Chapter 13: Spinal Cord & Nerves Flashcards
CNS
Brain and Spinal cord
- Most neurons in the body
- NO NERVES
- Nuclei & Ganglia
Gray Matter
Cell bodies, unmyelinated axons, neuroglia, synapses
- Integration and processing
- Posterior Dorsal Horn
-Anterior Ventral Horn (Somatic & motor)
- Lateral Horn (visceral & motor)
White Matter
Myelinated axons and fibers
- arranged in tracts (bundle of axons)
- conducting
- looks like a butterfly
Nuclei
Masses of cell bodies embedded in white matter in the CNS
PNS
Remainder of the nervous system in the body (Outside of brain and spinal cord)
- Tracts & Nerves
Nerves
Bundles of nerve fibers in PNS; Receptors and nerve endings (Neuromascular Junction)
31 Spinal Segments
Gives rise to dorsal and ventral roots
Cranial Nerves
Nerves to/from brain
Ganglia
Collection of cell bodies outside of the CNS
Spinal Nerves
Nerves to/from spinal cord
Adult Spinal Cord
- Extends from L1-L2
- 18 Inches
- Not unifrom in diameter
- 31 Spinal segments
Filum Terminale
Thin fivrous connective tissue which extends from the conus medularis, anchroing cord in the vertebral canal.
Cervical Enlargement
Nerves to shoulders and arms
Conus Medularis
Cone shaped ending of spinal cord
Dorsal Root
- Leads to dorsal horn
- Afferent (Sensory)
- Unique dorsal root ganglia - cell bodies of sensory neurons
Lumbar Enlargement
Nerves to pelvis and legs
Spinal Nerves
31 Pairs of mixed nerves (efferent & afferent)
- Result from the union of dorsal and ventral roots
- Exit between vertebrae (Interebral foramen)
Ventral Root
- Leads away from ventral horn
- Efferent (Motor)
Thoracic Nerves
T1 - T12
Cervical Nerves
C1 - C8
Sacral Nerves
S1 - S5
Lumbar Nerves
L1 - L5 (Spinal cord ends L1/L2)
Coccygeal Nerve
C0
Cauda Equina
- Collection of spinal nerves in lumbar region
- Horse’s Tail
Arachnoid
- Internal to Dura Mater
- Spider web extensions
- Subarachnopid space filled with spinal fluid
Spinal Meninges
-Continuous with cranial meninges
- Cover CNS
-Provide stbility and shock absorption
- Dura Mater
- Arachnoid
- Pia Mater
Dura Mater
Outer covering of spinal cord and nerves
- “Tough Mother”
- Tapers to coyccygeal ligament which merges with the filum terminale
Epidural Space
Separates dura mater from walls of vertebral canal
- filled with fat
Cerebrospinal Fluid
- shock absorber
- fluid for diffusion of nutrients and waste products
- Extends to inferior lumbar regions
Pia Mater
- “Delicate Mother”
- Adheres to spinal cord surface
- Meshwork of elastic and collagen fibers
- Blood vessel rich
- Innermost meningeal layer
Posterior Median Sulcus
- Longitudinal Groove
- Separates into left and right parts
Anterior median fissure
- Deeper groove (left and right)
Columns of White Matter
Six Columns (Three on each side)
- Anterior
- Posterior
- Lateral
Tracts to and from the brain
Ascending
Sensory info into the brain
Descending
Motor commands to spinal cord
White Commisure
Axons communicating between anterior columns
Gray Commisure
Bridge of gray matter connecting the right and left sideof the spinal cord
- Axons conduct signals between right and left sides
- Has the central canal
Central Canal
- Contains CS fluid
- Extends the length of the spinal cord
- Little hole in the center
Peripheral Nerves
- Includes spinal nerves & cranial nerves
- Bundle of nerve fibers (axons), blood vessels heald together by layers of connective tissues
- Epineurium
- Perineurium
- Endoneurium
Epinerium
Outer
Perineurium
Surrounds fascicles
Endoneurium
Surrounds each fiber
Spinal Nerve
Union of Dorsal (Sensory) and Ventral (Motor) roots
- Very short
- Branches to form rami
- Rami are mixed roots are NOT
- Rami communication is part of the ANS
Dorsal Ramus
Sensory and motor innervation to the skin and muscles of the back
Ventral Ramus
Supply the ventrolateral body, surface, body wall, and limbs
Dermatones
- Specific bilateral region of skin surface monitored by single pair of spinal nerves
- Each pair of nerves monitors one dermatome
Organization of spinal nerves
- Sensory impulses enter spinal cord dorsally
- Dorsal root ganglion - cells bodies of spinal nerbe
- Dorsal root –> drosal horn
- Motor impulses exit ventrally
- Ventral horn –> Ventral root
- Somatic fibers leave by way of spinal nerves
- Visceral (autonomic) fibers leave abd ebter a ganglion
Dorsal Rami
Innervates the back of the body
Ventral Rami
Extends towards the front
Nerve Plexus
Intertwining of nerves from several spinal nerves
- gives rise to alternate pathways for impulses to travel
- damage to one branch does not result in total loss of sensation and control
The Cervical Plexus
Extends from C1-C5
- Innervate muscles of neck and diaphragm
- ! Phrenic Nerve ! (Innervates diaphragm
- respiration
Brachial Plexus
Extends from C5 - C8 & T1
- Innervates shoulder and arm
- radial & ulnar nerve
Lumbar Plexus
T12 - L5
- anterior thigh, leg, and foot
Sacral Plexus
L5 - S4
- posterior thigh, leg, and foot
Sciatic nerve
- largets nerve in the body
Sensory Neurons
- Deliver information to the CNS
- 10 million
Motor Neurons
- Carries impulses to effector organs (muscles and glands)
- 500 million
Interneurons
- Integrate information, process and analyze
- in the CNS
- 20 billion (Most numerous)
Neuronal Pools
Functional group of interconnected neurons
Simple neural pathway
Reflex
Complicated neural pathways
- scattered or localized
- output may be excitatory or inhibitory
- typical interneurons have
1,000 –> 10,000 synapses
Reflexes
Rapid, predictable, automatic responses to stimuli
- sensory to CNS (Sensory in) motor fibers to effectors (Motor out)
Reflex Arc
Pathway of a simple reflex
Innate Reflexes
-Result from connections that from between neurons during development.
- Withdrawal from pain; blinking
Reflex Arc Steps
- Arrival of stimulus and activation of receptor
- Activation of sensory neuron
- Information processing
- Activation by motor neuron
- Response by effector
Acquired Reflexes
Learned, and typically more complex
- Driving
Cranial Reflexes
- Reflexes processed by the brain
Spinal Reflexes
- Interconnections and processing events that occur in the spinal cord
Somatic Reflexes
- Control skeletal muscle
- Some can be consciously modified
Visceral Reflexes
- Controls activities of involuntary muscles
- Photo pupillary response
Monosynaptic Reflexes
Stretch reflex
- Automatically monitors skeletal muscle for length and tone
Ex. Patellar reflex
Polysynaptic Reflexes
Tendon reflex
- Monitors external tension produced during a muscle contraction
- Control of several muscle groups
- Prevents tearing of tendons & gives coordination
Withdrawal Reflexes
Touch something hot –> withdraw
Polysynaptic
Crossed Extensor Reflex
Step on something painful, remove leg (withdrawal), extend other leg to support weight (extensor)
Plantar Reflex
Sole of foot stimulation; toes curl