Where is CSF produced?
Choroid plexuses, mostly in brain
Spinal Tap location?
Must be below Conus Medullaris (inferior to)
Adult: Between L3-L4, or L4-L5
***Children: L4-L5*** (spinal cord extends to L3)
Where does the dural sac end?
Where does the filum terminale end and attaches?
Where does the spinal cord end in children/adults?
Dural Sac - S2
Filum Terminal End/Attach - Co1
Spinal Cord End:
Adult - L1
Child - L3
What yields the first and second pop during a spinal tap?
Ligamentum Flavum (sudden yield, first pop)
Dura mater (sudden yield, second pop)
